Is there a new human species waiting to be discovered?

(CNN)It may be time to add more branches to the human family tree. Researchers have come up with a estimation tool to determine the traits we have in common with early humans, Neanderthals and Denisovans, and how our histories crossed paths.

In the process of comparing these ancient populations from 50,000 to 70,000 years ago against modern ones, the researchers encountered an intriguing question mark. When looking at the process of admixture, the transfer of genes from one isolated population to another, they realized that ancient human history might be more complex than previously thought.
    When applied to the modern populations of Europe and East Asia, the model works reasonably well. But within the modern population of Pacific Islanders living in Melanesia -- which includes Fiji, Papua New Guinea, Vanuatu and the Solomon Islands -- the model suggests that something is missing in the equation.
    Researchers have only a few bones that even point to the existence of Denisovans, but fossilized DNA that could be sequenced has allowed us to learn more about them. This year, new studies suggested that both Neanderthals and Denisovans interbred with our ancestors.
    More studies that look at African populations can further our understanding of who we are and where we came from, Bohlender said. More research could even answer the question of whether there are more early human ancestors waiting to be discovered.

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    "There is more diversity in Africa than there is anywhere else in the world, and it seems to be very clear at this point that this is where we all came from," he said. "But it's hard to work that far back in the past. There is a more considerable amount of work being done right now to sequence more African genomes, but it will take a while for that data to be studied and added to our current understanding."

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