A new review of the fossil records has come up with a provocative conclusion: Neanderthals and modern-day humans, who shared the Earth for approximately 10,000 years, saw each other as kindred spirits and, when conditions were right, they mated.
Falls Church, Va.: Marc:
I recall reading many years ago that Louis Leakey theorized that Neanderthals may have spread further than we realize. Are any searches for Neanderthal remains going on outside Europe? If homo erectus reached Java and China, why not Neanderthals?
Marc Kaufman: Good morning, everyone, and welcome to the world of Neanderthals. As today's story suggests, the reality of the Neanderthal may be quite different from the dull-witted caricature we grew up with. What's more, many of us may have some remnant of Neanderthal genes in us. This remains an area of intense scientific debate, and there are no consensus answers at this point. But with ever more sophisticated methods for analyzing and understand the fossil remains and genes of Neanderthals and early modern humans, you can expect to read more about these issues in the future.
As for the question of whether Neanderthals spread further than initially thought, there have been some claims of Neanderthal-like finds in East Asia and elsewhere beyond the European and Central Asia area where they are thought to have generally lived. But at this point, I believe the general consensus is that most Neanderthals lived in that large, but more limited, area.
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Beijing, PRC: With what we know now of the behavior of early hominids and their migration/hunting patterns, cannot a prima facie case be made that inter-breeding between subspecies and gradual tribal assimilation would have been inevitable, and perhaps even common place, and that this is the most likely explanation for the so called neanderthal 'extinction'?
Why is there such a large number of scholars who, for decades, appear to dismiss this rather simple, likely possibility out-of-hand?
Have the limited mitochodrial DNA and other explorations been so conclusive as to establish, without doubt, that humans and neanderthals were really that different in general physiology other than physical appearance?
Sincerely, Steven
Marc Kaufman: Your premise is indeed the one that Erik Trinkaus has embraced and I wrote about, but there are some considerations. For instance, breeding between different species or sub-species is not the norm, though it does happen, especially in times of stress. Some researchers believe that Neanderthals and the more modern humans were different enough to limit breeding -- that the mating would have involved something akin to bestiality. That position appears to be losing ground, but it remains a factor in scientific thinking. And then we do have those limited mitochondrial DNA results that show no distinctly Neanderthal presence in the modern human genome. On the other hand, I believe they also show a very close similarity between the Neanderthal and current human genomes.
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Charlotte, N.C.: If we got our start in Africa, where did Neanderthals begin?
Marc Kaufman: Just as there has been a long debate about the nature of evolution, there has also been a long debate about how it might have worked in terms of humans. For a long time, scientists believed that a variety of early, proto-humans evolved from other primates in different parts of the world. Under this theory, people in Europe, China, Australia, southern Africa and elsewhere would have evolved from early humans that lived in their regions. The "out-of-Africa" theory and research of the last 20 years or so posited that our ancestors all came from Africa, and that these modern sophisticated and evolved humans displaced the indigenous early humans of all other regions.
The theory I discuss today is essentially an "out-of-Africa" one, but with what the author describes as "admixture." By this he means that there was enough breeding between the indigenous Neanderthals and the modern African humans to really matter.
As to the question of where the Neanderthals came from, it is generally held that both they and the later African humans had common ancestors, but that they split into two seperate species 500,000 to 1 million years ago and evolved differently in different areas. Unclear where this occured, but I believe researchers tend to say east Africa or perhaps further north in what is now the Middle East.
Charlotte, N.C.: If we got our start in Africa, where did Neanderthals begin?
Marc Kaufman: Just as there has been a long debate about the nature of evolution, there has also been a long debate about how it might have worked in terms of humans. For a long time, scientists believed that a variety of early, proto-humans evolved from other primates in different parts of the world. Under this theory, people in Europe, China, Australia, southern Africa and elsewhere would have evolved from early humans that lived in their regions. The "out-of-Africa" theory and research of the last 20 years or so posited that our ancestors all came from Africa, and that these more modern, sophisticated and evolved humans displaced the indigenous early humans of all other regions.
The theory I discuss today is essentially an "out-of-Africa" one, but with what the author describes as "admixture." By this he means that there was enough breeding between the indigenous Neanderthals and the modern African humans to really matter.
