Deep in Human DNA, a Gift from the Neanderthals | Hacker News Reader

Deep in Human DNA, a Gift from the Neanderthals

nytimes.com

77 pointsdnetesn33 comments

Is it strictly correct to say Neanderthals became extinct if we carry some of their DNA? Or should we think of them as one of a few (sub?) species that fed into the origins of modern humans?

It seems odd to think of "them" and "us" as entirely different.

> Is it strictly correct to say Neanderthals became extinct if we carry some of their DNA?

Yes. Neanderthals as a population don't exist anymore.

The house cat and tiger shares 95% of the same genes. If tigers disappeared, you wouldn't consider it an extinction because we have house cats around?

https://www.csmonitor.com/Science/2013/0918/House-cats-and-t...

Also, the common ancestors of humans and the common ancestors of cats became extinct a long time ago. Are you saying those "creatures" aren't extinct because humans and cats are around?

Edit: An additional example for those interested. Birds today share same genes as tyrannosaur rex.

https://www.scientificamerican.com/article/how-dinosaurs-shr...

> Birds today share same genes as tyrannosaur rex

Really? Surely this claim would require the sequencing of the T-Rex genome, which I'm guessing is an impossibility.

Maybe not so impossible? https://www.nsf.gov/news/news_summ.jsp?cntn_id=111466

Strictly speaking, all liveforms on the planet share same genes because they descended from a common ancestor. You probably have 50% of common genes with plants and quite a few with microorganisms.

IIRC, ~70% with bananas.

it sounds like quite a stretch to say everything shares the same genes. A lot of the genes have come into existence long after distant species split apart, and other genes have disappeared from one specie while continuing in others.

> Yes. Neanderthals as a population don't exist anymore.

But then neither is the Homo Sapiens of that era, surely?

> The house cat and tiger shares 95% of the same genes. If tigers disappeared, you wouldn't consider it an extinction because we have house cats around?

If they interbred now and there was gene transfer within that 5%, I think that would be an entirely different situation to the one you describe.

The picture that is often painted of the Neanderthal following a parallel evolutionary course to 'us', Homo Sapiens. But 'us' is actually a hybrid of the two.

> Also, the common ancestors of humans and the common ancestors of cats became extinct a long time ago. Are you saying those "creatures" aren't extinct because humans and cats are around?

Of course not, and you seem to be entirely misunderstanding my question.

If humans and cats somehow interbred and the ongoing population of cat-human hybrids was what carried on, identifiable fully as neither, the picture is much more grey.

The house cat and tiger had a common ancestor; the Neanderthal WAS an ancestor of modern humans.

Saying "neanderthals as a population don't exist anymore" tells us nothing, because no ancient population exists anymore - they have all been replaced by their descendants. "Extinct" is not the same as "dead".

If we make a phylogenetic tree showing descent, extinction would mean the tree ends - there are no descendants. This is clearly not the case for Neanderthals.

The argument you are making here seems to be that Neanderthals and Homo Sapiens are not distinct species - which seems reasonable to me, given that the populations interbred to the degree they did.

The set of all the descendants of a given species is a valid concept, but it is not the definition of a species (note, for one thing, the awkward self-referentiality if it were.)

None of the extant speciation criteria seem testable across time, so the species distinction between an ancestor and its progeny seems difficult to navigate. This sort of event, of a species vanishing through the slow evolution of its progeny, is called "pseudoextinction" to distinguish from the other, true 'extinction' (the last surviving member of a lineage dies). In this case since we know that Neanderthal DNA lives on in its H. Sapiens descendants we can safely call this "pseudo" rather than a true extinction.

You can rephrase his example to e.g. wolves and chihuahua as one of the more absurd, but accurate, examples to confirm his point and challenge yours. And the interesting thing is is that was a crazy fast speciation by artificial selection. Not only does the "ancient population" still exist, but it'd be quite bizarre to suggest that wolves were not extinct, if they did go extinct, because chihuahuas exist. Speciation, even from a direct ancestor, is very much a thing.

For interbreeding purposes, wolves and dogs (including chihuahuas) are still the same species since they can create fertile offspring.

It seems mechanically challenging for wolves and chihuahuas to create offspring.

Not strictly, because species is not a strict definition. Whatever strict definition you adopt, you will arrive some "strictly speaking" problems.

Think of Neanderthals and humans as two big statistical clusters (of gene prevelance). So individual genes from the neanderthal cluster exist, but the cluster does not.

So e Neanderthals do have descendants though, us.

Among today's humans, could we find similar statistical clusters that would be as important as the difference between Neanderthal and Homo sapiens? We would have to give new names for those clusters.

Importance is largely a question of what happens after.

What we don't have is clusters as distinct from eachother as Neanderthals/Sapiens. Even within the sapiens cluster, there were more distinct sub clusters then than now. But, sure.. clusters still exist. My family are more closely related to eachother than to yours.

Probably not. The difference between any human and any neanderthal is about twice as big as the biggest difference between two humans.

One could now argue that if two differences in one thousand DNA bases constitutes different subspecies, then maybe one in a thousand does so, too, but at the very least it constitutes a different race. One could, and both thresholds would be arbitrary.

Most biologists these days have decided that defining the terms "species" and "subspecies" properly is futile, and they stopped using the term "race" altogether. So... all differences are now officially unimportant. Neanderthals were humans, too! Sort of...

We don't just carry some of their DNA, but somewhere between 25 and 30% (maybe more) of the Neanderthal genome exists in the non-African human population. Us non-Africans each have a small percentage of Neanderthal DNA in our genomes, but the genes are different between different individuals.

I think the question should be. Are there humans today that are descendants of the Neantherthals ? If true, then they live through us.

That question is answered. Pretty much all non African humans have Neanderthal DNA. Around 2% on average.

Did you follow the actual science? First neanderthal genome, 2010: about 6% admixture. Denisova, 2011: 2.5% admixture. Altai neanderthal, 2014: 1.5% admixture.

Every time the quality of the genome improved, the estimated admixture decreased. Isn't that a bit suspicious? And even if it isn't purely an artifact, the direction of the admixture was never established. Could be some neanderthal genes survived in humans, could be some human genes died with neanderthals. Could be that the analysis is no good.

I haven't followed it that closely, no, and your numbers are new to me.

I'll admit that the facts can be reinterpreted in the future with more data. But calling them "suspicious" makes it sound like there is some conspiracy now.

All the analysis comes from the same team (Pääbo and Reich), so no conspiracy is needed. And it's not even scientific misconduct, it's just incompetence.

You are correct, the article was full of the false idea that species are stable.

We are descended from Homo Erectus and share the vast majority of our DNA with that species, yet it is also extinct.

Species are about populations, extinct species occur when there are no extant populations.

You can dig down into the definition of species and what defines the boundaries between them, that's a big topic with basically no bottom.

Neanderthals are an offshoot, not an ancestor.

It seems like they might be both.

Homo sapiens and Neanderthals are both offshoots from a common ancestor.

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