BiologyClassroom
Human Evolution
Modern humans are a young species in geological terms. The earliest fossils that meet the criteria for archaic Homo sapiens, the genus and species name for humans today, date to about 400,000 years ago, while modern humans have been around for perhaps 170,000 years or so.
The apes that would ultimately evolve into the humans of today split from the so-called lesser apes about 7 million years ago. These are the Hominidae, or great apes. This is the approximate time frame given for the divergence of the human lineage from that of chimpanzees, humans’ closest surviving relatives. This divergence is believed to have taken place in Africa, with many early hominid fossils gathered in Kenya. Several different candidates exist in terms of which organism ultimately evolved into modern humans rather than ultimately dying off.
It was in the Miocene age that the family Hominidae split from the Pongidae(apes) family. Dryopethicus was the first in the evolution of man in the stages of evolution and some believe him to be the common ancestor of man and apes.
Dryopethicus:
He was the earliest known ancestor of man. Dryopethicus inhabited the European region and some parts of Asia and Africa. Dryopithecus is one of 40 genera representing up to 100 species of extinct apes that lived during the Miocene (22.5 to 5.5 million years ago). Dryopithecus fontani was the first fossil great ape discovered. It was discovered in France in 1856. Like all living apes, dryopithecines possessed relatively large brains. They also show apelike characteristics associated with a reduced reliance on smell and an increased emphasis on vision: they had shortened snouts and forward-facing eye sockets with overlapping fields of vision. Like all living apes, dryopithecines also lacked a tail. The skeletal remains indicate that dryopithecines were quadrupeds, walking on four legs. Scientists suggest that Dryopithecus was the likely ancestor of African apes and humans.
Australopithecus Afarensis:
This species lived between 3.9 and 2.8 million years ago. This species is one of the longest lived and well known. They are known to have survived for 900,000 years. This ancestor of modern humans would have been recognized as having both ape-like and human-like features. The earliest example was discovered in southern Africa in 1924 . Australopithecus means ‘southern ape’ and was originally developed for a species found in South Africa.
The word afarensis is based on the location where some of the first fossils for this species were discovered — the Afar Depression in Ethiopia, Africa ‘Lucy’ the famous fossil belonged to this species.
Australopithecus was 1.2 meters tall ( less than 4 feet ) . The fossils show the foramen magnum that was large to indicate upright walking. But still it retained many ape-like features including adaptations for tree climbing, a small brain, and a long jaw. The brain was small, averaging approximately 430 cubic centimetres .The forelimbs were different from those of the earlier ape-like ancestors. They had teeth like humans.
Homo Habilis — ’The handy man’:
Homo habilis, known as ‘handy man’ is a species of the genus Homo which lived from approximately 2.33 to 1.4 million years ago, during the Pleistocene period. The discovery and description of this species is credited to both Mary and Louis Leakey, who discovered the fossils in Tanzania between 1962 and 1964. This species is believed to have been ancestors of Homo erectus. Homo habilis is known as the ‘handy man’ because he was the first to make and use tools. The word habilis is based on a Latin word meaning ‘handy’ or ‘skilful’ . The first crude stone tools consisting of simple choppers, core tools and scrapers were made as early as 2.6 million years ago and are classified as Mode 1 technology.
Homo habilis had a larger brain than earlier human ancestors and this is reflected in significant changes to the shape of the skull. Brain averaged 610 cubic centimetres in size, representing 1.7 per cent of their body weight. Foramen magnum for the spinal cord was located in the centre of the skull base, showing that this species walked on two legs. Homo habilis ranged from about 3 1/2 to 4 1/2 feet tall, but weighed only about 70 pounds.
Homo erectus:
Fossils of these short and stocky humans, with their distinctive skull shape and large brow ridges, have mostly been found in China and Indonesia. This species lived between 100,000 and 1.6 million years ago, although some estimates extend this to between 35,000 and 1.8 million years ago. After years of searching Indonesia for ‘the missing link’, Dutchman Eugene Dubois finally uncovered part of a skull in 1891 (known as ‘Java Man’). He believed this fossil belonged to an ancient and ‘upright’ human and so coined the species name erectus.
Homo erectus is now one of the better known of our human relatives with over 40 specimens excavated from Java and many more from sites in China.Their brain showed an increase in size over earlier species and averaged about 1050 cubic centimetres. The structure of the brain was similar to that of modern humans. The face was large with a low, sloping forehead, a massive brow ridge and a broad, flat nose. limbs were like those of modern humans although the bones were thicker, suggesting a physically demanding lifestyle.
The remains of meals have been found at some Homo erectus sites in China. These show that they ate large amounts of meat supplemented with plant foods and, in general, had a diet similar to that of early modern humans. Moreover, there is evidence [bone protein released by hominid fire] to suggest the use of fire to cook food. This would produce a higher-energy diet, reallocating calories, and encouraging brain growth.
HOMO NEANDERTHALENSIS – THE NEANDERTHALS:
Neanderthals co-existed with modern humans for long periods of time before eventually becoming extinct about 28,000 years ago. This species lived between 28,000 and 300,000 years ago. A 45,000-year-old skullcap discovered in 1856 in Feldhofer Grotto, Neander Valley, Germany. This is the ‘type specimen’ or official representative of this species. Remains of this species have been found scattered across Europe and the Middle East. The eastern-most occurrence of a Neanderthal may be represented by a fossil skull from China known as ‘Maba’.
Neanderthals had more robust skeletons and muscular bodies than modern humans.Males averaged about 168 centimetres in height while females were slightly shorter at 156 centimetres.Back of the skull had a bulge called the occipital bun and a depression (the suprainiac fossa) for the attachment of strong neck muscles. jaws were larger and more robust than those of modern humans . Teeth were larger than those of modern humans.Limb bones were thick and had large joints which indicates they had strongly muscled arms and legs.
Evidence shows that Neanderthals had a complex culture. The Neanderthals had a reasonably advanced tool kit classified as Mode 3 technology that was also used by early members of our own species, Homo sapiens. The Neanderthals built hearths and were able to control fire for warmth, cooking and protection. They were known to wear animal hides, especially in cooler areas. However, there is no physical evidence that Neanderthal clothing was sewed together, and it may have simply been wrapped around the body and tied. Caves were often used as shelters but open air shelters were also constructed. The dead were often buried, although there is no conclusive evidence for any ritualistic behaviour. Neanderthals were very good hunters too.
Homo sapiens — The Modern Humans:
Homo sapiens represents us, the modern humans. Our species has existed for the past 160,000 years. ‘Cro-Magnon Man’ is commonly used for the modern humans that inhabited Europe from about 40,000 to 10,000 years ago. The name we selected for ourselves means ‘wise human’. Homo is the Latin word for ‘human’ or ‘man’ and sapiens is derived from a Latin word that means ‘wise’ or ‘astute’.
Fossils of the earliest members of our species, archaic Homo sapiens, have all been found in Africa. African fossils provide the best evidence for the evolutionary transition from Homo heidelbergensis to archaic Homo sapiens and then to early modern Homo sapiens.
Homo sapiens skulls have a distinctive shape that differentiates them from earlier human species. The earliest Homo sapiens had bodies with short, slender trunks and long limbs. Homo sapiens living today have an average brain size of about 1350 cubic centimetres which makes-up 2.2% of our body weight. Early Homo sapiens, however, had slightly larger brains at nearly 1500 cubic centimetres. Unlike other species of Homo, the skull is broadest at the top. The back of the skull is rounded and indicates a reduction in neck muscles. Face is reasonably small with a projecting nose bone. Jaws are short which result in an almost vertical face.Teeth are relatively small compared with earlier species.