Impact of Climate Change on Human Evolution: The Odyssey from Africa

by Phil Salmon

How a small group of people from Africa changed the world.

Paleoclimatology, the study of climate in the past all the way back to deep time, is one of the pillars of climate science. It shows us the wide range of climates that have existed on earth, from near-global glaciation in “snowball-earth” epochs to hothouses where the poles were forested. It puts in a correct perspective discussion about climate change – dismissing any notion that climate has ever done anything other than endlessly change. And it provides an alternative to computer simulated models of climate, in which, given enough knowledge of conditions and influences on climate at past times, virtual experiments can be run by fast forwarding from chosen time points, analyzing the climate record to disentangle cause from effect.

The trouble is, of course, that conditions on earth and influences on climate are poorly known in the distant past, and this knowledge deteriorates in quality with further rewinding to earlier and earlier times.

However in the most recent ten million years or so, the paleoclimate record is good enough for us to know quite precisely how important tectonic changes have occurred, such as the portentous joining of the two America’s, the formation of the Mediterranean Sea separating Africa from Europe, and the opening of a Rift Valley, Africa’s incipient tearing away from Eurasia to become in the future a colossal island on its own.

And within the last million years our knowledge is still further improved by the availability of ice core data showing us the detailed ups and downs of climate temperature (and, following obediently behind it, CO2) during the Quaternary period of alternating glacial and interglacial intervals.

Alongside climate science, another scientific field shares a focused interest in this recent timescale of a few million years: that of human evolution. It turns out that the two subjects are intimately linked. Not only did humans (self-evidently) survive the violent extremes of climate over the course of the glacial Quaternary period. It is considered by evolutionary biologists likely that the acute pressure on hominids to adapt or die as their habitats alternated between forest, grasslands and deserts, and as they periodically endured violent excursions of climate change, led to the run-away expansion of the human brain and our eventual attainment of consciousness accompanied by complex symbolic language and our imaginative, introspective inner world. And stemming from this, our farming, building of tools and machines led to the transformation of the earth’s surface. The physiological investment in a grotesquely bulbous head and huge brain consuming 25% of all our oxygen and energy, necessitated sacrifices in muscle mass, speed and strength. This increased our ancestors’ vulnerability to predation, leaving them even more in need of intelligent life strategies – thus the growth of mind ran along a positive feedback for a while.

Yuval Noah Harari’s recent book “Sapiens” focuses on a mysterious aspect of our evolution – namely that although our large brains and intelligence (complete with social, cultural and language abilities) have existed for at least 70,000 years, our agricultural, technical and intellectual achievements leading to our current industrialized lifestyle and landscape, have happened only in the last few centuries – relatively speaking in the blink of an eye. Why did this explosive advance wait for tens of thousands of years, when humans would have been capable of all that we do today, 70,000 years ago? (Apart, maybe, from “living on milk and alcohol”.) To date there is no clear answer to this question. In this article we will look at the possibility that climate might be at least partly responsible.

Climate change almost certainly played an important role in human evolution – as expounded for instance in John and Mary Gribbin’s book “Children of the Ice” (see references at the end.) And as we shall see below, the climate of prior glacial periods was violent beyond anything we have experienced on our mild and molly-coddled Holocene, possibly at times threatening our very existence. But paradoxically, at the same time, making us what we are.

Human evolution and the out-of-Africa migration

The last common ancestor of humans and chimpanzees lived 7 million years ago. Since then, contrary to superficial misconceptions of a single succession of ancestors leading to modern humans, an evolutionary tree grew out many branches of different human types, some which left descendants, others only genes.

Africa was the origin of the very first hominids and humans, several million years ago. (Our common ancestor with chimpanzees may even have been a bipedal hominid.) From Africa our ancestors radiated (spread out) into the rest of the world, at various times. Archaic humans of the species Homo erectus and Homo heidelbergiensis migrated out of Africa as long as 2 million years ago and spread widely throughout Eurasia and Europe. These early migrants left ancient descendants in Europe called the Neanderthals, and in Eurasia called the Denisovans. One remarkable group of even older humans (Australopithecines) made it as far as the Indonesian island of Flores, where a million years of isolation and island dwarfism led them to become so much smaller than other humans – only half the height – that scientists discovering their diminutive skeletons called them “hobbits” (to the legal indignation of Peter Jackson’s “Lord of the Rings” entourage of lawyers). This unique hominid Homo floresiensis survived on Flores until fifty thousand years ago – the time that we modern humans showed up. Whereupon the hobbits promptly died out.

However the more recent migration of modern Homo sapiens which took place 60,000 years ago had special significance. It was the first departure of Homo sapiens from Africa after they had become “behaviorally modern”, acquired skills of advanced tool use and language, and had begun creating art works. It should be noted that at this time there were only African modern humans on earth: today’s racial diversity of modern humans would come much, much later. For instance the pale skin of northern Europeans lay in a still distant future, less than 10,000 years ago in the Holocene interglacial.

The study of genetics compliments the discoveries of skeletal remains by paleontologists. The strings of DNA present in all the cells in our bodies are like mini-barcodes packed with a huge amount of information about ourselves and our ancestors. Genetic analysis shows that a single migration event took place about 60,000 years ago, by a small group of people genetically marked with “mitochondrial haplotype L3”. Astonishing, almost all humans on earth today, with the exception of some in Africa, are descended from this single exodus. This founding group of migrant ancestors consisted of just a few hundred individuals, the number of people at a typical wedding party. They departed Africa via the Red Sea and the Sinai mountains, foreshadowing the biblical Exodus. This small group of modern L3 labelled humans spread from Africa all over the world and are the ancestors of all humans outside Africa today.

(Please note that the fact that there were numerous “exodi” from Africa both before and after the 60 kya event, does not alter or contradict the clear evidence from genetics, from both maternal mitochondrial and male Y-chromosome analysis, that most humans today are indeed descended from that single 60 kya breakout. As Richard Dawkins showed mathematically in “The Ancestor’s Tale”, prior to 20,000 years ago, everyone alive was ancestor either to everyone living today, or to no-one.)

There was a dark side, however, to this sudden radiation of us moderns. It directly coincided with the disappearance of the Neanderthals, Denisovans, “hobbits” and other descendants of the much earlier archaic human radiations from Africa. This is circumstantial evidence of a kind of genocide – not our finest hour. Although the Neanderthals and other archaic humans did interbreed to a limited extent with moderns, such that today as much as 4% of our genome is of Neanderthal descent (if we are Caucasian) or Denisovan (if we are Asian) or from H. floresiensis hobbits (if we are from New Zealand).

A recent genetic study of present day people groups in Africa (Hammer et al. 2011) found that there had been interbreeding between modern humans and archaic remnants of Homo erectus in Africa as recently as 35,000 years ago.

Figure 1. A reconstruction of the face of a female ancient human of the species Homo erectus or Homo heidelbergiensis, made by the Smithsonian Museum of Natural History in the USA.

Ice ages and past climate chaos

The climate of our earth is chaotic and always changing, with or without human help.  This has been especially true in the last interval of slightly less than three million years, called the Quaternary Period. During this period the world has moved into glaciation, which means the appearance of large iced up areas at both the north and south poles.

The Quaternary period, which lasts until today, is the time frame over which humans have appeared. Technically speaking we are in ice age right now. This is where talking about being in an ice age gets complicated. For throughout all of the Quaternary so far, the earth has oscillated or “flip-flopped” between cold glacial ice age conditions and shorter interludes of warmer climate called “interglacials”. We are in such an interglacial right now – we call it the Holocene. Such warm intervals have typically lasted about 10,000-15,000 years; our own Holocene interglacial is just over 12,000 years old. This sounds like a long time – indeed practically all of recorded human history has taken place within the Holocene. However the frigid glacial periods which alternate with the interglacials are much longer, between 40,000 and 100,000 years in duration. Thus most of the Quaternary so far has been in a state of ice age.

