Possible New Hominid Species Identified

Startling news from the Neanderthal Genome Project at the Max Planck Institute for Evolutionary Anthropology may prove a watershed in the understanding of how our hominid ancestors left Africa, and just how many different human species shared our planet 40,000 years ago.

The report comes from Nature, and it involves a site in the Altai mountains of Siberia called Denisova Cave (pronounced de NEE soh va). The cave has been excavated since the 1970s and it has evidence of occasional human use beginning about 125,000 years ago. Of particular interest to this study is what Siberian archaeologists call the Altai Mousterian, or Initial Upper Paleolithic levels, dated somewhere between 30,000 and 45,000 years ago (uncalibrated years before the present).

These levels contain transitional Middle Paleolithic to Upper Paleolithic artifacts. In addition to basic Mousterian Middle Paleolithic stone tools, the original excavators found cylindrical beads, pendants, needles, carved ostrich shell and a fabulous polished dark green bracelet, all of which screams Upper Paleolithic. This mixture of Mousterian tools with UP objects is characteristic of the Altai Mousterian seen in other sites in the region. Very very few human remains have been discovered at the site so far, amounting to a couple of teeth and fragments of a tiny phalanx (finger bone). The finger bone is from a child, approximately 5-7 years old. We know that between 30,000 and 45,000 years ago, our planet was shared by our direct ancestors (Early Modern Human or EMH) and Neanderthals, but archaeologists were hesitant to say which (or both?) of these hominid cousins lived in Denisova Cave.

For the past several years, the Neanderthal Genome project at the Max Planck Institute has been cracking the genetic code for Neanderthals. You might remember that in February of 2008, the project published the first complete mitochondrial DNA sequence of a Neanderthal, proving to geneticists at any rate that Neanderthals and early modern humans are not very closely related at all.

Since that time, researchers have been searching for usable DNA from our hominid ancestors all over the world. So far they've looked at about 100 Neanderthals and several dozen early modern humans, and up to now, there haven't been any big surprises. The Neanderthals all seem to be alike, and the early modern humans also seem to be alike.

Exterior view of Denisova Cave, Siberia.
Photo Credit: Bence Viola

But the mtDNA signature from the phalanx from Denisova Cave isn't like either Neanderthals or EMH. Svante Paabo and Johannes Krause and colleagues believe that the mtDNA from this phalanx is of a descendant of people who left Africa a million years after Homo erectus, and half a million years before the ancestors of Neanderthals and EMH. Essentially, this tiny fragment is evidence of a human migration out of Africa that scientists were completely unaware of before this discovery.

What the researchers don't know, yet, is who left Africa a million years ago. Since we only have a handful of DNA evidence from any hominid of the period yet, and most of our understanding of our ancient ancestors was gathered by morphology (that is, comparing skeletal forms), it's possible, and perhaps likely that whoever left Africa was what scholars have already recognized as Homo heidlebergensis, or Homo floresiensis, or even a previously unidentified second wave of Homo erectus. Scientists have been unsure that these hominid ancestors were in fact separate species; it's possible that the Denisova Cave sample might help that discussion out some.

The researchers plan to conduct further excavations at Denisova Cave this summer, and they are currently completing nuclear DNA studies on the phalanx, both of which may enlighten us all to the Denisova Cave specimen. But additional research into other skeletal remnants of humans spread out over the world may show that there were actually several species of humans sharing our planet as recently as 30,000 years ago.

Sources and Further Information

• Denisova Cave, glossary entry with bibliography
• Neanderthal Sequencing
• Humans and Neanderthals Not Related
• Mousterian
• What is Behavioral Modernity?

Krause J, Fu Q, Good JM, Viola B, Shunkov MV, Derevianko AP, and Paabo S. 2010. The complete mitochondrial DNA genome of an unknown hominin from southern Siberia. Nature pre-publication, 24 March 2010.

News and Blogs

• A New Human Relative, From Siberia (Science Friday, NPR)
• Researchers Discover New Lineage of Ancient Human, Science NOW (Michael Balter)
• Ancient Mitochondrial Genome Points to Previously Unknown Hominin Group, Genome Web (Andrea Anderson)
• DNA decoded from human ancestor in Siberia; analysis may indicate new member of family tree Science News (Malcolm Ritter)
• New Type of Human Discovered via Single Pinky Finger (NatGeo)
• X Woman: Not human, not Neanderthal, what is she?, Christian Science Monitory
• DNA identifies new ancient human dubbed 'X-woman' , BBC News
• No Bones about It: Ancient DNA from Siberia Hints at Previously Unknown Human Relative, SciAm (Kate Wong)