Understanding Loxodonta as a genus of elephant has been a problem for modern zoologists and geneticists, as well as for paleontologists. Loxodonta emerged about 5 million years ago at the end of the Miocene (23 to 5 million years ago) and thrived throughout the early Pliocene (5 to 1.6 million years ago) in Africa. But about 2 million years ago it effectively vanishes from the African fossil record, replaced largely by a close relative of the Asian elephant, Elephas recki.
Loxodonta re-emerged in Africa about 500,000 years ago and in turn replaced Elephas, driving this genus rapidly to extinction in Africa. Based on the recent genetic evidence, what is now clear is that not one but two distantly related species of elephant re-emerged at about the same time. The geneticists "clocked" the divergence point between the African savanna and forest elephant and estimated a point of divergence around 2.5 million years ago. The prediction is interesting because this is close to the point when Loxodonta effectively vanishes from the fossil record of Africa. This implies that the two situations are linked and that whatever drove the reduction in numbers of Loxodonta also drove the speciation event. What is also surprising is that both species managed to thrive. Forest elephants are estimated to make up almost one-third of the total population of Africa's elephants.
Two paleontological mysteries arise in the face of the new genetic findings. The first is why Elephas recki, a successful grass eating elephant that lived throughout the Pliocene and Pleistocene (5 million years ago to 11,000 years ago) would relatively suddenly be pushed into extinction by the re-emergence of Loxodonta. The second question is why two species of Loxodonta?
Most isotopic studies of fossil elephants suggest that Loxodonta was also a grazer in its early stages before its reduction in numbers in the late Pliocene about 2 million years ago. Modern isotopic studies show that almost all African elephants, savanna and forest alike, prefer browsing to grazing, although some populations incorporate small amounts of grass into their diet. The question that must be asked is if Elephas pushed Loxodonta into the wooded and forested habitats to start browsing around 2.5 million years ago, why then was there a speciation event resulting in a savanna and forest variety of elephant?
As a final interesting and important note, conservationists are rushing to catch up with this discovery as it has critical implications for elephant conservation efforts. We can no longer just consider the number of "African" elephants anymore, but must recognize the number of each species present. Furthermore, and possibly more urgent, is the status of the elephants under present anti-poaching and ivory trade laws. The laws currently in place generally recognize Loxodonta africana specifically, thus creating a potential loophole for poachers and illegal ivory traders to take the "unprotected" Loxodonta cyclotis.
Lee R. Berger is director of the paleoanthropology unit for research and exploration at the University of the Witwatersrand in Johannesburg, South Africa. He has written for National Geographic and has appeared in many documentaries on human evolution. He received the National Geographic Society Prize for Research and Exploration in 1997.