As to the question of where the Neanderthals came from, it is generally held that both they and the later African humans had common ancestors, but that they split into two seperate species 500,000 to 1 million years ago and evolved differently in different areas. Unclear where this occured, but I believe researchers tend to say east Africa or perhaps further north in what is now the Middle East.
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Lanham, Md.: How long did Neanderthals and modern-day human co-existed? And approximately how many generations is that?
Marc Kaufman: The best thinking says that the two groups began coming into contact about 40,000 years ago in southeastern Europe -- the area around Turkey, Romania and Bulgaria. The migration of the modern African humans probably took place in small numbers at first, and so it wasn't a fast and dramatic interaction. It appears to have lasted for about 10,000 years, with the last known Neanderthals dying out in what is now Spain and Portugal. I don't know how many generations that might be, but I presume that they mated earlier than we do and lived a much shorter time.
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Louisville, Ky.: Has any Neanderthal DNA been analyzed? Is there anything about the demise of this species that is predictive--or ominous--about our future?
Rick
Marc Kaufman: Yes, some analysis of Neanderthal DNA has been done, and it has generally supported the "out-of-Africa" theory of evolution -- that humans are generally speaking the descendants of hominids from east Africa. However, some researchers - like Erik Trinkaus, about whom I wrote today -- question the validity off that DNA testing because it involves a very small part of the Neanderthal genome. However, an effort to map the entire Neanderthal genome is under way in Europe, and while there are some methodological controversies involved in that effort too, it could provide some very interesting results within several years.
Regarding the demise of the Neanderthals, I did not speak to any researchers who thought their fate was predictive of ours. They were a relatively small population -- I was given an estimate of 30,000 in all of Europe by a well-respected British researcher -- and the dynamics of their fate seem to have involved different factors than what lies ahead for us.
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Stamford, Conn.: Submitting early, so I have not had a chance to read the article yet, but I have taught human evolution in introductory anthropology classes.
The hypothesis that anatomically modern humans (Homo sapiens migrating out of Africa replaced all other species about 50,000 years ago without significant interbreeding has pretty much superseded earlier hypotheses. However, it seems to me that this hypothesis still leaves some significant anatomical continuities with earlier human species unexplained, notably the "shovel-shaped incisor" trait which is common in Homo erectus in Asia (Peking Man)and in modern Asian and American Indian populations but is rare in African populations.
The anatomical continuities between Neanderthals and anatomically modern humans are more ambiguous, and there is a good deal of debate over whether variations in leg length, robustness,and other traits can be attributed to hybridization. The big nose of European populations is often cited as the best evidence for Neanderthal heritage: big noses are found among Neanderthals and among Homo sapiens in Europe, but not in other Homo sapiens populations in cold climates such as the Inuit and the native peoples of Siberia (so they are not just an example of convergent evolution, an adaptation to cold climate).
However, all the studies of Neanderthal DNA which I am aware have found that it lies outside the range of modern Homo sapiens DNA, and these studies have failed to find evidence of recent inheritance of Neanderthal DNA by Homo sapiens (i.e. within the last 50,000 years). How does your new theory account for the negative results of these earlier DNA studies?
Marc Kaufman: Thanks for your good information.
Regarding the DNA findings, scientists such as Trinkaus reply that the mitochondrial DNA that is being tested is a very small part of the genome, and that it is very difficult to obtain the DNA without contaminating it with confounding inputs from the researchers themselves.
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Raleigh, N.C.: Almost everything I know, or "know," about this comes from The Neanderthal Enigma, a book I've read twice. Related to that book, my belief after reading that book was that Neanderthal genes were gone. Am I correct in deducing that the new findings contradict my reading of that book?
Second, were the offspring fertile themselves? The sentence about 10-20 percent of genetic material being from Neanderthals would be hard to explain withOUT the offspring being able to reproduce.
Finally, if they could reproduce, it seems to me, logically, that it's almost impossible for Neanderthal genes to have died out completely because there would have to have been so many "carriers." What is your response?
Marc Kaufman: According to Erik Trinkaus, there are a small number of people in Europe/America who have some of the distinct attributes of Neanderthal morphology -- related to jawbones, shoulders, etc. This does not mean that these people necessarily have more or less Neanderthal in them, but it certainly suggests that Neanderthal genes remain in the gene pool.
