What if there are two or three human species today?

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Closed
Aug 2014
302
New York, USA
Possible but that scenario is unlikely to happened. Unless proven that most hybrid Neanderthal give birth to male only or with a high probability.
They didn't have to give birth to male only right away, as long as the female ancestor gave birth to only sons at some point in the last 40,000 years (or whoever long ago the contact happened) Neanderthal mtDNA would be lost.
So if Neanderthal mother gives birth to a daughter who gives birth to a daughter who gives birth to a daughter who gives birth to a daughter who gives birth to a son who gives birth to a daughter, Neanderthal mtDNA in this case is lost, but Neanderthal DNA is preserved. That is how homo sapiens have Neanderthal DNA (and other hominid DNA) in them, but exclusively homo sapien mtDNA and Y-DNA.

We also have an archeological case where we have a Denisovan female mate with a male Neanderthal. But male Neanderthal already had a small % of Denisovan DNA, because he was an offspring of one of his ancestors ~8 generations prior that already mated with a Denisovan before!
The whole thing is very complicated, since it looks like a lot of the times when two diffirent hominids met, they were trying to have sex with each other! :)
Not just interbreed but interbreed and produce fertile offspring. But like I said before, we need to stop splitting hairs on this issue and try to stick to the original premise of the question of how history would unfold if we've had to share the planet with another hominid species all the way to the present day.
The whole species concept is very murky. There are some species that can crossbreed and produce viable offspring. For example, a bottlenose dolphin & false killer whale can make a wholphin, and we have one documented case where a wholphin ended up being fertile and was able to mate with other dolphins, to produce a 25% false killerwhale/75% dolphin offspring.
Wholphin - Wikipedia

With that said, I don't think any other hominid species that is very close to us would be able to survive in tact. If they didn't get slaughtered by human armies, they would have simply bred with and diluted into the bigger homo sapien gene pool.
 
Last edited:
Jan 2008
51
They didn't have to give birth to male only right away, as long as the female ancestor gave birth to only sons at some point in the last 40,000 years (or whoever long ago the contact happened) Neanderthal mtDNA would be lost.
So if Neanderthal mother gives birth to a daughter who gives birth to a daughter who gives birth to a daughter who gives birth to a daughter who gives birth to a son who gives birth to a daughter, Neanderthal mtDNA in this case is lost, but Neanderthal DNA is preserved. That is how homo sapiens have Neanderthal DNA (and other hominid DNA) in them, but exclusively homo sapien mtDNA and Y-DNA.

We also have an archeological case where we have a Denisovan female mate with a male Neanderthal. But male Neanderthal already had a small % of Denisovan DNA, because he was an offspring of one of his ancestors ~8 generations prior that already mated with a Denisovan before!
The whole thing is very complicated, since it looks like a lot of the times when two diffirent hominids met, they were trying to have sex with each other! :)

The whole species concept is very murky. There are some species that can crossbreed and produce viable offspring. For example, a bottlenose dolphin & false killer whale can make a wholphin, and we have one documented case where a wholphin ended up being fertile and was able to mate with other dolphins, to produce a 25% false killerwhale/75% dolphin offspring.
Wholphin - Wikipedia

With that said, I don't think any other hominid species that is very close to us would be able to survive in tact. If they didn't get slaughtered by human armies, they would have simply been bred out and diluted into the bigger homo sapien gene pool.

Thanks for that explanation.

When a male and female mate with each other, most of their DNA combines together in their offspring, and this is known as the recombinent (autosomal) DNA. Although it will tell you who the parents are, you cannot tell which parent each individual allele came from, because it all combines together.

However, there's a small segment on the Y-chromosome that doesn't combine with the X-chromosome, and it is transmitted in a pure (nonrecombinent) state down through the generations from father-to-son. This makes it possible to trace back a father-to-son lineage back to its origin in ancient times.

Coincidentally, there's an analogous but unrelated way to trace a female mother-to-daughter lineage. Mitochondrial DNA is located in the ova (the female sex-cell), but it's evidently outside the nucleus of the cell. And so it doesn't recombine with the rest of the DNA, as the autosomal DNA does. A mother transmits her mitochondrial DNA to all of her children, both sons and daughters. But because it's located in the ova (the egg, or female sex-cell), only the daughters will pass it on to their own offspring. And so a female mother-to-daughter lineage can also be traced back to it's origin in ancient times.

