Maybe they did exactly that and that's why we ended up with a lot of neanderthal DNA. If modern humans are any indication, a horny neanderthal would have attempted mating with just about anything loosely compatible with their urges. Just refer to your favorite porn sites for an overview of all the different things modern people find interesting. Bluntly put, if it had a hole, mr. Neanderthal would probably have been interested in exploring its potential for mating.

That is exactly what they did - all the Neanderthal genes in the current populations has come down via Neanderthal males and sapien female matings. Personally I blame Tinder, but it could have something to do with Haldane's Rule [0].

0 https://en.m.wikipedia.org/wiki/Haldane%27s_rule

Can you provide a citation for your first point? I don't see how Haldane's Rule would support that, but maybe I am missing something.

I am at home tapping away on my iPad so i don't have access to my papers, but it is known there are no Neanderthal genes on the X chromosome. This is what is expected with Haldane's rule where one cross between species is fertile and the other infertile.

I think you've got that backwards. If there were no Neanderthal genes on the x chromosome, then only men would have Neanderthal genes.

cool thanks

If a human male and a neanderthal female mated and produced female offspring, who then also reproduced, etc., how could you later tell that it was a human female and a neanderthal male? As far as I can understand, all we can speculate about is the sex of the offspring who reproduced, not the original pairings, correct?

Theoretically mitochondrial DNA (which is maternal-only) could do the trick.

In practice I don't think we have the sort of baseline sample it would take to work out which mitochondrial genes are neanderthal-derived. I suppose it might be possible to rebuild that list by looking at high-admixture populations and seeing where their mitochondrial DNA differs, then use that aggregate to compare an individual's mDNA to their DNA and see if it's is "more Neanderthal" (i.e. female line) or "more Sapiens" (i.e. male line)?

But realistically, I'm betting the answer is "admixture happened a bunch of times in a row, with different hominid groups in different places, even if there was a gender skew it's a mess that's impossible to discern".

> Theoretically mitochondrial DNA (which is maternal-only) could do the trick.

That is, sperm have just one mitochondrion, and they almost always dump it as part of fertilization.

But not always, so there is nonzero male contribution of mitochondrial genes.

I answered this in a post just above yours. You look at the X chromosome.

is this from analyzing dna outside of europe? if this information only came from analyzing european dna then during the bronze age all males in europe were effectively eliminated. this would imply that the eurasian steppe men who replaced them were the source for the neanderthal dna. this implies that the prior to this event europe was populated with people with no neanderthal dna.

I don't understand what you are trying to ask? The level of Neanderthal genes in east Asia is higher than in Europe.

I guess that's in the mitochondrial dna then?

All the mitochondrial lineages trace out of Africa in relatively recent times. This is more to do with genetic incompatibility between closely related species.

I think thats what actually happened. We only have DNA from either male or female Neanderthals, forgot which one though. As far as I know if the neanderthals were a certain gender then the hybrid would be infertile.