The timing of the glacial cycles over the Quaternary has had a certain rhythm and regularity, and this has not been by chance. Helping the climate system to roll on a regular basis between glacial and interglacial attractors are periodic changes in the earth’s spin and orbit round the sun, called the Milankovitch cycles after the Serbian mathematician who worked out this connection. (This had in fact been first realized by a Scotsman, James Croll, but it was Milutin Milankovitch who fully established how regular wobbles in our orbit translate into the timing of the ice ages). There are three Milankovitch cycles with different periods: eccentricity (100,000 years), obliquity (41,000 years) and precession (19-22,000 years). The glacial-interglacial cycle is principally driven by obliquity, constrained by eccentricity and precession, with a 6,500 year lag – the time it takes the sun to warm up the oceans.

Figure 2. Of the three Milankovitch cycles, obliquity plays the primary role in the timing of the glacial cycle during the late Quaternary. Every single interglacial coincides closely with a peak of obliquity lagged by 6500 years (thanks to Javier for this figure!). But not every (lagged) obliquity peaks produced an interglacial – only those that coincided with the right conditions of eccentricity, the modulation of precession and consequent 65 degree N summer insolation. 6500 years is the time taken for Milankovitch insolation increase to warm the deep oceans.

This behavior is in fact quite typical of a chaotic system such as the earth’s climate, flip-flopping between two “quasi-stable” states, glacial and interglacial, unable to “make up its mind” which one it prefers. By the way the few stable states between which such a chaotic system will jump, have a name – they are called “attractors”. Chaos theorists talk about a “probabilistic landscape”, in which attractors are the valleys of probability separated by improbable mountains but sometimes connected by a pass or “saddle” which allows the system state to roll – sometimes with a bit of help from outside – from one valley to another.

The chaotic dynamics of ice ages get still more complicated. Within the long glacial periods there is a lot of climate instability and very sharp episodes of climate change, far more dramatic than anything seen in recent decades. Although glacial periods are longer than the warm interglacials, paradoxically climate is intrinsically less stable during the glacial intervals since the bigger temperature gradient between equator and poles lends more energy to the ocean-atmosphere system as a whole. While today’s politicians and scientists do their best to avoid the hazards of one or two degrees warming over a century or so, during recent glacial intervals temperature changes many times larger, of 10 degrees or more, took place regularly over similar short timescales. Graphs showing frozen records of the temperature of the Northern Hemisphere from ice and sediment cores show this clearly over the last hundred thousand years. This represents the time interval between our Holocene and the previous interglacial called the “Eemian”. In this glacial period there are many sharp upward spikes, or “micro-interglacials” in which temperatures rose – then fell – by up to ten degrees within only a century or a few hundred years. The technical term for these excursions is Dansgaard-Oeschger (D-O) events. These would have been very traumatic times to live through.

Figure 3. The dO18/O16 isotope ratio indicating the violent swings of northern hemisphere climate temperature during the last glacial period between the Eemian and the Holocene. Fluctuations with amplitude of almost 10 degrees C over just a few centuries or millennia occurred many times during this glacial interval (Dansgaard-Oeschger events).

What did all this mean for human populations living during the last glacial period? Of course it had profound implications. It meant that every few centuries or millennia, their lives were heavily disrupted by rapid and severe episodes of climate change, either warming or cooling – or both in succession. Such major changes would be linked to shifts in atmospheric and ocean circulation that would in turn affect food availability for human populations trying to build a way of living. It might have been these traumatic swings of temperature and ecological stress associated with them, that prevented human civilization from taking root over a long period of millennia. This could answer the question of Yuval Harari, of why human technical and cultural advancement only really gathered pace within the last part of the Holocene.

Yes there is a role for CO2

The odyssey from Africa took place about 60,000 years ago. From graphs of temperature over the last glacial cycle, it can be seen that this was not quite the coldest part of the glacial period. That lay ahead at around 20,000 years ago, the “glacial maximum” during which the climate also became very dry, with high winds blowing dust storms from arid plains. Ice core records show that, at that time, the air even at the poles carried clouds of dust from vast and windy deserts. One possible reason for the dust and aridity in mid and high latitudes during the last glacial maximum was the fall of carbon dioxide (CO2) concentration in the atmosphere to low levels of less than 200 ppm (parts per million) – levels at which CO2 “starvation” begins to cause stress to plants, and which cause ecosystems to change from forest to grasses and grasses to desert. For instance at less than 200ppm CO2, tree regrowth after fires can become too slow for new trees to be big enough to resist the next fire, so trees are replaced by grass (Bond et al. 2003). And the 1930’s dustbowl years in the USA show how tree loss can lead to soil loss, dust and aridity. Robert Ellison has advanced a hypothesis that this aridity at the glacial maxima, accentuated by CO2 starvation, formed a component of a feedback loop that decreased albedo on dust-covered ice sheets and brought about the abrupt termination of each glacial maximum. Clearly our human ancestors would have suffered severe perturbation to their way of life during the cold, arid and dusty glacial maxima.

Recent research by Jessica Tierney of the University of Arizona, USA, reconstructed climate at the “Horn of Africa” – the region including Ethiopia and Somalia at the south of the Red Sea – from cores of sediment from the Arabian Sea. Tierney’s team looked for chemical traces of the wax from leaves blown out to sea in the sea-floor sediments, allowing them to reconstruct which periods over the last 200,000 years were either arid and dry or green and wet. They discovered – to their surprise – that at the period around 60,000 years ago, when the exodus of modern humans from Africa took place, the Horn of Africa had turned arid and dry. This is puzzling – it would have made our Odyssey from Africa more challenging – but evidently it didn’t stop it from happening.

It is considered by scientists that this staccato pattern of repeated sharp climate changes was a key factor in the evolution of large brains and intelligence that resulted in the emergence of us humans. With repeated alternation of large parts of Africa between forest, savannah and desert, our ancestors would have needed to be smart and to anticipate and make contingencies for the future, and to quickly innovate to exploit new unexpected circumstances. Without doubt they “lived in interesting times”!

Ice age animals that are now extinct.

At that time around 60,000 years ago, many creatures lived on earth which are now no longer with us. This includes Eurasian populations of straight-tusked elephants, hippos, rhinos and cave bears. Further north nearer the glacial fronts, woolly mammoths, woolly rhinos and the musk ox roamed the frosty plains. Now extinct predators that still lived at that time included sabertoothed cats, and also cave lions and a European leopard. And on Madagascar the great giant elephant bird Aepyornis – a ratite like ostriches but way, way bigger, was king of all it surveyed.Figure 4. The skull of a sabertooth cat, species Smilodon, and an artistic reconstruction. Note the large bony crest at the rear of the skull (left) for powerful jaw muscle attachment. I don’t think that this reconstruction (right) does justice to how terrifying a creature Smilodon was.

Over the Atlantic, 3 million years ago at the start of the Quaternary, North and South America had only just joined together at Panama, leading to a convulsion of migration and mixing between the two hitherto separate continents. Many great megafauna lived then in the Western Hemisphere that have since disappeared: giant sloths, the American lion, a giant tortoise, sabertooth cats, camels, the “dire wolf”, the mastodon and the armadillo-like glyptotherium.

Where did they all go? What caused so many wonderful big creatures to die out? Scientists speak of two principal causes, with ongoing debate as to their relative importance; these are, stress from changing climate, and hunting by us humans. A human hand is evident in some extinctions. In North America especially, creatures that had never been exposed to modern human hunters suddenly confronted them 12,000 years ago when melting ice (and still decreased sea level) allowed modern humans to cross for the first time into the American continent from Siberia and East Russia. The American megafauna’s naivety to humans led to their demise. By contrast, African megafauna – our elephants, hippos, lions, giraffes and so on – had experienced the company of us humans for millions of years throughout our evolution. This enabled them to adapt to survive alongside us; at least so far.

