What do you think happened to the Neanderthals?

darjeeling wrote: »

The gender imbalance idea doesn't fit with the data. We've never found one live person with Neanderthal mitochondrial DNA or a Neanderthal Y chromosome, so both the male- and female-specific Neanderthal genetic lineages have died out. If what had occurred was extensive interbreeding with highly sex-biased mating, this wouldn't be the case.

The guys behind the study seem to be arguing it's more likely these genes cam from the males, not the other way around. Well like you point out no evidence of mtDNA from Neandertals has shown up, but it is in the nuclear it seems. If there was hanky panky going the other way to any degree you'd expect to get some indication from the mtDNA I'd have thought. More matings from archaic male-modern female seems to fit the bill for what they've discovered so far. There may well have been flow the other way, but not large enough to echo to today.

As a first approximation, before we had the first Neanderthal genome sequence, we reckoned that modern humans had 0% Neanderthal DNA. Now we've a full genome, that estimate has turned out not to be a bad one - the amount of Neanderthal DNA in modern non-African humans is under 5%.

They don't have anything like a full Neandertal genome for a start. It's a very patchy sequence and it's from just three (male IIRC) Croatian Neandertals. Other studies on the mTDNA (the stuff that there's a lot more of than nuclear)of these guys has suggested that they were living in much more isolated groups compared to moderns. So it would seem to me to be an incredible stroke of luck to get sequences from such a relatively isolated snapshot in genetics and time that represents all or most Neandertal DNA and how that ended up in some modern populations? My own hunch? I'll lay a bet now that if they get more Neandertal nuclear DNA across their geographical and temporal range, they'll show three somewhat distinct groups. Western European Neandertals, Levantine Neandertals and west Asian ones.

Secondly, the difference between 0% and 5% is actually a huge difference. The difference between the original estimate and this new data and what it may tell us is a major thing that 0-5% in raw figures doesn't begin to describe. It blows the hardline "pure" out of Africa replacement model up for a start. Some recent studies are suggesting that these archaic genes(inc Denisovans, which had an even bigger impact on east Asians) may have even given an advantage to some modern human populations. http://www.zmescience.com/medicine/genetic/human-mating-with-neanderthals-made-our-immune-system-stronger/

From the analysis, the scientists estimated that more than half of the genetic variants in one HLA gene in Europeans could be traced back to Neanderthal or Denisovan DNA. Asians owe up to 80%, and Papua New Guineans up to 95%.

The jury is still out, but it is interesting. Denisovan influence on Asian populations appears to be even more than Neandertal and that's from just one fingerbone.

We're only now getting to the stage of population genomics, where we can sequence the genomes of thousands of people. This should show us whether the modern human population has picked up genes from across the entire Neanderthal genome, with different modern populations harbouring different relics of quite divergent Neanderthal DNA, or alternatively if only a small fraction of the Neanderthal genome is represented in our genomes and that fraction is not very diverse and is consistent across all Eurasians. If we find the latter, that would support the idea that modern human-neanderthal mating was a rare event that occurred soon after our ancestors left Africa. If the former, then that would suggest that hybridisation took place over a longer period and a larger gographical range.

Yea there's is defo more to be discovered that's for sure. The lack of good archaic DNA over wider areas is a bit of a stumbling block though. Though going on the current stuff, it seems these matings happened early on, likely in the Levant were we and them hung out for a couple of 1000 years. If they had happened later on in Europe then Asians probably wouldn't have the markers as their ancestors had long left. Like I say though the Neandertal stuff is from a tiny sample in one location and time. If they ever get to sample and sequence a western European Neandertal, say a Spanish or French one we may well find more markers surviving in the modern European population. Could you try that without the Neandertal DNA? Or narrow down were to look? IE look at European, Asian and African folks and look for the tiny differences between them. Then apply "genetic clock" type deduction. Would those small areas be ones to concetrate on when trying to sequence archaic dna?

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darjeeling wrote: »

The evidence for male or female-mediated gene flow is very weak in comparison with other cases where it's been clearly demonstrated.

Oh yea it's weak but apparently more likely according to the bods who've been responsible for the findings on this. I'd add in another possible influence on the more male to female transmission*. Cultural showing up in the genetics. Females tend to move around more. You see this in modern populations, especially isolated ones. The Male lines in such populations tend to stay more geographically stable.

So how can you tell if Neadertals were similar. For a start going by the bones and stones they do seem to be quite low in population size and very "local" with it. What evidence there is of them or their goods moving big distances is scant. Their tools come from nearby sources. The odd example shows some greater distances involved but nothing like when we come along. Now it appears when we come along some trade might be happening, but it seems Neandertals were quite isolated from each other culturally. They shared a culture but not as much as we did and do. If there were meetups simple trade, long distant trade anyway wasn't on the cards on the evidence so far, but...

