Does anyone know where I could find rough human population estimates for the period of our emergence till around 12,000 years ago? Wikipedia tells me that the census population around 200kya was 100-300,000 (with an effective or reproductive pop of around 10-30,000), and that 12kya it was around 1-10 million. But do we have any inkling as to what things were like in the years in between, in which we evolved behaviourally, culturally, and left Africa?
Thanks!
Great question! The answers mostly come from population genetics. I’d have to dig through my sources to come up with a thorough response, but in general, the volcanic winter caused by the Toba super-volcano about 74,000 years ago was a near-extinction event (population bottleneck) for H. sapiens. About 10,000 years later, the “Out of Africa” migration and population explosion began. Hunter-gatherer societies have relatively stable population sizes, so most of the population growth occurred by territorial expansion. Once the earth was basically “filled,” the next population spurt accompanied the invention of agriculture. Understandably, Mesopotamia was the most populous place on Earth for a time.
Here’s a good overview:
Abstract
Genetic and paleoanthropological evidence is in accord that today’s human population is the result of a great demic (demographic and geographic) expansion that began approximately 45,000 to 60,000 y ago in Africa and rapidly resulted in human occupation of almost all of the Earth’s habitable regions. Genomic data from contemporary humans suggest that this expansion was accompanied by a continuous loss of genetic diversity, a result of what is called the “serial founder effect.” In addition to genomic data, the serial founder effect model is now supported by the genetics of human parasites, morphology, and linguistics. This particular population history gave rise to the two defining features of genetic variation in humans: genomes from the substructured populations of Africa retain an exceptional number of unique variants, and there is a dramatic reduction in genetic diversity within populations living outside of Africa. These two patterns are relevant for medical genetic studies mapping genotypes to phenotypes and for inferring the power of natural selection in human history. It should be appreciated that the initial expansion and subsequent serial founder effect were determined by demographic and sociocultural factors associated with hunter-gatherer populations. How do we reconcile this major demic expansion with the population stability that followed for thousands years until the inventions of agriculture? We review advances in understanding the genetic diversity within Africa and the great human expansion out of Africa and offer hypotheses that can help to establish a more synthetic view of modern human evolution.
Edit: Here’s a link to the above PDF: https://www.ias.ac.in/public/Volumes/reso/024/06/0711-0718.pdf
I hope you have taken the time to check out the link offered to you by @pevaquark.
It seems to offer the kind of detail you crave!
Nat Genet. Author manuscript; available in PMC 2015 Feb 1. Published in final edited form as:
Nat Genet. 2014 Aug; 46(8): 919–925.
Published online 2014 Jun 22. doi: 10.1038/ng.3015
PMCID: PMC4116295
EMSID: EMS58900
PMID: 24952747
By Stephan Schiffels and Richard Durbin
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The publisher’s final edited version of this article is available at Nat Genet See other articles in PMC that cite the published article.
Associated Data Supplementary Materials
Go to:
The availability of complete human genome sequences from populations across the world has given rise to new population genetic inference methods that explicitly model their ancestral relationship under recombination and mutation. So far, application of these methods to evolutionary history more recent than 20-30 thousand years ago and to population separations has been limited. Here we present a new method that overcomes these shortcomings. The Multiple Sequentially Markovian Coalescent (MSMC) analyses the observed pattern of mutations in multiple individuals, focusing on the first coalescence between any two individuals. Results from applying MSMC to genome sequences from nine populations across the world suggest that the genetic separation of non-African ancestors from African Yoruban ancestors started long before 50,000 years ago, and give information about human population history as recently as 2,000 years ago, including the bottleneck in the peopling of the Americas, and separations within Africa, East Asia and Europe.
One caution worth mentioning is that the dates in any article prior to 2012 are slightly off because the human mutation rate was revised. Here’s the explanation: Revising the human mutation rate: implications for understanding human evolution
Thanks @pevaquark and @Jay313. Very helpful and much appreciated; will have a good read when I get some time tomorrow.
Another related question: the H.Sapiens’ founder population from around 200kya wasn’t one big community or group of 100-300,000 people, was it? Sometimes that can be the assumption when one hears a term like ‘founding population’. How was that population divided - I assume some form of small hunter-gatherer tribes/clans which were closely situated?
You should read up on how little diversity there is in the human race OUTSIDE of Africa. After all, only a few sub-samples of the human genome ever got out of Africa.
In contrast, the human population that stayed within Africa continued to diverge into all sorts of human genetic cul de sacs!!!
This is something I’m aware about (though not in much detail)! Im white and my wife is black and when I found out about it, particularly that two black people are more likely to be more genetically diverse than each other than a white and black person are, I couldn’t believe it! It’s now one of my favourite scientific ‘facts’!
(I believe it was a 1972 paper by Richard Lewontin that showed this. According to the geneticist Adam Rutherford, whose book I’m holding!)
Outside of Africa you can look to Australian aborigines as fairly distinct from the rest of humanity outside of Africa.
If you are interested in smaller groups of interesting divergence, there are the Ainu in Japan!
Some attempts were made to label them “caucasian”, but they seem to be more related (distantly) to the origins of the North American Amerindians than to Western Europeans.
Maybe. I think the pop gen evidence for this is weak.
Quite likely there were multiple groups with varying traits and varying degrees of genetic isolation, but there’s not a whole lot of evidence to go on. There is genetic evidence for admixture with a well-separated population within Africa – akin to the admixture with Neanderthals – but without ancient DNA from that population (or those populations), the evidence is weaker than for Neanderthals.
Can you point me to anything? I may have to come back and have you explain it to me, though. haha
Here are two blogs that discuss some of the story behind Toba along with the evidence or lack thereof:
https://anthropology.net/2018/03/23/debunking-toba-catastrophe-theory/
Thanks for the tip! Fascinating stuff. The blogs both point to the same Nature paper, and this caught my eye at the end: received 23 July 2015; accepted 2 February 2018. Those poor authors waited 2-1/2 years from submission to acceptance! I hope that’s not normal.
I try to stick with consensus science in my work, but when that’s not always clear, report the dissenting view too. The conclusion of the Nature paper said:
Our results raise the question of whether the modern human population on the south coast of South Africa was the sole surviving population through a decade or more of volcanic winter, or whether populations elsewhere in Africa thrived through the YTT event and the ensuing MIS4 glacial phase. This question can now be tackled by applying the same suite of field and laboratory procedures used here to other archaeological sites in Africa.
I’ll have to keep an eye on this one and see what develops. I did run across another Nature paper while I was poking around that has some bearing on the question: A dispersal of Homo sapiens from southern to eastern Africa immediately preceded the out-of-Africa migration. Here’s the abstract:
Africa was the birth-place of Homo sapiens and has the earliest evidence for symbolic behaviour and complex technologies. The best-attested early flowering of these distinctive features was in a glacial refuge zone on the southern coast 100–70 ka, with fewer indications in eastern Africa until after 70 ka. Yet it was eastern Africa, not the south, that witnessed the first major demographic expansion, ~70–60 ka, which led to the peopling of the rest of the world. One possible explanation is that important cultural traits were transmitted from south to east at this time. Here we identify a mitochondrial signal of such a dispersal soon after ~70 ka – the only time in the last 200,000 years that humid climate conditions encompassed southern and tropical Africa. This dispersal immediately preceded the out-of-Africa expansions, potentially providing the trigger for these expansions by transmitting significant cultural elements from the southern African refuge.
You guys are making my brain hurt. haha
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