Instructor in Biology Dr. Hagler Speaks on Use of Ancient DNA to Understand Genetic Relationships

Ancient DNA can be used to study the ancestry of the human race. Dr. Jeremiah Hagler, Instructor in Biology, presented the first of the 2007-2008 Science Seminar Series lectures on this method on Wednesday. His lecture was titled “The Changing Face of Archaeology: The Role of Ancient DNA in the exploration of our Genetic Roots.” Hagler first talked about the recent controversies and emerging technologies in the field of Paleontology. Ancient DNA, genetic material preserved in remains, can be studied for past genetic relationships and is imperative evidence in finding connections between the past and the present. The relationship of Neanderthals and Homo sapiens is being closely studied and debated. New data is changing the proximity of Neanderthals to us on the phylogeny tree. To study ancient DNA, it must first be isolated from its fossil, extracted, ground up, and then amplified by Polymerase Chain Reaction (PCR). PCR works by heating up the DNA pieces so the strands denature and separate. These strands are then mixed with a heat tolerant DNA polymerase enzyme that does not denature, which replicates target sections of DNA for further study. However, many problems arise when PCR is attempted on ancient DNA. “First off, this stuff is very dead,” said Hagler. Very little DNA remains due tot of cosmic rays, UV radiation and various other contaminants. Also, there is contaminating DNA from dead organisms such as detritivores, bacteria, and human DNA from modern handlers of the material. Additionally, human contamination is a problem because “even after [the archeologists] clean off the bone…there is still some human DNA inside the marrow cavity, maybe because the bones are dry and porous,” said Hagler. With the evidence of these bones and the gene DNA sequencing of one million base pairs, the similarity of Neanderthals to modern day humans can be gauged. By comparing the mitochondrial DNA of homo neanderthalensis, it was discovered that only 22 nucleotides different between a Neanderthal and a Homo sapien. However, mitochondrial DNA is only passed on through the maternal line and this makes the father invisible in reference to lineage. With autosomal DNA analysis through the Y chromosome, it can be found whether Homo sapiens and Neanderthals interbred at one point in time. This theory is based on the fact that both species populated similar regions of Europe, although Homo sapiens prevailed in the end. This data supports the theory that human and Neanderthals split 706,000 years ago while Neanderthals ceased to exist 28,000 years ago. Hagler said, “Technology is getting pretty good.”