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Detroit, Mich.: How different were Neanderthals from humans that lived at the same time period? (That is what is known about possible differences in intelligence, habits, way of life?)
Marc Kaufman: This remains something of a black box in evolutionary knowledge, and the fossil record so far is limited. But based on what is available, there is something of a consensus that Neanderthals and modern humans had craniums of roughly the same size -- suggesting that they could have similar levels of intelligence. But we don't know what brain systems and chemistry the two groups might have had that could have separated them more substantially.
According to Chris Stringer at the Natural History Museum in London, evidence exists to suggest that the modern humans were more adept at creating and adapting to new technologies, tools, and ways of organizing themselves socially. Indeed, there appears to be some agreement on the issue of the modern humans -- called by some Cro-Magnons - did have more sophisticated social and perhaps language skills.
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Washington, D.C.: Mr Kaufman, I very much enjoyed reading your piece on admixture hypotheses this morning, but I am confused about the disconnect between the headline and the article. Why are Neanderthals only kindred spirits to "Modern Men"? You article is very clear that you mean "modern humans" -- have you been the victim of a sloppy headline writer? Keira
Marc Kaufman: I certainly would have preferred "Modern humans" in the headline. Sometimes the words "modern man" are used in the same gender-neutral way as "mankind," but I can see why some would consider that inaccurate.
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FtL, FL: The Basque language is unique, unrelated to any other; Etruscan is similarly mysterious. It is believed the Neanderthals last refuges were in the Iberian peninsula. (why not the Italian peninsula also?)
Not so wild speculation: Any possible connection between either and Neanderthal speech? Could either population be relatively more closely related to the Neanderthals, than other Europeans? A Neanderthal fan
Marc Kaufman: Interesting thoughts. I know that with the Basques, there has been considerable speculation about their possible connection to Neanderthals. Under Basque myth, their origins come from the "basajaun", who were stocky people who lived in the forests of the Iberian Pyrenees. They are believed to have come into being around the time that the modern humans began moving into Europe. Could they be an admixure of Neanderthals. Possible, but no real strong evidnece so far.
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Federal Way, Wash.: There is now a controversial body of theory that the high incidence of autism and Asperger's Syndrome among northern Europeans is attributable to the intermingling of Neanderthal genes. According to the theory, these conditions were adaptive for Neanderthals, even though they no longer are. It probably can never be proved, but there is strong circumstantial evidence. See http://www.rdos.net/eng/asperger.htm
Do you find this theory convincing?
Marc Kaufman: I don't feel well enough informed to have an opinion on the theory, but it certainly is interesting. In my story, I write about some research from Bruce Lahn at Univ. of Chicago in which he finds a posits that a gene related to cognitive development came into the modern human genome from the Neanderthals. Unclear how that gene effects the brain -- expect that when it is damaged a child may be born with microcephaly (a small head and impaired nervous system.)
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Andersonville, Tenn.: So calling certain people Neanderthals may not be entirely irrelevant or prejudicially pejorative?
Marc Kaufman: Correct on both counts, though the amount of Neanderthal DNA we may have is probably small -- with many features having been lost over the centuries.
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Annapolis, Md.: Could a large part of the idea of different sub-species and being so different as to inhibit mating between Neanderthal and modern man be the result of the pictoral representations which showed Neanderthal as brutish and ape-like while modern man was fully upright and "clean cut"?
Marc Kaufman: Yes indeed. The image of the brutish Neanderthal comes from mid-19th century paleontology and archeology, and has never really caught up with the emerging scientific evidence that they were not so different from our more modern ancestors. Trinkaus of Washington University told me that if you cleaned up both an early human and early Neanderthal child, they would both fit into a play group with similar results.
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Washington, D.C.: If Neanderthals and modern humans could reproduce together, then why are they considered separate species? Why wouldn't Neanderthal be considered a race of humans with distinctive physical characteristics? For example, we all know that skulls of Europeans will show narrower nose structures than skulls of Africans and Asians, but all these racial groups are still of the same species of human. Since Neanderthals could breed with modern humans, were Neanderthals just a race of humans?
Marc Kaufman: I believe that terms such as species and race are inexact, or unresolved, when it comes to humans. Both Neanderthals and the African modern stock are both considered "humans," I'm told, and both come from the evolutionary tree of "hominids." I have seen references to Neanderthals as a species of "Homo" and a subspecies--one that split from the "Homo" family 500,000 to one millions years ago--but never as a race.
