Neanderthal viruses dating back 500,000 years has been discovered in modern human DNA when scientists studied links between 'endogenous retroviruses', which are hard-wired into DNA, and modern diseases such as AIDs and cancer. The researchers compared DNA from Neanderthals and another group of ancient humans called Denisovans with that obtained from cancer patients and found evidence of Neanderthal and Denisovan viruses in modern DNA, suggesting they shared a common ancestor more than 500,000 years ago. Neanderthals co-existed and possibly interbred with our ancestors in Europe for thousands of years, but belonged to a different sub-species, eventually becoming extinct around 30,000 years ago.
'I wouldn't write it off as "junk" just because we don't know what it does yet,' said Dr Gkikas Magiorkinis, an MRC Fellow at Oxford University's Department of Zoology. 'Under certain circumstances, two "junk" viruses can combine to cause disease – we've seen this many times in animals already. ERVs have been shown to cause cancer when activated by bacteria in mice with weakened immune systems.'
Dr Gkikas and colleagues are now looking to further investigate these ancient viruses, belonging to the HML2 family of viruses, for possible links with cancer and HIV.
How HIV patients respond to HML2 is related to how fast a patient will progress to AIDS, so there is clearly a connection there,' said Dr Magiorkinis, an author on the latest study. 'HIV patients are also at much higher risk of developing cancer, for reasons that are poorly-understood. It is possible that some of the risk factors are genetic, and may be shared with HML2. They also become reactivated in cancer and HIV infection, so might prove useful as a therapy target in the future.'
The team is now investigating whether these ancient viruses affect a person's risk of developing diseases such as cancer. Combining evolutionary theory and population genetics with cutting-edge genetic sequencing technology, they will test if these viruses are still active or cause disease in modern humans.
'Using modern DNA sequencing of 300 patients, we should be able to see how widespread these viruses are in the modern population. We would expect 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,' said Dr Robert Belshaw, formerly of Oxford University and now a lecturer at Plymouth University, who led the research.
'Last year, this research wouldn't have been possible. There were some huge technological breakthroughs made this summer, and I expect we'll see even greater advances in 2014. Within the next 5 years, we should be able to say for sure whether these ancient viruses play a role in modern human diseases.'
This latest finding, reported in Current Biology, will enable scientists to further investigate possible links between ancient viruses and modern diseases including HIV and cancer, and was supported by the Wellcome Trust and Medical Research Council (MRC).
This past May, researchers believe they pinpointed the skeletal remains of the first known human-Neanderthal hybrid, according to a study published in the peer reviewed scientific journal PLoS ONE. The finding came from northern Italy, where some 40,000 years ago scientists believe Neandertals and humans lived near each other, but developed separate and distinctly different cultures. A segment of a jawbone found during an archaeological dig in the area reveals that the bone’s owner had facial features attributable to both modern humans and Neanderthals, the study explains.
A remarkable finding in 2011 could answer the question whether our human ancestors and the Neanderthals interbred some time after both species left Africa many thousands of years ago. Only 10 years after scientists triumphantly decoded the human genome, an international research team mapped the genes of the long-extinct Neanderthal people and report there's a pinch of Neanderthal in all of us.
The 2011 report capped more than five years of intensive work by a group of 56 international scientists led by German paleogeneticist Svante Pääbo and Richard E. Green of UC Santa Cruz.
The project's scientists used tiny specks of powdered bone retrieved from three Neanderthal females who died in a Croatian cave more than 40,000 years ago to complete the draft of the Neanderthal genome. They then compared the genes to those of modern humans living today in five different regions of the world: France, Papua New Guinea, China, and southern and northern Africa.
The research concluded that humans living today carry between 1 and 4 percent of Neanderthal genes that carry the code for proteins in our bodies. Those genes must have entered our lineage sometime during a 50,000-year period when the Neanderthals and humans left Africa through the Middle East and spread throughout Europe and Asia. The Neanderthals became extinct about 30,000 years ago.
The complete genomes of the Neanderthals and modern humans, whose lineages separated from some unknown common ancestor at least 400,000 years ago, are 99.5 percent identical. They are, in fact, our closest evolutionary relatives. By comparison, humans and chimpanzees share 98 percent of their genes.
The scientists analyzed 4 billion units of Neanderthal DNA, called nucleotides - at least 60 percent of the Neanderthal's entire genome. While incomplete, Pääbo told reporters during a teleconference this week that 60 percent "is a very good statistical sample of the entire genome."
Finding the Neanderthal genes in people living today provides "compelling" evidence that thousands of years ago some interbreeding occurred between the two species, Green said.
Image Credit: With thanks to http://en.wikipedia.org/wiki/Neanderthal