The First Hominines

Homo Habilis

Studies in genetics, biochemistry, and anatomy confirm that chimpanzees and gorillas are humans closest living relatives, It is noted they are closely related to human than either is to orangutans. At the genetic level, humans and chimpanzees are at least 98% identical, so it is estimated that from a common ancestral stock somewhere between 5.5 and 8 million years ago.

In addition, fossils tell us humans were going their seperate evolutionary way by at least 4.4 million years ago. the best evidence is that our ancestry lies amoung a groupe of apelike animals living in Africa that were forced by climatic changes down onto the ground to get from one stand of trees to another as well as to supplement food that was becoming increasingly scarce in the trees.

Since they did not have the arms as long as those of modern apes nore as massive upper bodies, they tend to move on their hind legs when on the ground, with their bodies in an upright position. Advantages of this kind of bipedal locomotion were that the arms and hands were free to quickly gather food, to transport it to safe places for consumption, and to wield objects effectively in thereat display to protect themselves against ground-dwelling predators.

Additionally, they could transport offspring more effectively than merely allowing latter to hang by themselves. Finally, erect posture on the ground minimized the body area exposed to the hot sun, thereby helping to minimize overheating.
Next ------------------------------------------------------------ The First Hominines

The first undoubted hominines ( humans, or in this case, near humans) are represented by fossils from East Africa that go back 5.6 million to 5.8 million years. All are extremely fragmented, although about 45% of one individual is known from a site in Ethiopia.

Known as Ardipithecus, it is 4.4 million years old. Though much smaller than a modern chimpanzee, it is more chimpanzee-like in its features than any other hominine. However, unlike chimpanzees, and like all other hominines, it walked in a full human manna, that is, bipedally. Unlike other early hominines, Ardipithecus lived in a woodland environment, so it may represent an aberrant side branch of human evolution.

All other inhabited more open country and are assigned to one or another species of the genus Australopithecus. Opinions vary on just how many species existed; for the sake of simplicity, it suffices for our purpose to them simply as australopithecines. The earliest australopithecines fossils date back as many as 4.2 million, if not 5.6 million to 5.8 million, years ago,3 whereas the most recent ones are only about 1 million tears old. They have been found along the length of eastern Africa from Ethiopia to South Africa and westward into Chad.

None of these early hominines were as large as most modern people, although all were more muscular for their size. The structure and size of the teeth are more like those of modern people than those of apes, and the condition of the molars indicates food was chewed in hominine fashion: that is, with a grinding motion, rather than simply up and down movement of the jaws. Unlike the apes, no gap exist between the canines and the teeth next to them on the lower jaw, except in some of the earliest hominines. These retain some other apelike features, but otherwise australopithecine jaws are very similar to those of ealy Homo. The brain and body ratio, which permits a rough estimate of australopithecine intelligence, suggest this was comparable to that of modern chimpanzees or gorillas. In any event, the outside appearance of the brain is more apelike than human, suggesting that cerebral organization toward a human condition had not yet occurred. 4

Australopithecine fossils also have provided anthropology with two striking facts. First, by at least 4.4 million years ago, this hominine was fully bipedal, walking erect. Second, hominines acquired their erect bipedal posture long before they acquired their highly developed and enlarged brain. Bipedalism was an important adaptive feature in the savanna environment. A biped could not run as fast as a quadruped but could travel long distances in search of food without tiring. It could carry food to safe places, it could carry infants (rather than relying on them to hang on for themselves), and it was exposed to less direct heat from the sun than when in a quadrupedal position.

