neanderthalhomo sapiens hybrid essay

Implications of Neanderthal-Homo Sapiens Hybrid from the Abrigo do Lagar Velho (Portugal)

In a recent excavation at Abrigo do Lagar Velho in Portugal, Duarte et al (1999) unearthed what was later to be recognized as early human skeletal remains which pointed to interbreeding between Neanderthal and Modern Humans during the mid – upper Palaeolithic transition. The morphology of the remains, belonging to a child of approximately 3-4 years old, indicates a Neanderthal typology in post-cranial features, and more modern cranial features. The find has been cited as evidence of hybridization between the two traditionally separate human lines, and offers an explanation to the question of Neanderthal extinction. (Trinkaus 1999) Anthropologists are now offered a line of evidence pointing to the contemopranity of Moderns and Neanderthals in parts of Europe and assumptions can be made about their contact:

“The discoverers…are making a ground-breaking claim, that the skeleton shows traces of both Neanderthal and modern human ancestry, evidence that modern humans did not simply extinguish the Neanderthals, as many researchers had come to think. Instead the two kinds of human were so alike that in Portugal, at least, they intermingled…for thousands of years.” (Kunzig, 1999)

By examining the theories of human evolution, and looking at the cultural evolution of tool technology as well as the biological transitions and differences between the two types of humans, we can see that this hybridization just might be the answer. Perhaps this find will be able to tell us what exactly did happen to the Neanderthals.

Firstly, it is useful to have an overview of the different theories of human evolution, or I should say the two most widely accepted views as accepted by palaeo-anthropologists in the field. For some years now it has been the contention that the origins of modern humans stem from either a continuous evolution from archaic to modern humans in local regions from an earlier dispersal of Homo erectus, or conversely from modern humans evolved in Africa only which then dispersed to replace those hominids in said regions. These two theories are known as the Continuity or Regional model and the Replacement or Out of Africa model respectively. The fossil (skeletal) and cultural (technological) evidence thus far has pointed to convincing arguments on both sides, which proponents are quick to defend.

Neanderthals can be distinguished from anatomically Modern Humans by the presence of prominent brow ridges, low forehead, occipital bun, facial prognathicism, large nasal aperture, and shorter, sturdier skeletal features most notably, distinguishing them from Moderns who were taller and had longer limbs, higher foreheads, lass prominent browridges and rounder skulls. It should be noted that the cranial capacities of both were comparable, with the Neanderthals being even slightly larger. (Klein: 1989)

Many proponents of a regional theory claim that such morphological differences show a continuity and depending on how they are viewed can be seen as evidence of variation within a species, not distinct species. This would mean that the Neanderthal morphology developed as an adaptation to the colder glacial climate of Europe and elsewhere. (Wolpoff:1980) From a replacement standpoint however, these differences in morphology are too distinct to be variables on a theme and in conjunction with dates provides evidence supporting that view. (Mellars and Stringer:1989)

Neanderthals occupied Europe and the Middle East during a time range usually agreed upon as ranging from roughly 130 kya – 35 kya to as recent as approx. 26kya. Modern populations are seen as early as 100kya in the Middle East and around 40 kya in Europe.

At some sites in the middle east, both populations lived in very close proximity to one another for what is thought to be a time range of about 40 000 years. (Akazawa et al:1998)

