It’s been a landmark season for big finds in paleoanthropology. Probably many of you have already heard of the new human species, Homo naledi, reported by Lee Berger and his crew. If you haven’t, here’s why it’s such big news.
For one thing, even though the age of the specimens aren’t dated yet (they were found in a subterranean cave, which makes dating difficult), they are astonishingly complete. Many paleonanthropological finds often consist of one or a few bones, such as characteristic teeth or femurs, leaving much to the imagination. Whereas the Rising Star cave has provided an absolute treasure trove of well-preserved Naledi fossils, as the picture below attests. According to Berger, the fossils recovered represent a minimum of 15 hominin individuals, which is astounding. And it’s currently uncertain as to how presumably an entire family of Naledi ended up in the cave (whether they got trapped or were posthumously placed there), as the cave is extremely difficult to access– preventing even Berger himself from taking part in the field work process.
Second, these human relatives share a combination of primitive and modern features. For instance, compared to Autralopithecus africanus, Naledi has notably smaller canines and molars. The new hominin also has a smaller brain casing compared to (presumably) more recent human ancestors. And finally, its feet are decidedly human-like, with the large toe in line with the rest of its toes, yet its hands, torso, and shoulders exhibit some primitive characteristics indicative of tree climbing.
The Sima People
In the mid-1990s, a large collection of hominid fossils were found in Sima de los Huesos, a cave in the Atapuerca Mountains of Spain. The Sima people, who are more ancient than Neandertals by several hundred thousand years, share many physical characteristics in common with them and so it has been long believed that both Neandertals and modern humans may have arisen from this or a closely related line.
Recent genetic evidence reported by paleogeneticist, Matthias Meyer, of the Max Planck Institute suggests that the Sima people and Neandertals were indeed quite closely related; however, the Sima were less closely related to modern humans. Meyer suggests that the evidence supports an earlier split in time between the lines of Neandertal and modern human than was originally thought, perhaps even as long ago as 700,000 years, which is 100,000-400,000 years earlier than once believed.
Back to Africa
In reference to the much more recent past, geneticists have found that an Ethiopian man who lived 4,500 years ago, a time prior to recent African migrations, shows evidence of genetic intermixing with Europeans, most notably with those from the Middle East.
Furthermore, when researchers looked at the genomes of other modern Africans spanning deeper into the continent– including pygmies of the Congo–, they found that there was evidence of more genetic intermixing than was ever realized. So it seems that, even though there were multiple migrations out of Africa in early human history, Middle Eastern farmers in the more recent past migrated back and intermixed with the local populations to a considerable extent.
I guess it’s not true that you can never go home again.