Human evolution: the unsolved mystery

THE EVOLUTIONARY history of the apes is interesting, as they were the first animal having some sort of intelligence. Australopithecus was one of the first such ape species, which gradually evolved into Homo erectus. A systematic study of the fossils of all these creatures indicates that the¥ gradually adopted a bipedal character, and lived in groups. The most important character of these creatures was the progressive expansion, elaboration and evolution of their brain. The increase in the size of their brain increased their intelligence, which resulted in their domination over other animal groups. They started to make tools which they used to hunt for food.

Charles Darwin is symbol of the greatest transition in biological sciences. The process of natural selection according to Darwin is gradual, in which most evolutionary changes is the result of forces acting slowly over long periods of time. He believed that changes resulted from modifications in the animals or plants that improved its ability to survive and reproduce. Among the original components of Darwin theory are that evolution is gradual and that the nature of the change is dictated by natural selection. The concept of evolution according the Darwin is descent with modifications. The second concept that all species are descended from one or at most a few ancestors was also original at that time there was no evidence to prove this but in recent years the discovery that all species use the same genetic code is stunning. He observed that species produce more offspring than can survive in the environment. Darwin believed that after many generations each changing slightly from the previous and the latest will look so different from its ancestor, that the two will constitute separate species. He called his theory “Gradualism”.

In 1972, two American paleontologists, Stephen Jay Gould and Niles Eldredge suggested that evolution does not proceed gradually as Darwin believed but it proceed in bursts of rapid change, interspersed with long periods of little change in established species. They called their theory “Punctuated Equilibrium”. This new theory has generated a lot of excitement among scientists of the world. But it does not clarify a crucial point that is how and why a species springs up. There is a vast conceptual difference between the two groups. Gould asserts that species arise relatively quickly, that is in relation to the rate at which fossils accumulate. According to Gould, Darwin deduced the gradualist view of evolution by the slow pace of change. While the theory of punctuated equilibrium seems to attract the modern mind and reflect modern trends.

Darwin in the nineteenth century shock the nation that he has been created by a divine force and holds a privileged position in all of creation and proved his ancestry to the animal kingdom. Gould in the twentieth century has gone a few steps ahead in disproving evolution as a gradual process with man as its height of perfection. There is no saying what is to follow next.

The human story on the other hand is very recent in terms of geological history of the earth. The humans have surpassed all other living beings in having more elaborate mental activities, commonly called intelligence. Mankind has used this intelligence to obtain food and other resources from its environment but, in doing so, has also caused great harm to its surroundings. Humans have polluted air, land and water resources. If our destructive activities continue, it is feared that one day we may harm our environment so much that it may not sustain our own existence.

Brain capacity of Hominids is given below:

Australopithecus Afarensis

Australopithecus afarensis is supposed to be the oldest known, generally accepted hominid which was derived from Australopithecus family.

Locality: The fossils were first discovered from Tanzania but more complete better fossils were found from Hadar, South Ethiopia.

Age: 4 million years ago.

Brain Size: A. afarensis also had a relatively small brain size 380-430 cc.

Skull structure: The head of these was still ape like, while the body was much similar to human. Australopithecus afarensis walked on two legs.

Australopithecus Africanus

Locality: Most of the fossils of Australopithecus Africanus are found from South Africa.

Age: 2 to 3 million years old.

Brain Size: The brain size has been estimated at about 485cc, little more than a chimpanzees but much less than the 1300 to 1400cc of modem people.

Skull Structure: The structure of the skull and other parts of the body shows affinity towards Hominidae. Shape of the teeth and flatness of the cheek bones are the prominent features Australopithecus Africanus.

Australopithecus Robustus/ Paranthropus robustus

Locality: Fossil sites found are only in South Africa in Kromdraai, Swartkrans, Drimolen, Gondolin and Coopers.

Age: Australopithecus Robustus lived between 2 and 1. 5 million years ago

Brain size: Brain size was up to 525cc with no indication of speech capability.

Skull structure: It had a body similar to that of Australopithecus africanus but a larger and more massive skull and teeth. Its huge face was flat and with no forehead. It had large brow ridges.

