The journey of human evolution, Homo sapiens, has been a topic of great biological interest. The idea that man is a creation of a supernatural power prevailed for a long time. However, biologists view the process of human evolution using knowledge on morphology, physiology, embryology and fossil records.
Man is placed under the family Hominidae of the order Primate. They differ from other anthropoid apes by having: a larger sized brain with a greater functional ability (Maximum in Gorilla = 650 c.c., Minimum in Man = 1000 c.c.) The braincase is larger than the face region.
The face is flatter with less protruding lower jaw. There is a continuous growth of long hair on the head which is spare and short on the body. Generalised hands with well-developed thumbs and long legs with a non-opposable big toe. Man is terrestrial by nature and walks erect on two feet. They surpass all animals by possessing the exclusive ‘human features’.
Our evolutionary history is written into our genome. The human genome looks the way it does due to all genetic changes that affected our ancestors. The exact origin of modern humans has always been a topic of debate.
Modern humans (Homo sapiens), is Latin for ‘wise man’. The human species is the only surviving species of the genus Homo but where we came from has been a topic of much debate. We originated in the African continent in the past 200,000 years and evolved from their most likely recent common ancestor, Homo erectus, meaning ‘upright man’ in Latin. It is an extinct species of the human race that lived between 1.9 million and 135,000 years ago.
Two key models have been put forward to explain the evolution of human beings mainly the Homo sapiens, namely the ‘out of Africa’ model and the ‘multi-regional’ model. The ‘out of Africa’ model at present is the most accepted model. It proposes that Homo sapiens evolved in Africa before they migrated across the world.
The ‘multi-regional’ model proposes that the evolution of Homo sapiens took place in several places over a long time. The mixing of the various populations eventually led to the single Homo sapiens species we see today.
The earliest anthropoids, Parapithecus, Propliopithecus, etc., represented by the remains of jaws were first discovered in the Oligocene bed of Egypt.
The fossils of anthropoids of the Miocene period show considerable diversity with some possessing pre-human features. They may have evolved into human line and others leading towards the great apes. Dryopithecus, an anthropoid fossil, is regarded to stand close to the point of divergence.
Discoveries of remains of earliest ancestors and races give an idea of the process of human evolution. The major forms, as recorded until date, are as follows:
The remains of these hominids (Australopithecus, Zinjanthropus, etc.) were discovered in Mid-Pleistocene or earlier in Transvaal, South Africa in 1925 and Olduvai Gorge Tanganyika in 1959. A wide range of skulls and some skeletal parts have been discovered.
They bear the following characteristics:
The skulls are smaller in size than that of modern man.
The volume of the brain ranged between 600-700 c.c.
The forehead was higher than in apes and the face was protruding.
The brow ridges were prominent.
The occipital condyles were ventrally placed and the rear part of the skull was rounded.
The jaws were observed to be large with small incisors.4
It also had large and spatulate canines and large cheek teeth.
Fragmentary remains of Pithecanthropus erectus were discovered in the Mid-Pleistocene of Solo River near Trimil, Java from 1891 until 1945.
The features are:
A flattish-topped skull and projected behind.
The brow ridges were solid above the orbits.
The brain volume was between 775-900 c.c.
The imprint of the brain indicated the ability of speech.
The jaws were protruding with teeth arranged in an even curve.
The remains of skulls and parts of the skeletal structure of Pithecanthropus (Sinanthropus) pekinensis were discovered up to 1943 from the Mid-Pleistocene caves at Choukoutien (South-west of Peking), China.
The noted features are:
The skull was small and the brain volume was 850-1300 c.c.
The skull was low-vaulted.
The brow ridges were stout.
The imprint of the brain suggested the ability of speech.
Signs of implements of quartz and other rocks have been discovered. The hearths showed the use of fire.
The remains of the transitional man were discovered in the Pleistocene bed of East Africa. They were the makers of crudely chipped stone tools. This species of the human race represents an intermediate stage between the Australopithecus and Pithecanthropus erectus. The mean capacity of the brain was 680 c.c.
One lower jaw of Homo heidelbergensis was discovered in 1907 in a sandpit at Mauer near Heidelberg (Germany). The remains were of the Mid-Pleistocene period. The jaw was massive with very broad ascending ramus which indicates that they had powerful jaw muscles. There was no chin. They also had stout teeth and the canines were not enlarged. Associated tools were not found.
The remains of the Neanderthal man from the late Pleistocene bed (before or during first Ice Age) were first discovered in Spain and North Africa to Ethiopia, Mesopotamia., Gibraltar, Neanderthal Valley near Dusseldorf (Germany), Southern Russia from 1848-1861.
The features of the Neanderthal man are:
Massive long and flat-topped skull.
The forehead was receding with heavy brow ridges.
The nose was broad.
The orbits were large.
The average brain volume was 1450 c.c.
The jaws were protruding but the chin was receding and they had large teeth
The attachment sites of the occipital region of the skull and the cervical vertebrae indicate the existence of powerful neck muscles.
The females were shorter than males. The Neanderthal man lived in caves and rock shelters made with stone tools and weapons. There was also evidence of the use of fire. The period is estimated around 100,000 years ago
[Images will be uploaded soon]
Q1. What are the Biological trends in Human Evolution?
Ans. The evolution of man involves the following important changes:
The switch from being four gait apes to the bipedal gait of the man.
The perfection of hand for tool making.
Increase in the size of the brain as well as improved intelligence.
Change of diet (From hard nuts and fruits to sifter food)
Increased ability to communicate with others.
Q2. Who is the Rhodesian Man?
Ans. The remains of the Rhodesian man from the late Pleistocene age were found in 1921 at Broken Hill, Rhodesia (South Africa). A similar skull was discovered in 1953 in Capetown as well.
The remnants consisted of one skull, upper jaw, parts of the skeletal structure. The volume of the brain was estimated to be about 1300 c.c. The characteristics of the face, brow ridges, orbits, palate and limb bones were similar to modern man.
Q3. Write the salient features of the Cro-magnon Man?
Ans. Some of the distinguishing features of the Cro-magnon man were:
A long and high skull with now brow ridges
The facial features were similar to the modern man.
The occipital region of the skull was rounded.
A developed chin.
The average brain volume was estimated to be about 1590cc
The male was about 5ft 10inches tall.