Ardipithecus ramidus - 4.4 million years old. Name means “ground ape” and “root.” May represent the first human ancestor after the common anscestor with chimps. Others believe that it is actually in the chimp lineage and not human. Appears to have unique method of locomotion.
Australopithecus anamensis: lived around 4 million years ago?
Australopithecus afarensis: lived 3.9 to 3 million years ago.
Australopithecus africanus: 3 to 2.3 million years ago. Had powerful arms and short legs. Teeth show wear patterns similar to modern primates that feed maily on leaves and fruit. Anatomical evidence indicates that these early homonids spent much of their time among tree branches avoiding predators on the ground as well as in the air.
Austrolopithecines had apelike bodies and smaller brains than Homo, but they were definitely bipedal, which marks all homonids. They have the spinal hole in the skull at the base of the skull, not at the rear as in four-legged primates. Scientists have identified at least 7 spp of australopithecines, including several species called robust australopithecines. The robust types had larger jaws for crushing tough plant foods in their high fiber diet.
Move to bipedalism spurred by: (1) shift to drier, open woodland, (2) fruit gathering from small trees where it was more efficient to gather from the ground than from the branches, and (3) higher energy efficiency to stay on two legs between trees than to repeatedly raise and lower the body. Consequently, the hands were freed to do other things.
Evolution of foot adaptations for walking upright came slowly. Some fossil evidence indicates that the ankle had anatomical modifications that preceded changes in the toes. One homonid fossil has a human-like ankle but still has a big toe that could deviate outward like an apes, or point forward for walking. Evolutionary changes don’t come in huge leaps, but through the accumulation of many small, usually gradual changes.
Bipedalism allowed homonids to gather a wider varitey of foods. Walking upright also exposed more skin to moving air to cool them on the open plains, and exposed less skin to absorb solar heat. During the period of highest heat load, a biped gets only one-third the heat load that a quadruped receives.
Pollen trapped in ocean floor sediments along coasts tell us a lot about past climates by telling us what plants were growing in the area at the time. Vegetation patterns can tell us about temperature and rainfall. Prior to 3.5 million years ago, Africa was warmer and wetter with more extensive rain forests. Then North and South America moved closer together and the Isthmus of Panama rose and changed global circulation patterns. Rain forests in Africa got smaller, broad stretches of grassland divided forests, and Africa became cooler and drier. This shift in the weather pattern of Africa may have promoted the split between Australopithecus and Homo. Australopithecus inhabited much of Africa around 4 million years ago. The genus Homo appeared around 2.5 million years ago. There have been at least 3 genera of Homo: H. habilis, H. erectus, and H. sapiens. Why Australopithecus disappeared and Homo became so widespread is one of the persistent mysteries of anthropology.
Human brains use about 20% of the body’s total energy production. Australopithecines had a mainly herbivorous diet. Early Homo species added meat to the diet and increased the caloric intake per meal. Higher calorie meals and a higher quality diet allowed a reduction in gut size, which in turn allowed more energy invested in the further development of the brain. Members of the genus Homo were also tool makers and could cut through thick hides that teeth could not tear, crack open bones for fatty marrow and cut up and collect meat from larger animals, perhaps the victims of large predators. These three traits, enlarged brain size, high-quality diets and toolmaking all influenced each other’s development.
Homo habilis is one of the earliest known species of the genus Homo. Lived 2.5 to 1.6 million years ago. Homo erectus evolved later, followed by Homo sapiens. Just as Australopithecus had a split and evolved a robust line, the genus Homo had a split, probably at the Homo erectus stage and diverged into Homo sapiens and Neandertals.
NEANDERTALS
Named because fossils were first found in the Neander Valley in Germany. Neandertals appeared around 300,000 years ago and lived up until 30,000 years ago. They were resourceful, intelligent, and social humans. They used a variety of tools, were mainly carnivores and adapted to life in cold, harsh climates. They cared for their injured and made grave offerings when they died. The Neandertals were in Europe during periods of glaciation, and were adapted for the cold. They had short, stocky bodies which helped conserve body heat. They were very muscular, and had broad noses which would help warm air and add moisture to the cold, dry air they inhaled. They had larger brains than we do today. They used fire and made stone hearths. Their hyoid bone, which supports the voice box, is indistinguishable from ours, indicating that they were probably vocal, though we have no idea how complex a language, if any, they had.
Neandertals used not only hand axes, but also scrapers and points (flaked tools). Modern humans developed blade tools. Neandertals hunted with wooden spears with a sharp point, some may have had stone tips. They hunted cooperatively to bring down large animals and to kill numerous animals in a single hunt. Had to move in close to their prey and thrust spears into them. Very dangerous and often suffered injury. The pattern of injuries is most comparable to those suffered by modern rodeo riders. Indicates they were engaged in fairly violent activity. Life was tough with clans constantly on the move. The average life expectancy of the adult was 30 years of age.
We may share Homo erectus as a common ancestor with Neandertals, but that is still subject to debate. Homo erectus was the first hominid to leave Africa. Modern Homo sapiens began to spread throughout Europe some 40,000 years ago, and within 10,000 years Neandertals vanished. Did Homo sapiens kill them off by conquest, kill them off by disease, or simply outcompete them?