Contents Updated: Tuesday, August 24, 1999
The step from monkey to ape required a change in mobility at the shoulder and adaptation of the muscles of the abdomen to the upright rather than horizontal posture. 20 million years ago apes were common—monkeys were rarer. Only from about ten million years ago has the situation reversed. In the intervening period significant changes occurred. The linking of land masses gives an opportunity for evolutionary divergence and it was about 18 million years ago that Africa collided with Eurasia causing a flurry of evolutionary activity. Antelopes, pigs, elephants and rodents have all evolved since then.
Part of the reason for this was the evolution of grass from about 24 million years ago, the potential of which was achieved only when the world became colder and more arid 15 million years ago, providing an environment to be exploited by the grazing animals.
David Pilbeam, an Englishman teaching anthropology at Yale, has shown that by ten million years ago there were two major groups of apes, the dryopithecines having apelike teeth, and the ramapithecines, having human-like teeth with reduced canines and a flatter face. If their teeth differentiated dryopithecines and ramapithecines, a significant change of eating habits must have led to their evolutionary separation. Ramapithecus proved a very successful ape, its remains having been found in Europe, Asia and Africa. But despite its teeth, a carefully reconstructed specimen looks too like an orangutan for it to be a sure ancestor of human beings. The teeth remain a puzzle. Why do they look so human?
The Taung baby mentioned above was a much later type of ape (later even than Lucy) called Australopithecus africanus or A.africanus for short. Its teeth, says Don Johanson, a teeth and jaws specialist, are very similar to those of ramapithecus. Perhaps a link is still possible. In the four million years separating ramapithecus and Lucy, even the experts speculate unashamedly simply because there is no evidence.
Gribbon and Cherfas have suggested that the original brachiating apes, similar to orangutans or gibbons, emerged near the Indus which was then surrounded by dense forest. From there the apes spread out. Some moved Eastward through lush rainforests, ideally suited to them, to Indonesia where they still live relatively unchanged—the orangutan and the gibbon! Others migrated Westward via Arabia into Africa. They did not meet such familiar conditions. As they slowly migrated, the forests disappeared through increasing desiccation and the apes found themselves having to spend more time on the ground. By the time they reached Africa they had become knuckle walkers, and eventually chimpanzees and gorillas. Some chose to shelter in what woodland or forest the could find but others adapted to open grassland.
Orthodox savannah theorists believe that the apes were already in Africa but increasing desiccation forced some of the forest apes to adapt to woodland then to open country. A gradation of evolutionary niches were thus occupied by the apes; the apes which stayed behind in the deep forest became today's gorillas, in woodlands were the chimpanzees and on the savannah, man's family, the hominids.
The grassland's new visitors lacked the obvious requirements of success on the plains, being slow, unarmored, relatively weak and without claws or powerful teeth, unlike their competitors already there, but they survived and had made the transition by the time of Lucy. They must have had some advantages. What were they? Are they factors in the growth of intelligence?
Desmond Clark has put forward one intriguing speculation based on tentative evidence. He found burnt tree stumps associated with remains of fossil hominids four million years old. Did Lucy's contemporaries already use fire, keeping flame going by keeping tree stumps alight as farmers do today in India? If the answer is yes, fire could have been the vital factor that allowed hominids to move on to the savannah without having to fear predators. Domesticating fire might have been the essential step to humanity, and it might have happened very early on. A thought which must be regarded as not yet proven.
Other advantages were more evident: their binocular vision; their manipulative hands able to grasp a branch or a stone; their brachiating arms giving them the ability to brandish sticks and to throw stones; their well developed brains. Once on the savannah, lack of the usual specializations for grassland living forced them to compete by using these other advantages and by developing new ones, amongst which was the ability to stand erect. The apes had to be wary, and to use their keen vision to maximum advantage they had to stretch to their full height to look out for approaching cats or hyenas.
They took to walking bipedally, a habit which then proved to have other advantages. Hands and arms were permanently freed to grasp and wield the natural weapons that lay about and to allow the apes to change and improve those weapons. Groups of the new savannah creatures could, with the aid of stones and sticks, keep off dangerous predators. They also found that, with stones they could stun and maim at a distance. A well thrown stone is a remarkably good weapon.
As Richard Leakey puts it:
The extraordinary ability of modern humans to throw objects with force and with astonishing accuracy, even at moving targets is interesting... The brain mechanisms that underlie this unique accomplishment may have their evolutionary roots in the hunting activities of Homo erectus (the variety of man that went before us).
The sort of skill Leakey means can be seen on the cricket field and the baseball diamond where outfielders can place the ball with amazing precision even from distances of 60 or 70 yards.
Having learned a variety of hunting skills, meat would have given the savannah apes an additional advantage because the energy and protein of meat is concentrated. But the gathering of fruit, roots, berries, grubs, insects and fungus would have continued to provide their basic needs.
In the gap in the fossil record between ramapithecus and Lucy when did the forest and savannah apes separate? Differences in DNA show that mankind is more closely related to the chimpanzees, the common chimp and the pygmy chimp, than the other great apes. Man is the third species of chimpanzee, or alternatively, chimpanzees are two other species of men. They differ less in DNA than do some populations of the same species. The three parted company with their next closest relative, the gorillas, about nine million years ago.
Carl Linnaeus, the founder of modern taxonomy, classified mankind into a special category. Regretting his decision later, he said:
If I had called man an ape, or vice versa, I would have fallen under the ban of all the ecclesiastics. It may be that as a naturalist I should have done so.
Had Linnaeus had the courage to defy the churchmen, we might now be less anthropocentric, more humble and have more empathy with the other inhabitants of the planet.