Neanderthal-Homo Sapien Cross-breeding Idea Doubted

Neanderthal breeding idea doubted
(bbc.co.uk)
(Altered the headline a bit for the post title since it wasn't explicitly clear)

Similarities between the DNA of modern people and Neanderthals are more likely to have arisen from shared ancestry than interbreeding, a study reports.

That is according to research carried out at the University of Cambridge and published this week in PNAS journal.

Previously, it had been suggested that shared parts of the genomes of these two populations were the result of interbreeding.

However, the newly published research proposes a different explanation.

Did humans and Neanderthals interbreed? A lot of attention and movement towards acceptance of that concept has been garnered lately, but it may have been premature. Another study looks at factors that may indicate the similarities in ours and Neanderthals DNA has to do with our origins from an earlier common species, and not from any possible crossbreeding.

They argue that the amount of DNA shared between modern Eurasian humans and Neanderthals - estimated at between 1-4% - can be explained if both arose from a geographically isolated population, most likely in North Africa, which shared a common ancestor around 300-350 thousand years ago.

When modern humans expanded out of Africa, around 60-70,000 years ago, they took that genetic similarity with them.

The article goes into more detail on the DNA similarities among species of humans. The gist of it is, the idea of humans and Neanderthals cross-breeding may be premature.

Fascinating stuff. Thanks for posting.

This is interesting, but I see it as just a possible explanation than actual evidence. Obviously one would have to look into it more to see why they think this is a more likely explanation as to how 1-4% of all non-African genomes contain Neanderthal DNA than simple crossbreeding.

Things that make me doubt this is a more likely explanation are firstly I think if humans and Neanderthals were able to crossbreed, chances are they probably would have. Secondly I do not see how a population would become ‘geographically isolated’ in the north of Africa and not have any genetic drift into the south at all. This in itself seems far less likely than humans simply breeding with Neanderthals once they crossed into Eurasia.

The landbridge into Eurasia itself lies very close to the Nile River which would have been the main route that north Africans would have also travelled south. One has to wonder why the entire population of H. Sapiens who shared common DNA with Neanderthals would only choose only ever to travel north and never once headed down into the rest of Africa, while at the same time not once breeding at all with the other north Africans who stayed in Africa but did choose to travel south.

I think the trouble with explanations such as this is that they often seem to assume it has to be one way or another, when chances are the real truth probably lies somewhere in the middle. Also they often seem to only consider one source of information as gospel (their own) while ignoring other lines of reasoning such as common sense…

It has always been highly doubted they interbred due to the size of the cranium versus birth canal between the species.

Common ancestor rather than interbreeding makes sense.

reply to post by zazzafrazz


You seem to assume that only male Neanderthals bred with female humans. I'm sure many Homo Sapien men probably got lucky with the Neanderthal ladies in which case the baby's resulting smaller cranium size would make no difference.

In fact it would probably be safer overall therefore increasing the survival rates for both mother and infant.

Not saying this would completely offset the amount possibly lost through Neanderthal male/human female births but over thousands of years would definitely be significant in such relatively small populations.

reply to post by 1littlewolf


I rarely assume anything

They are different birth canals. One species can't just pop out of another. Neandertals and humans have different patterns of pelvic sexual dimorphism.

reconstructed birth canal indicates that childbirth was about as difficult in Neandertals as in present-day humans, but the canal's shape indicates that Neandertals had a more primitive birth mechanism. A significant shift in childbirth apparently occurred quite late in human evolution, during the last few hundred thousand years. Such a late shift underscores the uniqueness of human childbirth and the divergent evolutionary trajectories of Neandertals and the lineage leading to present-day humans.

For more info read here :

www.pnas.org...

Something I heard on the TV many years ago 'if the toe next to your big toe is longer than your big toe, you have Neandathal ancestry' that stuck in my memory, as I am really into history.

