During the time of one of our ancient ancestors the Neanderthals there also lived a long extinct hominid known as Denisovan. Whilst very little is known about Denisovans we do know that we share some common DNA and that they might have contributed a positive factor to our immune system. They also shared a common DNA with their Neanderthal cousins.
     Until recently our total knowledge of Denisovans has been based on two teeth and a finger bone, which were all found in a cave in the Altai Mountains in Siberia. There has now been a exciting fourth find, that of a baby tooth, on the same site back in November 2015. Extensive research has now been carried out on the tooth by the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.
     The tooth was found in a sedimentary layer which has been dated at between 128,000 and 227,000 years old, pre-dating previous Denisovan finds by between 50,000 and 100,000 years! To put this in perspective this time span would indicate that the Denisovans had occupied the site for a longer period than modern humans have occupied Europe.
     Vivian Slon, from the Institute, is quoted as saying "Such a long span of time increases the chances that the Denisovans and the Neanderthals may have interacted and interbred". The main point of note is that all Denisovan finds so far have emanated from one site. Without further finds from other locations the researchers are unable to determine whether the finds so far represent the entire spectrum of Denisovan genetic diversity or are an isolated branch.

Edited from LiveScience (10 July 2017)