Furthermore, it could see farther and sopt both food and predators. Although these hominines were accomplished bipeds, evidence from the arm, hand, and foot skeletons of australopithecines indicates they had not given up tree climbing altogether. One reason may be that trees, sparsely distribute though they were becoming on the savanna, continued to be important places of refuge in a land teeming with dangerous predatory animals. Another is that food was still to be found in trees. Dental and skeletal evidence suggest that the males, who were about twice the size of the females, fed more often on the ground and lower levels of trees than females, who had a higher proportion of fruit in the diet. 5

A similar pattern is seen today among orangutans, where it is a response to highly dispersed resources. A major difference, of course, is that orangutn males still forage in the forest, whereas australopithecines did not. In such a situation, these latter may have been tempted to try out supplementary food sources on the ground, especially as existing sources became scarcer. This likely occured: A cold, dry climate episode has been identified for the crucial period between 2.3 million and 2.6 million years ago.

The major new food source was animal flesh, but, as we shall see, the activities of females were every bit as important as those of males for incerasing the amount of meat in the hominine diet.

------------------------------------------------------------

Homo Habilis

The increased comsumption of meat by evolving hominines is a point of major importance. On the savanna, it is hard for a primate with a digestive system like that of humans to satisfy amino acid requirements from available plant resources. In any event, failure to do so has serious consequences: growth depression, malnutrition, and ultimately death. The most readily accessible plant sources would have been the proteins available in leaves and legumes (nitrogen-fixing plants; familar modern examples are beans and peas). The problem is, these are hard for primates like humans to digest, unless they are cooked. The leaves, and legumes available contain substance that causr the proteins to pass right through the gut without being absorbed.

Chimpanzees have a similar problem when out on a savanna. In such a setting, they spend about 37% of their time going after insects, such as ants and termites on a year-round basis while increasing their predation on eggs, and vertebrate animals. Such animal foods not only are easily digestible, but also they provide high-quality proteins that contain all the essential amino acids in just the correct precentages. No one plant food does this by itself. Only the correct combination of plants can provide what meat does alone in the way of amino acids.

Nonetheless, abundant meat can be had on most savanna. One should not be surprised, if own ancestors solved their " protein problem" in much the same way chimps on the savanna do even today. Much has been written of a popular nature about the addition of meat to the hominine diet, often with many colorful references to "killer apes." References as such are absolutely misleading, not only because hominines are not apes, but also because they obtained their meat not by killing live animals but by scavenging, or even by stealing it from other predators.

It is significant that the teeth like those of australopithecines are poorly suited for meat eating. Even chimps, whose canine teeth are far larger and shaper,frequently have trouble tearing through the skin of other animals. What hominines need for efficient use of meat, in the absence of teeth like those of carnivorous animals, are sharp tools for butchering. The earliest tools of this sort, found in Ethiopia, are about 2.5 million years old. The only tools used before this time were probably heavy sticks to dig roots up, or ward off animals, unsharped stones to use as missiles for defense or to crack open nuts, and perhaps simple carrying devices made of knotted plant fibers.

The earliest identifiable tools consist of a number of implements made by striking flakes from the surface of a stone core, leaving either a one, or two-faced tool. The resultant choppers, flakes with sharp edges, andhammerstones were used for cutting meat, and cracking bones to extract marrow. These, together with the cores they were struck from, are known as Oldowan tools. Their appearance marks the beginning of the Paleolithic, or Old Stone Age.

Since the early 1960s, a number of the deposits in South, and East Africa that have produced Oldowan tools have also produced the fossil remains of a lightly built hominine with a body all but indistinguishable from that of the earlier australopithecines (7) except the teeth are smaller and the brain is significantly larger, relative to body size.

As a matter of fact: the inside of the skull shows a pattern in the left cerebrial hemispheir that, in human is associated with a speach area. This however, does not prove hominines could speak; it is clear that a marked advance in information - processing capacity over that of australopithecines occurred. Since a major brain size incerases, and a tooth size reduction are important trends in the evolution of the genus Homo, but not of any species of australopithecine, it seems as if these hominines, now known as Homo habilis ( which means " handy man), were evolving in a more human direction.

Most significant is that the earliest fossils to exibit such trend appeared about 2.4 million years ago, very soon after the earliest evidence of stone tool-making, and increased meat consumption.