However before we get too judgmental of our rapacious ancestors, it seems that opinion is moving in the direction of climatic stress as the culprit for most megafaunal extinctions. The severe cold of the last glacial maximum combined with rapid climate fluctuations, the “micro-interglacials” (D-O events) discussed above, traumatized ecosystems and contributed to the extinctions of these large creatures.

Mount Toba and the great bottleneck

One baleful climatic player in the ancient history of both humans and other animals needs to be mentioned. Mount Toba was an island in Indonesia which exploded in a devastating volcano – what scientists call a supervolcano – about 75,000 years ago. A supervolcano is thousands of times bigger than ordinary volcanos, able to disrupt climate globally, and Mount Toba is estimated to have erupted 3,000 cubic km of rock as pulverized ash, covering much of South Asia in a 6 inch (15cm) deep ash layer. This unimaginably violent eruption is many times bigger than anything experienced in recorded history. (By contrast the Mount St Helens volcanic eruption in Washington state, USA in May 1980 ejected less than 3 cubic km of ash.) Up to ten years of global winter followed the Mount Toba supervolcano. Genetic analysis suggests that the worldwide human population was decimated by Mount Toba to a mere 1000 breeding pairs – the population of just one small town or village today. Some other animals also show evidence of the “genetic bottleneck” of a similar drastic decline in population, such as orangutans and tigers in Asia and chimpanzees and cheetahs in Africa. Eventually humans, animals and ecosystems recovered from this catastrophe. It happened a few thousand years before the time of the 60 kya odyssey, and partly explains why on the earth at that time, “few in number were the people”.

(In fact the reason that the 60,000 year ago breakout group from Africa became ancestral to all the world’s population outside Africa now, might be partly good luck: they were the first exodus from Africa after Mount Toba decimated worldwide populations descended from earlier breakouts of modern humans, of which there is evidence as far back as 120,000 and even 200,000 years.)

Could mount Toba even have been the near-fatal stressor that pushed humans into that final expansion of brain and mind, in a desperate fight for survival, that led to the “great leap forward” to modernity, language, culture and cave art, 70,000 years ago?

Earth’s violent geological history did not quite kill us, but helped to make us what we are – creatures with the intelligence to discern good from evil, and the freedom to choose one or the other.

A narrative poem about the 60 kya breakout

Although much has been written about the paleontology and evolutionary biology of developing humans, there is very little fiction or poetry written about the majority of human history, the 200,000 years that anatomically modern – and the 70,000 years that behaviorally modern – humans have lived on earth. There has been little expression of curiosity in the form of story-telling about most of this period. Our focus has been exclusively on the tail end of the Holocene, with an echoing silence from most of our long history before that.

In an amateur attempt to put this right, I wrote up as a narrative poem a run-on story that I told to my daughters some years ago when they were of that age where they demanded a bedtime story every evening. My three girls provided many of the illustrations for the book I eventually wrote. Although the story is lighthearted in character, it makes some important points about our prehistory and exodus from Africa. Climate, for instance, is an important player, a threat in the background that drives the migration event.

The result of this effort is “Odyssey from Africa (and the Adventures of Ipiki)”, a story about a small group of people who inadvertently changed the world, sixty thousand years ago. Fleeing a village witch-hunt, a fisherman with his wife and twin children embark on a flight for survival, that grows into a journey of discovery and inspiration. Joined along the way by companions both animal and human, the scope of their odyssey expands into something far greater than they would ever have imagined.

“…And our world is so much larger

Than the limits of our vision

What to us seem wide horizons

Are a spot upon the surface

Of a world immense and wondrous

Filled with things beyond our knowledge”

It’s written in the same inverse iambic pentameter meter of the poem “Hiawatha” about a legendary native American hero, by Henry W. Longfellow; it’s also about the same length.

At the Amazon page for this book (available in paperback and Kindle, link below), you can read the first few chapters by clicking on “preview” or “look inside”.

Here are the first seven verses:

Mvuvi (The Fisherman)

At the dawn of humankind in

Africa’s great land of sunlight

This adventure of survival

Of a family’s arduous journey

One of exile and betrayal

And of hopeful brave endurance

Happened long before all memory

Only scattered bones bear witness

Mighty ice-sheets of the Arctic

Would again repeat their south-march

Hold the world in age-long winter

Then retreat to warming sunshine

All between this ancient voyage

And the present time of writing

Days of our long distant fathers

Few in number were the people

Somewhere on the south-east seaboard

Was a modest fishing village

Where a hundred families prized their

Living from the restless ocean

Here lived Han with his wife Kwona

Their son Matto, daughter Lisa

Twins of near a dozen summers

Old enough to help their parents

Lisa watched her mother’s fingers

Make, like magic, food and clothing

Matto learned beside his father

As a fisherman’s apprentice

References [References]

Moderation note:  As with all guest posts, please keep your comments civil and relevant.

77 responses to “Impact of Climate Change on Human Evolution: The Odyssey from Africa

  1. The discovery of 180,000 year old H. sapiens in Israel just announced in this week’s Science may require a bit of revision here.

    • Not to mention the discovery of 5.7 million year old hominid footprints in Crete. https://www.nature.com/articles/d41586-017-03029-9

    • Phil Salmon,

      Thank you for this excellent article. Very well written and very enjoyable. Filled in some dates and other information I wasn’t aware of.

    • WS, was covered in the article. Earlier outmigrations of homoSapiens did not survive for reasons that might include Toba, insufficiently developed tools, whatever. There is lotsnof evidence both genetic and archeological that the successful wave of outmigration from Africa occured as described in the post. What is really interesting is how fast all of Eurasia got populated. Aborigines arrived in Australia ~50000ya based on two skeletal remains.

  2. Walter
    As so often the journalist reporting the science here is adding their own personal, wrong and misleading perspective. It’s really not news at all that there were many breakouts from Africa starting at least 2 million years ago. Even of moderns from 200kya. Yawn. What the article points out is the 60 kya breakout is confirmed by genetics as the one that is ancestral to all humans outside Africa today. Yes some genes from other breakouts are mixed in, just as we also have up to 4% Neanderthal DNA. These are the exceptions that prove the rule. The 60kya breakout was ancestral to you and I (unless you are African).

    • Phil Salmon is a true philanthropist-

      Few things coud do more to improve contrarian discourse than compelling its authors to emulate Longfellow and write in trochaic tetrameter , which would greatly improve the conversation by putting both authors and readers to sleep within a few stanzas.


      From the heartland of Chicago
      By the Gitchi Gumi waters
      Come these legends and traditions,
      With their frequent repetitions,
      And their wild reverberations
      Of drumbeat memes as they hear them
      From the lips of S. Fred Singer
      The musician, the sweet singer.
      As of echoes in a chamber
      Should you ask where Heartland grifters
      Found these songs so wild and wayward,
      Found these legends and traditions,
      I should answer, I should tell you,
      From some K-Street PR sachem
      Likely by the name of Idso…

  3. Climate Change and Human Evolution: How The Two Biggest Pseudo-Scientific Frauds Made It Into The Same Post.

    Film at 11.

    Andrew

    • It is a contradiction, I’ll give you that. The consensus of climate scientists today is that the world was created in 1850. (Research is ongoing into why this year was called “1850”…) At least they all agree it’s worse than they thought.

