Today's news about X-Woman, an unknown hominin that coexisted with Neanderthals and our species 30,000 to 50,000 years ago, suggests that at least four different forms of humans were in Europe and Asia after Homo sapiens migrated out of Africa. (Homo floresiensis, aka "Hobbit Human," is the fourth.)

The Big 4



(Credit: Cristoph Zollikofer)



???? (We don't know what she and her species looked like yet, save for the fact that they must have worn heavy clothing, since they lived in the mountains of Siberia, and hunted big game like woolly mammoths, based on archaeological finds.)


Homo floresiensis- "Hobbit Human"

Homo floresiensis- "Hobbit Human"

(Credit: FunkMonk)


Homo sapiens- Us!

Homo sapiens- Us!

(Credit: timothy)

Since at least three of these species lived very near each other, that's comparable to having someone today live in the same town as Neanderthals and Homo erectus.

It's not yet known what species X-Woman belonged to, but she was on the human family tree and shared a common ancestor with Neanderthals and modern humans one million years ago, according to the study, published in the journal Nature.

While the researchers now suspect that many different migrations of humans out of Africa occurred, here's what the basic timeline looks like now:

1.9 million years ago- Homo erectus leaves Africa.

1 million years ago- X-Woman and her species may have left Africa.

500,000 to 300,000 years ago- The ancestors of Neanderthals leave Africa. It's suspected that they were Homo heidelbergensis or Homo rhodesiensis. 

50,000 years ago- Anatomically modern humans (meaning our species, Homo sapiens) make the journey out of Africa.

Until X-Woman's discovery, scientists were only able to describe different types of humans based on the morphology of fossilized bones. Since X-Woman was documented based on a mitochondrial DNA sequence extracted from a bone, this will probably lead to further genetic analysis of ancient human remains, likely leading to the identification of more new human species in future.

Co-author Svante Paabo also does not rule out that interbreeding took place, since the different types of humans were living so close together. This has already been proposed as occurring between Neanderthals and modern humans for similar reasons.

One of many questions we're left with is: Why did all of the other human species die out, leaving only us? Genocide, environmental factors, competition and more have all been theorized, but I'm hopeful that the "make love, not war" hypothesis proves true. In this scenario, the other more recent hominid species were absorbed into Homo sapiens due to the aforementioned possible interbreeding.

Paabo told me, "This is another reason why we want to sequence as much of the nuclear genome as we can. It would allow us to say if there is evidence for any interbreeding with any present-day humans."

He and his colleagues plan to conduct that follow-up research over the next several months. Stay tuned, as the results could change the way that we view ourselves and past human history.