for National Geographic News
A team of researchers led by paleoanthropologist Meave Leakey sparked a
controversy among evolutionary scientists and the press alike earlier
this year when they announced the discovery of a new genus and species
of ape-man.
They named their find Kenyanthropus platyops,
the "flat-faced man of Kenya." Ordinarily, the find itself would be
enough to spark a flame of controversy in the heart of any follower of
human origins research. But this find also highlighted an ongoing debate
within the scientific community over the adoption of a new system for
naming, ranking, and classifying organisms.
The debate is not confined to ivory tower scientists. The fossil discovery was widely reported. The New York Times referred to the new genus as a hominid; National Geographic reported on the find as a hominin. National Geographic subsequently received several hundred e-mails complaining about the poor editorial work of the staff that had clearly erred by replacing a "d" with an "n."
But were they really wrong, and more important, does it really matter?
Linnaean Classification
The taxonomic classification system devised by Linnaeus in 1758 is still used in modified form today. Animals are identified, in descending order, as belonging to a Kingdom, Phylum, Class, Order, Family, Genus, and finally a Species. This classification system is based largely on the animal's physical characteristics; things that looked alike were placed together.
In the Linnaean system, humans would be categorized first as Animalia; then Chordata because we have a backbone; Mammalia because we have hair and suckle our young; Primates because we share with apes, monkeys, and lemurs certain morphological characteristics; Hominidae because, among a few other criteria, we are separated from the other apes by being bipedal; Homo being our generic classification as human; and finally sapiens, a species name meaning, rightly or wrongly, "wise."
The Linnaean system also recognizes such groupings as superfamilies and sub-families. In the case of the human lineage, the most often recognized superfamily is the Hominoidea (hominoids), which includes all of the living apes. It is from this point onward that most of the present human origins classification debate begins.
The traditional view has been to recognize three families of hominoid: the Hylobatidae, the Hominidae, and the Pongidae. The Hylobatidae include the so-called lesser apes of Asia, the gibbons and siamangs. The Hominidae include living humans and typically fossil apes that possess a suite of characteristics such as bipedalism, reduced canine size, and increasing brain size such as the australopithecines. The Pongidae include the remaining African great apes including gorillas, chimpanzees, and the Asian orangutan.
New Molecular Evidence
Modern-day genetic research is providing evidence that morphological distinctions are not necessarily proof of evolutionary relatedness. Recent evidence suggests that humans are in fact more closely related to the chimpanzee and bonobo than either species is to the gorilla. Chimps and humans share something like 98 percent of genes, indicating that we share a common ape ancestor.
Divergence times between the two groups based on a molecular clock suggest that the chimpanzee/human split occurred between five and seven million years ago. In turn, the African apes, including humans, are more closely related to each other than any are to the orangutan.
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