Neanderthals: Behaviorally, Genetically, and Physiologically Humbling

There is a lot of debate concerning the place of Neanderthals in human phylogeny. Researchers believe that Neanderthals could have been either a different species, Homo neandertalensis, or a subspecies of Homo sapiens, Homo sapiens neandertalensis. The more that is illuminated about Neanderthals, the more complex the controversy becomes. Behavioral, genetic, and physiological evidence indicates that Neanderthals were a subspecies of Homo sapiens. The analysis of Neanderthal remains declare that they were a subspecies of Homo sapiens, Homo sapiens neandertalensis, and that a prejudice of exceptionalism does not belong in human evolution.

Behaviorally, Neanderthals are fairly advanced and have many attributes similar to contemporaneous Homo sapiens sapiens, with the differences due to environmental factors. The material culture suggests the similar level of cognitive ability between Neanderthals and H. sapiens sapiens. The most common Neanderthal tool, the Levallois flake, had symmetry and could be sharpened. Neanderthals required precision to make this versatile toolkit (Lewman 9:00-11:00). This toolkit also implies planning and abstract thinking, as the materials to make this tool originated far away from the site (Churchill 56-58). Neanderthals also used a birch bark-derived glue substance to attach stones to wooden shafts to make spears to increase the effectiveness and safety of hunting. The process involved in making this pitch involved a complex heat treatment of the bark (Lewman 12:00-17:00). Beyond the wide array of tools that the Neanderthals used, the Mousterian toolkit suggests that language may have been essential to be able to teach offspring how to reproduce these precise tools (Cho). This technological advancement distinguishes Neanderthals from other Archaic Homo species and supports the idea that their cognitive complexity is on the same level as Homo sapiens. Neanderthal material culture indicates that modern Homo sapiens sapiens had equals in our evolutionary history. These tools show Neanderthals close similarities, but evidence of symbolism and social behavior also supports the idea of Neanderthals as a subspecies of Homo sapiens because it resembles the complexity of modern H. sapiens sapiens.

Neanderthals and H. sapiens sapiens occupied territories with different available resources. Early H. sapiens sapiens adapted to their resource-deficient environment by occupying larger home ranges in larger populations with sexual division of labor, while Neanderthals adapted to their resource-rich environment by migrating around smaller home ranges as entire, though less dense, populations (Finlayson 116-118). This may appear to distinguish Neanderthals from H. sapiens, but the cohesion species concept (CSC) considers different criteria than the manifestation of social organization to be important to speciation. This speciation concept says two populations of the same species “should be ecologically interchangeable” (Jolly 194). While Neanderthals cannot be tested in the environmental conditions from which H. sapiens sapiens emerged, H. sapiens sapiens did adapt to the environment of the Neanderthals. The survival of H. sapiens sapiens in Neanderthal habitats suggests, according to the CSC, that they are of the same species, and capacities for symbolism and language also suggest that Neanderthals and H. sapiens sapiens are not so different.

The capacity to communicate and the use of symbolism in Neanderthal material culture suggest that Neanderthals were a subspecies of Homo sapiens. Language originates in H. sapiens from the gene, FOXP2, and Neanderthals have the same FOXP2 gene sequence as modern H. sapiens (Lewman 26:00). There is no way of knowing if Neanderthals had the brain structures and all soft tissue characteristics that anatomically modern Homo sapiens (AMHS) possess that give H. sapiens sapiens our language complexity, but it is significant that they had the genetic capability of speech, as well as a similar hyoid bone for tongue muscle attachment and basicranial flexion that would lower the larynx and pharynx, both of which are necessary for the particular human form of communication (Cho). Neanderthal social organization did not necessitate communication as much as the larger groups of early H. sapiens sapiens, but Neanderthals needed communication to pass on their material culture and possessed the genetic code, and some of the bone structures, necessary for language. H. sapiens sapiens may have not been alone in the animal kingdom as the species to use language and act in more sophisticated behavioral patterns, thus suggesting that human exceptionalism does not apply to human evolutionary history.

Additionally, symbolic behaviors similar to H. sapiens sapiens have been associated with Neanderthals. Neanderthals used Manganese Dioxide as a material with which to draw images and hematite to adorn shells they wore (Lewman 33:00-36:00). There is also a case for acknowledgement of the dead from Neanderthal remains uncovered in a rock fall. There were panther paws nearby with no signs of predation on the Neanderthal remains. These remains are argued to have been deposited with the panther paws as funeral offerings and then buried under rocks (39:00-40:00). These symbolic behaviors were reserved for H. sapiens sapiens, and now suggests that Neanderthals were no different than modern humans in behavioral aptitude and complexity; it was simply the environments that affected the social organizations that distinguishes them in the paleoanthropological record. H. sapiens sapiens adapted to the Neanderthal biomes and therefore fulfill the CSC, although there is no testing the reciprocal and no evidence to suggest the reciprocal is true. There are other speciation concepts that focus on the genetic and phylogenic remains which can shed more light on Homo sapiens neanderthalensis.

