IntroductionThere are many debatesin the anthropological community about the disappearance of Neanderthals. Somethink that rapid global climate change was the sole cause of their demise whileothers believe that rapid global climate change along with contributing factorssuch as competition of resources and technological insufficiencies led to theirextinction. It is now known that climate change was not directly responsiblefor the extinction of Neanderthals; however, it was a contributing factor.While this may give researchers a theory to rule out, there are still manyother theories that support other reasons of Neanderthal disappearance. Acompeting model that argues against such claims is the Assimilation Modeltheory, in which researchers believe that the disappearance of Neanderthals wasnot because of complete catastrophic extinction per se, but rather a slowassimilation of the Neanderthal gene pool into the Anatomically Modern Humangene pool. The two articles that will be the subject of analysis are “The assimilationmodel, modern human origins in Europe, and the extinction of Neanderthals” byFred Smith, Ivor Jankovic, and Ivor Karavanic and “Neanderthal Extinction byCompetitive Exclusion” written by William E. Banks, Francesco d’Errico, A.
Townsend Peterson, Masa Kageyama, Adriana Sima, and Maria-FernandaSanchez-Goni. The first article is an analysis of the migration of anatomicallymodern humans and through this analysis, the authors suggests the case ofNeanderthal extinction through assimilation while the second article analyzesthe disappearance of Neanderthals through a climatic and ecologicalperspective. From this point on I will refer to both articles (Smith et al) and(Banks et al) respectively. The Assimilation modelproposed by Smith et al., suggests that Neanderthals did not go extinct in theclassical sense, but rather they were slowly assimilated into anatomicallymodern humans emerging and migrating from Africa through genetic exchange. TheCompetitive Exclusion model suggested by Banks et al., uses paleoclimaticsimulations to define eco-cultural niches associated with Neanderthals andanatomically modern humans to suggest that it was the rapid expansion ofanatomically modern humans that led to a competition of resources which in turnled to the disappearance of Neanderthals.
The purpose of this paper is toanalyze both competing models and assess which model holds more value in thecase of Neanderthal extinction. Research Methods andResults (if applicable)According to Smith etal. uses four different sets of information to assess the discuss the currentdebate about Neanderthal extinction.
First, they use the morphological andchronological information on archaeological artifacts. Analyzing information onNasion projection from the bi-fmt line and the incidence of occipitalbone, specifically the suprainiac fossa and occipital bun to compare andcontrast between Neanderthals and anatomically modern humans. The second set ofinformation is the comparison of ancient DNA to modern DNA. Mitochondrial DNAwas analyzed from four different Neanderthal fossils and was then compared tothe mtDNA of modern humans. In 1997, researchers analyzed About 378 base pairsegment of mtDNA was isolated from the right humerus from Feldhofer 1, aNeanderthal skeleton discovered in 1856 (Smith et al. 2005). The other threeNeanderthal skeletons that were analyzed was an infant from Mezmaiskaya,Russia, a specimen from level G3 at Vindija, Croatia, and another fossil fromFeldhofer, Germany (Smith et al.
2005). The third is the use of thearchaeological record spanning the late Mousterian, Initial Upper Paleolithic,and Aurignacian cultural periods of the Paleolithic. The fourth set ofinformation Smith et al. uses is the population patterns of Neanderthals and anatomicallymodern humans associated with chronometric dates in Europe and other parts ofthe western “Old World.” Morphologicalsimilarities of the occipital buns between early anatomically modern humans andNeanderthals may be evidence of morphologically continuous traits of latePleistocene Europeans (Smith et al., 2005). Looking at the data in Table 2.
, wecan see the percentage of found individuals that feature the the Occipital bun.About eighty percent of European Neanderthals were found with the occipital bunfeature while sixty-eight percent of early upper paleolithic anatomicallymodern humans excavated had this feature. Smith et al.
believes that the mostlogical explanation of the high frequency of occipital buns present in earlyupper paleolithic anatomically modern humans is that Neanderthals influencedtheir gene pools.The result of mtDNAanalysis showed that when Neanderthal mtDNA is compared to modern human mtDNA,there are about twenty-seven differences between them. When comparing modern humanmtDNA with other modern mtDNA, the average number of differences was 8 (Smithet al.
, 2005). It is also estimated that Neanderthals diverged from the line inthe phylogeny which leads to anatomically modern humans between 550 and 690thousand years ago (Smith et al., 2005). All four specimen mtDNA sequences thatwere analyzed clustered closer together and fell at the extreme edge of recenthuman variation. Through the results provided, it seems that Neanderthalsindeed do belong within their own category, however Smith et al. does notaccept this idea.
They argue that the sample of four segments of mtDNA foundfrom four different Neanderthals cannot possibly be a large enough sample sizeto make an accurate statement that Neanderthals belong in their own category.However, these are just assumptions that Smith et al. are positing from theirown perspective that must have assimilated into the early modern human genepool. From comparing ancient and modern DNA, there is not enough compellingevidence to completely exclude Neanderthals from the ancestry of early modernhumans (Smith et al. 2005).
To produce thecompetition model, Banks et al. applied new methodology by integratingarchaeological and chronological data with high-resolution paleo-climaticsimulations to define eco-cultural niches associated with Neanderthal andanatomically modern human adaptive systems during alternating cold and mildphases of Marine Isotope Stage 3. The result of these simulations suggestsNeanderthals exploited the same eco-cultural niche across the three climaticphases, pre-H4 to H4 to GI8, as anatomically modern humans (Banks et al.,2008). Results are defined interms of eco-cultural niche modeling, ECNM for short (Banks et al., 2008).
