Homo naledi is the newest member of our genus to be discovered. And ironically, it might also be the oldest; although it has yet to be reliably dated. Anatomically, it isn't that revolutionary. It already fits in with what we already knew about human evolution. However, it does show some key behaviour is older than we thought.
One other changing behaviour is how this discovery is published. Traditionally, when a fossil is discovered all the pieces are picked up by its finders. They then spend a few years painstakingly examining it, before publishing it all in one huge special edition of a journal, book, or monograph.
Homo naledi is mixing things up. The discoverers have made a bunch of information open access. You can even download a 3D model of the bones. You know, in case you get a sudden hankering for doing some research whilst at home. They're also publishing their findings as they go. So every so often there's a burst of new information as the researchers update us on their findings.
The latest update comes with some fascinating findings. Homo naledi 's place as one of the first members of our genus is more firmly cemented. And the researchers find that there's an additional member of the species in the cave. Except this one is a juvenile, potentially shedding light on the growth and development of the species.
Heads
The head is perhaps the most important part of Homo naledi as it shares many similarities with our genus. Thus, it is one of the strongest lines of evidence that it belongs to our group. In fact, even creationists have trouble disputing this line of evidence. Crucially though, the head also has a handful of unique characteristics. This confirms that whilst it does belong in Homo, it isn't part of any existing known species.
This update confirms this basic trend, showing it shares more similarities with us than apes; but is still unique enough to be classified separately. For example, the size of the brain overlaps with other early representatives of Homo. The general shape of the braincase is quite similar also. However, Homo naledi doesn't have the long, low skull or pronounced brow ridges present in most other members of the genus.
Since we don't know how old Homo naledi is it's hard to say what the evolutionary significance of these findings is. It could be the earliest example of these key Homo features appearing. Or if it's a bit younger, it might represent a unique offshoot of our lineage, combining these typical features with some more "experimental" adaptations. Either way, the species is a fairly significant finding.
Whilst some aspects of this discovery are still up in the air, one solid conclusion can be made from their skull: it's fairly consistent. Many individuals have been found, of varying size and age. Even a juvenile, as discussed below. There are some signs of sexual dimorphism, but for the most part the entire species looks fairly similar. This stands in stark contrast to the variation that accumulated in later species like Homo erectus. Some have even ( wrongly) argued they should contain two different species!
A brand new Homo naledi
The other main discovery in this new databurst is the discovery of a new Homo naledi individual. Or rather, the realisation that one of the previously found fossils actually represents another individual.
Identified from a jaw, this fossil clearly belongs to a juvenile. As such, it was given the memorable name DH6. This brings the total number of named fossils in the cave to. . . 6. As the name DH6 kind of gives away. However, rough estimates suggest there may be up to another dozen or two skeletons worth of material yet to be processed. Prepare for more DH numbers!
Finding a juvenile is a big deal for a fossil. Their bones haven't fully fused so are much rarer. So when we do find them, they offer a valuable insight into the development of the species. After all, think about how much humans change over the course of their lifespan.
Unfortuantley, in it's current state DH6 is a little too fragmentary to shed much light on the subject. However, it's a strong indication there may be more juvenile remains in the cave. So with a bit of luck more of DH6 will be found and more light will be shed in the growth of this crucial species.
References
Feuerriegel, E.M., Green, D.J., Walker, C.S., Schmid, P., Hawks, J., Berger, L.R. and Churchill, S.E., 2017. The upper limb of Homo naledi. Journal of Human Evolution, 104, pp.155-173.
Laird, M.F., Schroeder, L., Garvin, H.M., Scott, J.E., Dembo, M., Radovčić, D., Musiba, C.M., Ackermann, R.R., Schmid, P., Hawks, J. and Berger, L.R., 2017. The skull of Homo naledi. Journal of human evolution, 104, pp.100-123.
Marchi, D., Walker, C.S., Wei, P., Holliday, T.W., Churchill, S.E., Berger, L.R. and DeSilva, J.M., 2017. The thigh and leg of Homo naledi. Journal of Human Evolution, 104, pp.174-204.
Williams, S.A., García-Martínez, D., Bastir, M., Meyer, M.R., Nalla, S., Hawks, J., Schmid, P., Churchill, S.E. and Berger, L.R., 2017. The vertebrae and ribs of Homo naledi. Journal of Human Evolution, 104, pp.136-154.