Physical remains provide similarities and differences between Neanderthals and H. sapiens sapiens, and gene flow and selective pressures on physiology suggest that Neanderthals are a subspecies of Homo sapiens. One speciation concept that deals with the physical remains is the biological species concept (BSC), which states that species are differentiated in terms of their ability to produce reproductively viable offspring (Jolly 193). Dr. Svante Pääbo sequenced the Neanderthal genome, while other researchers investigated specific variations between the Neanderthal genome and the AMHS genome. Pääbo’s conclusion was that the disparity in shared nuclear DNA with Neanderthals between humans of Eurasian origins over humans of African origin would have been impossible if Neanderthals and AMHS were reproductively isolated (Lewman 29:00-31:00). While the percentage of similar nuclear DNA is small, 1%-4%, and the interbreeding events necessary to bring about such a percentage fall into a low, broad range, 197-430 events, it does not mean that these interbreeding instances did not occur and are not significant (Currat and Excoffier 15132). Each event could have been the key to the inheritance of the immunity genes to H. sapiens sapiens which helped them to survive pathogens as they expanded into the Neanderthals territories (Lewman 49:00-50:00).

Inspecting mitochondrial DNA (mtDNA), the DNA of mitochondria in the body’s cells passed matrilineally, from mother to offspring, Dr. Churchill of Duke University has concluded that Neanderthal sequences are not within the limits of AMHS mtDNA variation (Churchill 27). Those who see Neanderthals as a separate species in the genus Homo, use this evidence to claim that interbreeding did not occur, but they overlook the possibility that interbreeding could have occurred solely between Neanderthal males and H. sapiens sapiens females. This could account for the mtDNA deviation and allows for interbreeding to have occurred for us to share 1%-4% of our nuclear DNA with Neanderthals. Dr. Sankararaman’s findings on the X chromosome sequences of Neanderthals and AMHS advances this hypothesis, in that Neanderthal sequences, when translated in hybrids, would have caused male sterility (Sankararaman). The male-Neanderthal, female-H. sapiens sapiens interbreeding hypothesis explains why the X chromosome differs between Neanderthals and AMHS, because if only male Neanderthals and female early H. sapiens sapiens could interbreed, then the Neanderthal X chromosome sequence could have only been passed on to the hybrid females. The second generation after hybridization had a 25% maximum chance of producing sterile males through female hybrids, because the chance of producing a male is 50% and the chance of the female hybrid passing on the Neanderthal X chromosome is 50%. This hypothesis represents the opportunities for gene flow from Neanderthal populations to AMHS, declaring Neanderthals to be a subspecies of Homo sapiens in the BSC. To reason that they are Homo sapiens neandertalensis under the phylogenic species concept (PSC), scrutiny must turn to comparisons of teeth and dentition.

Morphologically, Neanderthals and AMHS can be perceived as different species, but it can also be considered that Neanderthals are just one extreme of the spectrum of human variation. The phylogenic species concept stresses the consistency of identifiable, physiological or developmental traits across a species (Jolly 193). Because teeth are preserved in the best condition over time, dentition is crucial to morphological comparisons. In comparisons of long-line periodicity, the “number of daily increments between successive long-period lines” on teeth between Neanderthals, early H. sapiens sapiens, and AMHS show that Neanderthals, with a periodicity of 7.4 days, had a shorter periodicity than H. sapiens sapiens contemporaneous with Neanderthals, 8.0 days, who in turn had shorter a periodicity than AMHS, 8.3 days (Smith, Tafforeau and Reid 20924-5). There is a trend in the lengthening of long-line periodicities over time. The .3 difference between AMHS and early H. sapiens sapiens gives an idea of how much the long-line periodicity lengthens over the span of time of 30,000 years between the disappearance of H. sapiens neandertalensis and today. Given that early H. sapiens sapiens arose in Africa 100,000 years ago, and that Neanderthals left Africa 800,000 years ago, the .6 difference in long-line periodicity could have been a primitive H. sapiens trait from which H. sapiens sapiens diverged that Neanderthals did not due to the geographical isolation of the populations and the chance mutations affecting those developmental genes (Lewman 42:00). The latitude selective pressures have on the distinctions between Neanderthals and early H. sapiens sapiens can settle many of the morphological disparities between these two subspecies, including that of molar formation.