Reproductively it gets interesting. The Sidron Neandertals in Spain** had their MtDNA examined and where it gets interesting is in the gender diffs. The men all had the same mtDNA type(haplotype?) so their mothers were close relatives. They share a maternal bond. The women on the other hand have a wide range of different mtDNA. The men were bound by "blood" the women came from outside that. Maybe from a different kind of "trade" when different tribes met every so often. makes good sense as far as keeping the genes healthy. If this was their reproductive culture, it's not unlike some tribes today and if we did meet and weren't trying to bate the head off each other we may have traded women as part of that culture.

Now of course that goes both ways, we may have taken in their women as part of that deal. So why would I still think it's more neandertal male - sapien female surviving to today? One possibility is like I said above their calorie needs were much higher than ours. A pregnant Neandertal woman "eating for two" even more so. Ditto for suckling. We may not have been able to sustain such a mouth to feed as well as her own people. One of our women with them would not have this difficulty. It wouldnt have to be by much to have an effect either. Slightly higher mortality or slightly lower fertility in Neandertal woman-Sapien man matings would over time lowered the amount of DNA surviving in a Sapiens group.

All the mtDNA samples to date actually seem to show Neanderthals being relatively genetically homogeneous. Samples from as far apart as Spain and southern Siberia are not very diverse.

Well compared to other great apes, yea, but they're diverse enough. They're as diverse as all modern humans across the planet in distinct populations today. The feldhofer Neandertals, the Russian ones and the Croatian ones differ by 12 base pairs. That's much higher than modern Euroasians in the same area(and even further east in Asia). Diversity wise they're more similar(but slightly more diverse than) to modern Africans who have the largest genetic diversity of any modern humans. They've pretty much the range of all modern humans today so they do appear to be isolated enough as a people.

However, the Denisovans turned out to be quite distinct from Neanderthals when comparing mitochondria, so there was evidently variation out there. Denisovans were closer to Neanderthals when the nuclear genome was sequenced, and many now consider the Denisovans to be akin to an eastern Neanderthal.

Well I dunno. They were as different to Neandertals as we are to Neandertals which is a bit of a gap. If we draw a sub species line between them and us, then we have to draw a similar enough line between them and them so to speak.

They're an interesting bunch if this single woman is representative of her population. They're an old population of humans sharing an old ancestry with Neandertals but apart long enough to be different humans. Maybe they are eastern "Neandertals". Some are positing Erectus for these people. I'd disagree and I'd think another way.

I've mentioned this before in the Paleontology forum here. My take for a long while now? For me Erectus was the first "real" human. He was one of us. Leaves Africa 1.5 odd million years back and goes walkabout all over the world. These people continued to evolve locally wherever they settled. I call the result Erectus 2.0. In Europe we get (Heidelbergensis then) Neandertals. European Erectus 2.0. In Africa we get early Sapiens, African Erectus 2.0. in Asia... Well this has always been the sticking point for me. The accepted view is that Erectus 1.0 stays on in Asia doesn't do much, then dies out and we come in and replace them in the environment. That makes zero sense to me considering the huge wealth of environments and evolutionary pressures in Asia. Outside of Africa(which gave rise to much of who we are remember) Asia has the most environmental diversity on the planet. So I have believed for a long time that there was indeed an Asian Erectus 2.0 and IMHO these Denisovan folks are them, or a partial window into them. It explains their similarities too, but differences from their European Erectus 2.0. And from us.

Where it gets real interesting is where these folks dna shows up in people today. They're in the middle of nowhere, but their bloodline shows up far away all over south east Asia and most of all in people from Papua New Guinea. Those folks have up to 8% of their DNA from Denisovans(and Neandertals). I think this may show some interesting population dynamics. For a start it likely shows that Denisovans were pretty widespread as a group, and/or we moved into their areas deep inland on a migration and took their genes with us and they survive best of all in places like New Guinea because of the isolated island populations. Like the clarly African folks who are to be found on the Andaman islands far from home.

[BTW the Neanderthal nuclear genome sequence has come from females as far as I know *]

Ah right. I dunno where I got that idea. I read stuff and it lodges in the grey matter, but the same grey matter doesn't do "links or GTFO" :D

It's unfortunate that the debate became marked by entrenched polarisation between the OOA and multiregional camps for a long time. It's useful to have alternative models, and generally one starts with simple cases - either pure replacement by modern humans from Africa or pure evolution from local populations. But it's a mistake to turn these models into dogma, and indeed as the evidence comes in, the models should and do get refined. That said, the current model is now much closer to the simple OOA model than the simple multiregional one.

Oh I agree, but it makes our human story so much more interesting and that's with pretty small samples of archaic dna so far found. Can't wait to see more!

We don't have a Neanderthal Y chromosome sequence, but all modern human Y chromosomes genotyped (including African) date to a common ancestor around 60,000 years ago, and this ancestor must - given all else we know - be a modern human and not a Neanderthal.

