In the
video called "Journey of Man" we learned that a "time
machine" is essentially DNA that can help us look back into history. All
of our ancestors originated in Africa around 50,000 years ago and then
migrated. The tribe that is still present today that is the most genetically
similar to our ancestors is the San tribe men in the Kalahari Desert. They
display many of the phenotypes that races today have. A genetic marker is a mutation
in chromosomes and DNA that took place in one individual and was passed down
and inherited. This shows us where all our ancestors split and started having
really different mutations. After starting the migration from Africa, the next
place we found evidence of our ancestors being present was Australia. This is a
problem because this would have been a huge distance to cover and we think that
our ancestors walked along the coast to reach Australia. The problem is that
there was a lot more land back then due to the ice caps being large and still
very frozen. So the route they took is now underwater. Essentially though we
are all descendants of early Africans. This poses the question of: Does race
really exist? If we were all related to each other 50,000 years ago and our
pretty genetically similar than how did race develop? The answer is in the
genes of races. Scientists decided to collect data from alus. Alus are short
pieces of DNA that are similar in sequence to one another. This is a class of
polymorphisms. Polymorphisms are in genetics the presence of variation in a
population upon which natural selection can operate. Aluses once they
replicate, they can spilt and then reinsert itself into a chromosome, and once
inserted those alus will become permanent for a very long time and be
inherited. These alus can be analyzed and provide information for people
sharing a common ancestor. Scientists took a bunch of alus data from different
races and then blindly, without knowing what race corresponded to what organized
them into four groups. When they “applied” the labels and discovered what
sample was from what race then they saw that they sorted them by similarities
and most were from the same area of the world. This has been conducted several
times, all yielding similar results that we can sort data into five major
groups. These groups are; Sub-Saharan Africans, Northern Africans/ Europeans,
West of the Himalayas Asians, East Asians, and Native Americans. It is easier to distinguish between people
from isolated and very separated parts of the world than analysis of people in
a population of one country. The one country population in comparison would be
very muddled. Natural selection in evolution sets up our standards of what race
is. We usually distinguish race based on pigmentation of skin that has been
caused by natural selection. Africans and Aborigines in Australia may have the
same pigmentation of the skin because it protects them better from the harsh
sun in those areas but their alus polymorphisms are very different.. The
questions this brings to light is that in society should we change things like
the race questions on standardized tests to be more scientifically correct and
only state 5 clear races? Should we then change the norm for referring to races
based on something other than phenotypes? Polymorphisms also can have
beneficial aspects such as how people with one copy of a sickle cell in the
Mediterranean area can be resistant to malaria. If such things are possible can
we genetically engineer to make all individuals contain beneficial polymorphisms
in their genes?
We will continue watching this video next class time.
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