Recent developments in genetic studies have begun to open new lines of evidence in the relatedness of Neanderthals to current modern human populations. By studying the genes of both, we can compare the similarities and differences and calculate whether the two are close enough to say there is a relation or not. This line of research had been theory mostly because the skeletal remains on record had no organic material available from which to extract genetic material (i.e.: collagen in the bone). DNA from a Neanderthal specimen would be able to confer or oppose the ” Mitochondrial Eve” theory put forth by Cann et al in 1987 (Foley and Lahr 1992: 526; Klein 1989:352) which stated that the common ancestor for modern human populations could be traced to approx. 200kya in Africa. When DNA was finally extracted from a Neanderthal specimen, this could be addressed. The DNA in question, retrieved from the original Neanderthal find from Neander Valley, is mitochondrial. Mitochondria have their own DNA outside of the nucleus and are inherited only through the mother. Unlike nuclear DNA, mitochondrial DNA (mtDNA) does not recombine with reproduction. The variation that exists between two mtDNA sequences is instead solely the result of mutation. Because mutations are thought to occur at a set rate, the amount of time that has passed since two mtDNA sequences diverged can be calculated). Researchers can then trace the lineage of that gene, and find how old it is, or rather how far back that particular gene goes. The results from the Neanderthal mtDNA show an ancestor which goes back much farther in time in Africa, and would seem to refute any connection with Modern populations after that time. There are some flaws with the mtDNA studies though and further research is needed. Other lines of genetic research include R.M. Harding’s studies which look at variation in the betaglobin gene Harding found that one major betaglobin gene lineage, thought to have arisen more than 200,000 years ago, is widely distributed in Asia but rare in Africa, suggesting that archaic populations in Asia contributed to the modern gene pool. Studies of the Y-chromosome by M.F. Hammer, indicate migrations back and forth into Africa. (Harris and Hey 1999:84)

In a nutshell, the technological differences between Neanderthal middle Palaeolithic technology and the Modern upper Palaeolithic technology can be narrowed down to flake and blade technologies. The transition between the two can be viewed again as either gradual or sudden. Some middle Palaeolithic tools in Europe, the Middle East and Africa, regardless of the hominids associated with them can show a variety of technologies. Certainly, at about 30 000 years ago, there was a shift in technologies to include art and personal adornment along with the finer micro-blade technologies. However, it is debatable as to whether these features were practiced by preceding Neanderthals or whether these innovations were brought into Europe by Moderns who would replace them. (Thorne and Wolpoff:1992)

The question of the transition from the middle to upper Palaeolithic surrounds whether or not the transition was gradual or sudden. Evidence of burials within Neanderthal populations indicates that such cultural indicators were derived from those populations by other successive modern populations.

The remains discovered by Duarte et al at Abrigo do Lagar Velho in Portugal “present a mosaic of European early modern human and Neanderthal features” according to Erik Trinkaus (1999). It is this blending of features that implies interbreeding between the two. It could be that the replacement model is somewhat supported in that it was the hybrid which gradually replaced pure Neanderthals, or that the regional model is somewhat supported in that the Neanderthals, or rather their descendants, indeed became fully modern. The translation of this evidence depends on who is looking at it, and what view they support in the first place. This brings up the issue of bias in the field and indicates that the study by its nature cannot be exact and is certainly open to interpretation.

It is apparent that there can be no consensus as yet to the fate of the Neanderthals. Arguments on both sides can be quite compelling, but perhaps the most compelling is that of the third hypothesis, the middle ground, being that there needs to be further investigation into the possibility of hybridization between Neanderthal and Modern populations. Erik Trinkaus, staking his reputation on the claim, has lent his support to this hypothesis: “If you have two populations of hunter-gatherers that are totally different species, that are doing things in very different ways, have different capabilities–they’re not going to blend together,” Trinkaus says. “They’re going to remain separate. So the implication from Portugal is that when these people met, they viewed each other as

people. One group may have looked a little funny to the other one–but beyond that they saw each other as human beings. And treated each other as such.” (Kunzig 1999)

Evidence which could be used to corroborate such a theory include further DNA research, including both mitochondrial and nuclear extractions if possible. Obviously one sample from a single specimen is not enough to base a clear argument on. Perhaps with more research, the archaeological record will be corroborated by the biological record, and show that indeed the transition from mid to upper Palaeolithic was gradual and due to the interbreeding of two types of humans, which replaced the local population from which much of the technology was derived. Further excavations which produce similar remains as that of Abrigo do Lagar Velho may also show increasing evidence of hybridization. Only by seeking to expand the fossil record, and exacting reliable dates will we be able to tell the whole story of human evolution, for which the Neanderthal question is but a small part. By answering this question though, we can piece together the real story of our origins and begin to understand the whole picture of hominid evolution.

References:

Bower, B.

