Introduction second article analyzes the disappearance of

Introduction

There are many debates
in the anthropological community about the disappearance of Neanderthals. Some
think that rapid global climate change was the sole cause of their demise while
others believe that rapid global climate change along with contributing factors
such as competition of resources and technological insufficiencies led to their
extinction. It is now known that climate change was not directly responsible
for the extinction of Neanderthals; however, it was a contributing factor.
While this may give researchers a theory to rule out, there are still many
other theories that support other reasons of Neanderthal disappearance. A
competing model that argues against such claims is the Assimilation Model
theory, in which researchers believe that the disappearance of Neanderthals was
not because of complete catastrophic extinction per se, but rather a slow
assimilation of the Neanderthal gene pool into the Anatomically Modern Human
gene pool. The two articles that will be the subject of analysis are “The assimilation
model, modern human origins in Europe, and the extinction of Neanderthals” by
Fred Smith, Ivor Jankovic, and Ivor Karavanic and “Neanderthal Extinction by
Competitive Exclusion” written by William E. Banks, Francesco d’Errico, A.
Townsend Peterson, Masa Kageyama, Adriana Sima, and Maria-Fernanda
Sanchez-Goni. The first article is an analysis of the migration of anatomically
modern humans and through this analysis, the authors suggests the case of
Neanderthal extinction through assimilation while the second article analyzes
the disappearance of Neanderthals through a climatic and ecological
perspective. From this point on I will refer to both articles (Smith et al) and
(Banks et al) respectively.

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The Assimilation model
proposed by Smith et al., suggests that Neanderthals did not go extinct in the
classical sense, but rather they were slowly assimilated into anatomically
modern humans emerging and migrating from Africa through genetic exchange. The
Competitive Exclusion model suggested by Banks et al., uses paleoclimatic
simulations to define eco-cultural niches associated with Neanderthals and
anatomically modern humans to suggest that it was the rapid expansion of
anatomically modern humans that led to a competition of resources which in turn
led to the disappearance of Neanderthals. The purpose of this paper is to
analyze both competing models and assess which model holds more value in the
case of Neanderthal extinction.  

Research Methods and
Results (if applicable)

According to Smith et
al. uses four different sets of information to assess the discuss the current
debate about Neanderthal extinction. First, they use the morphological and
chronological information on archaeological artifacts. Analyzing information on
Nasion projection from the bi-fmt line and the incidence of occipital
bone, specifically the suprainiac fossa and occipital bun to compare and
contrast between Neanderthals and anatomically modern humans. The second set of
information is the comparison of ancient DNA to modern DNA. Mitochondrial DNA
was analyzed from four different Neanderthal fossils and was then compared to
the mtDNA of modern humans. In 1997, researchers analyzed About 378 base pair
segment of mtDNA was isolated from the right humerus from Feldhofer 1, a
Neanderthal skeleton discovered in 1856 (Smith et al. 2005). The other three
Neanderthal skeletons that were analyzed was an infant from Mezmaiskaya,
Russia, a specimen from level G3 at Vindija, Croatia, and another fossil from
Feldhofer, Germany (Smith et al. 2005). The third is the use of the
archaeological record spanning the late Mousterian, Initial Upper Paleolithic,
and Aurignacian cultural periods of the Paleolithic. The fourth set of
information Smith et al. uses is the population patterns of Neanderthals and anatomically
modern humans associated with chronometric dates in Europe and other parts of
the western “Old World.”

Morphological
similarities of the occipital buns between early anatomically modern humans and
Neanderthals may be evidence of morphologically continuous traits of late
Pleistocene Europeans (Smith et al., 2005). Looking at the data in Table 2., we
can see the percentage of found individuals that feature the the Occipital bun.
About eighty percent of European Neanderthals were found with the occipital bun
feature while sixty-eight percent of early upper paleolithic anatomically
modern humans excavated had this feature. Smith et al. believes that the most
logical explanation of the high frequency of occipital buns present in early
upper paleolithic anatomically modern humans is that Neanderthals influenced
their gene pools.

The result of mtDNA
analysis showed that when Neanderthal mtDNA is compared to modern human mtDNA,
there are about twenty-seven differences between them. When comparing modern human
mtDNA with other modern mtDNA, the average number of differences was 8 (Smith
et al., 2005). It is also estimated that Neanderthals diverged from the line in
the phylogeny which leads to anatomically modern humans between 550 and 690
thousand years ago (Smith et al., 2005). All four specimen mtDNA sequences that
were analyzed clustered closer together and fell at the extreme edge of recent
human variation. Through the results provided, it seems that Neanderthals
indeed do belong within their own category, however Smith et al. does not
accept this idea. They argue that the sample of four segments of mtDNA found
from four different Neanderthals cannot possibly be a large enough sample size
to make an accurate statement that Neanderthals belong in their own category.
However, these are just assumptions that Smith et al. are positing from their
own perspective that must have assimilated into the early modern human gene
pool. From comparing ancient and modern DNA, there is not enough compelling
evidence to completely exclude Neanderthals from the ancestry of early modern
humans (Smith et al. 2005).

To produce the
competition model, Banks et al. applied new methodology by integrating
archaeological and chronological data with high-resolution paleo-climatic
simulations to define eco-cultural niches associated with Neanderthal and
anatomically modern human adaptive systems during alternating cold and mild
phases of Marine Isotope Stage 3. The result of these simulations suggests
Neanderthals exploited the same eco-cultural niche across the three climatic
phases, pre-H4 to H4 to GI8, as anatomically modern humans (Banks et al.,
2008).

