There are still plenty of mysteries left to uncover in the history of human evolution. While scientists have identified a handful of early humans, new research shows that the puzzle is far from complete.
For one, it turns out that early human species Denisovans consist of at least three genetically different groups.
Study Opens Up Possibility Of Multiple Denisovan Branches
In a comprehensive study published in the journal Cell, researchers analyzed genetic data of living individuals from Indonesia and Papua New Guinea.
Findings reveal that interbreeding between modern humans and Denisovans occurred as recently as 15,000 years ago.
However, the researchers also noticed that the genomes of those from Papua New Guinea speak to how complex the Denisovan lineage is. Genetic analyses show that the living Papuans carry genes from two different Denisovan lineages. One has previously been identified in the genes of Papuans and South Asians, while the other has never been identified before.
Even more interestingly, these two Denisovan lineages are genetically different from the Denisovans originally discovered in Siberia.
"What we thought was a single group — Denisovans — was actually three very different groups, with more diversity among them than that seen today in modern humans," Murray Cox, senior author and a population geneticist at the Massey University in New Zealand, tells Live Science.
The newly discovered Denisovan group reportedly split from the other two as far back as 363,000 years ago. It's as genetically different from the original Siberian Denisovans as that group is to the Neanderthals, according to Cox.
In a report in Phys.Org, Cox points out that scientists used to believe only modern humans and Neanderthals walked the Earth. Now, as multiple research papers have suggested, it's clear that there used to be many human-like lineages that existed in the past.
Shining A Spotlight On 'Understudied' Regions
The study, which was undertaken to provide genomic data to improve healthcare in islands of Southeast Asia, highlights how important the region is in the bigger picture of human evolution.
For a long time, scientists have focused their efforts in Europe and Eurasia, because of the breadth of ancient DNA found in these areas. It led many to believe that the majority of hominin activity were centered in these regions.
However, these new findings — as well as the recent discovery of a new human species in the island of Luzon, Philippines — reveal that this is not the case. Ancient DNA simply don't survive as long in tropical climates compared to the cold climes of Europe and Eurasia, but it doesn't mean that hominin diversification did not take place in the Southeast Asian region.
"If you look at modern human diversity, and biological diversity in general — for example, plants and animals,— most diversity is in the tropics," Cox says in UPI. "This study — and the Luzon hominin — fits into a much bigger body of scientific findings that show that this was also true for archaic hominins; their center of gravity was in the tropics too."