  4. Walter Starck noted that if only humans really were able to heat the globe, “and it helps to prevent another ice age, this would be the most fortunate thing that has happened to our species since we barely escaped extinction from an especially cold period during the last ice age some 75,000 years ago.”

    • It is likely that if humans do cause a significant warming that hastens the melting of summer or year-round Arctic Ocean sea-ice, it will only hasten the beginning of the next glacial stage. See Global Warming: Prelude to the Next Glacial Stage? (http://kennethpiper.com/global-warming-next-glacial-stage/).

      • Sorry to be replying under another comment. I can’t find the reply button at the end of the article. I found this article to be very enjoyable. It brings up a couple of topics that I have spoken and written about for years: Causes of climate change, and the evolution of human intelligence. For the former, see, for example my earlier articles at http://kennethpiper.com/category/science/climate-change/; for the latter my article http://kennethpiper.com/has-society-made-us-less-intelligent/.

      • And, we are told the Antarctic was ice-free until it “suddenly appeared” some 35 million years. Fans of of modeling will have a difficult time arguing with findings that the cause of the shift apparently was caused by too greenhouse (mostly CO2) gases in the atmosphere.

        “That’s what climate models are good for. They can give you plausible reasons for such an event,” Huber says. “We found that the likely culprit was a major drop in greenhouse gases in the atmosphere, especially CO2. From the temperature data and existing proxy records indicating a sharp drop in CO2 near the Eocene-Oligocene boundary, we are establishing a link between the sea surface temperatures and the glaciation of Antarctica.” (see, Science 2.0: Why Did Ice In Antarctica Suddenly Appear 35 Million Years Ago? CO2, Says Study)

  5. Thank you for this very interesting and informative account of human history and its potential relationship to climate change.

  6. Should we get ready for a new ice age? In the meantime, the link to “Odyssey from Africa” doesn’t work. I think it should be

    https://ptolemy2.wordpress.com/2018/01/12/odyssey-from-africa-and-the-adventures-of-ipiki/

  7. I would suggest that ancient people moved more for safety than climate. Man also has a desire to look for better places. In recent decades the US has seen a large migration of people due to climate, they have moved to Florida and Arizona. People still live in the Arctic, I have been there and I ask why? Explorers also risked their lives to explore Antarctica, and Mt Everest.

    • Scott
      It surprises me that there were few and discreet migration events, rather than a continuous stream. But that’s where the genetic evidence points. Maybe the Sinai region was mountainous, arid and forbidding so there was little motivation to head into it not knowing it wasn’t the end of the world. The book Odyssey from Africa speculates at a reason – a kind of ideological/mystical wanderlust. Under the influence of a certain king Ptolemy the second.

  8. “the bigger temperature gradient between equator and poles lends more energy to the ocean-atmosphere system as a whole”
    Quibbling here. It should read potential energy. There is less total energy in the system when it is cold. There is more potential energy when it is cold because the gradient between the poles and equator increases.

    The concept of probability holes amuses me. Upside down determinism we just don’t understand…

  9. I’ve always been fascinated by the science of paleo-anthropology, and the series of little tidbits its practitioners are able to put together into grand syntheses. For example, there’s Lucy, Mother of Man. How did they know her name was Lucy? Well, it was one of those crazy flukes of science. During the renovation of the Cleveland, OH post office, a post card was found lodged between the wall and the mail chute. Dated 3.2 million BC, it was addressed to “Lucy, Mother of Man, Awash Valley, Ethiopia.” Sure enough, when paleo-anthropologists went to the site, they were able to dig up the remains of the poor young woman who had never received her card.

    I’ve not been able to trace my own family history back further than my great grandfather, Rush Kelly. He was the first great star of silent radio. Not many people know of him today. In fact, not many people knew of him back then.

    I hope this has clarified things.

    • Thanks. Had a good laugh.

    • Michael
      Silent radio indeed existed way back in the depths of human antiquity. It’s installations were later mistaken for religious structures around the world such as the standing stones of Stone Henge in England. And your account of Lucy is also enlightening, possibly clearing up an archaeological mystery. What was that strange stone bearing runic inscriptions found next to Lucy’s skeletal remains? Now we know – it was a partly filled in complaint form to her local post office. But how you might ask did she know that a relative in Ohio had sent a post card? By silent radio of course.

    • I am frequently saddened by the fact that humans of today will not be present to encounter intelligent-civilized humans, since of course, many of us suspect, hopefully, that we at this time – are the missing link.

  10. the availability of ice core data showing us the detailed ups and downs of climate temperature (and, following obediently behind it, CO2) during the Quaternary period of alternating glacial and interglacial intervals.

    Nicely put!

  11. While today’s politicians and scientists do their best to avoid the hazards of one or two degrees warming over a century or so, during recent glacial intervals temperature changes many times larger, of 10 degrees or more, took place regularly over similar short timescales. Graphs showing frozen records of the temperature of the Northern Hemisphere from ice and sediment cores show this clearly over the last hundred thousand years. This represents the time interval between our Holocene and the previous interglacial called the “Eemian”. In this glacial period there are many sharp upward spikes, or “micro-interglacials” in which temperatures rose – then fell – by up to ten degrees within only a century or a few hundred years. The technical term for these excursions is Dansgaard-Oeschger (D-O) events. These would have been very traumatic times to live through.

    The climate is more volatile in colder periods and less volatile in warmer periods. Warmer is better. There is nothing to fear about warmer. I’ve been pointing this out for ages.

    What can we do to delay the next abrupt cooling even and reduce it’s magnitude?

    Well, one obvious answer is that we could stop our irrational policies that are trying to stop the planet warming (by minutiae).

    The CO2 mitigation polices are having two bad effects:

    1. The climate industry is costing around $1-2 trillion per year, for no benefit. That’s a significant damage to world economic growth, and hence to improving human well-being.

    2. The polices are increasing risk of an abrupt cooling event starting sooner rather then later

    3. Preventing or slowing global warming is retarding the global economy – global warming is economically beneficial (several lines of evidence presented in many comments over several years).

    • Peter
      I also have the feeling that the rising clamour for ever more extreme climate mitigation policy is far worse than anything that a mildly warming climate (during an ice age!) and modest CO2 fertilization would ever wreak on humanity. Plus there’s only so much fossil fuel we can burn, we’re probably burnt half of it already. The palaeo record really undermines any basis for alarm at rising CO2 (e.g. 10-40,000ppm CO2 during the Cambrian nursery of all multicellular life). Furthermore, I am slightly suspicious of the nature of CO2 increase – not that it is happening, it clearly is – but its absolutely monotonic unchanging rate of increase. If it was mostly from human activity one would expect some features – accelerations and deccelerations liked to uneven changes in rate of human emissions. It’s stark uniformity makes it look more like a long term geological process – maybe exactly the same happened during the MWP?

    • I would say that the apparent benefits of warm or warmer weather over much colder weather (for longer periods of time) – is well understood by the layman. Thus is why any nation’s wealth (economy) is always more considered by the layman than the most current Doomsday (Clock) theory.

  12. I’d be very interested in your thoughts about the possibility that CO2 starvation in the early Oligocene led to the evolution of C4 grasses, which developed a new version of photosynthesis that was effective in low nutrient, low CO2 and drought conditions. As explorer Sir Richard Burton has it ‘Needs must and the Devil drives.’ CO2 may not be driving climate change now, but it surely drove C4 grass evolution?
    Howard Dewhirst

    • Petro, there is a lot of information on the convergent evolution of C4 in 19 different plant families maybe 30mya. You can dig it out using googlefu. It appears the unifying factor was not low CO2 but rather arid conditions. C4 plants need less water. Is why half of C4 plants are grasses found in arid grasslands or savannahs such as the Sahel. A specific example isC4 teosinte (maize ancestor) that evolved in the arid Mexian uplands.