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Seattle, Wash.: There has been recent speculation that Neanderthals may not have been "naked apes" but might still have had extensive hair/fur. (In part, because genetic studies suggest that the human clothes louse is only 40,000 years old, i.e., that humans wore no clothes before that.) How does this affect the conclusion?
Marc Kaufman: I wasn't aware of that research, but it certainly is interesting. I wonder if that means the modern humans from Africa had similar, full-body coiffures.
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Jacksonville, Fla.: Dear Mr. Kaufman, I pasted below a short abstract of a Scientific American article I read a few years ago that really got me thinking, considering the history of human wars and the otherwise inexplicable past four years of U.S. folly in the Middle East: Did cromagnon simply wipe out our cousins, the other hominids, for the same reason men climb mountains, because they were there, or because they could? In your article on the subject of whether early hominids and cromagnons interbred to share genetic material, Trinkaus's alternative / complementary theory of what happened to the hominid "cousins" is that cromagnon's more "evolved social structure" and greater "ability to develop new technologies" allowed cromagnon to outcompete other homonids for the same ecological niche. Earlier hominids were therefore relentlessly outclassed and disappeared. After reading Ian Tattersall's piece I continue to wonder if "evolved social structure" doesn't mean an ability to delude ourselves into following a leader, or even a myth of a leader (god figure), into prehistoric genocide. And, of course, "superior use of technology" can easily mean cromagnons outclassed the doomed cousins in superior weaponry.
So, the idea that cromagnons peacefully interbred, making love not war, is appealing, although I am not sure so realistic as raping, pillaging, and wiping out several species of earlier man in the time they all shared Europe.
"Once We Were Not Alone; The Human Odyssey" Exclusive Online Issues; by Ian Tattersall; 8 Page(s)
"Homo sapiens has had the earth to itself for the past 25,000 years or so, free and clear of competition from other members of the hominid family. This period has evidently been long enough for us to have developed a profound feeling that being alone in the world is an entirely natural and appropriate state of affairs.
"So natural and appropriate, indeed, that during the 1950s and 1960s a school of thought emerged that claimed, in essence, that only one species of hominid could have existed at a time because there was simply no ecological space on the planet for more than one culturebearing species. The "single-species hypothesis" was never very convincing-even in terms of the rather sparse hominid fossil record of 40 years ago. But the implicit scenario of the slow, singleminded transformation of the bent and benighted ancestral hominid into the graceful and gifted modern H. sapiens proved powerfully seductive-as fables of frogs becoming princes always are."
Marc Kaufman: Thanks for your thoughts and information. I asked several researchers about the issue of war and violence, and whether the Neanderthals could have been wiped out by the newcomers that way. Trinkaus said there is no evidence of that happening, and Springer said it seemed unlikely because the populations were so small -- perhaps 30,000 Neanderthals in Europe 40,0000 years ago, and maybe 30,000 modern humans by 30,000 years ago, at which point the Neanderthal population was almost gone. His point was that with so much space and so few early humans, the pressures that lead to conflict may have been low. But this remains a largely unanswered question.
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Silver Spring, Md.: Hi Mr. Kaufman - I enjoyed reading your article this morning and wanted to mention something you didn't really address. As I understand it, (based on having spoken to geneticists myself) an animal species is only considered a true, separate species if it has been apart from the original stock for more than 3 million years.
I don't think there is any evidence that Neanderthals had been separate (no interbreeding) from others of the genus Homo for even 1 million years. Besides the fact that if two 'species' can successfully interbreed and produce viable offspring - they are not separate species, but rather sub-species.
Given that - and the intriguing new genetic evidence emerging that suggest some ancient Europeans possessed both neanderthalensis and sapiens traits in their skeletons (if not their genes), this would strongly indicate that Neanderthals were not a separate species from sapiens, but rather a 'cold weather' adapted subspecies, which was reabsorbed into the sapiens gene pool when 'modern' humans ventured north from Africa.
How come paleoanthropologists haven't acknowledged this? It's basic genetics. (Then again, if we were to classify H. sapiens the way we do other animal species, we would be a subspecies of chimp!)
