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Modern humans, known as Homo sapiens, are not the only type of humans. There have been several other species of humans throughout history though we are the lone surviving group. In November 2013, researchers Robert Belshaw and Gkikas Magiorkinis, of Plymouth University and Oxford University respectively, revealed that ancient Neanderthal viruses have been discovered in DNA of modern humans.
In 2010 the genome sequences of Neanderthals and Denisovans, another extinct group of humans, were unveiled for the first time. A separate group of researchers, led by Jack Lenz of Albert Einstein College of Medicine, began to look for evidence of endogenous retroviruses in the ancient humans' genome sequences back in 2012. The retroviruses most likely infected our "common ancestors" more than 500,000 years ago.Retroviruses are capable of creeping into their host's DNA sequence. Mr. Lenz's team noticed changes in the Neanderthal and Denisovan genomes caused by ancient retroviruses. Traces of the viruses were found in the "junk" sequence areas of the genome. No, this section isn't actually made of junk. The "junk" sequences do not contribute any information to the building ofproteins, hence the name. Fourteen distinct traces of the viruses were found in the genome. When this group of scientists compared the fourteen retroviral sequences to the modern human genome no matches were found.
Robert Belshaw of Plymouth University and Gkikas Magiorkinis of Oxford University, both from the U.K, decided to study the ancient genome sequence to see if there is a correlation between viral DNA sequences and disease in modern humans. Needless to say, their
Why were the results so different between the two studies? Belshaw explains that the other team led by Mr. Lenz used the "human reference genome" to search for the matches. The human reference genome is composed of data from multiple individuals but "any given position in that genome contains information from just one person." Coincidently, the particular genomes the first team studied came from people who does not have the altered DNA sequences passed down from the Neanderthals.
The data from both studies reveals how different humans can be from each other. "The results show that we can find individuals today who share loci with Denisovans or Neanderthals, but not with other humans alive today," explains Magiorkinis.
The findings suggest that there may be a connection between having these particular 14 sequences and the likelihood to get cancer. Belshaw and Magiorkinis's new project is to determine how "widespread" the retroviral DNA is in today's human population. The scientists will use state of the art DNA sequencing on 300 patients. Belshaw expects "viruses with no negative effects to have spread throughout most of the modern population, as there would be no evolutionary pressure against it. If we find that these viruses are less common than expected, this may indicate that the viruses have been inactivated by chance or that they increase mortality, for example through increased cancer risk."
In the next five years Belshaw says that his team should be able to say for certain whether the ancient retroviruses cause disease in modern humans.
References:
Barras, C. "Neanderthal virus DNA spotted hiding in modern humans." New Scientist. November 20, 2013.
University of Oxford. "Neanderthal viruses found in modern humans." University of Oxford. November 19, 2013.
Yirka, B. "Virus DNA first found in Neanderthal genome identified in modern humans." PHYS.ORG. November 19, 2013.
Images:
Neanderthal Man: MareCrisium (via Flickr).
DNA: Wikimedia/Public Domain
