The Evolution of Hominins
Classification of Humans:
Primates
'Primate' is the highest order of classification for mammals. The general characteristics of primates are:
- Arboreal life (in the trees), therefore primates have the ability to rotate their arms in their shoulder socket, which enables them to swing through trees
- Prehensile (grasping) digits with opposable thumbs and sometimes opposable toes
- Flat nails on digits
- Binocular vision (forward facing eyes)
- Colour vision
- Have large brains compared to the size of their body
Hominids
The term 'hominids' refers to organisms within the family hominidae of the order primates, which includes the great apes (chimpanzees, gorillas, orangutans) and hominins. The distinguishing features of hominids includes:
- No tail
- Shorter upper limbs and longer lower limbs
- Upright gait/bipedal locomotion (the ability to walk on 2 legs)
Hominins
The term 'hominin' refers to homo sapiens (modern humans) and our upright walking ancestors. The general characteristics of hominins are:
- Bipedal locomotion
- Living on the forest floor
- Curvature of the spine
- Shorter and broader pelvis than the great apes
- Longer lower limbs and shorter upper limbs
- Anterior foramen magnum
- Non-opposable big toe that in aligned with the other toes
How did hominins diverge from apes?
Approximately 6 to 8 millions years ago, a common ancestor of both modern Homo sapiens and chimpanzees was alive in Africa. Some scientists have inferred that the population must have been separated by a geographic barrier, such as a mountain range, that prevented any gene flow occurring between the populations. This caused allopatric speciation to occur. Over time, the different selection pressures that each population was exposed to would cause different mutations to arise in each populations gene pool (MacAndrew, 2003). Eventually, even if the two populations were brought back together, they would be unable to interbreed to produce viable, fertile offspring.
Species of Hominins
Ardipithecus ramidus lived in Ethiopia and northern Kenya, Africa 4.4 to 4.2 millions years ago. A team led by the American paleoanthropologist, Tim White found 110 specimen samples from approximately 35 different individuals of A. ramidus in Aramis, Ethiopia between 1992 and 1994.
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Australopithecus anamensis was present in northeast Ethiopia and Kenya, Africa 4.2 to 3.8 million years ago. An arm bone of A. anamensis was originally found by Bryan Patterson in 1965 in Kenya, but this one arm bone wasn't enough to prove that this was a different species of hominin. In 1994, paleoanthropologist Meave Leakey found more fossils of A. anamensis at the same site, and was able to identify A. anamensis as a new species of hominin.
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Australopithecus afarensis lived in Ethiopia and Tanzania, Africa approximately 3.9 to 2.8 million years ago. Fossils of A. afarensis were discovered in 1978 by two seperate fossil hunting teams, one in Ethiopia, the other in Tanzania.
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Kenyanthropus platyops evolved in Kenya, Africa over 3.5 to 3.2 million years ago. In 1999, a research team lead by Meave Leakey discovered a cranium and other fossils of K. platyops in northern Kenya.
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Australopithecus garhi is a species of hominin that evolved in Ethiopia, Africa approximately 2.5 million years ago. The fossils of A. garhi were discovered by a team lead by the Ethiopian paleoanthropologist, Berhane Asfaw and the American paleoanthropologist Tim White between 1996 to 1998.
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Australopithecus africanus evolved in South Africa 3.2 to 2 million years ago. Fossils of A. africanus were first discovered in 1924 at Tuang, South Africa. It took scientists another 20 years after 1924 to accept that Australopithecus were apart of the human family tree.
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Homo habilis inhabited Kenya and Tanzania, Africa 2.3 to 1.5 million years ago. Between 1960 and 1963, a team led by scientists Louis and Mary Leakey discovered fossils of H. habilis in Tanzania, Africa.
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Paranthropus robustus lived in South Africa 2.3 to 1.0 million years ago. In 1938, a schoolboy found fossils on a hillside at Kromdraai, South Africa. These fossils were brought to Robert Broom, who then discovered fossil fragments at the same site in South Africa. Broom then discovered that P. robustus was a new species of hominin, since the features of the skull were different to other hominin species.
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Paranthropus boisei evolved in Ethiopia, Kenya and Tanzania, Africa over 2.3 to 1.0 million years ago. In 1959, paleoanthropologist, Mary Leakey discovered a skull of P. boisei in northern Tanzania.
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Fossils of homo naledi were found in South Africa in 2015, however the age of H. naledi is currently unknown since the fossils were found in the Rising Star cave system and are difficult to date using either relative or absolute dating techniques.
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Homo rudolfensis lived in Uhara, Malawi and Lake Turkana of Kenya, Africa around 2.4 to 1.8 million years ago. In 1972, a team of scientists led by Richard Leaky uncovered fossils of H. rudolfensis near the shores of Lake Turkana, Kenya.
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Australopithecus sediba is an extinct species of hominin that was present in Malapa, South Africa 1.95 to 1.78 million years ago. In 2008, paleoanthropologist Lee Berger and his son, Matthew Berger uncovered fossils of A. sediba in Malapa, South Africa.
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Homo ergaster was a species of hominin present in Africa and Eurasia approximately 1.9 to 1.5 million years ago. In 1975, Colin Groves and Vratislav Mazák re-examined jaw fossils that were previously believed to have belonged to Homo habilis. They realised that these jaw fossils were different to those of H. habilis and re-classified them as H. ergaster.
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Homo erectus lived in Asia and Java, Indonesia 1.8 million to 300,000 years ago. In 1891, the dutch surgeon Eugène Dubois found the first homo erectus fossil in Indonesia.
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Homo heidelbergensis was a species of hominin that inhabited Africa, China and Europe approximately 800,000 to 100,000 years ago. The first fossil of H. heidelbergensis was found in 1907 in a quarry at Mauer, a village near Heidelberg, Germany.
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Homo floresiensis evolved in Indonesia about 190,000 to 60,000 years ago. A team of scientists comprised of both Australians and Indonesians found a nearly complete female skeleton of H. floresiensis in Liang Bua cave on the island of Flores, Indonesia.
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Homo neanderthalensis lived in Europe, the Middle East, Russia and North Africa 300,000 to 28,000 years ago. The first neanderthal specimen to be recognised as an early human fossil was found in 1829 in Germany. The species that the fossil came from was given the name homo neanderthalensis in 1864 by the geologist, William King.
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Archaic Homo sapiens evolved 300,000 years ago, however modern Homo sapiens evolved 180,000 years ago and are currently present today all over the world.
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