TheECNM during the pre-H4 climate range for Neanderthals indicate a potentialdistribution across 40 degrees to 50 degrees’ latitude, while climaticconditions were in the range of minus one degree to plus 12 degrees Celsius andrainfall of less than 1095 mm/ yr (Banks et al., 2008). ECNM during the pre-H4range of anatomically modern humans does not reach as far north as theNeanderthals during this time period. The ECNM of H4 climate conditions showsthat Neanderthals during this time occupied all of the Iberian, Italian, andBalkan peninsulas, with a temperature range of zero to ten degrees Celsius andrainfall of less than 730 mm/ yr. In contrast, the ECNM range of anatomicallymodern humans are almost the same as the Neanderthals except they did notoccupy southwestern Iberia yet (Banks et al., 2008). During the GI8 period, theECNM of Neanderthals show a reduced occupation zone, in which they were mostlyrelegated to the Mediterranean and Iberian Regions with temperature ranges ofsix to fourteen degrees Celsius and average rainfall of less than 730mm/ year.
However, it is during the GI8 period in which anatomically modern humans expandthe most and occupy most of central and southern Europe with broadertemperature ranges of zero to fifteen degrees Celsius and average rainfall ofless than 1095 mm/ yr (Banks et al., 2008). These findings are indicative of ashared ecological niche between both Neanderthals and anatomically modernhumans; however, during GI8, we see a significant reduction in the Neanderthaleco-cultural niche and an exponential increase of the anatomically modern humaneco-cultural niche (Banks et al. 2008). Therefore, the assumption is thatanatomically modern humans were better suited to the changes in their adaptivezone and thus outcompeted the Neanderthal for resources which led to theirextinction. DiscussionThe competitiveexclusion model proposed by Banks et al. suggests strong evidence thatNeanderthals did not assimilate into the gene pool of anatomically modernhumans, but instead were outcompeted for resources by anatomically modernhumans.
Compared with the assimilation model in which Smith et al. positsthrough cited material across many different fields, Banks et al. uses a newscientific methodology to further analyze the disappearance of Neanderthals.
That is to say, the competition exclusion model holds stronger evidence as ituses current archaeological and chronological data sets to simulate and predictthe ecological niche of past human populations (Banks et al. 2008). The benefitof this method allows to help identify mechanisms such as niche conservatism,niche contraction, etc. behind changes occurring across time and space in therelationship between adaptive systems and environments by projecting areconstructed human eco-cultural niche into a different paleo-environmentalframework (Banks et al 2008). It was through thismodel that the climate replacement model of Neanderthals was proven incorrect.As one can see from the figures provided, during the pre-H4 to GI8 period,while there were climate fluctuations, but it was not drastic enough to fullycause the extinction of Neanderthals. Neanderthal populations were actuallysteady and growing between the pre-H4 to H4 period and it is only during theGI8 periods in which we see the decline of Neanderthal occupations.
This ishowever the opposite to that of anatomically modern humans in which we see thatduring the GI8 period there was an exponential increase in modern humaneco-cultural zone while and the same time, a massive decrease in theNeanderthal niche. It was the methodology used that enabled Banks et al. tosuggest such a claim and by doing so, Banks et al. was able to prove at leastone theory of Neanderthal extinction wrong. Smith et al.
usesevidence found through cited research on Archaeology, Chronology, DNA analysis,and Morphology to suggest an assimilation model of Neanderthals. But mainlyuses DNA to explain the assimilation model. While Smith et al. uses a myriad ofsources, many of the sources actually suggest a different outcome than that ofassimilation. The analysis of the four Neanderthal specimens, in which theirmtDNA was compared to that of modern humans, showed that the grouping betweenthe mtDNA of Neanderthals was closer with each other and further away from modernhumans (Smith et al.
, 2005). It is also suggested from the mtDNA analysis ofNeanderthals that they diverged from modern humans around 550-690 thousandyears ago. The assimilation model that Smith et al. proposes is a model basedon the idea of genetic exchange. Yet, the sources that Smith et al. mention,suggests the opposite of an assimilation model. Smith et al. furtherquestions this idea and posits that there may have been an early anatomicallymodern human that could be more closely related to Neanderthals genetically.
However, this is disproven with the discovery of two early modern humans datedto twenty-four thousand years ago from Paglicci, Italy, subsequent mtDNAanalysis showed that they are more closely related to current modern humans (Caramelliet al., 2003). It is then hard to recognize the theory in which Neanderthal DNAcontributed to the gene pool of early modern humans through assimilation whenno Neanderthal-like mtDNA sequences were found in the two early modern humanspecimens. Through all of the genetic evidence however, Smith et al.
simplyrefuses to accept the importance of mtDNA analysis by suggesting that they donot provide compelling evidence for totally excluding Neanderthals from thephylogeny of anatomically modern humans. ConclusionThe competitiveexclusion model was created by using new methodology to re-create eco-culturalniches of the past. Originally used to estimate ecological niches of species,research has shown the potential of using this new methodology to constructeco-cultural niches of past human populations. Banks et al. combined large setsof archaeological and chronological data from the phases of Marine IsotopeStage 3 to reconstruct the eco-cultural niches of Neanderthals and earlyanatomically modern humans.
Smith et al. uses amyriad of sources and information from different anthropological fields to maketheir case about the assimilation model. The evidence that is provided isconsiderably weaker than the competitive exclusion model in that Smith et al.provides poor reasoning and counter evidence to the DNA information citedwithin the article. The mtDNA analysis resulted in showing the abouttwenty-seven differences between Neanderthal and modern human mtDNA while alsoshowing up at the extreme edges of modern human genetic variation.
Coupled withthe mtDNA analyzed from two early modern specimens dated to twenty-fourthousand years ago, it is highly unlikely that Neanderthals contributed theirgene pool to early anatomically modern humans. However further research isrecommended as both are not definitive sources on the exact cause ofNeanderthal extinction.