  13. Interesting summary of what is known about human evolution and paleoclimate change. However one has to be aware that a big part of this knowledge is probably wrong. Particularly problematic points are:

    1. Human ancestry.
    Paleoanthropology is one of those subfields where there is a huge incentive to get certain results. To make it big you have to find a new Hominin, and it has to be a putative human ancestor. Expeditions are extremely expensive and can only be monetized by sales. The public knows about Lucy, but doesn’t know at all about European Hominins that cannot be our ancestors. To put some perspective, all we know of 25 million years of chimpanzee evolution is three teeth found in a cave. If our ancestors lived in the forest until about 1 million years ago we would not have any remain of them. So as in the old joke, we are searching for the keys where there is light, but maybe not where they were lost. A tantalizing possibility is that the entire Australopithecine branch are distant cousins, not ancestors. For a very poorly equipped Hominin to become a hunter in the open spaces requires a big brain, but to acquire a big brain it has to be a hunter. Predators tend to be smart, herbivores tend to be dumb, but fast. Once a Hominin left the tree cover and wasn’t a smart hunter his evolutionary path led him away from human development. Both branches of Australopithecines, gracile and robust, were evolving away from generalized hunter into specialized open space non carnivorous, like mandrills. Chimpanzees, however, demonstrate how a similar Hominin can be a successful hunter in the forest and evolve a bigger brain before going out into the open spaces and take over the world. The first victims would be his closest relatives that occupied a similar niche. The sudden extinction of all Australopithecines in Africa (the beginning of the great megafaunal extinction), marks the appearance of our real ancestor, that very likely came from the forests.

    2. Out of Africa.
    The first serious attempt from H. sapiens to push out of Africa that we know about was around 100,000 years ago. At that time H. neanderthalensis was well established in the Middle East and was a formidable enemy for these pre-modern humans, but first contact and first successful interbreed took place. H. sapiens turned South East into Asia, where remains attested that they arrived before the successful second migration of 60,000 BP. As the glacial period progressed to a colder state, neanderthals became thinner and humans better equipped culturally. The second push 60,000 years ago was successful in breaking neanderthal resistance. While neanderthals were being defeated and decimated, a second successful interbreed episode took place.

    3. Toba eruption.
    Extremely controversial. Catastrophism is alive and well since Cuvier’s times despite numerous defeats. The evidence that the human species suffered a bottleneck and was at the brink of extinction is weak and arguable. The Cheetah bottleneck does not date from the Toba eruption. As usual a case of a fantastic, but appealing, story built from very little evidence.

    4. Holocene cultural explosion.
    It can be argued that cultural advancement depends critically on the human species collective brain mass, thus simply through population growth cultural advancement should speed up. The greatest advanced civilizations took place at places of highest population density and created positive feedbacks to both population and cultural advance all the way to collapse.
    However climate appears to have played a major role. If I remember correctly we have already discussed the role of CO₂ and Holocene climate in agriculture in this blog.
    Richerson, P. J., Boyd, R., & Bettinger, R. L. (2001). Was agriculture impossible during the Pleistocene but mandatory during the Holocene? A climate change hypothesis. American Antiquity, 66 (3), 387-411.
    The title says it all. During the Eemian Homo wasn’t ready. Interglacials are also punctuating our cultural evolution. The coming next glacial period (in a couple of millennia if I am correct) is going to be a good kick in the posterior. The result is impossible to predict.

    • Javier
      Thanks for commenting.
      (1) This article’s focus wasn’t so much human origins prior to H. sapiens, but you could well be right about those. This history was no doubt ugly with internecine wars to the death. We are unusual in a sinister way to be the solitary member of our genus with no living relatives. Speed of evolutionary change is far from constant, sometimes rapid, sometimes very slow or static. Thus the story told by genetics is sometimes very different to that told by anatomical relatedness. The most enduring human species so far is Homo erectus, who lived for 2 million years. We have a long way to go before equalling that record. Several human species which had lived stably for a very long time, abruptly disappeared when modern H sapiens appeared on the scene.

      (2) There were many break-outs from Africa. What was special about the 60 kya one was (a) it was the first exodus by humans after the attainment of behavioural modernity ~70 kya, and (2) the first after Mt Toba, which may have decimated descendants of previous breakouts.

      (3) I’m not an expert on Toba, maybe I am wrong. But several lines of evidence point to it having had a big impact, from genetic bottlenecks in several species including humans, to geology. Note that in complex ecosystems with species linked in nonlinear networks, chains of extinction or near extinction don’t always require a big external force, the triggering event can be small or even nonexistent. This is explained in John Gribbin’s book on chaos, “Deep Simplicity”.

      (4) “Harari’s conundrum” is indeed puzzling – although we haven’t changed biologically in 70,000 years why did we only depart the stone age 5000 years ago and begin the scientific enlightenment 500 years ago? It appears that the needed ingredients included prolonged agricultural prosperity (helped by stable climate), sustained concentrated urban populations and cultural and societal continuity (ie not being wiped out by a neighboring tribe). Plus no doubt some good luck. In “Odyssey from Africa” I speculate as to whether, even way back 60 kya, under the right leadership and geographic conditions, a culturally and technologically sophisticated society could have arisen, in “the island kingdom”. Under the reign of king Ptolemy the second, assisted by liberal consumption of “the amber nectar”. Who knows?

      • Hi Phil,

        Thus the story told by genetics is sometimes very different to that told by anatomical relatedness.

        The story told by genetics is also uncertain and subject to interpretations. A genetic bottleneck only implies that the rest of the species did not contribute to living descendants, not that they died suddenly in a cataclysm. Archeological remains in India and Australia show that human habitation in the region of the eruption continued afterwards. Sediments in Lake Malawi, in Africa, where the Toba layer has been identified, show no evidence of climatic disruption.

        https://www.forbes.com/sites/davidbressan/2017/08/11/early-humans-may-have-lived-through-a-supervolcano-eruption/#71921cf11bcf

        https://www.livescience.com/29130-toba-supervolcano-effects.html

        As you have stated the Last Glacial was marked by great climatic instability. There is no evidence that climatic effects from the Toba eruption were, in global terms, outside Last Glacial climatic variability range. Then by logic: The Homo genus was spread at the time all over the Old World as far as ice sheets allowed, and was culturally equipped to build refuges and control fire. To nearly wipe out Homo, the eruption should have extincted countless other animals and plants first. Where are the corpses? Clearly Neanderthals and Denisovians made it, and the second wave of megafaunal extinctions did not pick up speed until 50 Kyr BP. The Toba hypothesis requires that modern humans were particularly sensitive to the eruption, when the opposite is to be expected.

        Whatever climatic effects the Toba eruption caused, they clearly did not mean an existential thread to Homo on a global basis. That much is clear. The genetic bottleneck explanation lies elsewhere. My favorite hypothesis is advanced language. We know of mutations that impair language. Opposite mutations that allowed language might have happened and would leave no paleontological trace. Such mutation would spread rapidly within the original population for the advantage it conferred, and would soon associate with other genetic variability that enhanced its effects. At the same time it would confer reproductive isolation through sexual selection, as people capable of advance language would not readily mate with people unable. Thus through inbreeding, the original population would become reproductively isolated, and through the advantage advanced language confers, it would progressively substitute all other human groups that left no descendants. Of course no evidence for this can ever be found, but it is important to note that the Toba hypothesis is not required to explain a genetic bottleneck. Rapid evolution can have the same result.

      • Javier
        The language conferring mutation (Babel gene) idea is a compelling one – self-selecting a genetically isolated population by sexual selection. This elegantly meets the requirement of population isolation for significant genetic change to become established in a species. As with many attributes or pathologies it has been hard to find a single decisive gene, instead one gets a “Manhatten plot” of many associated genes. Ones that have received attention include FOXP2 and the SPCH1 region on human 7q31. However the decisive mutation for language was probably an organising or control gene somewhere in an intron region that shuffled the organisation of activity of many genes.