Results are defined in
terms of eco-cultural niche modeling, ECNM for short (Banks et al., 2008). The
ECNM during the pre-H4 climate range for Neanderthals indicate a potential
distribution across 40 degrees to 50 degrees’ latitude, while climatic
conditions were in the range of minus one degree to plus 12 degrees Celsius and
rainfall of less than 1095 mm/ yr (Banks et al., 2008). ECNM during the pre-H4
range of anatomically modern humans does not reach as far north as the
Neanderthals during this time period. The ECNM of H4 climate conditions shows
that Neanderthals during this time occupied all of the Iberian, Italian, and
Balkan peninsulas, with a temperature range of zero to ten degrees Celsius and
rainfall of less than 730 mm/ yr. In contrast, the ECNM range of anatomically
modern humans are almost the same as the Neanderthals except they did not
occupy southwestern Iberia yet (Banks et al., 2008). During the GI8 period, the
ECNM of Neanderthals show a reduced occupation zone, in which they were mostly
relegated to the Mediterranean and Iberian Regions with temperature ranges of
six to fourteen degrees Celsius and average rainfall of less than 730mm/ year.
However, it is during the GI8 period in which anatomically modern humans expand
the most and occupy most of central and southern Europe with broader
temperature ranges of zero to fifteen degrees Celsius and average rainfall of
less than 1095 mm/ yr (Banks et al., 2008). These findings are indicative of a
shared ecological niche between both Neanderthals and anatomically modern
humans; however, during GI8, we see a significant reduction in the Neanderthal
eco-cultural niche and an exponential increase of the anatomically modern human
eco-cultural niche (Banks et al. 2008).  Therefore, the assumption is that
anatomically modern humans were better suited to the changes in their adaptive
zone and thus outcompeted the Neanderthal for resources which led to their
extinction.

Discussion

The competitive
exclusion model proposed by Banks et al. suggests strong evidence that
Neanderthals did not assimilate into the gene pool of anatomically modern
humans, but instead were outcompeted for resources by anatomically modern
humans. Compared with the assimilation model in which Smith et al. posits
through cited material across many different fields, Banks et al. uses a new
scientific methodology to further analyze the disappearance of Neanderthals.
That is to say, the competition exclusion model holds stronger evidence as it
uses current archaeological and chronological data sets to simulate and predict
the ecological niche of past human populations (Banks et al. 2008). The benefit
of this method allows to help identify mechanisms such as niche conservatism,
niche contraction, etc. behind changes occurring across time and space in the
relationship between adaptive systems and environments by projecting a
reconstructed human eco-cultural niche into a different paleo-environmental
framework (Banks et al 2008).

It was through this
model 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 fully
cause the extinction of Neanderthals. Neanderthal populations were actually
steady and growing between the pre-H4 to H4 period and it is only during the
GI8 periods in which we see the decline of Neanderthal occupations. This is
however the opposite to that of anatomically modern humans in which we see that
during the GI8 period there was an exponential increase in modern human
eco-cultural zone while and the same time, a massive decrease in the
Neanderthal niche. It was the methodology used that enabled Banks et al. to
suggest such a claim and by doing so, Banks et al. was able to prove at least
one theory of Neanderthal extinction wrong.

Smith et al. uses
evidence found through cited research on Archaeology, Chronology, DNA analysis,
and Morphology to suggest an assimilation model of Neanderthals. But mainly
uses DNA to explain the assimilation model. While Smith et al. uses a myriad of
sources, many of the sources actually suggest a different outcome than that of
assimilation. The analysis of the four Neanderthal specimens, in which their
mtDNA was compared to that of modern humans, showed that the grouping between
the mtDNA of Neanderthals was closer with each other and further away from modern
humans (Smith et al., 2005). It is also suggested from the mtDNA analysis of
Neanderthals that they diverged from modern humans around 550-690 thousand
years ago. The assimilation model that Smith et al. proposes is a model based
on the idea of genetic exchange. Yet, the sources that Smith et al. mention,
suggests the opposite of an assimilation model.  

Smith et al. further
questions this idea and posits that there may have been an early anatomically
modern human that could be more closely related to Neanderthals genetically.
However, this is disproven with the discovery of two early modern humans dated
to twenty-four thousand years ago from Paglicci, Italy, subsequent mtDNA
analysis showed that they are more closely related to current modern humans (Caramelli
et al., 2003). It is then hard to recognize the theory in which Neanderthal DNA
contributed to the gene pool of early modern humans through assimilation when
no Neanderthal-like mtDNA sequences were found in the two early modern human
specimens. Through all of the genetic evidence however, Smith et al. simply
refuses to accept the importance of mtDNA analysis by suggesting that they do
not provide compelling evidence for totally excluding Neanderthals from the
phylogeny of anatomically modern humans.

Conclusion

The competitive
exclusion model was created by using new methodology to re-create eco-cultural
niches of the past. Originally used to estimate ecological niches of species,
research has shown the potential of using this new methodology to construct
eco-cultural niches of past human populations. Banks et al. combined large sets
of archaeological and chronological data from the phases of Marine Isotope
Stage 3 to reconstruct the eco-cultural niches of Neanderthals and early
anatomically modern humans.

Smith et al. uses a
myriad of sources and information from different anthropological fields to make
their case about the assimilation model. The evidence that is provided is
considerably weaker than the competitive exclusion model in that Smith et al.
provides poor reasoning and counter evidence to the DNA information cited
within the article. The mtDNA analysis resulted in showing the about
twenty-seven differences between Neanderthal and modern human mtDNA while also
showing up at the extreme edges of modern human genetic variation. Coupled with
the mtDNA analyzed from two early modern specimens dated to twenty-four
thousand years ago, it is highly unlikely that Neanderthals contributed their
gene pool to early anatomically modern humans. However further research is
recommended as both are not definitive sources on the exact cause of
Neanderthal extinction.