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TOWER HILL EDUCATIONAL FUND
A/C 20067
Bank of Nova Scotia
1-3 Knutsford Blvd.
kingston 5,
Jamaica

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THE ORIGIN OF MAN

By Brian Freeman
Professor of Animal Ecology, 
University of the West Indies
Mona Campus, Kingston 7
Jamaica

The question of human origin is bound inseparably to the process of organic evolution. But the fact that this process was not discovered much earlier than the nineteenth century, may be due to retrogressive features in the philosophy of Plato, and especially to that of his idealism. Plato's explanation of variation, the primary component of evolution, rested on the concept that for any species there was an ideal. There existed an abstract but perfect cat, a perfect horse and a perfect man and woman. Within any species the bulk of all individuals fell short of the abstract ideal and this provided an easily understood explanation of their variation. They were inferior.

With the crucial influence that Platonic philosophy had on the development of the Christian church, as distinct from the teachings of Jesus of Nazareth, species were seen as the creations of an omnipotent being. Hence they must be perfect and immutable. To suggest that one species could evolve into another would be clearly blasphemous. And beware the Inquisition!

In eighteenth century Europe, agriculturalists and horticulturalists promoted selective breeding of their stock and crop plants, tapping the inherent variation of these organisms. But the changes in the characteristics of the species they wrought were viewed as revealing this variation within each species, not that one species could be changed into another. Hence, everything was still kosher as far as creation and the immutability of species were concerned. But what the breeders had unwittingly tapped into was the prodigious power of natural selection to promote organic change. One could call it artificial selection now but that matters little: much later (1950) Koopman was the first to generate speciation in the laboratory by this very process.

But to return. The next clue to the nature of organic evolution came from an unlikely source: civil engineering. At the end of the eighteenth century massive improvements were being made to existing roadways by means of embankments, drainage and cuttings. Additionally a canal system was started in England. This travail revealed the general existence of geological strata. The scale of this work was, of course, far greater than could ever have been accomplished by geologists themselves, but provided them with an immense collection of fossils in their respective strata. These fossil sequences could only be interpreted as revealing that one species evolved into others over time. Hence, species were indeed mutable. The discovery of this process of phylogenetic change, which was first argued for by the -Charles Darwin's grandfather, the multi-talented Erasmus Darwin, about 1770, and later promoted more famously by the French biologist Jean Baptiste Lamarck, ranks as a major achievement in human understanding.

The mechanism causing this change was first thought to be the inheritance of acquired characters. Features acquired during the fife of the individual in its interaction with the environment would be transmitted to the offspring. Again, this mechanism was first suggested by Erasmus Darwin, and later developed by Lamarck, much to his detriment.

The influence of natural selection in promoting evolutionary change, however, began to be suggested in the early part of the nineteenth century by relatively unknown biologists: Wells, Blyth and Matthews. Although Erasmus Darwin was probably close to describing natural selection at the end of the previous century, the political climate in England (For King and Country!), as a reaction to the French Revolution, was against him. Somewhat later the geologist von Buck following his studies in the Canary Islands, proposed a theory of geographical speciation as early as 1825. But the fully developed theory of evolution by natural selection by Charles Darwin and Alfted Wallace did not come until 1858.

Charles Darwin wrote two seminal works, the "Origin of Species" in 1859 and "The Descent of Man" in 1871, both of which are characterized by immense detail as any one who has slogged through them will testify. In the latter book Darwin argued for man's affinities with apes and monkeys on the basis of comparative anatomy, embryology and behavior, not on the basis of a fossil record. This was for the very cogent reason that in Darwin’s day man's knowledge of the fossil record was extremely scant. The only decent material was from a cave in the valley of the River Neander, near Dusseldorf. One current opinion was that these were the remains of an adventurous Cossack officer who had deserted in the war of 1814. Later, of course, these proved to be the fossilized bones of an arthritic individual of Neanderthal Man. You can see there was little expertise in human palaeontology at that time.

Milestones in the quest for "missing links", as they were then called, were the discovery by Eugene Dubois in 1891 of Java Man and in 1929 of the closely related "Peking Man." These remains were originally thought to be of ape-men of the genera Pithecanthropus and Sinanthropus, respectively But they are now regarded, along with a large amount of material from Africa, Asia and Europe, as belonging to an early species of man, Home erectus, a species which existed for almost two million years, having only recently become extinct (30,000 years ago) in Indonesia. They were men rather than ape-men because they made stone tools with a consistent pattern, referred to as the Acheulian Culture.

Raymond Dart discovered the first true ape-man, Australolpithecus africanus back in 1925 in the Transvaal. But the English anthropological establishment (Elliot-Smith, Keith and Zuckerman) were emotionally prejudiced against man having his origins in Africa. Consequently, they spent a small fortune fruitlessly scouring China! Dart's work, later assisted by the charismatic Robert Broom, produced on a shoe-string budget a great deal of ape-man material. There were clearly two species: a heavy-jawed vegetarian, which became known as Australopithecus robustus, and a fighter, hunting species of the late Pliocene savannahs, A. africanus. The latter probably did not make tools to any characteristic pattern but employed suitable bones and horns in their stead.

