The partial replacement model incorporates both the complete replacement

The
partial replacement model incorporates both the complete replacement model and
the regional continuity models. It is also known as the assimilation model. The
emergence of the partial replacement theory is a result of the failure of the
complete replacement model and regional continuity model in accounting for the
fossils and genetic data. According to Gunter Breuer from the University of
Hamburg, the first humans evolved in Africa and then later migrated to other
parts of the world without replacing existing human populations. Rather, they
interbred with late archaic populations to some degree resulting in hybrid
populations (Peter & Robert, 2005). For example, in Europe, the first model
humans appear in the archeological record suddenly around 40,000 years ago.

There
is substantial evidence supporting the partial replacement theory. First, there
was migration from Africa to the rest of the world through the Mediterranean
coastal route. During this period, interbreeding took place and the partially
hybridized predominantly Cro-Magnon population ultimately became modern day
Europeans. To be specific, in 2003, a discovery was made in Romanian cave which
supported this hypothesis. The discovery was a partial skeleton of 15-16 years
old male Homo Sapiens who is believed
to have lived 30,000 years ago. The skeleton had a mix of old and new
anatomical features. He had features of both archaic and modern humans. This
explains the result of interbreeding with Neandertals.

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To
further add on the evidence, a research was conducted by Erik Trinkaus of
Washington University which reported that computer-based analysis of 10
different human DNA sequences suggests that there has been interbreeding
between people of Asia, Europe, and Africa for about 60,000 years ago (Clark,
2009). This is in line with the hypothesis that humans expanded more out of
Africa and these emigrants interbred with existing human populations in Europe
and Asia. There is a possibility that also people from outside Africa migrated
into Africa.

The
evidence proposed is beyond reasonable doubt since it is verifiable and
tangible. Migration is not an issue or occurrence that begun yesterday but
rather many years ago. With migration, interbreeding occurs and new species are
developed. In addition, the use of computer-based analysis of a range of DNA
sequence is the most correct method of verifying data. The generic diversity of
today can be explained through interbreeding. Perhaps, it is due to the ability
of verifying evidences of this model that makes it a suitable model when
compared with complete replacement and the regional continuity models.

Although
this is the most correct model of human origin, it is important also to consider
the regional continuity model as far as human origin is concerned. This model
proposes that modern humans evolved more or less simultaneously in all major
regions of the world from local archaic humans. For instance, the modern-day
Chinese are seen to have evolved from Chinese archaic humans and most probably
from Chinese Homo erectus. The proponents of this model believe that the
ultimate common ancestor of all modern people was African Homo erectus who lived 1.8 million years ago (Clark, 2009). Furthermore,
since then, there was a steady gene flow between Africa, Europe and Asia to
prevent long-term reproductive isolation and the subsequent evolution of
distinct regional species.

The
regional continuity model is supported by the fossil evidence. It claims that
there has been a continuity of some anatomical traits from archaic humans to
modern humans in Asia and Europe. The Asians and Europeans’ features have
antiquity in these regions going back more than 100,000 years. There are direct
generic links between Asian Homo erectus
and modern Asians. Scientific data from studies of contemporary DNA especially
mitochondrial DNA reveal that humans are homogeneous with relatively little
variation. The low amount of generic variation in modern human populations
implies that our origins may reflect a small founding population of Homo
sapiens.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

References

Clark,
S. L. (2009). Essentials of Physical
Anthropology. Discovering Our Origins. W.W. Norton Company: Columbus.

Peter,
J & Robert, B. (2005). Not by Genes Alone: How Culture Transformed Human
Evolution. Journal of Bio-economics,
Vol.10, Issue 2, pp 193-198.