Australopithecus Boisei/ Paranthropus boisei

Locality: Olduvai Gorge, Tanzania and Koobi Fora near the Lake Turkana region.

Age: Australopithecus boisei lived between 2.1 and 1.1 minion years ago.

Brain Size: The brain volume is quite small, about 500 and 550 cc.

Skull Structure: The space inside the Cheekbones is large to accommodate an unusually powerful jaw muscles. Australopithecus boisei sported a gorilla like bony crest and was the most robustus among all the Australopithecines, which thrived for almost a million years only to come to an evolutionary dead end. It had a much wider face.

Homo Habilis

This is the earliest specimen that has been given the name homo, which is Latin for “man”.

Locality: Its fossils were found only from Northern Kenya and Tanzania.

Age: 2.2 to 1.6 million years old.

Brain Size: The brain size of Homo habilis ranges between 500-800cc and had an increased cranial capacity. There was large brain expansion with this species.

Skull Structure: The skeleton of Homo habilis in structure has a great resemblance with the Australopithecus but the fundamental difference between the two is the trend towards larger brain case, which is the prime qualification of human generation.

Homo Erectus

Homo erectus is another modified form of Homo habilis.

Locality: Homo erectus was the first species of human to migrate out the Africa and started burning fire. Its fossils were found in Asia from China, Indonesia and Valley of Narbada River (India).

Age: Fossilized remains 1.8 and 1.0 million years old have been found in Africa (e.g., Lake Turkana and Olduvai Gorge), Europe (Georgia, Spain), Indonesia (e.g., Sangiran and Trinil), Vietnam, and China (e.g., Shaanxi).

Brain Size: Brain case was estimated to be 900cc. The brain case of the Homo erectus from China was up to 1200cc, which is very much near to the size of modern man.

Skull Structure: They used to carve different and complicated stone tools. The most prominent skeleton changes are the larger brain case, continued flattering of the face and the development of big brow ridges. It appears that Homo erectus was the first traveler. He probably went from Africa up the Nile valley to Eurasia, Java, China and Indonesia.

Homo Sapiens archaic

Locality: These traces are found only in Europe and Middle East.

Age: Homo sapiens archaic provide the bridge between Homo erectus and Homo sapiens during the period 200,000 to 500,000 years ago.

Brain Size: Brain averaged about 1200cc and speech was indicated.

Skull structure: Many skulls have been found with features intermediate between the two. Skulls are more rounded and with smaller features. Molars and brow ridges are smaller. The skeleton showsa stronger build than modern human but was well proportioned.

Homo Sapiens neanderthalensis

Locality: Homo sapiens neanderthalensis lived in Europe and the Midde East.

Age: 150,000 35,000 years ago

Brain Size: Brain sizes averaged larger than modern man at about 1450cc but the head was shaped differently being longer and lower than modem man.

Skull Structure: Homo sapiens Neanderthalensis coexisted with H. sapiens archaic and early H sapiens sapiens. Recent DNA studies have indicated that the Homo sapiens neanderthalensis were an entirely different species and did not merge into the H. sapiens sapiens gene pool. His nose was large was different from modern man in structure. He was a massive man at about 56″ tall with an extremely heavy skeleton that showed attachments for massive muscles. He was far stronger that modern man. His jaw was massive and he had a receding forehead, like Homo erectus.

Homo Sapiens (Modern man)

All human beings that live on the Earth today belong to Homo sapiens. Even though we are rather different in size, body stature, skin and hair color, we all belong to not only the same species, but also the same subspecies. The oldest Homo sapiens appeared 40.000 years ago. Brain size of Modern Man is about 1650 cc.

In Pakistan, the one and only Natural History Museum is Pakistan Museum of Natural History, Islamabad which preserves the natural past in the form of flora and fauna. Pakistan Museum of Natural History has series of human skull specimens which reveal the mystry of human evolution. Some of these skull specimens have been donated by African Countries in the form of replicas, while few have been collected by the researchers of Pakistan Museum of Natural History from local regions.

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