        But it’s a novel idea – a mutation conferring advantage and isolation by self-selection (did you ever read “The Chrysalids” by John Wyndham?) looking, from the perspective of current day gene analysis, like a genetic bottleneck.

        However Toba – if indeed it reduced human survival to isolated refuges, as many consider plausible, would also have created the ideal conditions of small isolated groups to allow a new mutation to become established in the population. So maybe a compromise – language mutation plus Toba? However I concede that Toba may not have been as globally catastrophic as is sometimes portrayed. And I have made the point myself many times that, taking the nonlinear network model of an ecosystem, that spontaneous mass extinctions are possible with no external stressor at all.

        One final thing. You say:

        The Toba hypothesis requires that modern humans were particularly sensitive to the eruption, when the opposite is to be expected.

        Humans were not behaviourally modern when Toba happened. The decisive attainment of language and culture that we have been talking about had not yet happened – or was happening at about the same time (hinting at a causal linkage). Yuval Noah Harari in “Sapiens” points out the huge difference in the position of humans in the ecosystem and food chain, before and after language and behavioural modernity. Before it, we weren’t really all that spectacular. A common and garden ape. Hunting but also being hunted, and somewhat marginal, evidently susceptible to numerous local extinctions. The effect of Toba on old non linguistic Homo would be much more devastating than if it had happened after language and full modernity were already established.
        Anyway lets see where the field goes on Toba.

      • Before it, we weren’t really all that spectacular. A common and garden ape. Hunting but also being hunted, and somewhat marginal, evidently susceptible to numerous local extinctions.

        Phil, I must strongly disagree. Homo erectus was anything but a garden ape. It had the most widespread distribution to date of any large mammal in the entire Pleistocene and likely before. None came close to it. It controlled fire, and by 280,000 BP its descendants possessed projectile weapons. Early sapiens was quickly replacing heildebergensis and other erectus descendants in Africa and Asia before Toba, so it was more advanced.

        If such advanced creatures, whose ancestors had caused the first megafaunal extinction in Africa around 1.5 million years ago, and that were so well equipped compared to other animals at the time, and spread all over the old world, were reduced to isolated groups as you say, we should be finding the mountain of corpses produced by less resilient, more geographically constrained species. And we don’t. There is no peak of extinctions at ~ 70 kyr BP.

        There is absolutely no evidence that the Toba eruption significantly affected not only Homo species, but any other. A coincidence in the time of the eruption and a proposed genetic bottleneck is no evidence, because correlation is not causation, and genetic bottlenecks are hard to date. Hypotheses that do not have strong backing evidence and are based on circumstantial evidence should be disregarded, except as interesting ideas.

      • “Humans were not behaviourally modern when Toba happened.”

        Toba happened around 75 KYA.

        “In 2008 an ochre processing workshop consisting of two toolkits was uncovered in the 100,000-year-old levels at Blombos Cave, South Africa. Analysis shows that a liquefied pigment-rich mixture was produced and stored in the shells of two Haliotis midae (abalone), and that ochre, bone, charcoal, grindstones and hammer-stones also formed a composite part of the toolkits. As both toolkits were left in situ, and as there are few other archaeological remains in the same layer, it seems the site was used primarily as a workshop and was abandoned shortly after the pigment-rich compounds were made. Dune sand then blew into the cave from the outside, encapsulated the toolkits and by happenstance ensured their preservation before the next occupants arrived, possibly several decades or centuries later.

        https://en.wikipedia.org/wiki/Blombos_Cave

        It’s difficult to gauge when humans became behaviorally modern because the only we have to go on are artifacts and most of the artifacts are perishable. Even in Blombos Cave, you see how lucky it was that sand covered the toolkits or they would have been lost.

      • Javier
        I was wrong to disrespect H erectus; my timeline was out – Homo was indeed already top predator prior to 70k modernity.

        Also I looked around at more research and it seems that the Mt Toba ecosystem perturbation may have been no greater than that of the many D-O events during the last glacial. So I’ll revise my opinion about the importance of Toba.

      • James
        Examples of advanced human culture earlier than 70k such as the one you mention are interesting. I’ve heard it suggested that the “ great step forward” to artistic expression and advanced language may not have been a biological change or new mutation, but possibly something that became possible with high enough population density allowing an elite to be released from a struggle for survival and able to turn to creative intellectual activity. This could have happened at different times and places.

      • ptolemy2,

        I was wrong to disrespect H erectus; my timeline was out – Homo was indeed already top predator prior to 70k modernity.

        An excellent example of intellectual honesty and respect. Many CE denizens could gain by following his example. (including me)

      • Peter
        No-one died of humble pie 🥧

      • Javier
        That comparison of Toba with a D-O event is remarkable when put the other way round. It means that the magnitude of climate and ecosystem disruption of the D-O events was comparable to that caused by an explosive volcanic eruption 🌋 discharging 3000 km^3 of vitreous ash into the stratosphere only 2 degrees from the equator where global spread would be maximised. And there were twenty or so such D-O events during the last glacial interval. This supports the argument that a violent climate would have periodically disrupted human populations and and incipient civilisations.

        Broken and deserted lay the
        Cities once so full of people

    • Thanks for the reminder of humans surviving rapid glacial to Holocene warming. More evidence of migrations. e.g., See:

      the values and ranges of the Holocene temperature rise are very similar in both areas (8°-10° to 12°-13°C during the first 500 yr).

      Two terrestrial records of rapid climatic change during the glacial–Holocene transition (14,000–9,000 calendar years B.P.) from Europe Hilary H. Birks, Brigitta Ammann, PNAS February 15, 2000 Vol. 97 No. 4, 1390-1394
      There is interesting recent migration evidence:

      New dating of fossils from Israel indicates that our species (Homo sapiens) lived outside Africa around 185,000 years ago, some 80,000 years earlier than the previous evidence. . . .Three separate dating methods, conducted in three separate laboratories unaware of the others’ results concluded that the fossilised remains were between 177,000 and 194,000 years old.

      Modern humans left Africa much earlier Pallab Ghosh BBC News

      • David,

        Once culturally equipped, modern humans did not only survived to rapid climate change, they took advantage of it to thrive and expand, many times at the expense of other species.

  14. If we may “soon” experience another cold period, would it not make more sense to save hydrocarbon reserves for the future?

    • Plenty of coal. Plenty of natural gas thanks to shale fracking. The only hydrocarbon of concern is oil. The tight oil fracking bonanza is deceptive, and not a long term solution to the fundamental problem of nearing peak production of conventional plus unconventional. Conventional crude peak was ~2008. See several essays in the energy section of ebook Blowing Smoke for details, examples, and references

    • +dodgewith, one hundred years from now humans will no longer be the dominant species. Or if by chance we are, thanks to strict regulations on the development of AI, alternative energy sources will have been discovered. There’s adequate proof that development of fusion reactors is beyond our limited human intellect, but robots may be able to crack it quite easily.

  15. your referring interpretation of some chaotic flip-flop on the state change between glacial-interglacial is wrong as well as the Milancovic cycles interpretation is incomplete. I have long proposed and proved that the change between glacial-interglacial is caused by temporal solar wind pause associated to Milancovic cycles. You can follow my work an solar activity and climate variability here https://www.facebook.com/solarclimate/ .
    (by the way humans are not supposed to originate from africa. the oldest humanoids have been found in the current area of greece and bulgaria. the oldest technical construction also is a 70000 year old stone wall in the current area of greece too.)