Ontogenetic patterns of molars show that Neanderthals are an extreme variation of Homo sapiens molded by natural selection. M1 molar crowns fully form on average at three years of age in AMHS, while in Neanderthals, they are said to have completed formation about six months earlier. Neanderthal juvenile remains indicate that M3 formation began at 5.9 years of age, two to four years earlier than the average AMHS. However, in the harsh climates of the regions above the tropic of

Cancer in the Late Pleistocene, Neanderthal young adult mortality was high. Natural selection favored those individuals whose teeth developed earlier, sooner than was necessary in sub-Saharan Africa for early H. sapiens sapiens, where the young adult mortality was not as high (Smith, Tafforeau and Reid 20925-6). Neanderthals’ adaptation to the cold climates of Europe and Asia during the Late Pleistocene explain these ontogenetic differences in dentition as a polarization of H. sapiens characteristics favored by natural selection. The PSC involves drastic, definitive analysis of morphological features over an entire species. The long-line periodicity and the age of molar formation have changed between early H. sapiens sapiens and AMHS. These morphological traits have not been consistent enough to state that Neanderthals are not a subspecies of the Homo sapiens species, and this inconsistency is a root of the case for a more complex, humbling evolutionary history for humans.

The differences between H. sapiens sapiens and Neanderthals in exhibited social organizations do not imply that they are a different species under the CSC. The criterion instead is the ability of one population of H. sapiens to inhabit the territory of another population, which H. sapiens sapiens fulfilled. Just because Homo sapiens sapiens behave differently does not make us different from Neanderthals. Genetic evidence defines them as a subspecies under the BSC because they managed to interbreed, even if it was admittedly minimal. No evidence has accumulated that distinguishes Neanderthals as a separate species in the genus Homo according to the PSC. Neanderthals’ being H. sapiens neandertalensis suggests that their extinction would have been as critical as the extinction of “Anubis baboons”, one subspecies of many in Africa with its distinct genetic variations, to the genus Papio (Jolly 197). Looking at their extinction as the end of a line of genes that were compatible with modern ones, Dr. Clive Finlayson has considered there to be effects of their extinction on the individual as well as at the population level for H. sapiens as an entire species (Finlayson 90). Neanderthals as a subspecies add a little more humility to the history of human variation, in that H. sapiens sapiens are not the only beings to have ever existed with the broad capabilities often attributed solely to humankind, because other humans existed that affected AMHS but were slightly different, and they are called Homo sapiens neandertalensis.

 

Works Cited

Cho, Helen. “Humankind Evolving.” Davidson College, Davidson, NC. 11-16 Nov. 2015. Lecture.

Churchill, Steven E. Thin on the Ground: Neandertal Biology, Archeology, and Ecology. Ed. Matt Cartmill and Kaye Brown. New York: John Wiley & Sons, Inc., 2014. Print.

Currat, Mathias and Laurent Excoffier. “Strong Reproductive Isolation between Humans and Neanderthals inferred from Observed Patterns of Introgression.” Proceedings of the National Academy of Sciences of the United States of America 13 September 2011: 15129-15134. Jstor. Web. 2 Nov. 2015

Decoding Neanderthals. Dir. Nick C. Powell. Perf. Lance Lewman. Prods. Johanna Woolford Gibbon and Ben Harding. PBS, 2013. Film.

Finlayson, Clive. Neanderthals and Modern Humans: an Ecological and Evolutionary Perspective. Ed. Robert A. Foley, et al. Cambridge: Cambridge University Press, 2004. Print.

Jolly, Clifford J. “A Proper Study for Mankind: Analogies from the Papionin Monkeys and their Implications for Human Evolution.” American Jounal of Physical Anthropology 116 (2001): 193-201. Web. 2 Nov. 2015.

Neanderthal Tools. N.d. Digital Photograph. American Museum of Natural History. Web. 13 Nov.
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Sankararaman, Sriram, et. al. “The Genomic Landscape of Neanderthal Ancestry in Present-day Humans.” Nature 507.7492 (2014): 354-357. Proquest Central; Proquest Environmental Science Collection. Proquest. Web. 2 Nov. 2015

Smith, Tanya M., et al. “Dental Evidence for Ontogenetic Differences between Modern Humans and Neanderthals.” Proceedings of the National Academy of Sciences of the United States of America 107.49 (2010): 20923-20928. Jstor. Web. 2 Nov. 2015.

Tattersall, Ian, and Jeffrey H. Schwartz. “Hominids and Hybrids: The Place of Neanderthals in Human Evolution.” Proceedings of the National Academy of Sciences of the United States of America 96.13 (1999): 7117–7119. Jstor. Web. 2 Nov. 2015