1993 Neanderthals take a big step back in time. Science News 143(15):228-230.

Flanagan, Ruth.

1996 Out of Africa. Earth.5(1): 26-35.

Harris, E.E. and J. Hey
1999Human demography in the Pleistocene: Do mitochondrial and nuclear genes tell the same story? Evolutionary Anthropology 8(3): 81-86.

Klein, Richard G.

1989 The Human Career. Chicago: University of Chicago Press.

1992 The archaeology of modern human origins. Evolutionary Anthropology 1(1): 5-14.

1998Why anatomically modern people did not disperse from Africa 100,000 years ago. In Takera Akazawa, Kenichi Aoki and Ofer Bar-Yosef, editors, Neanderthals and Modern Humans in Western Asia, New York,: Plenum Press, pp. 509-521.

Kunzig, Robert.

1999 Learning to love Neanderthals. Discover 20(8): 68-75.

Leitzes, Nicholas
1994 Brutes or brothers? Earthwatch: The Journal of Earthwatch Institute 15(3): 22-26.

Mellars, Paul
1995 Neanderthals in perspective. Antiquity 68(260): 656-658.

Rouhani, Shahin.

1989Molecular genetics and the pattern of human evolution: Plausible and implausible models. In P. Mellars and C. Stringer, editors, The Human Revolution. Princeton: Princeton University Press, pp. 47-61.

Shreeve, James.

1994 Phenomena: Comments and notes. Smithsonian 25(6): 7-9.

Stoneking, Mark and Rebecca L. Cann.

1989 African origin of human mitochondrial DNA. In P. Mellars and C. Stringer, editors, The Human Revolution. Princeton: Princeton University Press, pp. 17-30.

Stringer, C.B.

1989Documenting the origin of modern humans. In Erik Trinkaus, editor, The Emergence of Modern Humans: Biocultural adaptations in the later Pleistocene. Cambridge: Cambridge University Press, pp. 67-96.

1998Chronological and biogeographical perspectives on later human evolution. In Takera Akazawa, Kenichi Aoki and Ofer Bar-Yosef, edotors, Neanderthals and Modern Humans in Western Asia, New York,: Plenum Press, pp. 29-37.

Stringer, C.B., J.J. Hublin, and B. Vandermeersch.

1984 The origin of anatomically modern humans in Western Europe. In Fred H. Smith and Frank Spencer, editors, The Origins of Modern Humans: A World Survey if the Fossil Evidence. New York: Alan R. Liss, Inc., pp. 51-135.

Tattersal, Ian and Jeffrey H. Schwartz.

1999Hominids and hybrids: The place of Neanderthals in human evolution. Proceedings of the National Academy of Sciences. 96(13): 7117-7119.

Thorne, A.G. and M.H. Wolpoff
1992 The multiregional evolution of humans. Scientific American 266(4):76-83.

Trinkaus, Eric
1989 Issues concerning human emergence in the later Pleistocene. In Erik Trinkaus, editor, The Emergence of Modern Humans: Biocultural adaptations in the later Pleistocene. Cambridge: Cambridge University Press, pp. 1-17.

1999The early Upper Paleolithic human skeleton from the Abrigo do
Lagar Velho (Portugal) and modern human emergence in Iberia. Proceedings of the National Academy of Sciences. 96(13): 7604-7609.

1999Direct radiocarbon dates for Vindija G1 and Velika Peina Late Pleistocene hominid remains. Proceedings of the National Academy of Sciences. 96(22): 12281-12286.

Wilson, A.C. and R.L. Cann
1992 The recent African genesis of humans. Scientific American 266(4): 68-73.

Wolpoff, Milford H.

1980 Palaeoanthropology. New York: Alfred A. Knopf.

1989 The place of Neanderthals in human evolution. In Erik Trinkaus, editor, The Emergence of Modern Humans: Biocultural adaptations in the later Pleistocene. Cambridge: Cambridge University Press, pp. 97-141.

Also see:
http://www.anatomy.usyd.edu.au/danny/anthropology/sci.anthropology.paleo/archive/september-1995/0106.html

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