    • Dimitris
      Back then (7mya) there was no Mediterranean. Bulgaria and Greece were part of Africa.

      • I don’t know if europe was connected to africa back then. but why call this region africa? it was europe anyway.

      • Well connected anyway. No sea in between.

      • ptolemy2, 70,000 years ago, not 7 million ya. The Med then was similar to now, much of it with depth under 25 metres, and what we now call Bulgaria and Greece were not part of Africa.

      • A 23,000 year old stone wall in front of Theopetra cave in Kalambaka, Greece (in the middle of the Greek mainland), probably built to protect its residents from cold winds at the height of the last ice age, is the oldest known example of a man made structure.
        Some of the what was found, like remnants of fire, flint and quartz tools, early jewelry from deer teeth, animal bones and stone implements, are typical of the Mesolithic human archaeological sites. Other elements of the find were more notable:
        Of interest are finds from the Mesolithic age related to ceramic production and cultivation. There is barley, wheat, and lentil in wild (Paleolithic age) form, but also as cultivars, which suggests that these people had discovered cultivation as the result of millennia-long efforts and not as the result of population movements from the Near East.

        Read more at https://archaeologynewsnetwork.blogspot.com/2010/03/oldest-man-made-structure-found-in.html#psk8c93EwrC8CVTo.99

      • A jawbone complete with teeth recently discovered at Israel’s Misliya cave has now been dated to 177,000-194,000 years ago. The finding indicates that modern humans were present in the Levant at least 50,000 years earlier than previously thought.

        “This finding — that early modern humans were present outside of Africa earlier than commonly believed — completely changes our view on modern human dispersal and the history of modern human evolution,” says Prof. Israel Hershkovitz of the Department of Anatomy and Anthropology at Tel Aviv University’s Sackler Faculty of Medicine. Prof. Hershkovitz led the international team of anthropologists who conducted the study in collaboration with Prof. Mina Weinstein-Evron of the Zinman Institute of Archaeology at the University of Haifa. The research was recently published in the journal Science.

        The common consensus of anthropologists has been that modern humans appeared in Africa roughly 160,000-200,000 years ago, based on fossils found in Ethiopia, and that modern humans evolved in Africa and started migrating out of Africa around 100,000 years ago.

        Read more at https://archaeologynewsnetwork.blogspot.com/2018/01/remains-of-earliest-modern-human.html#BHoPjbHxeZtbxa6c.99

      • David L. Hagen

        Demitris and ptolemy2 Re Mediterranean
        Zanclean flood of the Mediterranean (5.33 Ma)
        During the last deglaciation, global sea level rose at about 20 mm/year. For interest, when the Mediterranean sea flooded, its water level rose at a more spectacular 10s of m/year – ~ 1000 times faster.
        Mediterranean Sea filled in less than two years: study Dec. 9, 2009

        This extremely abrupt flood may have involved peak rates of sea level rise in the Mediterranean of more than 10 metres a day,”

        https://phys.org/news/2009-12-mediterranean-sea-years.html
        See:
        Garcia-Castellanos, D., Estrada, F., Jiménez-Munt, I., Gorini, C., Fernàndez, M., Vergés, J., De Vicente, R. (10 December 2009) Catastrophic flood of the Mediterranean after the Messinian salinity crisis, Nature 462, pp. 778–781, doi:10.1038/nature08555

        The Mediterranean Sea became disconnected from the world’s oceans and mostly desiccated by evaporation about 5.6 million years ago during the Messinian salinity crisis. The Atlantic waters found a way through the present Gibraltar Strait and rapidly refilled the Mediterranean 5.33 million years ago in an event known as the Zanclean flood. The . . .incision in the early stages of flooding imply discharges of about 108m3 s21 (three orders of magnitude larger than the present Amazon River) and incision rates above 0.4m per day. Although the flood started at low water discharges that may have lasted for up to several thousand years, our results suggest that 90 per cent of the water was transferred in a short period ranging from a few months to two years. This extremely abrupt flood may have involved peak rates of sea level rise in the Mediterranean of more than ten metres per day.

        See also:
        Revisiting the time scale and size of the Zanclean flood of the Mediterranean (5.33 Ma)from CFD simulations Marine Geology · October 2016 DOI: 10.1016/j.margeo.2016.10.008

        Dimensions of the Atlantic-Mediterranean connection that caused the Messinian Salinity, Crisis Dirk Simon, Paul Meijer Marine Geology 364 (2015) 53–64

      • Faustino
        Great name btw!
        I repeat the paragraph in my article:
        Please note that the fact that there were numerous “exodi” from Africa both before and after the 60 kya event, does not alter or contradict the clear evidence from genetics, from both maternal mitochondrial and male Y-chromosome analysis, that most humans today are indeed descended from that single 60 kya breakout. As Richard Dawkins showed mathematically in “The Ancestor’s Tale”, prior to 20,000 years ago, everyone alive was ancestor either to everyone living today, or to no-one.

        Indeed starting with the appearance of H sapiens about 200,000 years ago, there were periodic break-outs from Africa. The claims about the 60 kya breakout are not that this was the only breakout. This is a common misunderstanding or oversight. No – the claim – backed up by genetic evidence, is that it was this 60 kya breakout, the first to happen after humans became behaviourally modern about 70 kya, was the one to which nearly all humans outside Africa today trace their descent. This is shown for instance by the mitochondrial haplotype L3 labellling of this migrating group. Some groups exiting Africa left desendants. Others did not – or left only a small trace of their genes.

        Science writers and journalists are a lot to blame for this muddle and for inaccurate, biased and politicised reporting of scientific research in general including in climate science. When these media copy-writers try to dumb down a research publication for a press release, they use the report as a vehicle for all their own predjudices, policy agendas and pet ideas. So I have learned to ignore the pre-amble in media reports of scientific findings and just read the abstract directly, and if possible the paper also.

        It has been known for years that H sapiens exited Africa as long ago as 200, 000 years, with the well known discoveries in India, China and the Levant (endlessly re-reported as new findings). We are told that this discovery at Misliya cave in Israel dated to 177,000-194,000 years ago, changes everything in human origin research. It changes nothing and is not even new. These reporters seem never to have heard of genetics.

      • ptolemy2, point taken, thanks.

      • David
        In addition to the events surrounding the spectacular Zanclean flood, another important development starting around the Messinian was the formation of the Sahara desert which would form a barrier between Europe and Africa. A barrier that would only be crossed by the very rare out-of-Africa migrations.

        https://ptolemy2.wordpress.com/2017/06/05/did-the-first-humans-come-from-greece-not-africa/

  16. “A 23,000 year old stone wall in front of Theopetra cave in Kalambaka, Greece (in the middle of the Greek mainland), probably built to protect its residents from cold winds at the height of the last ice age, is the oldest known example of a man made structure.”

    It was only built after a bitter political battle between Emperor Tubae and Senator Testicles, who voted for the wall but then took funding for it off the table because of Tubae’s opposition to allowing the Etesians into Greece. Emperor Tubae eventually won the day by famously saying “Look, it’s 20,983 BC. We’ve got to look ahead to 20,000!”

  17. Off topic but important; vote here to set things right. Climate Etc has a pseudo science rating but skeptical science is rated as trustworthy?!!! https://mediabiasfactcheck.com/climate-etc/

    • What a load of rubbish at Shonky Media Stuff the Facts! site (I’ve voted “None.” Based on the Judith Curry entry, a waste of time with no credibility. I’d give them a shonky-max assessment.

