The Mammuthus Moment: Are You a Neanderthal?

In this, EvC Forum's second column, Mammuthus considers the question of human/Neanderthal relatedness. The column appears below, or you can click here to view in a separate window. If the subject interests you, please feel free to begin a discussion in this thread.Edited by Admin, : Fix background color.

...bump!

Perhaps a link to the Applying Science to Past Events thread? This would seem to overlap with that discussion somewhat.

Can we change the colors so us Neaderthals can read it? I have to highlight the article to even see the black of blue-black type.

---

Aslan is not a Tame Lion

Work has also been done on ancient anatomically modern human remains from the same time period. The mitDNA sequences of those samples was different that the neander sequences dating 3,000 years older but closely matched living human sequences. Also, there are no regional differences in neander to living human sequences. This is important since neanders have only been found in Europe and not in asia or africa. Therefore, if there was interbreeding we would expect a closer match to living europeans than to asians or africans. This is not the case, and therefore supports the case for limited or non existant interbreeding between anatomically modern humans and neanderthals.Mammuthus's point of mitDNA being a maternal lineage and nuclear DNA being both maternal and paternal is important. However, I find it unlikely that only male neanderthals mated with human femals and human males only mated with neanderthal women when interbreeding did occur. However, the possibility does exist. Post natal development in humans and neanderthals seems to argue against interbreeding as well, which would be independent of mitDNA lineages. So far, fossil remains of neanderthal children seems to indicate a different maturation process than that seen in human populatins. If interbreeding were occuring we would expect a melding of the two maturation processes, but we find the opposite.The only conclusion that I have been able to draw from the data is that interbreeding was not a common occurence. The possibility of occasional interbreeding still remains. Modern human lineages may only represent those lineages that survived form the period and may not reflect interbreeding lineages present at the time of neanderthal and human cohabitation of Europe. Also, the data, to this point, does support the theory that humans and neanderthals were two different species in that genetic flow between the populations was either severely limited or non-existant. Therefore, it is possible that both neanderthals and humans are both daughter species of Homo heidelbergensis.

I can't control the colors - it's just an HTML of a Word document with black text on a white background. What happens if you click on the link in the introductory paragraph. It should bring the document up in a new browser window all by itself.You haven't somehow disabled CSS, have you? Or are you using a non-CSS compliant browser? Or perhaps an older (very older) browser version?Is anyone else seeing the same thing?--Percy

Link works jess fine for old eyes. The browser I'm using is kinda old, Firefox 1.0 pre-release. I'll check and see what the current build is.

---

Aslan is not a Tame Lion

quote:

---

Work has also been done on ancient anatomically modern human remains from the same time period.

---

Do you meant he Mungo Lake results or cro magnon?
Mungo Lake is really controversial and is probably an artifact. The cro magnon results have as yet, not been independently replicated so are tentative.

quote:

---

Mammuthus's point of mitDNA being a maternal lineage and nuclear DNA being both maternal and paternal is important. However, I find it unlikely that only male neanderthals mated with human femals and human males only mated with neanderthal women when interbreeding did occur.

---

Actually, depending on how they co-existed, I would expect this to be the case. If they were competeing for resources, neandertal and human males would most likely produce hybrids via rape. That would mean introgression of neandertal and human Y chromsomes into each others populations but maintenance of separate mtDNA gene pools.Another problem is given the relatively low amoung of genetic diversity of humans relative to other great apes, we may simply have lost a lot of genetic diversity by chance and thus the haplotypes are simply not detected when screeing mondern humans but are a part of our genetic history. This was actually the conclusion drawn from the Mungo Lake study where they found a really different mtDNA haplotype in an anatomically modern human fossil from Australia that was very old.

Funny how I've always imagined you to be in your late 20's or early 30's.

