When studying animal remains from the past, it usually seems like common sense that the more specimens we find, the clearer the details of a lineage becomes. However, it often goes the opposite way in reality: a single specimen or several specimens can often disrupt what may have seemed like a fairly clear-cut set of relationships among related species, introducing new confusion where little existed before. Such is the case with a recent find of 1.8 million-year-old hominid fossils in the Lake Turkana basin, an area spanning across across the border between Kenya and Ethiopia.
Of course, the details of the relationships between advanced non-modern-human hominids has never been terribly simple, and has always been riddled with a certain amount of confusion and uncertainty. This new find introduces yet another piece into the puzzle. Discovered and described by the esteemed Leakey family, the new specimens include a beautifully preserved upper jawbone that may (or may not) belong to Homo rudolfensis, which is important because the holotype for this species lacks this bone. Another of the new specimens discovered by Dr. Leakey is a lower jawbone that appears to match up with the upper one. These bones are likely from the same species, but not necessarily the same individual - they seem to belong to H. rudolfensises of different ages.
So why is this situation confusing for the hominid relationship situation? Well, even though these bones mesh well together, and seem to match the holotype as well, they do not match up with another famous fossil found in the same area decades ago, which - of course - has also been assigned to H. rudolfensis all this time. This old bone, discovered in 1973, is now considered to more or less be a completely unknown species because of this new find.
It's always possible that the discrepancy can be explained by ontogeny or a degree of sexual dimorphism previously unknown in hominids, which would be very interesting to the field of human evolution for a different reason. But Dr. Leakey doesn't think so, nor does she think the old fossil was Homo habilis, which was also around at the same time and place - it looks too different. What this means is there were probably at least three different species of advanced Homo coexisting in the same time and place in Africa a little under 2 million years ago. A similar degree of diversity is well-known to have existed around 40,000 years ago, where modern humans, Neanderthals, Asian Denisovans and the Indonesian Flores "hobbits" all coexisted around the same time. Other than modern man and Neanderthals - and indeed it is now well-known that Neanderthals and modern man even interbred for a time - these four hominids would have been separated by pretty vast geographical distance. The really remarkable thing about H. habilis, H. rudolfensis and this new/old species of Homo is that they were all coexisting on the east-African savannah.
So, what's the big deal? Well, this opens up a lot of questions about human origins that are gaining more interest among anthropologists. This coexistence of at least three pre-human hominids suggests that hominids underwent intense adaptive radiation, meaning that an earlier common hominid ancestor must have differentiated in response to changing environments and food sources. This raises a host of other questions, such as: how did these extremely similar yet different hominid species differ in their food sources, habitat preferences, physical abilities, and cultures? What caused them to eventually become extinct? While there was of course never any reason to expect otherwise, it's becoming more and more clear that human evolution involved as many complexities and as much radiation as any other animal observed in the fossil record, and that our evolutionary history is far from linear.
It's difficult to come up with a "monthly question" when our article topic is merely a new discovery, but thinking about ancient hominid species coexisting with one another - both at 40,000 years ago and much earlier in Africa - made me start to wonder how modern man would react to a similar situation. I am going to go out on a limb and predict that most people's answers to this question will not be optimistic. But in any case, this month's question is: If a population of closely-related but definitely distinct species of hominid was discovered in some remote and isolated jungle, how do you think our modern society would react? How would we treat this new species, so like us yet so different? Would we afford them the same rights that we afford other members of our species, or would they be treated more like… animals?
My own answer to this question is probably more complex and more dependent on specifics that I could really go into here. First off, even if they are afforded the same rights that humans have, I don't think that they shouldn't be studied by science - humanely, of course. Discovering a living sister-group to H. sapiens would be an enormously important event, and one that could add a huge amount to our current anthropological knowledge. Aside from that, I do think that they should probably be afforded the same rights that humans have, since such a closely-related species would be very unlikely to not have a very largely overlapping range of reasoning ability, communicative faculties, and emotional depth. It's very difficult to imagine how this would play out in practice, though, and it would probably depend a lot on the specifics. If such a small population is discovered, they would probably fit the bill for "endangered species" right from the start, and in this case "treating them like animals" could also probably include trying to bolster and protect their population in order to prevent them from going extinct. But if they were true legal and moral equals to humans, would that kind of meddling behavior be appropriate, or should they be free to make their own decisions about the fate of their populace?
The idea of discovering a new species of living Homo raises a huge number of scientific and ethical questions that humanity hasn't faced since we dwelt alongside Neanderthals in the caves of our Pleistocene past. Five hundred thousand years ago, it's difficult to think about humans and Neanderthals in a way other than the sort of competition between animals we see all the time in nature. It's very difficult to imagine how a similar situation would play out in the present.