    • My e-mail to Media Bias/Fact Check:

      I’m amazed at your assessment of Judith Curry’s Climate Etc site. I’ve been following the alleged catastrophic anthropogenic global warming issue since the 1980s, I was briefed by the IPCC’s Chief Scientist Sir John Hughton in 1989 or ’90 and have provided advice on the issue to the Australian and Queensland governments. At one time I accepted the need for precautionary measures while better understanding was developed, but it became clear to me that, whether or not human-driven global warming was occurring and whether or not it would have a net harmful effect, the anti-emissions programmes were not a good solution. They will make little or no difference to potential warming in the distant future, while causing serious economic damage now which will, inter alia, reduce our capacity to deal with whatever befalls – the future always surprises us, we should adopt policies which promote growth, innovation, flexibility and resilience, helping us now and making us better prepared for all future contingencies.

      Climate Etc is one of the best blogs on the issue, it has some excellent contributors. Judith is a leading climate scientist, an acknowledged expert on Arctic ice and tropical cyclones. She is not funded by the oil industry or anyone else, she has a highly-regarded hurricane forecasting firm whose clients might well, and unsurprisingly, include oil firms.

      Judith fully accepted the CAGW story, it never occurred to her that her professional colleagues might lack her own high standards. She first went to Steve McIntyre’s Climate Audit blog out of curiosity, to see what drove his argument – I recall that she had a very hostile reception from CA posters. It was only after looking at McIntyre’s evidence and arguments that she began to realise that all might not be well in the global warming camp, that the case might not be as solid as was claimed and which formed the basis of (misguided IMHO) policies.

      She therefore began CE as a place for all voices, where argument and information could be exchanged without prior assumptions as to the validity of the CAGW case.

      I find your assessment of Judith and her blog as being very unprofessional and with no solid basis. Based on this entry, I would rate your credibility as Zero.

    • Yes vote at the Jan’s link. Their review is off base and sophomoric.

  18. “although our large brains and intelligence (complete with social, cultural and language abilities) have existed for at least 70,000 years, our agricultural, technical and intellectual achievements leading to our current industrialized lifestyle and landscape, have happened only in the last few centuries”

    This is wrong. Rice was cultivated in China and pigs domesticated in Mesopotamia 13,000 years ago, even earlier than the Holocene. The Great Pyramid in Egypt is 4,500 years old and still considered an engineering marvel. Astronomy started in Egypt 5,000 years ago. The Pythagorean theorem was known to the Babylonians 4,000 years ago. Eratosthenes computed the circumference of the Earth 2,200 years ago and its accuracy had not been surpassed until the 16th century. The Archimedes principle was discovered 2,200 years ago and still taught today in engineering schools.

    The idea that modern knowledge started in the Renaissance is a myth. In fact, the Renaissance rediscovered ancient knowledge.

    • Dr Strangelove
      Your last point raises an interesting contradiction. The “renaissance” is a paradoxical misnomer. As was nicely demonstrated in John Gribbin’s “Science: a history”, it was up to the time of the renaissance that scholars felt inferior to, and in the shadow of, classical learning and civilisation. However with the likes of Galileo, Regiomontanus and Vesalius establishing the experimental deductive scientific method, and Copernicus, Brahe, Newton and many others building on this, European civilisation actually broke free of the shadow of the ancient Greeks, Romans and Arabs and started on the road leading to the present scientific and industrial revolution. So the “re” in renaissance is superfluous – it was “naissance”.

      • Gribbin is wrong. Galileo was reading and following the works of Archimedes. Vesalius was following Galen. Copernicus was following Aristarchus. Newton read Euclid. They did not break free from the ancient Greeks. They continued the science of ancient Greeks. Tell Gribbin to read Carl Sagan and Lancelot Hogben who wrote on the history of math and science before Gribbin was born.

  19. “What did all this mean for human populations living during the last glacial period?… It meant that every few centuries or millennia, their lives were heavily disrupted by rapid and severe episodes of climate change, either warming or cooling .. Such major changes would be linked to shifts in atmospheric and ocean circulation that would in turn affect food availability for human populations trying to build a way of living. It might have been these traumatic swings of temperature and ecological stress associated with them, that prevented human civilization from taking root over a long period of millennia.”

    This is not a good storyline. The glacial period and DO events affected only the Northern Hemisphere. But the tropics was always relatively warm and ice free. There were aborigines in Australia since 30,000 BC and the earliest civilizations in Egypt, Mesopotamia and Syria were in the tropics.

    My storyline is the spread of agriculture in the tropics led to ample food supply that enabled populations to grow. With a large population, humans needed to get organized to avoid anarchy. This led to the invention of government, laws, religion, writing, army, kings, priests, trade, money, craftsmen, division of labor, and people had more free time to invent technologies, build temples and indulge in philosophy. In short, what we call civilization. Climate change had little to do with the rise of civilization. People migrated to the North bringing with them knowledge of earlier civilization and established new civilizations.

    • Indeed, as long ago as 60,000 years there arose the remarkable island kingdom under the reign of King Ptolemy the Second, where quite advanced technology and political structure had been developed. Apparently they even had a flag-waving form of internet. But by the glacial maximum it would all be gone.

  20. Pingback: Weekly Climate and Energy News Roundup #301 | Watts Up With That?

  21. Pingback: Weekly Climate and Energy News Roundup #301 |

  22. I found this article to be very enjoyable. Some may quibble over details, but it covers a lot of ground and is well written. It brings up a couple of topics that I have spoken and written about for years: Causes of climate change, and the evolution of human intelligence. For the former, see, for example my earlier articles at http://kennethpiper.com/category/science/climate-change/; for the latter my article http://kennethpiper.com/has-society-made-us-less-intelligent/. I have been watching with interest the early snow extent in Siberia. I will be writing more about evolution of intelligence in future articles.

  23. Matt Ridley’s Rational Optimist also gives a good account of the development of modern humans.

    Very good read.

  24. You might want to take a look at this. Although it repeats the Hershkovitz discovery which others have brought up, the web site in general has a number of references related to this topic. I think the author is on track about two major migrations, one before Toba and one after. The diagram illustrates the theory.

    https://6000generations.wordpress.com/2018/02/03/the-single-out-of-africa-theory-is-dying/

    • I would defend the ancestral primacy of the 60kya breakout since, while it was indeed one of many “exodi” from Africa, the genetic evidence is strong that most (not all) human descent outside Africa is from that event.

      Modern human remains predating the 60kya breakout are old news – ones in India, China and around Israel and the Levant have been in the literature for a decade. They are periodically re-reported as new findings, as now.

      Indeed starting with the appearance of H sapiens about 200,000 years ago, there were periodic break-outs from Africa. The claims about the 60 kya breakout are not that this was the only breakout. This is a common misunderstanding or oversight. No – the claim – backed up by genetic evidence, is that it was this 60 kya breakout, the first to happen after humans became behaviourally modern about 70 kya, was the one to which nearly all humans outside Africa today trace their descent. This is shown for instance by the mitochondrial haplotype L3 labellling of this migrating group. Some groups exiting Africa left desendants. Others did not – or left only a small trace of their genes.

      Just to be clear – the fact there were numerous “exodi” from Africa both before and after the 60 kya event, does not alter or contradict the clear evidence from genetics, from both maternal mitochondrial and male Y-chromosome analysis, that most humans today are indeed descended from that single 60 kya breakout. As Richard Dawkins showed mathematically in “The Ancestor’s Tale”, prior to 20,000 years ago, everyone alive was ancestor either to everyone living today, or to no-one.

      It has been known for years that H sapiens exited Africa as long ago as 200, 000 years, with the well known discoveries in India, China and the Levant (endlessly re-reported as new findings). We are told that this discovery at Misliya cave in Israel dated to 177,000-194,000 years ago, changes everything in human origin research. It changes nothing and is not even new. Reconstruction of human history is not about choosing between palaeontology or genetics. It’s both together.

  25. Pingback: That’s not climate change … | Pursue Democracy

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