Thanks for @glipsnort for this in-depth look at population genetics.
What I find disappointing about this article is that it fails to mention that human genetic diversity is smaller than we see in most other species. If you are going for an objective presentation of the facts it is a good idea to give the complete picture.
The genetic diversity of our species not what we see in animals that were all over the globe for the last million years, but rather is consistent with a migration from a single population in southern Africa 100,000 years ago, and absorbing a couple of smaller populations (Neanderthal and Denisovan) as they covered the globe.
Very nice article!
Thanks, Steve, for an article even a caveman like me can understand!
I’m looking forward to reading this from a true expert, @glipsnort . Thanks.
I very much enjoyed your article and find that what you say harmonizes with what I learnt in my study of scripture while getting my MDiv degree in Theology and my study of genetics while getting my MD in medicine. It is so refreshing to see one science respecting it’s limits when discussing a topic that cuts across multiple fields. In this case genetics and theology. Yet adding knowledge it legitmately can add to the subject.
My understanding Genesis’s report of man origins was to present an ordered story about the beginning of the world and man in contrast to Babylonian chaotic story of creation that the Israelites were exposed to during Babylonian captivity.
I have a similar education background though I went into physics rather than medicine.
Interesting… would like to hear more about this.
I tend to take the A&E story more seriously with minimal adjustments (subtracting magical elements) to fit scientific discovery (and without trying to force science into the story). Doesn’t mean I don’t find literary explanations like what you suggest interesting. It is possible for both to be true, I think.
Thanks, @glipsnort. Had to bookmark this one. It was pretty well written for a guy with just two English degrees.
Question: Population genetics’ tools and methodology to measure a two-person bottleneck all seem to peter out around 500,000 years ago. Do you think this will change in the foreseeable future? In other words, are technological or methodological breakthroughs likely to change that date?
I doubt the limit is going to change very much. When you go that far back, you start to get down to a handful of lineages that we all descend from, and it becomes impossible to distinguish four ancestral lineages that happen to survive from four created genomes.
Great article. The figures were very helpful. I understand population genetics a little better now
Many thanks Steve for this helpful article.
It could be interesting to extend the reasoning to the 8-person bottleneck at the end of Noah’s flood.
On the basis of the data we find in Genesis it is fitting to date the flood at the end of the Neolithic and dawn of civilization.
On the other hand, the estimate range of the whole Homo sapiens population at that time is 10-14 million.
From your essay I infer:
Computational population genetics rules out such a recent 8-person bottleneck, and rather supports that today’s humanity descends from a several million population at the end of the Neolithic.
Is this conclusion correct?
I believe your conclusion is correct, but I have not personally looked into the time range over which population genetics can rule out an 8 person bottleneck. You might want to inquire about it on Josh Swamidass’s site (https://discourse.peacefulscience.org/), since I know he has looked into this specific question.
Everything I have been reading about population bottle necks in the human species reveals a terribly complex situation because of migration where large populations are descended from fairly small populations which migrated to different areas. For example, it is thought that all the Native Americans are descended from a population of 70 which came across the Bering Strait.
I also saw a claim that there was a worldwide population bottleneck around 70,000 years ago possibly due to effects of a massive volcanic eruption in Indonesia.
Are models to estimate a minimum population bottleneck that complex?
I was looking at this study which suggest that some of the work uses some pretty complex models. But with so many variables and unknowns it may take many studies like this before we come up with one that gives a high degree of confidence.
My conclusion is that we are perhaps in early days yet with the means to make such calculations.
I was also looking at this study of population bottlenecks from earlier in human evolution. They talk about many such population bottlenecks. It seems to support my own idea that a great portion of evolution happens in small populations struggling for survival on the brink of extinction.
Hi @glipsnort thanks for posting this blog about genetics and Adam and Eve. It is good to see how constructive the discussion on this issue three years ago on this forum has been in the longer term. I have not done much fresh thinking on this issue since then, but every so often I have noted a paper newly published in the literature that has relevance. Your blog prompts me to have another think about all this. Would you mind pointing me to the exact datasets you used from the 1000 genomes project, please? Was it the exome data, or more recent whole genome re-sequencing?
I thought the human population has never been below 10,000. I think it was Darrel Falk who said this.
Hi @RichardBuggs. I used the whole-genome sequence data from Phase III of the project. I think the portal for accessing the data has changed, so I’m not sure exactly how to go about finding it again. The data files I used have catchy names like ALL.chr1.phase3_shapeit2_mvncall_integrated_v5a.20130502.genotypes.vcf.gz
This was the subject of intense debate some time ago. The consensus is that we can’t really say that. I attempted to sketch the limits of what we can say with confidence in the blog post linked above.