Fossil records indicate that the earliest primates probably appeared as prosimians only during the Paleocene (up to 65 MYA) and Eocene (up to 55 MYA) epochs. Animals more nearly like monkeys appeared in the Oligocene epoch (23-38 MYA). Fossil records reveal remains of monkey-like creatures for 10 million years, from 18-8 MYA. It has been postulated that the common ancestor of chimpanzees and humans lived about 6 to 7 MYA. The oldest fossil hominid yet discovered, Sahelanthropus tchadensis, found at the Toros-Manalla site near Lake Chad, was dated to between 6 and 7 MYA. The small skull was almost compete and was found to have small teeth, and a short face, but the upper face has strong brow ridges; and the teeth have thick enamel. This combination of traits has not been seen in any fossil ape. Sometime thereafter, the two species–chimpanzees and humans–went their separate ways.
Tim White, Ph.D., from the University of California, Berkeley, and his Ethiopian colleagues in the Middle Awash Project, Berthane Asfaw and Giday WoldeGabriel, working in the Afar Desert of Ethiopia, made a crucial discovery in 1994. They unearthed a nearly complete skeleton–125 bones in all–of a 4.4 million year old female Ardipithecus ramidus, which comes very close to what would be expected in the common ancestor of chimpanzees and humans, one of evolution’s holy grails. Ardipithecus’s foot was of special interest in that it had the ape feature of a separate grasping big toe, but was in all other respects similar to that of modern humans, built for bipedalism. Indeed, the skeletal remains were a fascinating mosaic of traits, some very primitive, some quite advanced, and some definitely hominid. The creature was both quadruped and bipedal, which makes it a very important intermediate ancestor between apes and humans.
Fossils were found in the Great Rift Valley of Africa dated to around 3.5 million years ago (MYA), by the work of the Leakeys, that showed the emergence of human form, Australopithecus africanus, which had obvious characteristics indicative of having come out of nonhuman antecedents. The complete skeleton of an adult female, informally called Lucy, which was found in Hadar in the badlands of Ethiopia, provided a superb specimen for study. Brain size was not much different than that of antecedent apes (about 1/3 the size of modern man’s), but the spinal cord entered the skull from below and not toward the back which meant that this creature walked upright; and this was confirmed by the structure of the pelvis. There are multiple evidence in Lucy’s skeleton that suggest that she was an intermediate species between Ardipithecus and the genus Homo. The genus, Homo, began to appear about 2.3 MYA, the earliest representative being Homo habilis, the handy or skillful man. Habilis had a larger brain (including a brain case that showed indentations from Broca’s and Wernicke’s areas), smaller teeth (especially reduced rear molars), an erect posture, relatively gracile (slender and delicate) features, and a thumb which was more flexible than that of modern chimps. Homo habilis is the first unequivocal complex tool user, having been found with a variety of flaked stone tools. He co-existed, at least in time, if not in actual proximity, with at least three other hominins—Paranthropus (or Australopithecus) boisei, robustus, and aethiopithecus. All of these had massive skulls, heavy chewing teeth, sturdy bones, and small brains; and all were extinct by 1.1 MYA. Habilis also lived during the same time period as three other members of genus Homo—ergaster, rudolfensis, and erectus. Homo habilis, dated from about 2.3-1.85 MYA, is a questionable human ancestor because its body was too small. It did have a similar skull with about a 750 milliliter capacity and with no vertex cresting. Many experts consider habilus to be more closely related to the australopithecines.
The genus, Homo, began to appear about 2.3 MYA, the earliest representative being Homo habilis, the handy or skillful man. Habilis had a larger brain (including a brain case that showed indentations from Broca’s and Wernicke’s areas), smaller teeth (especially reduced rear molars), an erect posture, relatively gracile (slender and delicate) features, and a thumb which was more flexible than that of modern chimps. Homo habilis is the first unequivocal complex tool user, having been found with a variety of flaked stone tools. He co-existed, at least in time, if not in actual proximity, with at least three other hominins—Paranthropus (or Australopithecus) boisei, robustus, and aethiopithecus. All of these had massive skulls, heavy chewing teeth, sturdy bones, and small brains; and all were extinct by 1.1 MYA. Habilis also lived during the same time period as three other members of genus Homo—ergaster, rudolfensis, and erectus. Homo habilis, dated from about 2.3-1.85 MYA, is a questionable human ancestor because its body was too small. It did have a similar skull with about a 750 milliliter capacity and with no vertex cresting. Many experts consider habilus to be more closely related to the australopithecines.
scientiffic reconstruction of a Homo habilis עברית: שחזור מדעי של הומו הביליס (Photo credit: Wikipedia)
The genus, Homo, began to appear about 2.3 MYA, the earliest representative being Homo habilis, the handy or skillful man. Habilis had a larger brain (including a brain case that showed indentations from Broca’s and Wernicke’s areas), smaller teeth (especially reduced rear molars), an erect posture, relatively gracile (slender and delicate) features, and a thumb which was more flexible than that of modern chimps. Homo habilis is the first unequivocal complex tool user, having been found with a variety of flaked stone tools. He co-existed, at least in time, if not in actual proximity, with at least three other hominins—Paranthropus (or Australopithecus) boisei, robustus, and aethiopithecus. All of these had massive skulls, heavy chewing teeth, sturdy bones, and small brains; and all were extinct by 1.1 MYA. Habilis also lived during the same time period as three other members of genus Homo—ergaster, rudolfensis, and erectus. Homo habilis, dated from about 2.3-1.85 MYA, is a questionable human ancestor because its body was too small. It did have a similar skull with about a 750 milliliter capacity and with no vertex cresting. Many experts consider habilus to be more closely related to the australopithecines.