Originally posted by zazzafrazz
reply to post by 1littlewolf

 

I rarely assume anything

They are different birth canals. One species can't just pop out of another. Neandertals and humans have different patterns of pelvic sexual dimorphism.

reconstructed birth canal indicates that childbirth was about as difficult in Neandertals as in present-day humans, but the canal's shape indicates that Neandertals had a more primitive birth mechanism. A significant shift in childbirth apparently occurred quite late in human evolution, during the last few hundred thousand years. Such a late shift underscores the uniqueness of human childbirth and the divergent evolutionary trajectories of Neandertals and the lineage leading to present-day humans.

For more info read here :

www.pnas.org...

Thanks for the interesting link. But the article does not at all suggest that Neanderthal females would have any issues popping out the resulting smaller offspring through breeding with human males. It does not even suggest that human females would have issues with Neanderthal babies.

Given that just in the past 100 years the average birth weight for humans has more or less doubled within the developed world and the majority of women are still having natural births suggests that they may well have not had too many issues at all.

Neanderthals and modern day Homo Sapiens were really not that different; and no one has suggested that any successful birth would not have resulted in viable offspring.

reply to post by 1littlewolf


I think it should perhaps be reread, It clearly states what I said. That it is not physically viable for one species to birth the other. It is a good article Its not the just cranium size so much as how a turn/birthing is different through each birth canal.

reply to post by pikestaff


LMAO, I just checked

reply to post by zazzafrazz

Originally posted by zazzafrazz

I think it should perhaps be reread, It clearly states what I said. That it is not physically viable for one species to birth the other. It is a good article

Its not the just cranium size so much as how a turn/birthing is different through each birth canal.

Hey zazz,

I reread the article but have still not found anything that suggests that a Neanderthal/Human hybrid would be significantly harder to give birth to than a non hybrid, especially if the mother is a Neanderthal. In fact I can’t find anything in the article which mentions anything about Neanderthal/Human hybrids. It does definitely state that human birth canals are different to those of Neanderthals, but that’s pretty much the extent of it as far as I can see. If you could quote the part which ‘clearly states what you have said’ it might help a bit.

But let’s pretend that what you have said about the article is true. For starters it is based on the pelvis of only one Neanderthal female and reconstructions made using quite a few assumptions about comparative sexual dimorphism between human males vs. females and Neanderthals. Then these assumptions are used to create a model and compared to the one workable female Neanderthal pelvis to see if it accurate.

Doing this to recreate the Neanderthal birth canal is one thing, but making wider assumptions about the Neanderthal/Human breeding is completely different. The very fact that they can do this means that humans and Neanderthal are in fact very similar which would then suggest that they probably wouldn’t have too many issues giving birth to a hybrid baby. This is assumption is also supported by the fact that nowhere has it been suggested that a hybrid baby would not be viable.

Other points which would still need to be addressed are why native Africans carry no Neanderthal DNA at all. As I mentioned above the OP’s article says that this population remained in the north of Africa and would have crossed into Eurasia very close to the main access point (the Nile) which links both northern and southern Africa. It is very unlikely especially that none of these individuals went south at all or at the least bred with the north Africans which did remain in Africa, especially considering the migration north would have occurred over many thousands of years.

The only common sense theory which would explain why no native African carries any Neanderthal DNA is that the mixing did not occur until after the humans left Africa.

reply to post by 1littlewolf


the thing is, they haven't found any evidence of any mitochondrial dna from neanderthals, which is passed maternally, in homo sapiens so that claim you are making is dead in the water.
this means that humans would have to only be male, and if we never mated with neanderthals(a huge possibility) it hardly matters if a hybrid was viable or not.
we may have been split off so long that we wouldn't mate with neanderthals anyway, or so rarely that even if we could we didn't and didn't produce a hybrid.

here is a report on it from 2007.
i hope you do realize that while we can combine animals to make hybrids, such as mules, and ligers, they don't happen naturally. i figure it is the same with humans and neanderthals,

the thought is that neanderthal were highly adapted to colder climates and as the climate got warmer the neanderthal migrated north to keep to that climate. that is why there is no DNA found in south african people, because when humans evolved the neanderthal lived in the colder regions farther north.
also neanderthal hunting tactics didn't work in grasslands and many of the animals they hunted didn't live there either.

