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!