A skeleton of an adult female with a transition form from 200,000 years ago (KYA) was found to have mtDNA (mitochondrial DNA) almost exactly like that of modern humans; so, she was informally dubbed “Eve”. Mitochondrial DNA is better preserved, more abundant, easier to work with, than chromosomal or especially Y chromosomal DNA and is passed only through maternal lines, hence the reference to the first mother. H. erectus was abundant after the middle Pleistocene Era 7-10 KYA, and there is evidence that erectus, habilis, and the australopithicines occupied the same territories during their more ancient existence. Some experts believe that erectus and habilus hunted the australopithicines to extinction. The lateness of existence of erectus puts H. erectus and H. sapiens sapiens (wise, or knowing man) on the earth at the same time indicative of the evolutionary change that took place. Homo erectus holds the distinction of being the first human to leave Africa. Erectus disappeared from the fossil record between 300 KYA and 60,000 KYA, the differences being for different populations spread around the world, after an earthly presence of 1.5 million years. Homo heidelbergensis–which appeared around 600-500 KYA–was more human in appearance and characteristics, and most experts consider heidelbergensis to be a highly likely direct ancestor of our species. Heidelbergensis had very heavy brows and large strong tibias. The species was tall. Heidelbergensis appears to be an intermediary species possessing a strong reinforcing ridge rising up above the acetabulum similar to erectus, and absent from sapiens. They were excellent tool makers and adept hunters like the Neanderthals. Anecdotal histories suggest that H. floresceinsis were sighted by historically modern men on the island of Flores, one of the Indonesian Sunda Islands.
Other specimens have been found that contribute to the concept that the human phylogenetic tree was more aptly a bush. Human-like species branched and re-branched into multiple dead-end species, and the evolutionary interrelationships of the animal fossils discovered are a source of continuing debate. At several points in ancient history, several different humanoids occupied the earth at the same time–including Neanderthals–a species that scientists estimate never exceeded 15,000 individuals even at the height of their occupation of Western Europe. They became extinct around 28 KYA.
Neanderthals–though very similar in genomes and possibly even able to interbreed with Homo sapiens sapiens–were not intermediate forms between apes and men according to most researchers. Neanderthals had large brains, some even larger than those of modern humans. They made cave paintings of life-like creatures and also some designs that were suggestively symbolic. Some Neanderthal burial sites contained funerary offerings and ochre pigments, which, along with the cave paintings, are suggestive of the first indication of human-like religion. They vanished from the fossil record about 28 KYA. Aside from the few remaining Neanderthals, after 60 KYA, only modern human skeletal remains have been identified. Intermediacy has been roundly challenged and denied by creationists and hotly debated by evolutionists. As noted above, human-like species branched and re-branched into multiple dead-end species. Neanderthals co-existed with modern humans for thousands of years and apparently copied some of the artistic accomplishments of Homo sapiens. The general physical features of Neanderthals early on were highly suggestive that sapiens and neanderthalis were directly linked in the chain of evolution. It is known, for example, from research by Lalueza-Fox, and Holger Rompler of the University of Leipzig, et al, who isolated a pigmentation gene from a Neanderthal fossil from El Sidron, that some Neanderthals had red hair, pale skin, and freckles. They appear to share the gene MCIR, and superficially, this would appear to be evidence of a direct linkage.
The discovery that this direct linkage is untrue is one of the remarkable achievements of evolutionary science and a strong evidence of the ability to make corrections in suppositions by utilizing the scientific method. The MCIR of Neanderthals and red-haired humans of today have been found to be quite unlike, so much so that it is evident that Neanderthals and humans developed the trait independently (convergent evolution). The recent (1987, verified by scientists working independently in laboratories in Munich and Pennsylvania) spectacular finding of measurable DNA in a Neanderthal arm bone from a specimen found in Neander Valley, Germany in 1856 revealed dramatic differences from all living humans in a study of 1000 people from around the world, differences more extensive than the differences between chimpanzees and humans. Further evidence from CT scans of the ear ossicles of Neanderthals and modern humans revealed distinct differences in shape. The DNA studies indicate that Neanderthals and humans separated genetically more than 500 KYA. Recent evidence indicates at least eight–found by a third generation of Leakeys–humanoid lines appeared and eventually disappeared, lacking the survivorship of H. sapiens sapiens.
The cultural record reveals very simple chipped stone tools found in conjunction with the hominin/humanoid fossils of around 2 million year old age for the earliest time. They were found near the broken bones of other, smaller animals suggesting that they may have been used for butchering and/or cleaning hides. Homo habilus fossils, found in Kenya’s Olduvai Gorge overlooking the Serengeti plain and dated to 1.8 MYA were found with stone tools and bones with evidence of butchering. An Israeli site yielded hand axes, evidence of elephant butchery, and slabs of worked wood dated to 800 KYA. During the next 500,000 years the tools became more sophisticated and were associated with the remains of larger animals. Aurignacian tool-making (finer stone point and even wood spear shaft construction) appears to have come from Asia to Europe.