And so humans today, in their autosomal DNA, evidently do carry a small percentage ( 2 to 4 %) of Neanderthal autosomal DNA. But there's evidently no known direct Y-chromosomal (father-to-son) lineage for the Neanderthal line. At some point it must have been broken by a daughter, who carried on the lineage, but the Y-chromosomal line was lost. The same situation applies to the mitochondrial (mother-to-daughter) lineage. There's no known direct mitochondrial lineage for the Neanderthal line, so at some point it must have been carried on by a son, who didn't transmit the mitochondrial Neanderthal lineage to his offspring.
 
Last edited:
May 2019
64
Afrique
Again that explanation is still unlikely to happend, since I can argue and ask you why it didn't happened to the Y-dna. Since one female is enough to totally suppresse a Y-dna lineage. It works for both side.
And I am not categoric and say that they were zero mother Neanderthal but probably and if it happened it was in a very low number. The Y-dna and the mt-dna are equally probable (1/2 male 1/2female) so if one overturned the other it's means that they were a higher population of one sex. At most it can be explain by the fact that potentially women Neanderthal give birth to more male than female.
 
Last edited:
Oct 2015
1,196
California
The whole species concept is very murky. There are some species that can crossbreed and produce viable offspring. For example, a bottlenose dolphin & false killer whale can make a wholphin, and we have one documented case where a wholphin ended up being fertile and was able to mate with other dolphins, to produce a 25% false killerwhale/75% dolphin offspring.
Wholphin - Wikipedia
https://en.wikipedia.org/wiki/Wholphin

Killer whale is a confusing name since "killer whales" aren't whales at all they are dolphins. I believe they got that name because of some confusion regarding their habit as whale killing dolphins. instead of "Whale Killers" they became known as "Killer Whales." Anyway would venture a guess that the difference between a false killer whale and a bottle nosed dolphin is comparable to the difference between a Homo Sapien and a Neanderthal. If a bottle nosed dolphin and a false killer whale are able to produce viable offspring all the time regardless of the gender of the parents then it could be likely they are a subspecies of each other rather than a different species. It used to be dogs and wolves and coyotes were considered separate species, but since they are able to produce fertile offspring together, they are now regarded as a subspecies of each other. The dog being a subspecies of the wolf.

With that said, I don't think any other hominid species that is very close to us would be able to survive in tact. If they didn't get slaughtered by human armies, they would have simply bred with and diluted into the bigger homo sapien gene pool.
Assuming of course human societies accept them enough to intermarry with them. Which leaves the question at what point would homo sapiens begin to recognize Neanderthals as a separate species and regard intermarriage with them as taboo, and the offspring of such unions be outcasts?
 
Oct 2015
1,196
California
The "classic "neanderthal was an extreme form of the sub-specie
the middle east neanderthal were much less bulky
while the "classic" Cro-Magnon was hardly typical of today's human , they were extremely tall
Cro Mags were taller and lankier and designed for long distance running which is another secret to their success since they were able to pursue prey at great distances . Neanderthals did not have this advantage.

cromg.jpg
Neanderthal (left) Cro Magnon (right)
 
Sep 2012
932
Prague, Czech Republic
It was the unanimously accepted opinion among the scientists that Neanderthals were a separate species and there was no interbreeding between them and humans; until that speculative, fame-seeking 'research' appeared.
You know little about the history of palaeoanthropology, it appears. It has never been universally accepted that there was no interbreeding with Neanderthals. On the contrary, that has at several points been a minority opinion. Nowadays, of course, it's almost unanimously rejected. Funnily enough, even the authors of the (more than a decade old) article you cite earlier in the thread now accept the evidence for interbreeding with Neanderthals. Because people change their opinions as evidence mounts.

Now, we can't discuss the genetics that make this conclusion so certain here. But we don't need to in order t see how wrong you are. The idea of our ancestors interbreeding with Neanderthals dates back to the 19th century; and the thought that our ancestors interbred with other human varieties they encountered never went away. The below is from 1953:

In many instances, however, population change must have resulted from gradual genetic penetration, and much of human evolution in the Pleistocene could easily have been powerfully affected by introgressive hybridization. In this regard it should be remembered that anatomical differences do not necessarily indicate genetic incompatability between groups, and that there is no evidence of reluctance to hybridize even between widely different human types. If rapid and dramatic group replacement did occur it must have been a rare event occurring in special circumstances.
Strong evidence in favour of hybridisation predates the genetic confirmation of course, in the form of putative hybrid fossils (which have since been confirmed as such) like those discovered in Pestera cu Oase in 2002, which the researchers immediately noted combined distinctive 'modern' and 'Neanderthal' traits:

It therefore combines a derived early modern morphology with archaic Homo features and, possibly, a Neanderthal trait
Genetic analysis has of course since confirmed that Oase II had a Neanderthal in her family tree within a very recent generation.

