Siberian cave hosted Neanderthals, Denisovans, and modern humans | Hacker News Reader

Siberian cave hosted Neanderthals, Denisovans, and modern humans

sciencemag.org

69 pointsbenbreen15 comments

OT: I have a question about Neanderthals and other non-modern humans that early modern humans interbred with.

People of Asian or European ancestry have 1-2% of their DNA from Neanderthals. People of African ancestry usually have no Neanderthal DNA.

But consider the identical ancestor point [1] (IAP) for humans. The IAP is the most recent point at which each individual then alive either (1) has zero now living descendants or (2) every now living person is one of their descendants.

Most estimates put the human IAP at less than 20k years ago (some estimates much less).

Neanderthals went extinct around 35k-50k years ago.

I have Neanderthal DNA (23andMe tells me I have 240 markers with at least one Neanderthal variant, about average for 23andMe customers). Therefore I have a Neanderthal ancestor who must have lived 35k or more years ago.

Unless the estimates of the human IAP are so far off that it was actually before my Neanderthal ancestor lived, I therefore must have an ancestor who was alive at the human IAP and who had Neanderthal DNA.

Since that ancestor of mine has at least one living descendant (me) and was alive at the IAP, everyone now alive must be a descendant of theirs. Thus I can conclude that everyone alive now has Neanderthal ancestry--including all those Africans with no Neanderthal DNA.

This at first seems contradictory, so what's the deal?

Is it simply that humans have about 30k genes, your children each only get half of your genes, and so after about 16 generations it is possible for someone to be a descendant of yours but not have any genes that came from you?

[1] https://en.wikipedia.org/wiki/Identical_ancestors_point

> Is it simply that humans have about 30k genes, your children each only get half of your genes, and so after about 16 generations it is possible for someone to be a descendant of yours but not have any genes that came from you?

Yes, the difference between genealogical ancestry and genetic ancestry is just the reason. The modelling which gives those estimates for the IAP assumes very infrequent migrations of individuals – one per generation is enough. That level of migration would likely leave no genetic heritage at all. Probably many Africans have literally zero genetic inheritance from Neanderthals, but almost certainly those same Africans have Neanderthals in their ancestor tree, albeit through only a few lines of descent.

According to the wikipedia article you linked, those estimates were derived from simulations. I have trouble imagining that the simulations accurately model the diversity of human cultures, mating patterns, migration behaviors, etc. for the whole world over, spanning hundreds of thousands of years. If we sequenced the genome of every single person on earth, we'd still have trouble nailing down the truth because of various external sources of mutation, independent but identical mutation, etc.

I don't know enough about this to give a real answer, but there is some neanderthal ancestry in modern day African populations.

https://www.sciencemag.org/news/2020/01/africans-carry-surpr...

The importance is with "at the same time" or "at different times".

Another way to put it, is "This cave is so amazingly good that Neanderthals, Denisovans and modern humans stayed in there".

This technique of ancient soil DNA extraction seems quite a game changer. I wonder if it has to be a cave environment / permafrost or simply any layer of undisturbed soil / sediment. Imagine if you can go around the planet collecting soil cores creating a completely new window into prehistory...

[1] https://arstechnica.com/science/2017/04/no-bones-needed-anci...

[2] https://www.popularmechanics.com/science/archaeology/a361770...

[3] https://scitechdaily.com/extracting-ancient-dna-of-long-exti...

Does the fact that they're finding human remains at this site suggest that perhaps this isn't so much a place where people lived as it is a place where people were interred after they died?

The excellent Who We Are And How We Got Here book by David Reich among many other interesting details mentions Neanderthal and modern humans mixing.

A counterintuitive finding Reich brings up in the book, iirc, is that the Neanderthal genes in current Europeans comes from Asian Neanderthals and not from European.

Modern humans came out as winners by controlling the cave market.

They were on top for a while, but they've had a massive decline in market share in recent centuries. It's gotten to the point that they've had to resort to building artificial caves!

I think you mean below for awhile...

I'm pretty sure ancient humans didn't live in caves.

It's just that caves preserve their contents pretty well, while the rest of the outside is impermanent.

Caves were often used as burial grounds even in the historic era, so that might contribute too.

After all, why dig a hole for the body when nature provided a ready-made hole already - and, as a bonus, with an eerie atmosphere suitable for last rites.

I would like to marry a Neanderthal woman and make a baby with her.

I would much rather do that than go to Mars with SpaceX.

I know it isn't lawful to create a Neanderthal woman from the Neanderthal genomes that we have already sequenced, but if it was, I would like to try it.

If I knew someone in a lab who had access to the technology, I would ask them to undertake this project with me in secret.

I know this is controversial, but something kind of similar happened with Jennifer Lawrence in the movie Passengers and she ended up falling in love with the guy.

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