At school, back in the 1870s, we were told that Neanderthals were where ginger people came from and this is why they should be feared and shunned.

Crazy double post

reply to post by demongoat

Originally posted by demongoat

the thing is, they haven't found any evidence of any mitochondrial dna from neanderthals, which is passed maternally, in homo sapiens so that claim you are making is dead in the water.
this means that humans would have to only be male, and if we never mated with neanderthals(a huge possibility) it hardly matters if a hybrid was viable or not.
we may have been split off so long that we wouldn't mate with neanderthals anyway, or so rarely that even if we could we didn't and didn't produce a hybrid.

here is a report on it from 2007.

Hey demongoat,

The article you reference made no mention of mitochondrial DNA, and a quick Google search did not turn up anything along those lines either. The article in fact only discusses morphological features of one particular skull found in Romania and makes no mention of DNA at all.

The best I found was this article from two days ago which is well referenced and though not at all supportive of hybridization is still littered with phrases such as

Scientists at Cambridge University currently are saying that humans from Europe, Asia and Oceana may not have mixed with Neanderthals…..
……………….
Studies in the past reported that only non-Africans had Neanderthal genes, namely Europeans and Asians. Then came studies showing Denisovans in Asia, a cousin to Neanderthals, but different from Neanderthals showed up in some Asian peoples today, including those in Oceana, such as in Papua and New Guinea in one to six percentage of their genomes. So research must continue.
……………….
The question remains whether they interbred or not.
………………….
But now the new study conflicts and says there's no proof they mated. Instead, they may have simply had the same common ancestor from further back in time, about 300,000 years ago.
…………………..
Science can't prove conclusively that humans and Neanderthals didn't breed. But researchers say it would have been much less than what last year's research reports claimed, that one to four percentage of Neanderthal genes in non-Africans..

This certainly does not suggest a solid case for no hybridization at all.

Now assuming you are correct about your assertions of mitochondrial DNA (which I cannot find any support for), one would assume that if a human male mated with a Neanderthal female that female would continue to live with her Neanderthal tribe which as we all know has become extinct. If a Neanderthal male mated with a human female chances are that female would still continue to live with other humans and therefore no mitochondrial DNA would have been passed on through her offsping.

This does not at all leave my claims ‘dead in the water’, and in fact to introduce mitochondrial DNA into the greater human population would introduce another layer of complexity (female hybrid mating with human male and having a female child) which although may well have happened but probably not at a scale large enough to have seriously impacted the greater human genome.

I have not claimed that Neanderthal/Human breeding ever happened on a large scale, or that this is the sole cause of Neanderthal extinction. As I said in my original post in this thread

I think the trouble with explanations such as this is that they often seem to assume it has to be one way or another, when chances are the real truth probably lies somewhere in the middle.

Keep in mind also that the Neanderthal population was pretty small (prob. Max 10,000 at any one time) and would have likely existed in sparse groups across Europe. It would have been fairly brutal existence and I have no doubt that in most Human/Neanderthal meetings the result would have likely been quite violent. This would have meant a lot of death but also a lot of rape…

i hope you do realize that while we can combine animals to make hybrids, such as mules, and ligers, they don't happen naturally. i figure it is the same with humans and neanderthals,

They do if one isolated population invades the territory of another and they are similar enough in form and habit to actually mate in the first place

the thought is that neanderthal were highly adapted to colder climates and as the climate got warmer the neanderthal migrated north to keep to that climate. that is why there is no DNA found in south african people, because when humans evolved the neanderthal lived in the colder regions farther north.
also neanderthal hunting tactics didn't work in grasslands and many of the animals they hunted didn't live there either.