Later on the Leakey family began to gather a rich harvest of fossil ape-men and early man in East Africa. Most importantly, they discovered what is possibly the first, tool-making man, Homo habilis. This little fellow, the immediate ancestor of Homo erectus, was clearly derived from Australopithecus africanus. Indeed,. upon its discovery, debate centred as to whether the species were truly distinct. But as more material was collected and an association with tool artifacts established, Leakey's claim to have found the first true man was strengthened.

More recent additions to our knowledge of man's origins come from Ethiopia. Studies on human affinities with the great apes by molecular geneticists have defined the chimpanzees as our nearest living relatives. Some 98% of our genes are the same as in these apes and such studies point to an evolutionary split with their stock only 6 million years ago. Too close for comfort, some say. The fossil evidence, however, before the new Ethiopian finds, stopped at about 3 million years ago. Then in 1979 Donald Johanson, working in the Afar Valley in the north east of the country, discovered Australopithecus afarensis, which was dated between 3.0 and 3.8 million years ago. Most interestingly, these ape-men already had completely rounded, humanoid pelvis and other features showing that they were completely agile on the ground. But the features of the skull were much more ape-like than A. africanus. The left and right molar rows were parallel to each other, as in apes, and there were large upper canine teeth. Their long arms and relatively small size, however, would still have allowed them to be good tree climbers.

Late in 1994, yet another ape-man was discovered by Tim White in older, early Pliocene deposits in Ethiopia. So far we are in possession of only skull and arm material and are therefore unsure as to whether the locomotion of these creatures was arboreal or terrestrial. It has been named Ardipithecus ramidus, the "root ape-man". The dental structure, however, places it much nearer to the chimpanzees than even Australopithicus afarensis, while the dating is about four and a half million years ago.

Further discoveries indicate that ultimately the course of human evolution will prove to be a complex one. We have long passed the stage of "missing links" in a linear path. More appropriate would be the concept of a tangled web, for we now have some fifteen probable men and ape-men in the known fossil record. And this number will surely increase. For instance the genus Australopithicus also gave rise to three more modem species of ape-men, in the genus Paranthropus who lived about 1. 5 to 2.2 million years ago. The original A. robustus has been transferred to this genus and P. boisei and P. aethiopicus recognised. And in the new Millennium a new primitive species, Kenyanthropus platyops, has been described by Meave Leakey. It is dated at about 3.5 million years ago and provides a possibly new evolutionary pathway to Homo.

These fossils, taken in conjunction with information concerning palaeo-climatic and palaeo-botanical changes during the last five million years, give the following possible evolutionary scenario for man and his ape-man ancestors upon a primarily African stage.

At the start of the Pliocene era five million years ago, drying of the continent led to a contraction of the formerly massive tropical rain forests and a concomitant increase in the areas of savannah. Man's evolution involved two major features. Firstly, the comparatively rapid process of terrestrialisation, taking only, perhaps, half a million years, and secondly the long process, of development as co-operative hunters on the savannahs and later of other regions. Probably the most telling features of the second phase are the redistribution of hair to promote cooling, the reduction in the weight of the alimentary system to give a better power-to-weight ratio (typical of carnivores), and the ultimate development of communication by speech and hence radical modifications to the mouth, tongue and teeth, and the cerebral evolution to handle such a detailed transfer of-information.

Tropical rain forest and savannah are sharply-contrasted environments, the first characterised by stability and the availability of water and shade, and the second by extremes of temperature, humidity and immolation. Probably the only way for man's early ancestors to achieve the transition would be to use riverine gallery forest as a refuge and home base, while making increasingly ambitious excursions into the adjacent savannah for hunting purposes. This may well have been the life style of the australopithecines, A. ramidus and A. afarensis. Dart's discovery of A. africanus in the Taung Caves, however, suggests that by this phase of ads evolution he was independent of forest. Further, man's conquering of the harsh savannah environment my well have preadapted him for his later migration to all parts of the world. Such an expansion of population took place during the Homo erectus phase of his evolution, and again in the emigrations of our own species from Africa perhaps 70,000 years ago. In this connection, it is noteworthy that modem man is virtually the only primate to live naturally outside the tropics (the Japanese and Rhesus Macaques are further exceptions).

Man brings a whole baggage of his evolutionary past into his present world which has been exhaustively hammered in a series of books by Desmond Morris. But in conclusion, we have space here to touch on just two aspects which highlight the differences in evolutionary background of men and women. The co-operative hunting of the men was clearly the root of the importance we place on sports both as participants and spectators. In these, physical skill, courage and male bonding are at a premium. Sport is essentially male in terms of participation, particularly so in contact sports: consider;. the following. Firstly, in almost no sport do men compete against women. Secondly, numerically and financially men dominate sport. Finally, women (as well as men) are extremely interested in watching male sporting activities. Think of wrestling.

Younger adult men even today have a much higher death rate than do women (the Canadian figures are four to one in the age group 15 - 30) and likely there would have been an even higher differential in primitive man. Hence we expect a strongly female-biased sex ratio at reproductive age and thus competition among them for mates. This is one explanation of the fact that today women spend much more effort in improving their personal appearance than do men. While the cosmetics industry has tried its level best to promote male cosmetics, these account for only a minor fraction of total sales. Indeed, men who rely overly in such products are usually regarded by women as being more interested in themselves than in prospective mates!

 

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