The Hominid Chronicles Homo neanderthalensis

1. The Hominid ChroniclesHomo neanderthalensis Meghan Flickinger Anth 311 Dr. Smith November 2007

2. Abstract Relationship between Homo neanderthalensis and Homo sapiens and the arguments surrounding the relationship. Research included articles on growth and development, cranio-facial, and post-cranial morphology, and mitochondrial DNA (mtDNA). Images from additional research on Neandertals are included after the conclusion of the essay.

3. Introduction From the first discovery of Homo neanderthalensis, scientists (including paleoanthropologists and biologists alike) have struggled to define the species in terms of how it is related to Homo sapiens, if at all. Several claims on how Homo neanderthalensis and Homo sapiens are related. It was because of the conflicting statements between that I decided to look into what arguments scientists were making. After researching the topic I have come to the tentative conclusion that Neanderthals and humans are two distinct species, which may have interbred in some regional areas.

4. Background Neanderthals lived in Europe and Western Asia between 150kya and 30kya during the Pleistocene (Conroy 2005). It wasn�t until 1864, that the name Homo neanderthalensis was given to the species by William King (Tattersall 2002). �the Neandertal skull resembles what you might expect if someone took a human skull made of rubber, grabbed it by the face and back of the head, and pulled� (Shipman 2004) Neanderthal morphology has often been blamed on disease of some kind including rickets, and vitamin D deficiency, and dietary iron deficiency leading to cretinism. (Tattersall 2002). The problem was that Neanderthalensis was discovered before the publishing of Charles Darwin�s On the Origin of Species, and at that time there was only two explanations for a creature like neanderthalensis; that it was a diseased individual as I described, or a member of a � �brutish� and �primitive� race of humans� (Tattersall 2002).

5. Figure 9.4(d) is an excerpt from Conroy�s Reconstructing Human Origins (2005), depicting the several species from the genus Homo. Included in this is Homo habilis (small and large), as well as Homo erectus, archaic Homo sapiens, Neanderthals, and early modern Homo sapiens. The excerpt includes information on height and body type, brain size, skull form, jaws and teeth, the area that the species lived, and the time range in which is was around (2005).

6. Figure 13.9 from Conroy, depicts the differences between H. neanderthalensis and H. sapiens. Neanderthals are heavily built in their vertebra, as well as the rest of their bodies.  All bones are shorter, and thicker, including the patella (kneecap) which is wider and thicker than on modern humans (2005).

7. Figure 13.8 is another sketch from Conroy, illustrates a Neanderthal skull and a modern human�s skull. The most noticeable differences being the higher domed forehead on the human, while the Neanderthal forehead is low and flatter. The same is true for the parietal bones, which are also shorter on the Neanderthal skull. The nasal opening is much larger and wider on the Neanderthal than on the human. The shape of the particular specimen also differs slightly from the human example (2005).

8. Methods H. neanderthalensis and H. sapiens Academic Search Premier and Medline, as well as J-Store Anatomy and genetics Widened my search to include medical journals

9. Results PETTITT Neanderthals experienced a �relatively short lifecycle.� within that lifecycle individuals would experience a great deal of �trauma� related to severe physical activity. This applied to both males and females. Lack of sexual division of labor, based on the robustness of both male and female Neanderthals, while anatomically modern human females appeared to �[gracilize] relatively quickly�� (Pettitt 2000) TATTERSALL �among all extinct hominids known [Neanderthals] have regularly been singled out� to be explained as some kind of �pathology� (2002). Jerome Dobson claims that Neanderthal morphology may be caused by and iron deficiency leading to cretinism His argument basically sums up to Neanderthals looking more like humans with cretinism rather than healthy ones. Tattersall argues that despite similarities that Dobson cites to occur between cretins and Neanderthals, that cretins look distinctively like cretins, and Neanderthals look distinctively like Neanderthals.

10. Neanderthals and humans are clearly from the same kind of blueprint, so to speak, as far as basic structure goes, but are also clearly different based on mtDNA research. The researchers were studying the perikymata - a series of ridges that form on the canines and incisors during tooth development. In humans one ridge is formed every nine days during tooth development, while ridges in Neanderthals were formed in a much shorter amount of time. Neanderthals, while a younger species than antecessor and heidelbergensis, took less time to form the tooth ridges. Neanderthals matured at a rate about 15 percent faster than humans (e.g. a 15 year old Neanderthal would be fully matured, while a human would not be until age 18). (Shipman 2004)

11. Shipman explains that the different morphology between humans and Neanderthals is present from very young ages, and includes a comparative photo of crania. Figure 2 shows the very different cranial morphology between Neanderthals starting from three years of age, then in adulthood.

