Opinion: How Do You Miss a Whole Elephant Species?
Lee R. Berger
for National Geographic News
|December 17, 2001|
How do you miss a whole species of elephant? They are, after all, the largest living terrestrial mammals on Earth, with male African elephants reaching an astounding 6,500 kilograms (14,330 pounds). But that's just what has happened.
Up until recently, scientists believed there were two species of elephant: the African elephant and the Asian elephant. Geneticists conducting a comprehensive DNA sampling of elephants from across Africa recently found that there are in fact two species of African elephants.
Until this announcement, most zoologists had lumped all African elephants together into a single species, Loxodonta Africana, with four widely recognized sub-species. Now, genetics has proven that one of those sub-species, Loxodonta africana cyclotis, commonly known as the forest elephant, is in fact a distinct species.
The newly identified species, named Loxodonta cyclotis, means that Africa is home to both the "savanna" elephant and the "forest" elephant.
The announcement of a new species doesn't come as a total surprise. A few astute zoologists saw the forest elephant for the distinct species that it was years ago. German zoologist Paul Matschie described the species Loxondonta cyclotis in a paper published in 1900.
In 1931, a French zoologist named Frade also offered his support for the existence of a forest elephant species based on, of all things, the number of toenails elephants have. Frade observed that a typical savanna elephant has four toenails on each forefoot and three on each hind foot. In contrast, the forest elephant, Frade observed, typically has five toenails on each forefoot and four on each hind foot. Unfortunately for Frade, what he failed to realize is that all elephants, savanna and forest alike, have five nicely shaped toenails on each foot, fore and aft, at birth. Because of the rough terrain they traverse, savanna elephants tend to lose a greater number of toenails as they mature, leaving them with the statistically averaged four front and three rear toenails.
Other zoologists noticed more definitive characteristics, such as the shape of the mandible, which is short and wide in the savanna elephant while being long and narrow in the forest elephant, and the shape of the ears, which are rounded in the forest elephant and pointed in the savanna elephant. In addition, the forest elephant is smaller, with males only rarely reaching above 2.5 meters (8 feet) in height. A large male savanna elephant can reach nearly 4 meters (13 feet), with averages commonly above 3 meters (10 feet). Despite these observed distinctions, most scientists didn't generally go as far as suggesting that these differences were great enough to warrant a division into two species.
Conservation authorities have noted for decades an extreme difference between the confiscated illegal ivory of the forest elephant and that of the other sub-species of Africa elephant. In the forest elephant, the ivory is long, skinny, and straight, with a pinkish tinge, and is highly valued for its hardness. The savanna elephant has the more familiar thick, curved ivory shape.
The long-standing debate over one species or two was considered definitively "settled" with the publication of two studies in 1958 and 1974. Both found that the L.a. cyclotis and L. africana interbred where their ranges overlapped; thus their differences could, by the "mate-recognition" concept of a species, be only "sub" specific. Scientists have since found that the actual areas where the forest and savanna elephants habitats overlap are few and far between, making their opportunities to hybridise actually quite rare.
The recent genetic recognition of two species overturns this idea of sub-specificity, although the study alludes to low levels of interbreeding in the isolated cases where the ranges of the two species meet. What is most surprising about the finding is the extent of genetic differences observed between the two species. The forest elephant is more than half as different genetically from the savanna elephant as the African elephants are from the Asian elephant Elephas maximus. To place this in perspective, the African forest elephant and African savanna elephant are more distant from each other genetically than a tiger is from a lion or a horse is from a zebra.
Following the Ancestral Trail
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.
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