Here are links to references for the two cases I brought up.Cro magnonCaramelli D, Lalueza-Fox C, Vernesi C, Lari M, Casoli A, Mallegni F, Chiarelli B, Dupanloup I, Bertranpetit J, Barbujani G, Bertorelle G. Related Articles, Links
Evidence for a genetic discontinuity between Neandertals and 24,000-year-old anatomically modern Europeans.
Proc Natl Acad Sci U S A. 2003 May 27;100(11):6593-7. Epub 2003 May 12.Mungo Lake
Adcock GJ, Dennis ES, Easteal S, Huttley GA, Jermiin LS, Peacock WJ, Thorne A. Related Articles, Links
Mitochondrial DNA sequences in ancient Australians: Implications for modern human origins.
Proc Natl Acad Sci U S A. 2001 Jan 16;98(2):537-42.Erratum in: Proc Natl Acad Sci U S A 2002 Jan 8;99(1):541.

quote:

---

Actually, depending on how they co-existed, I would expect this to be the case. If they were competeing for resources, neandertal and human males would most likely produce hybrids via rape. That would mean introgression of neandertal and human Y chromsomes into each others populations but maintenance of separate mtDNA gene pools.

---

Very good point. I tend to project current "mating strategies" on ancient cultures. However, if this were common you wouldn't expect large diffences in morphology. Afterall, neanderthals were put into a different group not because of their DNA but because of their morphology. I have always accepted that occasional interbreeding could happen and be undetectable in the fossil record and in DNA studies. However, consistent interbreeding would probably show up in both.

quote:

---

Another problem is given the relatively low amoung of genetic diversity of humans relative to other great apes, we may simply have lost a lot of genetic diversity by chance and thus the haplotypes are simply not detected when screeing mondern humans but are a part of our genetic history.

---

The verification of the Mungo Lake samples would go a long way towards testing this. Also, additional cro magnon samples would also help in clearing this up. Given that the geographic ranges of neanderthals and cro magnon overlap, we need an explanation as to how the mitochondrial genomes of each species were kept separate. My hypothesis is that it was due to sexual selection and not cross-species infertility. Is this the way you see it as well, more testing and sexual selection as a possible mechanism?

Remember, while we often say that ranges overlap, population density was also considerably smaller than today and physical barriers to travel were of a greater magnitude.If you have ever hunted, you will understand that even when you are in an area where it is known that your target species is available, it is often the case that you will never see a single critter. Even in our modern manicured wilderness, it's not unusual to find tracks crossing your path of a critter you never saw.With low density, it's possible that two species could live their lives in relatively overlapping territories yet not be aware of the other.

---

Aslan is not a Tame Lion

quote:

---

Very good point. I tend to project current "mating strategies" on ancient cultures. However, if this were common you wouldn't expect large diffences in morphology. Afterall, neanderthals were put into a different group not because of their DNA but because of their morphology. I have always accepted that occasional interbreeding could happen and be undetectable in the fossil record and in DNA studies. However, consistent interbreeding would probably show up in both.

---

I can think of a pretty nice example of two very similar AND interfertile species that remain both genetically and morphologically distinct. Loxodonta africana and Loxodonta cyclotis the savannah and forest African elephant respectively. They have clear morphological distinctions and their ranges overlap. Studies of microsatellites show that they do on occassion form hybrids but that even though their ranges overlap, introgression is minimal see Roca AL, Georgiadis N, Pecon-Slattery J, O'Brien SJ. Related Articles, Links
Genetic evidence for two species of elephant in Africa.
Science. 2001 Aug 24;293(5534):1473-7.Sexual selection or niche selection may prevent large scale introgression as each of the two species is specialized for a distinct habitat and the F1 hybrids (and beyond) may be less fit than either parent species.My worry about Mungo Lake is that the sequence obtained is almost identical to a Numt on chromosome 11 in all humans. They did not do a very rigorous study (at least not at the level Krings et al. 1997 did with the neandertal type specimen) and thus if it looks like a Numt it may very well be one. That would collapse their entire arguement and the conclusions would have to be thrown out.

I think the problem with that is there is (from dating of neandertal and cro magnon sites) overlap i.e. in Croatia there is a site where neandertal and cro magnon fossils are found in the same layers and have similar carbon dates. At about 28 Kya, the neandertal fossils stop appearing in the record and cro magnon continue.

quote:

---

My worry about Mungo Lake is that the sequence obtained is almost identical to a Numt on chromosome 11 in all humans. They did not do a very rigorous study (at least not at the level Krings et al. 1997 did with the neandertal type specimen) and thus if it looks like a Numt it may very well be one. That would collapse their entire arguement and the conclusions would have to be thrown out.

---

Agreed. It would seem that the evidence is still tentative and needs further validation from other labs, as well as experiments to rule out numts.