12. I read several articles discussing genetics, DNA and mtDNA in reference to Neanderthals and modern humans. Neanderthals are not a likely direct ancestor of modern humans. Based on a lack of mtDNA evidence in modern humans (Serre 2004; Weaver 2005). Surprisingly, there was just as much up to interpretation with mtDNA as there was with morphology. Problems with mtDNA testing; variation in testing techniques, and limited sampling. Figure 4, from David Serre, et al�s No Evidence of Neanderthal mtDNA Contribution to Early Modern Humans (2004) General type of depiction in the mtDNA articles. Figure shows three possibilities of where or when Neanderthals may have contributed to modern mtDNA.

13. A good example of how the two main models of evolution that found throughout the articles is written in the book Reconstructing Human Origins by Glenn Conroy Out of Africa model (OTA) claims that there is no genetic relationship between Neanderthals and humans; that humans completely replaced Neanderthals. Multi Regional Continuity model (MRC) claims that modern humans emerged from Neanderthals throughout Europe and Asia, with enough gene flow that the species evolved simultaneously. These are the two extremes that exist; there are other models that exist between them, one of which is the Weak Garden of Eden model. This model follows the claim that modern humans emerged within Africa, and then spread out, but also claims that some interbreeding may have occurred between some populations in some regions during different emergence events in human evolution (Conroy 2005).

14. Discussion Neanderthals had a different pattern of growth and development, as shown by Conroy, Pettitt, Shipman, and Tattersall. They grew up quickly, and lived physically strenuous lives, as shown in fossil findings. Based on the findings in the mtDNA articles my opinion is that Neanderthals and humans do not share a statistically significant amount of mtDNA to be very closely related; the data available leans more toward the OTA model than the MRC model. It seems more likely that modern humans came from Africa, and moved into Europe and Western Asia, then, once there, possibly interbred with Neanderthals to some extent. It seems most likely to me that the Neanderthals, while possibly coexisting in some areas with humans, were most likely out competed by sheer numbers of humans if not anything else. Humans may have a slower maturation rate, but had a much longer lifespan, even in the harsh conditions of the Pleistocene.

15. Summary & Conclusion People in the scientific community have long been interested in the relationship between H. sapiens and H. neanderthalensis, and have long tried to answer if and how the two species are related. This paper addressed the arguments for the two main opinions in the role of Neanderthals in human evolution. The Out of Africa model basically says that humans came from Africa and replaced Neanderthals, while the Multi Regional Continuity basically says that humans were a subpopulation of Neanderthals, and the two groups interbred with each other and between regions. Based my the research I find myself somewhere, close to the Weak Garden of Eden model; that anatomically modern humans evolved as a sub-population in Africa, and moved out across Europe and Western Asia, where they may have interbred to some degree with Neanderthals. Data on Neanderthals is definitely abundant; however, the issue lies in how that information is interpreted. As of now the data is still interpreted in ways that could support either of the two main arguments. What is needed is time to find more evidence that may help interpret the data we have and will find in the future, in a way that better answers the question of how Neanderthals influenced human evolution.

16. References Cited Conroy, Glenn C. 2005 Reconstructing Human Origins. New York, NY: W.W. Norton & Company, Incorporated Cooper, Alan, Alexei J. Drummond, Eske Willersleve 2004 Ancient DNAL: Would the Real Neandertal please Stand up? Current Biology 14:R431-R433 Hebsgaard, Martin B., Cartsen Wiuf, Thomas P. Gilbert, Henrik Glenner, Eske Willersleve 2007 Evaluating Neandertal Genetics and Phylogeny. Molecular Evolution 64:50-60 Pettitt, P.B. 2000 Neanderthal Lifecycles: Developmental and Social Phases in the Lives of the last Archaics. World Archaeology 31(3):351-366 Serre, David, Andre Langaney, Mario Chech, Maria Teschler-Nicola, Maja Paunovic, Phillippe Mennecier, Michael Hofreiter, Goran Possnert, Svante Paabo 2004 No Evidence of Neandertal mtDNA Contribution to Early Modern Humans. Plos Biology 2 (3):0313-0317 Shipman, Pat 2004 Growing Up Neandertal. American Scientist 92(6):506-509 Tattersall, Ian 2002 Commentary: Iodine and Neandertals. Geographical Review 92(1):94-97 Weaver, Timothy D., Charles C. Roseman 2005 Ancient DNA, Late Neandertal Survival, and Modern-Human-Neandertal Genetic Admixture. Current Anthropology 46(4):677-683

17. Interpretive Neanderthal Reconstruction