True but again there may be more to the story than "African Adam" or African Evee. One outlier is Australias "Mungo man". He's a fully modern human and a very early African migrant right at the edge of the known world for our ancestors at 40,000 years ago. His mtDNA is quite different and quite a bit older. Modern native Aussies(and the rest of us) have a different mtDNA heritage. Mungo man is a fully modern human who isn't a descendant of African mtDNA Eve. That's a bit of a shocker. He also looks different to later and modern native Aussies. So for his line to make it Australia, one of the first to come out of Africa, his maternal line must have been present in some numbers(or one helluva fluke) in the migration from Africa, yet his died out and the others haven't and we've no evidence of his line surviving along that route in ancient DNA. My prediction? I'd be asking someone to look at the Denisovan mtDNA and compare it to Mungo mans. I'll put the price of a feed of beers down that it'll have similarities.



* Sorry I should have defined this more. When I say more male to female, I should have said more male to female surviving down to this day in us.

**an interesting group of people. It seems they were all laid down at the same time, possibly as a result of intertribal fighting, or predation as all show signs of defleshing for meat. So it gives a better and very rare snapshot of what may have been going on. By comparison most samples could come from thousands of years apart in the same place.


PS sorry for the length (said the bishop to the actress).

PPS bear in mind the only qualifications I have are on my driving licence so pinches of salt at the ready.

Sea Sharp wrote: »

This is an interesting area.
Out of curiosity, have they compared DNA of Neanderthals with DNA of human remains from 20,000 years ago.
The 0-5% similarity between us and Neanderthals looses significance if there is anywhere near as much evidence of evolution in the human gene pool over that time period. Are we absolutely sure that people at the time of Neanderthals were at least 95% similar to us?
Similarly, if human remains from 20,000 years ago show more traces of Neanderthal DNA, then that would imply that natural selection (over time) favored our genetics over theirs.
The fact that there are so many more hypothetical scenarios for the 'multiregional' model might explain why currently the OOA model is more accurate.

Good point. Modern sapiens human genetic change has sped up over the last 10,000 or so years http://www.scientificamerican.com/article.cfm?id=culture-speeds-up-human-evolution. More than the preceding 100,000. A homo sapiens of 60,000 years ago was quite a different beast on the genetic level in a number of areas. Diet being one of the biggies. Older sapiens would be lactose and gluten intolerant for a start. While they did process and eat grains(even Neandertals did) those grains were much lower in gluten. Other changes involve sperm production which is an interesting one.

So yea there may well be something to what you're saying. That's why I suggested comparing Mungo mans mtDNA to Denisovans may throw up some interesting comparisons.

That's important to note. Popular culture leads us to believe that Neanderthals were nothing more than muck-savage apes, but what would they be like if they were alive in the 21st century?
I'd imagine the differences would be subtle (other than the fact that they could effortlessly kill us in a fight), perhaps it'd be a case of:
"Neanderthals are notoriously terrible drivers"
"Neanderthals don't have a sense of humor"

I dunno. I suspect they'd be behaviourally different to us, just as Cro Magnons at say 80,000 years ago might be. We look very "domesticated" in behaviour and I'd argue in physiology too. We're more neotonous for a start. Our physical features particularly facial features are more like juveniles of archaic humans. We've got highly reduced brow ridges in the male, less robust, smaller noses, thinner bones, shorter "snouts", smaller teeth. I'd compare older hominids to more like wolves and modern cultural humans as more like dogs. Same species near enough, but very different in look and behaviour. The facial features I noted above are very close to the differences between wolves and dogs.

So I strongly suspect a Neandertal brought to now in a time machine, would be very similar as a kid to any other kid, but when puberty hit the "adult" Neandertal would come out much more strongly. More aggressive, xenophobic, territorial and mobile than a modern human. In the same way you could easily enough have a wolf around the house/garden as a cub and would show little diffs to a alsation pup, but as they matured the adult comes out and problems would start(they've actually done experiments on this).

Of course if Neandertals had survived they wouldn't have stopped evolving either. There's good evidence they did when they were around. They became more gracile, more soft in the features. IE you'd see the diff btween a Neandertal from 200,000 years ago compared to one from 30,000 years ago. So if they survived it's likely they'd have continued on that vein and became more "domestic" themselves, or they'd have avoided a lot of that and stayed in the "wild" in smaller and smaller enclaves until they died out due to population drop. Which is kinda what happened. Happened with wolves and dogs too. Wolves are endangered all over the place, dogs are everywhere. So maybe that, not hunting strategy, or calorie needs or direct competition is what happened?



*inc older versions of us, we've dropped a lot of the earlier robustness in the last 40,000 years.

No worries MC, here ya go; The biface is pretty cool. There's a hollow in the flint that was selected for. For what reason who knows but it was defo selected for. It's very expertly fashioned, yet shows little sign of wear on the edges, but lots of wear on the main surface from handling. Also shows deep staining. IMHO from contact with leather. The point1 is a work of art in the hand. Serious workmanship(with some later losses on the bottom edge) and the biggest Levallois point I've yet seen. The scraper is another interesting one as the white inclusion seems to have been selected for and knapped around in a symmetrical way(no wear to the edges either). IMvHO they may be more cultural objects than practical. The blade is dictionary definition Levallois technique. You can even see where the original maker struck off the flake. 50,000 years ago. You kinda need to handle them in the flesh TBH. Pics don't really do them justice.