I remember that Eskimo were found to have rudimentary saggital crests before contact with Europeans - a trait that subsequently disappeared when their diet became softer - I think we should think carefully about how physical characteristics can quickly change - sometimes in a few generations - when the environment demands. That Europeans today are ill-equipped for cold may not be because they don't have Neanderthal genes, but because they developed efficient clothing and shelters to keep out the cold. Certainly their skins turned pale for the northern sun.
Besides - have you been to the beach during the summer recently? I have seen many Neanderthal traits expressed quite dramatically there Cheers, John
Marc Kaufman: I refer to an earlier question and reply regarding the vagueness of definitions of species and subspecies. But clearly the Neanderthals and modern humans at one point were part of the same evolutionary tree -- those chimps you refer to. They did separate at some point and I guess whether they became species or subspecies is a question of our interpretation.
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Washington, D.C.: If modern humans were so smart that they could form social structures and communication skills to out-compete the Neanderthals 30,000 years ago, then why did it take another 25,000 years before they learned how to read and write?
Marc Kaufman: I dont have a full answer to this question, but I suspect it has to do with the evolving size of the brain, the increasingly complexity of social environments and the growth of the population. That researchers estimate there were maybe 30,000 humans in Europe 30,000 years ago certainly suggests that they were a fairly isolated bunch.
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Washington, D.C.: What impact will this new research have on the auto insurance advertising industry?
Marc Kaufman: I believe an apology and formal correction is in order.
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Annapolis, Md.: In response to the question about body hair, I wouldn't be surprised to learn that Neanderthals were hairier than the immigrants from Africa. It would have been a selective trait from all the years in such a cold climate.
Marc Kaufman: Definitely so. But one question that still puzzles me is why Neanderthals, who had lived through so many changes in European climate and at times had to adapt to extreme cold, were displaced by southern people who had little experience with cold and perhaps less body hair. It suggests that strong forces were at work to either add other advantages to the southern newcomers or to diminish the competitiveness of the Neanderthals.
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Falls Church, Va.: So what did the modern "out-of-Africa" humans have that enabled them to eventually replace all other hominid groups within the past 100 to 200 thousand years (especially given the great climatic differences between Africa and Europe and Asia)?
Marc Kaufman: I just ruminated on part of your question in the most recent reply, but I would add that researchers often speak of a greater ability to adapt, to create and to form social organizations among the modern humans.
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Tuscon, Ariz.: Are Neanderthals the only so-called species that may have interbred with humans, or is it possible that we are a genetic admixture of cognitive abilities going back longer in time rather than the pure strain we've always assumed ourselves to be? And do human genes, shared or otherwise, prepare us for survival or extinction? Peter F
Marc Kaufman: I have read some work suggesting that the early humans (or proto-humans) of Africa migrated to the East well before they reached Europe, and may have mixed with indigenous people in India, China, Australia. The literature on these migrations appears to be limited, and the migrations themselves on a much smaller scale, but the same kind of mixing would seem to be possible/likely.
Regarding yr second question, the fact that humans have bred so successfully and totally taken over the world, I would say that the human gene pool has been extremely well suited for survival....so far.
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Annapolis, Md.: But didn't the migration from Africa take place as the climate was changing?
Marc Kaufman: I was told that the period of 30,000 to 40,000 years ago was indeed one of sometimes dramatic climate change in Europe and Eurasia. I am less familiar with what climate changes may have been taking place in Africa.
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Washington, D.C.: Dear Sir: You stated that the "analysis of modern humans' DNA" results appears to "points to a common East African male ancestor from about 100,000 years ago and a common East African female from 170,000 years ago." How can it be possible to draw conclusions from genetic material that is not available to test? Are we drawing genetic conclusions based on the modern-day African chimp and why?
Marc Kaufman: As I understand it, these DNA results come from DNA remnants in fossil samples that have been dated by other means.
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Norfolk, Va.: Could Neanderthals have been wiped out due to disease? For example, Europeans brought smallpox and other diseases to the New World which the native population had no resistance. The native populations were decimated within a few years of the European arrival.
Marc Kaufman: Certainly a possibility, though I believe there is no specific evidence of it. What Trinkaus and others propose is that Neanderthals may have to some extent been absorbed into the modern human group -- which is how and why they may live on.
Thank you all for your informed and interesting questions. I regret that I wasnt able to answer all the questions, but maybe next time...
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