Neanderthal Genome
Scientists have completed a “first draft” of the neanderthal genome. This is exciting on many levels. One of the burning questions of paleoanthropology is the relationship between humans and our closest cousins, the Homo neanderthalensis. Debate has gone back and forth over years, but this is a debate that can be resolved with evidence.
So now that we have taken a good peek at the neanderthal genome, what do we find? Svante Paabo, speaking at the AAAS, reports that his team could not find any evidence of interbreeding between neanderthals and humans. This does not mean there was absolutely no cross-species hanky panky, but it does mean that it was rare and contributed minimally to the human genome. There still might be a mutation or two to be found contributed to the human genome from neanderthals – or contributed to the neanderthals from humans. But the big question has been answered – the two populations did not merge.
We know that neanderthals and early Homo sapiens co-existed in Europe for thousands of years. We are extremely close genetically, sharing >99% of our genome and having the same number of chromosomes, so humans and neanderthals would almost certainly have been able to breed and have fertile young. We also know that humans survived and spread throughout the world, while neanderthals became extinct about 30,000 years ago.
This fact has lead to another burning question – why did they go extinct. The Darwinian bias is to think that they were unfit in some way, or were outcompeted or perhaps hunted to extinction by humans. This may be correct, and competition (in the absence of interbreeding) probably played some role. But it is interesting how deeply the “fitness” bias runs. I have seen dozens of documentaries on evolution, and it seems the running commentary cannot help to portray new emerging species as better and stronger, and species on the way out as feeble and inferior.
Rather, most species are just adapted to their local environment. The most common respnose to a changing environment is to migrate – habitat tracking. When that fails, the second most common response is extinction. Speciations tends to occur in small subpopulations on the fringes of a species’ range. Most species that go extinct were just unlucky – their environment changed and they could not migrate to a similar environment.
Humans are therefore not inherently superior to neanderthals just because we survived and they didn’t. However, having said that – there is independent evidence (other than the mere fact of our survival) that humans did have skills neanderthals lacks. Our tools were more sophisticated, and human tribes had a division of labor that may have made them more efficient. Also, only humans left behind evidence of art. There is no neanderthal art. From this we might infer a more nimble or expansive intellect.
But the truth is, we don’t really know. This remains an area of investigation and researchers are slowly exploring not only how humans and neanderthals differed, but how those differences may have related to differential survival. It is not always as simple as it may seem to make this connection.
Another question that has arisen as a consequence of sequencing the neanderthal genome is the possibility of cloning a neanderthal. While Paabo and others are saying this is not possible anytime soon – it eventually will be. We are already working on cloning the mammoth and recently extinct species like the Tasmanian tiger. One of the factors that affects how easy or difficult it will be to clone an extinct species is whether or not they have a close living relative – the closer the better. Mammoths have elephants.
Well, neanderthals have humans. I already stated that there is little difference between the human and neanderthal genomes. If we identify all those difference we could then close a neanderthal from a human by making the necessary changes. While it is difficult to say how long it will take for this technology to emerge, it is almost an inevitability. It will happen sooner or later.
Then, of course, the real question becomes one of ethics. The ethical issues will probably take much longer to work out than the technical ones.
I’m confused. If Neanderthals and H. Sapiens are different species then wouldn’t they be unable to have had offspring (or at least fertile offspring)? And if they could, then are they really 2 different species?
(Not remotely a biologist, sorry!)
If the researchers can’t get federal funding to clone neanderthals, they should pitch it to Geico.
SionH– Some pairs of distinct species can interbreed and even produce fertile offspring, but they have enough physiological differences, and don’t normally interbreed, that they are considered different species. For instance, lions and tigers have been interbred in captivity.
I believe that the definition of species is extremely difficult because as you say different species can interbreed (though not necessarily produce fertile offspring) It probably was non biological factors that stopped early Humans and Neanderthals mixing e.g. behaviour or perhaps each thought the other minging!
You say that “Our tools were more sophisticated….”, I thought some recent reasearch had cast some doubt on this: ‘Complexity’ of Neanderthal tools at http://news.bbc.co.uk/1/hi/sci/tech/7582912.stm
Be interested in your thoughts.
I take it neanderthals and humans were reproductively isolated by geographic factors and not physiological factors, and this is what makes them separate species, yet still retain the possibility of having viable young together.
It’s worth noting (as you do) that the effort to avoid naive progressivism can obscure an important truth: evolution often is progressive in an engineering sense. There’s no reason to suppose that a smarter, faster, or deadlier Whatsit is “better” than its ancestors (and natural selection can instead favor simpler, less specialized, or less costly strategies) but nature often does feature a sort of refining trend in which advantageous traits are reinforced.
Great comments. I’ll wait to see if Dr. Novella responds, the inquiries posed are important.
@SionH:
Are you assuming that there is evidence of neanderthals and humans copulating and producing offspring? I can’t understand what it is you’re confused about. Having common genes is no indication of any breeding between two species.
Max, “they should pitch it to Geico.” good one!, and @SionH: Aren’t you aware of some of the more esoteric goings on of homosapiens ? Nudge nudge.Wink and a nod.
SionH– Some pairs of distinct species can interbreed and even produce fertile offspring, but they have enough physiological differences, and don’t normally interbreed, that they are considered different species. For instance, lions and tigers have been interbred in captivity.
Exactly how much variance is required in the genome of two entities to classify them as “distinct species”. Initial estimates of chimp vs modern human dna were declaired a greater than 98% “common value”. However recently it has been reestimated to be rougly less than 95%. It makes you wonder how close Neanderthal will be to modern homo sapiens. This also makes me wonder about canine species. Is a breed a seperate species? If so they are easily able to interbreed and create progeny that are able to progreate at will. How much variance is there to the DNA of differant dog breeds? And if the individual breeds are not indiviatual species, well, why not? A comparison of the Poodle vs Boxer genome illustrated variance in the their content SINEs at approximatly 10,562 locations in their genomes. Maybe breed is a euphimism for species in dog language. As I am sure you are all aware there are differances in dog years vs human years and possibly a similar differance has manifested itself in the terminology commonly applied to canids. With these types of differances should each dog be classified as a separate species as opposed to a differant breed? And if not why wouldn’t a tiger and a lion and mountain lion simply be a differant breed of feline? If we are going to classify in this manner than wouldn’t we have to apply this to modern humans?
You say there is no Neandethal art – did Neanderthals bury their dead?