This only suggests Neanderthals did not ever return to Africa, but does not at all explain there is absolutely no Neanderthal DNA (from the ‘geographically isolated human tribe’ from which Neanderthals branched off as mentioned in the OP) left in native Africans at all.

reply to post by 1littlewolf

Secondly I do not see how a population would become ‘geographically isolated’ in the north of Africa and not have any genetic drift into the south at all.

The Congo Rainforest forms one of the largest geographical barriers in the world.

In addition to the major network of Rivers, such as the Congo River, and Congo Rainforest Drainage Basin.

As you can see, In between the Congo River, and the Nile and Lake Victoria... There exists mountainous terrain embedded within tropical rainforest.

These mountains are known as the Virunga Mountains... and some of them are still Active, with all of the terrain usually associated with Volcanoes.

en.wikipedia.org...

Not exactly the easiest thing in the world to bypass.

reply to post by ErtaiNaGia


But Congo only stretches from the middle of Africa to the West. The landbridge into Eurasia, as well as the major route humans travelled from North Africa down to the south exists on the east.

If they made it to the landbridge then there’s no reason they couldn’t have gone the whole way down, and this in no way suggests a ‘geographically isolated’ population…

reply to post by 1littlewolf

But Congo only stretches from the middle of Africa to the West. The landbridge into Eurasia, as well as the major route humans travelled from North Africa down to the south exists on the east.

If they made it to the landbridge then there’s no reason they couldn’t have gone the whole way down, and this in no way suggests a ‘geographically isolated’ population…

Well, I'm pretty sure that we are talking about a prehistoric human population, before the existence of the boat.

and I'm also pretty sure that I did mention the virunga mountain region, lake victoria, lake edward, and the nile.

reply to post by ErtaiNaGia

Originally posted by ErtaiNaGia

But Congo only stretches from the middle of Africa to the West. The landbridge into Eurasia, as well as the major route humans travelled from North Africa down to the south exists on the east.

If they made it to the landbridge then there’s no reason they couldn’t have gone the whole way down, and this in no way suggests a ‘geographically isolated’ population…

Well, I'm pretty sure that we are talking about a prehistoric human population, before the existence of the boat.

and I'm also pretty sure that I did mention the virunga mountain region, lake victoria, lake edward, and the nile.

How about feet?

The earliest pre-human remains are pretty much all found on the eastern side of Africa. To become geographically isolated an early human population would have to walk from the east into the west. Then in order for this isolated population to emerge in Eurasia they would have had to walk back over to the east where they would have again intermingled with other humans.

The only way for your example to work is if this isolated population trapped in the west actually did make a boat, and then sail it up the western coast of Africa, across the Mediterranean and land somewhere near the Rock of Gibraltar in Spain.

Keep in mind also by the time the Neanderthals died out an earlier wave of humans had long emerged from Africa 50,000+ years prior and these guys managed to walk all the way to Australia.

reply to post by 1littlewolf

The earliest pre-human remains are pretty much all found on the eastern side of Africa. To become geographically isolated an early human population would have to walk form the east into the west.

Technically speaking, all they would have to do to become geographically isolated is travel far enough in any given direction.

Circumnavigation of the globe seems an easy feat, when you can rely on something better than just walking in your bare feet.

Geographical Isolation, as a term, refers more to proximity to other groups, than it does to impassible barriers.


For example, if you have a group of people in east asia, and another one in siberia.... the intervening land is not all that impassible.... there is just a LOT of it between the one and the other. (Discounting the cruel siberian winter, of course.)

And travelling alone can be extremely hazardous, and in many cases, quite deadly.

This is why most migrations were group affairs.... and since this is the case, mobilizing your entire tribe to trek across vast regions of jungle, mountains, and desert would probably not be desirable, or even necessary.

en.wikipedia.org...

Geographic Isolation, and allopatric speciation merely refers to enough separation distance between two populations that they do not interbreed.

A Brick Wall could do this.