Scientists have discovered ancient viruses inherited from Neanderthals in modern human DNA, the Huffington Post reported.

Researchers at Oxford University and Plymouth University are looking for possible links between "endogenous retroviruses," which they found are characteristics of human DNA and modern diseases like AIDS and cancer, according to the Huffington Post.

"Using modern DNA sequencing of 300 patients, we should be able to see how widespread these viruses are in the modern population," co-author Dr. Robert Belshaw told the Huffington Post. "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."

After comparing genetic material from cancer patients with that of Neanderthals and Denisovans, another group of ancient humans, researchers found evidence of ancient viruses in modern human DNA. This suggests their genes originated in a common ancestor more than half a million years ago.

About 8 percent of DNA is made up of endogenous retroviruses, DNA sequence left by viruses which passed on from generation to generation. The retroviruses are part of the "90 percent of the genome, sometimes called 'junk' DNA that contains no instruction codes for making proteins."

"Under certain circumstances, two 'junk' viruses can combine to cause disease," Dr. Gkikas Magiorkinis, from Oxford University's Department of Zoology, who co-led the research, told the Huffington Post. "We've seen this many times in animals already. [Endogenous retroviruses] have been shown to cause cancer when activated by bacteria in mice with weakened immune systems. " 

The research team now plans to look for possible links between these ancient viruses, belonging to the human endogenous retrovirus-K family, and cancer and HIV/AIDS.

"How HIV patients respond to [human endogenous retrovirus-K] is related to how fast a patient will progress to AIDS, so there is clearly a connection there," Magiorkinis said.

In regards to ancient viruses, Belshaw said if they found "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."

"HIV patients are also at much higher risk of developing cancer, for reasons that are poorly-understood," Magiorkinis said. "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."