Activity 7 evolution of human

  EVOLUTION OF HUMAN BEINGS 

Apes are the closest kin to humans in size, form, physiology and behavior. They have bigger brains, and brachian style of locomotion which is related to the evolution of an erect body posture and elongation of arms. Besides humans, gibbons, orangutans, chimpanzees and gorilla are the only living forms of hominoids. Gibbons and orangutans are arboreal brachiators. Orangutan, chimpanzee and gorillas, when on ground walk on all fours, supporting their weight on their fists(knuckle walkers). Chimpanzees and gorillas are more intelligent, can use simple tools and have the ability to learn sign language. Studies of DNA sequences have shown that humans are more closely related to chimpanzees than to any other primates. Human and chimpanzee’s DNA are 99percent identical, that is not to say that the humans have descended from fossil chimps. A common fallacy about evolution is that humans evolved from some living species of ape share a common ancestor. This is not the case. Fossil records show that humans and apes share a common ancestor. Both ancestor we evolved from was an ape but it is now extinct and was not the same as present day apes. If it were not for the vanity of human beings, we would be classified as an ape. Our closest relatives are, collectively, the chimpanzee and the pygmy chimp. Our next nearest relative is the gorilla. Fossil records of human evolution are quite incomplete and we have much to learn yet. In 1863, T.A. Huxley explained human evolution in his book "Man's Place in Nature". In 1871, Charles Darwin published his ideas of human evolution in the 'book "The Descent of Man". Later on, many attempts have been made to find the missing link between man and ape in the form of an original creature or its fossil. Eugene Dubois unearthed the first fossil record of an ancestor of man in the form of a small part of skull and jaw bone. Between 1920 and 1930 many human-like fossils were found in China called "Peking Man" or Sinanthropus. But these fossil evidences do not form a neat chain of links leading from ancient ape to the modern human. Archaeological records of human evolution indicate that early humans started out as small bands of hunters who killed animals for food and gathered items. Humans began to farm seriously around 8,000 BC and there was full-fledged agriculture in many places just after 4000 BC. The agriculture allowed establishment of stable populations.

Fossil Ancestors of Man

As mentioned earlier, the paleontological record  for human evolution is not continuous: Ever since the theory of evolution become scientifically acceptable, biologists and anthropologists have been trying to find the missing link, the species that would bridge the gap between humans and the great apes which are the closest living relatives of humans. The fossils collected from various regions indicate possible trends in human evolution.

Parapithecus was a primitive primate ancestral to man, apes and monkeys. It was very small squirrel -like earliest primitive monkey having tarsier-like appearance. The jaw was conical, the two halves converging at an angle of 33 degrees. These creatures were probably adapted for arboreal mode of life and had opposable thumb, forwardly directed eyes and reduced snout.

Propliopithecus fossils were discovered from Fayum deposits in Egypt that comprised of a lower jaw with teeth. The jaw is smaller and more pointed than that of a gibbon, prognathous and deep. Canines were smaller and bunodont grinders had 5 bulbous cusps as in apes and man.

Dryopithecus or Sivapithecus was ancestral to Orangutan, chimpanzee and gorilla and resembled gibbon in stature. Most of the fossils are represented by jaw fragments and teeth ,with few exceptions such as a humerus and an ulna from France and a femur from Germany. The three genera, Dryopithecus, Sivapithecus and Proconsul have been placed in the sub family Dryopithecinae. Arms and legs were of same length and posture was semi-erect. Skull lacked the well-developed crests and massive ridges characteristic of modern apes. Dental arch was parabolic and dentition more man-like but canines where larger and lower premolar is sectorial. It was a brachiator Sivapithecus is believed to be the direct ancestor of Ramapithecus, whose fossils have been recovered from the same deposits in the Siwalik Hills and date from 17 to 8 million years old.

Ramapithecus, is fossil primate genus dating from the Middle and Late Miocene epochs. The first Ramapithecus fossils discovered in 1932 in fossil deposit in northern India. Face was short and jaw allowed sideway motion. Dentition was human and palate arched. Incisors and canines were small, permitting lateral chewing. Grinding teeth were large and broad with thick enamel coating, suggesting herbivore diet of grass, seed roots and perhaps raw meat. morphology over Sivapithecus that brings it closer to Australopithecus. They probably originated in Africa and later migrated to Eurasia