“Traces of a Distant Past”

Kevin Lin

Mr. Quick

A Block

Oct 22^nd

     Darwin knew that individuals were variable, so each individual in a population carried a unique set of traits. However, he did not discover that the reason behind it is genetic differences. Variation in the genes of individuals arises from several sources. Mutation, the alteration of existing genes to form new alleles, can arise from copying errors during DNA replication, DNA damage, and repair or recombination during cell division. Varation also arises from sexual reproduction, wherein new combinations of DNA are created through the independent assortment of genes. 

   In the Documentary movie “ The Journey of Man”, Spencer Wells, a geneticist, adheres to the out of Africa theory in which all of mankind stemmed from a single person who originated in Africa 60,000 years ago. His question is that how human possibly travelled from Africa and end up spread out in the rest of the world and also to find genetic evident to backup his theory. He is also wondering what caused human immigration. From his basis understanding, he believes that on genetic markers in Y chromosomes, which are only found in males. The idea behind this is that sons inherit Y chromosomes identical to that of their fathers. However occasionally mutations occur in the DNA and form a genetic marker which can be traced. By looking for different markers and analysing DNA in people all over the world today, a picture can be formed of where our ancestors were at certain points in time and this enables us to track their journey and the origins of man.

The article “Traces of a Distant Past” once again proof Spencer Wells idea that humans left Africa and gradually fanned out across Asia to Australia and then up to Europe; and then say 15,000 years ago, they crossed over what was then a land bridge to the Americas and gradually worked their way down to South America. Also, due to fast speed of globalization, discovering how genetics related to evolution is becoming an important issue. That has been the perspective of a number of population geneticists who have felt that we really need to carry out this research as soon as possible because of globalization, because of the mixing of peoples. That was the reason that in the early '90s, a very well-known population geneticists, Luca Cavalli-Sforza, suggested that at the same time that we begin a Human Genome Project, we begin something called the Human Genome Diversity Project that would go out and collect samples from many, many different indigenous populations from around the world and then have a basis for comparing that genetic diversity for researching the hypothesis that we're talking about, that humans originated in Africa and gradually spread out with this decreasing genetic diversity. There was a problem with that. Many of the people who they approached were not eager to have their blood sampled or to give samples of sputum because they felt that, one, this may be taking something that is intrinsic to their own belief systems, which is there are some groups that believe that taking the blood is in essence robbing the soul in some ways. Others had had bad experience with people coming and wanting to take plants and other types of materials that they've been using and patenting them.