Mum’s a Neanderthal, Dad’s a Denisovan: discovery of an ancient-human hybrid

That is not quite right - Asians actually have more Neanderthal genes than Europeans. The current best hypothesis is that there have been multiple Neanderthal/SSA hybridization events and that some occurred post the split between Europeans and East Asians (the first occurred in the near East and later events occurred in East Asia).

Whether Denisivans and Neanderthals are different species is mostly just a matter of semantics. We have had a pretty good look at the DNA of each and it's clear that the two were evolving in isolation for hundreds of thousands of years resulting in genetically distinct populations. The difference between Denisovans and Neanderthals is about half the difference between humans and either.

It's not at all unusual for two different species to be able to interbreed. Lions and tigers for instance or horses and donkeys. Mules, the offspring of horses and donkeys are sterile, though, so the two populations can't mix. Ligoers, the offspring of a male lion and female tigers, aren't entirely sterile but have very low fertility. With humans and neanderthals there are portions of the Neanderthal genome related to reproduction that were very heavily selected against in a way which seems to indicate that male hybrids at least had moderate fertility problems until those genes were removed. So it's not black and white at all. We have zero evidence for any reduction in fertility between Neanderthals and Denisovans since we have very few examples of hybrid offspring and this sort of analysis needs lots of data - so who knows.

Yes we do have the DNA of Denisovans and Neanderthals (extracted from bones), but more importantly we have the living descendants of both (Eurasians in the case of Neanderthals and Melanesian/Australian Aborigines in the case of Denisovans).

The issue if Denisovans and Neanderthals are different species to sub-Saharan Africans is complex (nothing in biology is simple). Looking at the gene flow into existing populations it appears all Neanderthal and Denisovan genes came in via the male side. This suggests that the offspring were subject to Haldane’s rule [0], which is a strong marker for interspecies not intraspecies hybridization.

More importantly, the three homo populations fit all the criteria for being different species that apply to the rest of the animal kingdom (i.e. genetically isolation and genetic adaptation to different environments).

We should not forget that different does not mean inferior. Lions and tigers are different species of the genus Panthera, can they interbreed (Liger) and are subject to Haldane’s rule. Despite this one is not a better cat than the other.

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

To be more precise, there are actually only a few known bone fragments of Denisovans, so details about their morphology is not known.

You can tell that they’re different species by analyzing the DNA to figure out when the lineage diverged from a common ancestor with Neanderthals. In the case of Denisovans and Neanderthals, if I recall correctly, they diverged like 400k years before the specimens which have been found were alive. Whether that qualifies as a different species depends on how you define species. But the divergence is similar in scale to the divergence between humans and Neanderthals, so if you consider humans and Neanderthals different species, then Denisovans are also a separate species. The alternative is to consider then all different varieties of human.

Edit: just wanted to add this write up by Razib Khan for anybody interested:

https://www.gnxp.com/WordPress/2018/08/22/hominins-are-still...

(1) They do have the DNA... That's actually how this discovery came about, and the reason for all the progress in this field over the last few years. Svante Pääbo at the Max Planck Institute and his team invented a method to extract DNA from ancient bone fragments a few years back.

(@) The term "species" doesn't really have a definition in biology. You seem to be suggesting that producing offspring defines two individuals as belonging to the same species. That's not a workable definition because most life on earth doesn't breed at all. It's also not the correct, obsolete definition, which had always been "producing offspring that is itself fertile". Otherwise, tiger and lion are one species (producing infertile liger when they mate).

I know that we don't all have the same sense of humour but rgrieselhuber did not deserve to be DVd. I will accept that their comment was not exactly useful but it could be construed as funny.

Why, HN, why?

It will never work. He's a man of the world, and her family are a bunch of cave dwellers.

A quick Google suggests Boskop man was a modern human and Adam's calendar are 16th century livestock enclosures . . . so I'm really not sure what you are trying to say.

> Adam's calendar which was discovered in 2003 in South Africa and predates Stonehenge by 10s of thousands of years.

Wikipedia wildly disagrees with you [1], it's few hundred years old

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