Running head:
MODERN HUMAN ORIGINS
Modern Human Origins
Jordan Woodbury
English 1010
29 April 2015
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Modern Human Origins
Utilizing fossil evidence and what scientists have discovered about the behaviors and
patterns displayed by Homo heidelbergensis, and later Neandertals and modern humans, they can
make very interesting inferences about which group, if just one, modern day humans owe their
life to. There are two popular theories about human origins and both have merit in their own
rights. The regional continuity model, or multiregional model, follows the theory that modern
humans evolved from separate populations of pre-modern humans all over the globe. The second
theory, the replacement model, follows a group, or groups, of humans, recently evolved from
African Homo heidelbergensis, that immigrated into Europe and Asia to later out-compete and
replace Neandertals and Asian Homo heidelbergensis populations. Starting with the first theory,
logical evidence supporting the regional continuity model and some of its roots will be given.
The regional continuity model, highly influenced by Milford Wolpoff, claims that local
populations in Asia, Europe and Africa evolved into modern humans almost independently. For
this to be true, there are a couple of ideas that have to be taken as truth. First, the theory suggests
that more fossils have yet to be found of modern humans in Europe and Asia. These new fossils
will be found to be around two hundred thousand years old, proving that the oldest modern
humans are not just found in Africa. Second, the theory implies large amounts of gene flow
between the populations took place, ensuring that no speciation would separate these groups and
each population would evolve, roughly, in the same direction.
In order to answer the question of Neandertals being European ancestors, scientists
utilized fossil evidence and nuclear DNA as well as simple evolutionary theory to prove their
relation (Wolpoff, 2011). This explains that, while theory and fossil evidence are helpful, the
final straw was the discovery of ancient nuclear DNA of Neandertals. Utilizing the newly
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sequenced genome of Neandertals and immediately comparing the results with modern humans,
scientists found that European and Asian populations still have small amounts of Neandertal
DNA (Wolpoff, 2011). “Neanderthals have contributed approximately 1% to 4% to the genomes
of non-African modern humans” (What does it mean to be Human?, 2015).
While the multiregional evolution model has merit and some evidence to back it up, so
too does the replacement model. The replacement, or “out of Africa” model is a look at Homo
sapiens' evolution in Africa and their developments afterward. This theory, outlined in (Human
Origins Evolution and Diversity, 2013, pp. 284-287), suggests that Homo heidelbergensis living
in Africa evolved into the first Homo sapiens. After the evolution, these humans left Africa as
they started entering Europe and parts of Asia approximately 60,000 years ago. This theory
explains why modern humans are so similar to one another and what happened to the Homo
heidelbergensis groups living in the Eastern Europe region along with sections of Asia. It can
also help to explain the absence of heidelbergensis features and characteristics in today's species
(Jurmain, Kilgore, & Trevathan, 2013).
With all of the newfound evidence, it has sparked countless arguments and counter
arguments leading to a very big debate as to where the human origins truly lie. Whether it be the
isolated evolution of separate species along the same timeline, or one species dominating the
landscape and becoming absolute as they spread throughout Europe. The most suitable theory is
a combination of the two. Recent evidence has given birth to another iteration of the replacement
modern that is called the partial-replacement model, also called the assimilation model.
As the newly evolved humans started immigrating into Europe, it is theorized that they
exterminated Neandertals and other pre-modern hominids. This extermination was not
necessarily of a violent nature, but rather a competition for resources and other necessities that
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humans won in the end. This does not exclude the definite possibility of violent killings between
the groups, but since there is Neandertal DNA among modern European and Asian populations, it
has to be accepted that some interbreeding was taking place between these new Homo sapiens
and Neandertals (Wolpoff, 2011).
The partial-replacement model, shown in (Human Origins Evolution and Diversity, 2013,
pp. 297-299), acknowledges that no complete extermination of other hominid species happened,
but more of an assimilation process. Homo sapiens leaving Africa experienced interbreeding
with separate hominid species and because of their superior technology and tools, they were able
to stand the test of time as a species. It's important to note that any breeding between hominid
species and Homo sapiens occurred after they had left Africa and moved into western Asia and
Europe. Very recent findings are shaking the roots of the “out of Africa” theory, claiming that
humans are being found in areas like China and Europe from as late as 125,000 years ago
(Roberts, 2010). If these new findings continue to compound, the total replacement model may
have to adapt if it is to keep afloat in this time of constant discovery and evolution (Jurmain,
Kilgore, & Trevathan, 2013).
The partial-replacement model, or assimilation model, has the strongest theory and the
most supporting evidence and groundwork. It is difficult to believe that multiple populations
were able to evolve to become almost identical in a genetic sense without having originated in
the same environment and circumstances. Even accounting for substantial gene flow, this
wouldn’t be enough for natural selection to work on such a large scale and on multiple
continents. The “out of Africa” model is not without fault. It has been quickly losing support due
to the fossil and DNA evidence that continues to stack against it. “It is apparent that both the
complete replacement and the regional continuity models have difficulty accounting for all of the
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fossil and genetic data” (O'Neil, 2013). Evidence points to modern humans first evolving in
Africa. As they migrated into other European areas, rather than replacing pre-modern species,
they interbred to create offspring with both sets of genetic DNA (Janette & H.J., 1999). This is
why Neandertal and even other species within the Homo genus can be found in the DNA of
today's humans.
African populations likely made their migration in a very gradual process as they slowly
migrated north and assimilated various populations along the way (Falsetti, Smith, & Donnelly,
2005). Brauer also admits that, while there is observable local continuity in European areas like
the Neandertal facial characteristics, modern Eurasians were largely due to migrations of African
populations into parts of the Old World. With real evidence working to disprove both the
regional continuity model and replacement model, the best informed and most suitable contender
of all of the theories of modern human origins is the assimilation model. Anthropologists will
continue to tirelessly chip away at the edges, searching for new evidence to push any one of
these theories to the next step. While waiting for more solid evidence, however, all that can be
done is to work with is the evidence that is already unearthed and the theory that is ever
changing.
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References
Falsetti, A. B., Smith, F. H., & Donnelly, S. M. (2005, June 14). Modern Human Origins.
American Journal of Physical Anthropology, 35-68.
J. D., & H. D. (1999). Fossil Evidence for the Emergence of Modern Humans.
Jurmain, R., Kilgore, L., & Trevathan, W. (2013). Human Origins Evolution and Diversity.
CENGAGE Learning.
O'Neil, D. (2013). Early Modern Homo Sapiens. Retrieved from Anthro.palomar.edu:
http://anthro.palomar.edu/homo2/mod_homo_4.htm
Roberts, A. (2010). The Incredible Human Journey. Bloomsbury.
What does it mean to be Human? (2015, 4 11). Retrieved from Smithsonian National Museum of
Natural History: http://humanorigins.si.edu/evidence/genetics/ancient-dna-andneanderthals/sequencing-neanderthal-dna
Wolpoff, M. H. (2011). Evolution or Extinction of Neandertals: A Brief History. Journal of
Cosmology, 14.