Unsplash / Hike Shaw

Quick notes

-Scientists have uncovered two new ancestors in human DNA

-If you’re keeping track, this brings the total number to four

So, this is a little embarrassing. It turns out we humans have a couple of cousins that, well… it looks like we forgot we had.

Research published this past July in the PNAS (Proceedings of the National Academy of Sciences of the U.S.) suggests not one, but two unknown hominins may have contributed to modern DNA. If you’ve been keeping track for the last several years, that’s a total of four other hominin species that homo sapiens apparently hooked up with to produce the amazing specimens we see in the mirror each morning.

Partying with the Neanderthals

Our species is the one that survived, but we weren’t the only hominins. For our particular species, life began in Africa. Then about 80,000 years ago, our ancestors moved north to the Eurasian landmass in an event known as the “Out of Africa” migration. For some time now we’ve known they interbred with Neanderthals as they made this migration. While neanderthals have a reputation for being somewhat dull intellectually, it turns out they were pretty hot as far as looks go.

Pixabay / Josch77

Then almost ten years ago, another ancestor turned up, when scientists announced that a DNA genome matched up with a handful of fossil fragments found in a remote Siberian cave some 30 years earlier. That species had been dubbed “Denisovans,” and just like that, we were part Neanderthal and part Denisovan.

Sort of. Actually, Aboriginal Australians and New Guineans are the only humans with substantial Denisovan markers in their DNA, a fact which considerably complicated our geographic migration map.

Partying with ghosts?

Now, within the past year, two more pieces of our DNA have turned out to belong to other hominin species. One of these, dubbed “EH1,” was announced earlier this year. Scientists discovered the “ghost” sequence proving this hominin’s existence with the help of artificial intelligence. In fact, so far no physical trace of this ancestor has been unearthed; only its DNA seems to survive.

Pixabay / PublicDomainPictures

The second species, “EH2,” was discovered last year, only the discovery wasn’t actually recognized at the time. Two researchers, biologist Joao Texeira, of the University of Adelaide, and his colleague, Alan Cooper, recognized the second “ghost” while doing a review of recent literature on DNA.

The return of the Hobbits

Part of the reason EH2 remained undiscovered initially is that it doesn’t appear in all human DNA. It only shows up in a very select group of humans who live in Indonesia near the Liang Bua Cave, and – get this –  it only appears in the DNA of short people. You may not immediately recognize the cave name, but it turns out to be precisely the cave where Homo floriensis, the so-called “hobbit” species was discovered in 2004. Coincidence? No one’s willing to say just yet.

And, in case you’re wondering, the hobbits do appear in some human DNA, which would make five distinct hominin ancestors for humans, only debate still rages over whether Homo floriensis is actually a different species from humans. Stay posted.

Mysteries remain

All four findings of DNA ancestors provide important clues not just to who we are but to how we got here. For instance, modern human DNA is about 2% Neanderthal. According to Texiera, this means the mixing occurred “probably around 50,000 to 55,000 years ago somewhere in the Middle East.” In a club known simply as Eden.

But other groups occupied the area as well, including the Denisovans, and homo sapiens were open-minded about who they mixed with. From there, migration continued towards southeast Asia, Australia, and the Philippines, with EH1 and EH2 being picked up along the way.

Deep mysteries remain, however. One of the deepest has to do with the fact that EH2 has remained almost completely contained in one tiny geographic area for 50,000 years. Why? Were they just really, really serious homebodies?

And are there more ancestors yet to be discovered?

Texeira notes, We knew the story out of Africa wasn’t a simple one, but it seems to be far more complex than we have contemplated.” Or maybe it isn’t. Ancient Aliens hasn’t weighed in yet. Perhaps there’s a simpler explanation after all.

A deeper dive — Related reading from the 101:

New species of hominid found in Philippine cave | History 101

Scientists uncover another pint-sized hominin

Neanderthal DNA reveals surprises about our past and our present | Science 101

Researches make some fascinating discoveries about our relationship to Neanderthals