The Evolution of Intelligence

Part 3: The Evolution of Human Primates

Renato M.E. Sabbatini, PhD
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Beginning with the comon ancestor which humans share with anthropoids, the branch of human primates started also in Africa, probably 6 to 8 million years ago and reach up to modern man (who arose probably around 150,000 to 200,000 years ago and then spread to the rest of the world). They were called Hominids, and are included in the superfamily of all apes, the Hominoidea, the members of which are called hominoids.

Man's evolutionary tree is not a single, continuous line along time, as many people think. Scientists have evidence that there were many "dead end" branches, with hominid species who died out without leaving descendants. It is very difficult to determine our direct evolutionary line, and there are still several missing links, not to mention that sometimes there is discordance among scientists about what constitutes the best guess.

The "family tree" of apes and humans. There is no fossil record for the great apes, so the
exact branching can be inferenced only on the basis of molecular biology analyses. The exact
lineage of extinct branches of Australopithecines (such as A. bosei, A. aethiopicus, A. robustus)
and the place of A. africanus in man's direct lineage are still open to dispute.

However, we know that our evolutionary line has had two main moments: the first and most ancient one was that of African hominids, which encompasses the Australopithecus genre. The second and most recent one is the Homo genre, including the extinct species which were almost surely our direct ancestors: Homo habilis and Homo erectus. They inhabited Africa earlier than 2 to 2.5 million years ago and their remains have been discovered in the Olduvai Gorge in Tanzania and in Lake Turkana, in Kenya. Homo habilis, in accordance to its name, was the first species to manufacture tools and use fire.

Sites in the world with sites where skeletal remains of hominids and prehistorical Homo have
been found. See how Southern and East Africa harbor the majority of findings.

Homo erectus was the first human to spread out of Africa to the world, including Europe, Middle East and Asia. This species became extinct in all locations except Africa,  where it developed into the so-called archaic Homo sapiens (there is still a clear a missing link from H. erectus to H. sapiens). Therefore, Southern Africa seems to be the "cradle of humanity".

Ancient Homo sapiens' evolution was bolstered by the genetic isolation caused by deserts and mountains in that part of the continent. This species later spread out again to Africa, Europe, Asia, 200,000 and 100,000 years ago), where it evolved into Homo sapiens neanderthalensis (the Neanderthal man, an adaptation to cold environments, and which is not considered a direct ascendant to modern man, but rather a closely related species ), and modern Homo sapiens sapiens, an adaptation to the warm environment of Africa.

Scientists have recently announced the probable discovery of a common ancestor of both Neanderthals and modern man, named as Homo antecessor. It lived 800,000 years ago, in what is now Spain. Ultimately, Neanderthals succumbed 30,000 years ago, probably due to competition with Homo sapiens sapiens, or by interbreeding with it, or both.

The "Turkana Boy", one of the first Australopithecus found in Africa, in Lake Turkana, Africa.

"Lucy", a remarkable find
of Australopithecus afarensis, found in Olduwai Gorge, 

Skull of the Taung girl, the first discovery of an
ape-man (Pitecanthropus, old name for Australopithecus)
made by Raymond Dart in South Africa

The so-called "Out of Africa" model has also been supported by evidence from molecular biology. Studies of the mitochondrial DNA suggest that all modern humans originated from a small population living in Southern Africa. Since mitochondrial DNA only pass along feminine lines, this ancestor of ours has been nicknamed the "African Eve".

Below we see a summary in table format of the main evolutionary line of the human species.

Australopithecus afarensis
3 million to 4 million years ago A short (1.2 to 1.5 adult stature), bipedal hominid, lived in Africa. It is the second oldest australopithecine found. Hands and teeth were very similar to modern humans, but its brain was no larger than a chimpanzee's. Fossil footprints of A. afarensis were also discovered.

Astralopithecus africanus
3 to 2,5 million years ago. With a very robust skeleton, A. africanus was the first hominid to be discovered, in South Africa, and was similar to A.. afarensis. Together  with A. robustus, A. aethiopicus and A. boisei, three other related species, they probably did not belong to the Homo lineage, but rather formed a distict branch which died out 1,5 million years ago.

Homo habilis
1.8 to 2.4 million years ago Was the first human to create stone tools and probably had communication by speech. It was the evolutionary transition between H. erectus. Arose and was limited to southern and eastern Africa, and probably spent part of its time in tress, because it had long arms. However was not much taller than australopithecines.

Homo erectus
1,600,000 to 250,000 years ago. Was the first human to travel widely and to occupy many continents. It was found in Java, Indonesia, China, Europe and Africa. It used tools and fire, lived in caves, hunted in groups and could survive in cold environments. Had about the same weight and height of modern humans.

Homo sapiens neanderthalensis
250,000 to 30,000 years ago. Considered a subspecies or a species which arose in parallel with Homo sapiens, it had a low skull with heavy brow ridges and a small forehead. Body and brain size was larger than H. sapiens. Lived in northern Africa, most of Europe and Middle East. They used clothing, caves,  fire, buried their dead, and may have had religion of some sort. Existed for some time simultaneously with H. sapiens, but disappeared misteriously.

Homo sapiens sapiens
250,000 years ago to present time This is the modern human being and the only living Homo species. Was preceded by archaic Homo sapiens, who appeared 500,000 years ago, lived in Europe and Asia and had a less developed brain. Has a high boded skull with the largest brain, no orbital ridges and a flat face.

The Author

Prof. Renato M.E. Sabbatini, PhD is a neuroscientist and a specialist in medical informatics, holding a doctoral degree in neurophysiology by the University of São Paulo, Brazil, and a post-doctoral fellowship at the Max Planck Institute for Psychiatry, in Munich, Germany. He is the director of the Center for Biomedical Informatics and associate professor and chairman of medical informatics at the Faculty of Medical Sciences, both at the State University of Campinas, Brazil.
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"The Evolution of Intelligence"
Renato M.E. Sabbatini, PhD
Brain & Mind Magazine, February/April 2001

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Copyright (c) 2001 Renato M.E. Sabbatini
State University of Campinas, Brazil
First published on: February 15th, 2001
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