Contents Updated: Tuesday, August 24, 1999
Sarich and Wilson found mankind and the chimpanzees to have separated as little as five million years ago. More unusual evidence of the date of our separation from the apes comes from DNA studies of the herpes virus. Herpes simplex causes cold sores and genital warts in primates. Though a single species, it exists in humans as two races each with its own preferred site for colonization. In the other apes, it exists as only one variety and does not mind whether it is introduced to the oral or the genital region. Why are there two herpes races for humans but only one for the other apes?
Herpes is only transmitted by intimate contact—in the apes by sexual contact. Female apes are only in oestrus occasionally and male apes, like many other mammals, use their noses and tongues to determine when the female is becoming receptive. The virus has plenty of opportunity to get from one orifice to the other. Human females however are receptive all the time. The male has no need of a test for oestrus. Kissing became the main show of interest and affection. Human behavior cut down the opportunities for the virus to swap sites.
Over several million years the virus has begun to evolve into separate species, one suited to genital transmission and one suited to oral transmission. Speciation is not yet complete possibly because oral sex, though serving no obvious purpose, is still indulged in by some humans for pleasure, an evolutionary anachronism.
An American team of microbiologists have used the molecular clock to date the human herpes virus to somewhere between 7.5 and 10.7 million years ago. This is earlier than the more direct estimate of the antiquity of mankind but ties in well with the gap between ramapithecus and Lucy when the human line probably separated. Possibly, the apes' behavior patterns were changing before the separation of the hominids occurred so that the emergence of the herpes races pre-dated it.
Interpolating as best we can, the hominids appeared perhaps seven million years ago, near the start of the gap in the fossil record which lasts until the time of Lucy (A.afarensis).
Not all hominids were man's ancestors. Some apes that made the transition from the woodlands (or evolved from the ones that did) failed to learn how to make stone tools and became extinct. Johanson and White regard A.afarensis as ancestral to Homo, the species of men, and also to A.africanus and A.robustus, the extinct lines. The Homo branch split off about three million years ago and the result was ourselves. The Australopithecine line proved a dead end when africanus evolved into the more specialized robustus. This became extinct about a million years ago possibly because of the unwelcome attentions of hungry Homo, and competition in the same ecological niche from some monkeys, which, faced with the same problems as our ape ancestors about four million years ago, moved to open country, sleeping in trees and caves. They were baboons.
Walking upright preceded any other human traits (kissing would have accompanied this change). A.afarensis stood fully upright but was not regarded by Johanson and White as Homo. If it were then all its descendants, the other upright Australopithecines, including robustus, would also have to be classified as being Homo. The key distinction between the Australopithecines and Homo is that only Homo seems to have made stone tools. Not that the Australopithecines did not use tools. Fairly surely they used what they found about them, perhaps even more so than chimpanzees which use objects found around them as tools and weapons, and can even fashion simple tools by stripping leaves from sticks. But only Homo has left evidence of manufacturing tools, by knapping stones, from about two million years ago onwards. Australopithecine hominids had been around for one or even two million years before tools are found, indicating that they did not invent them.
Not all anthropologists accept these ideas. Some believe that A.africanus is indeed in the human line and did make a very simple stone tool by striking a stone to give it a sharp edge. They argue that this released the brake on the evolution of intelligence and progress speeded up leading to man . Only A.robustus split off into an evolutionary dead end by sticking to a diet largely of fruit and leaves. With this diet they did not need to make tools and eventually, becoming easy meat for their brighter cousins, were hunted to extinction.