Where do we come from and who are we? Who were our ancestors? Why are we the dominant intelligent species on this planet and what made us be the first organism to create such a technological revolution? Who exactly are we? Who is Homo sapiens?
These questions have been occupying us for a long time and philosophy, religion and science have attempted many different explanations. It is now widely accepted that we have evolved over millions of years and many of our ancestors have been identified and many more are awaiting their discovery.
However, until about 33,000 years ago, at least two intelligent humanoid species lived on this planet: Homo sapiens and Homo neanderthalensis (Neanderthals). Modern humans were invading Europe from the South at the end of the last ice age. The continent was then inhabited by the Neanderthals who were very closely related to us. These humans were a little stockier and more muscular than modern humans. Furthermore, they had bigger heads with a strong and enlarged forehead and they were perfectly adapted to the cold European climate of the ice age.
But what happened to them? As recently as 2008 it was believed that modern humans pushed the Neanderthals out of their habitats and caused their extinction and that the two species never mated. However, it has now been suggested that both species actually interbred. In modern day Europeans about 2-4% of our genome comes from Neanderthals. This was the conclusion of a study that compared a partially isolated genome of Neanderthals with the DNA of modern humans.  The researchers compared the Neanderthal genome to samples from modern people inhabiting Southern Africa, West Africa, Central Europe, China and Papua New Guinea. Surprisingly, there were more similarities between the Neanderthals and the genes of the non-Africans than between the Neanderthals and the modern Africans. Thus, instead of being extinct, both species actually mixed to give rise to modern day Europeans.
This study was published last year by a group at the Max Planck Institute in Leipzig led by Svante Pääbo.
Though it is thought that Neanderthals and modern humans last shared a common ancestor more than 300,000 years ago, the fact that Neanderthals have more in common with modern humans from outside of Africa suggests, that when modern humans migrated North into Europe and Asia between 50,000 and 100,000 years ago, they mixed with the Neanderthals.
How would social interactions between these two hominid species have looked like? The Neanderthal was still quite distinct from the modern human.
In addition to this spectacular hypothesis, scientists also believe that interbreeding of different hominoid species such as modern humans and Neanderthals actually strengthened our immune system. The diversity introduced by the different genome has increased our capabilities to fight off bacteria and other deleterious infections and thus positively contributed to our survival and success in dominating our planet. This study was performed by a team of researchers led by Laurent Abi-Rached and Peter Parham of Stanford University School of Medicine in California.
Furthermore, it is also believed that modern humans mated with other coexisting hominid species, such as the newly discovered species dubbed Denisovans, adding to the diversity of modern day humans. In summary, the Neanderthal did not really become extinct at the end of the day. The species has survived in our genes and is part of us today.
The quest to find out who we are and how we came into existence continues and will for sure be a central question in research and philosophy for a long time. This discovery is a small piece in the puzzle and redefines some ideas of our past and most certainly who we really are.
Image reproduced from upload.wikimedia.org and www.spiegel.de
