Linfei's Bio Blog: Trace of A Distant Past --- response to the assigned article

Trace of A Distant Past

Scientists trace the path of human migrations by using bones, artifacts and DNA, as these are the evidences of evolution. Nevertheless, ancient objects are hard to find and are incomplete, such as fossils and artifacts. Thus, examining DNA is a better way to determine the trace of past. Yet, why DNA can help to determine our past? That is because “almost all our DNA --- 99.9 percent of the three billion nucleotides that make up the human genome is the same from person to person” (Scientific American 56). The last 0.1 percent of nucleotides indicates differences between races. Scientists are able to determine our common ancestor by analyzing the DNA of mitochondria. Mitochondrion is the cell’s energy-producing organelles, which are passed down through maternal line.

In 1987, Rebecca L. Cann and Allan C. Wilson of the university of California, Berkley reported that “humans from different populations all descended from a single female in Africa who lived about 200,000 years ago” (Scientific American 58). After this groundbreaking paper is published, scientists discover that mitochondrial DNA and the Y-chromosome remain powerful analytical instruments. Furthermore, scientists believe that with the help of mitochondrial DNA and the Y-chromosome, they would be able to prove that Africans are the common ancestors of all the population over the world. In 2010, the National Geographic Society, IBM and the Waitt Family Foundation have joined in the so-called Genographic Project that is primarily devoted to using these tools. This project is to gather DNA from up to 100,000 indigenous people worldwide; moreover, this project is made into a TV documentary, Journey of Man, in 2003. However, not every one agreed with this out-of-Africa theory. Despite lots of research and project indicate that the out-of-Africa theory is valid. (The out-of –Africa theory holds that humans with modern traits left Africa around 50,000 to 60,000 years ago to settle the world.) Some scientists believe that modern characteristics evolved not only in Africa, but also in archaic hominid populations in Asia and Europe. This competing theory is called the multiregional theory. Furthermore, the multiregional theory also states that interbreeding among all these groups, such as Africans, Asians and Europeans ensure that they remain as a single specie.