The 'single study' you claim proposed Neanderthal ancestry for modern populations was not a single study - it is a whole body of research now universally accepted. And it was not a wild idea advanced out of nowhere to upturn an overwhelming consensus. Rather, it was the evidence needed to settle a long debate.
 
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M.S. Islam

Ad Honorem
Jul 2012
3,333
Dhaka
You know little about the history of palaeoanthropology, it appears. It has never been universally accepted that there was no interbreeding with Neanderthals. On the contrary, that has at several points been a minority opinion. Nowadays, of course, it's almost unanimously rejected. Funnily enough, even the authors of the (more than a decade old) article you cite earlier in the thread now accept the evidence for interbreeding with Neanderthals. Because people change their opinions as evidence mounts.

Now, we can't discuss the genetics that make this conclusion so certain here. But we don't need to in order t see how wrong you are. The idea of our ancestors interbreeding with Neanderthals dates back to the 19th century; and the thought that our ancestors interbred with other human varieties they encountered never went away. The below is from 1953:
Multi-regional model, which is quite old, always presupposed admixture between archaic humans, but that model was discredited decades ago.


Strong evidence in favour of hybridisation predates the genetic confirmation of course, in the form of putative hybrid fossils (which have since been confirmed as such) like those discovered in Pestera cu Oase in 2002, which the researchers immediately noted combined distinctive 'modern' and 'Neanderthal' traits:



Genetic analysis has of course since confirmed that Oase II had a Neanderthal in her family tree within a very recent generation.

The 'single study' you claim proposed Neanderthal ancestry for modern populations was not a single study - it is a whole body of research now universally accepted. And it was not a wild idea advanced out of nowhere to upturn an overwhelming consensus. Rather, it was the evidence needed to settle a long debate.
The one single study I referred to was ultimately responsible for sequencing the supposed Neanderthal DNA. Their sample was faulty, their methodology was faulty, thus the outcome of their study - Neanderthal DNA sequence - is faulty. All genetic studies ('a whole body of research') that 'confirm' Neanderthal contribution in humans refers to that same faulty, made-up Neanderthal DNA sequence. Therefore, all of them are useless.
 
Sep 2012
932
Prague, Czech Republic
Multi-regional model, which is quite old, always presupposed admixture between archaic humans, but that model was discredited decades ago.
And yet was strongly argued by many palaeoanthropologists throughout.

The one single study I referred to was ultimately responsible for sequencing the supposed Neanderthal DNA. Their sample was faulty, their methodology was faulty, thus the outcome of their study - Neanderthal DNA sequence - is faulty. All genetic studies ('a whole body of research') that 'confirm' Neanderthal contribution in humans refers to that same faulty, made-up Neanderthal DNA sequence. Therefore, all of them are useless.
In addition to the original Altai Neanderthal genome sequence, there's now another high-coverage genome from Vindija, along with a low coverage genomes from the same site, plus the genomes from El Sidron and Mezmaiskaya, and the Neanderthal genome found in Denisova cave. Along with the Denisovan genomes themselves, of course. Probably some others I'm forgetting or not aware of.

So, no, research does not all refer to the same sequence.
 

robto

Ad Honorem
Jun 2014
6,223
Lisbon, Portugal
Multi-regional model, which is quite old, always presupposed admixture between archaic humans, but that model was discredited decades ago.
Giving the overwhelming evidence we gathered in the last 10 years, scientific consensus supports that both the single Out-of-Africa model and Multi-regional model are right. The origin and dispersal of homo sapiens came out to be more complex than previously believed.

We still know little about the history of Homo sapiens in Africa - prior the out-of-Africa migration, I should say. But we have enough evidence to determine that all current non-African people do overwhelmingly descend from one single migration out of Africa which took place between 100kya and 50kya. Nevertheless, there was also some admixture between these Out-of-Africa homo sapiens group and other extant homo species - and those were the Neanderthals and Denisovans. That admixture was also crucial for the divergence and diversity of many human populations today inhabiting Eurasia, Oceania and the Americas (and also many parts of Africa).

All modern human populations outside Africa do descend from one single group of Africans that ventured outside the continent, but they also mixed with other hominids as they went to repopulate the Eurasian landmass.

The one single study I referred to was ultimately responsible for sequencing the supposed Neanderthal DNA. Their sample was faulty, their methodology was faulty, thus the outcome of their study - Neanderthal DNA sequence - is faulty. All genetic studies ('a whole body of research') that 'confirm' Neanderthal contribution in humans refers to that same faulty, made-up Neanderthal DNA sequence. Therefore, all of them are useless.
So, you are saying that most scientists dealing with this issue for the last 10 years are absolutely wrong, but you somehow know more than all of them? That's quite a big statement to make.
 
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