human evolution
It is the aspect of evolution which is concerned with the emergence of human as distinct species. Various evidence support that humans and apes have descended from common ancestors.
The beginning of primates' evolution is presumed in the Eocene of the Tertiary Period (75-60 million year ago) in evergreen forest and later in Oligocene (25-30 million year ago). Its returns of the ground from the tree due to replacement of evergreen forest into dried savanna-Greenland. thus
The place of origin of humans is a grate controversial matter. The fossil of ancestral human forms is obtained from the widely diverse regions of Africa, Asia, and Central Asia, China, Java, and India (Shivalik Hills).
Many fossils have been discovered from East Africa (Olduvai Gorge, Lake CIctoria, and Lake Natron in Tanzania and Lake Turkana in Kenya) which indicate a significant role of Africa in regard to the site of origin of human.
Some changes that took place during human evolution are given below
(1) Skull and Brain increase in size, complexity, and intelligence.
(2) bipedal locomotion
due to bipedal locomotion forelimbs become free
(3) Forelimb
it is modified into an organ of manipulation and lengthening of hindlimbs and shortening of forelimbs.
(4) Thumb
the perfection of thumb opposability in forelimbs.
( 5) Toe
loss of opposability of great toe in hindlimbs.
(6) Upright posture
becomes of development of the lumbar curve.
(7) Jaw
Power reduction
(8) Teeth
due to omnivorous food habits, the size of incisors and canines reduced.
(9) Chin
development of the chin
(10) Pelvic girdle
development and broadening of iliac bones of the pelvic girdle.
(11) Social organization
and cultural evolution
History of human evolution
The study of living and fossil primates (including monkeys and man) shows that they have descended from a common ancestor and separated from the main stock ( of a homogenization) during the Oligocene period.
The evolutionary history of man can be divided into the following three staps only for the convenience of study
1. prior to the ape man
2. Apeman
3. True man (including living modern man)
Prior to the ape man
(1) Propliopothecus
* Discovery :
fossil obtain from Faiyum deposits of Egypt.
Fossils have Jaws and teeth.
It lived about 35-30 million yrs ago in the Oligocene epoch.
Characteristics
It was more or less ape-like.
These were short-statured with monkey-like teeth.
Their dental formula was 2,1,2,3, i.e. both jaws have 8 incisors, 4 canines, 8 premolars, and 12 molars like modern man.
Their incisor teen was vertical rather than directed forward.
Their molar has 5 cups each.
There are two views regarding ancestry. One says Propliopithecus directly gave rise toRamapithecus, while by another view Propliopithecus gives rise to Dryopithecus which in turn evolved into apes and humans.
(2) Aeggyptithecus
Discovery:
fossil found from Faiyum province of Egypt in 1980 by E Simon
Characteristics:
These were similar to Propliopithecus.
These live between 35-33 million yrs ago in the early part of the Oligocene epoch.
The predates divergence between hominoids (apes and humans) and old-world monkeys.
Limnopithecus and pliopithecus
Discovery
Fossils found from Faiyum deposits of Africa.
Characteristics
This existed in Miocene and Pliocene periods.
They had a short tail and 7 lumbar vertebrae.
They represent altogether a different line of evolution which diverged from the hominid line quite early and become extinct during the late Pliocene.
Proconsul (intermediate between apes and man)
Discovery
Fossil of proconsul Africanus was described by Louis SB Leakey(1948).
The fossils were obtained from the rock of East Africa near Victoria Lake in Kenya. It lives in the early Miocene
Characteristics
The face was prognathous.
Proconsul walked on its four legs.
Proconsul had long, point ape-like canines.
Proconsul has a man like a forehead.
Proconsul is not considered as the base ancestor of man because it walked on its four legs.
About four million years ago, during Proconsul, proconsul gave rise to the ancestors of chimpanzees and gorillas.
Diversion of chimpanzee and gorilla took place during the Pleistocene epoch about 2.3 million years ago.
Dryopithecus
Discovery
Fossil of Dryopithecus Africanus was obtained from rock of Africa and Europe.
Recently, a lower jaw of Dryopithecus Africanus was found from Haritalyanga in Bilaspur district of Himachal Pradesh, India.
Several members of Dryopithecus Africanus has been discovered from Shivalik hills as well.
Characteristics
It lived about 15 million years ago during the Miocene.
Dryopithecus Africanus shows close similarity to Chimpanzee.
Dryopithecus is considered to be a common ancestor of man and apes.
Dryopithecus Africanus was the direct forerunner of man.
Dryopithecus Africanus is apes with the same length of arm and legs.
Legs and heels in its feet indicate that Dryopithecus Africanus was of a semi-erect posture and Knuckle walker.
Dryopithecus Africanus was arboreal and herbivorous, which ate soft fruits and leaves.
Dryopithecus Africanus has large canines and incisors.
Shivapithecus
Discovery
Fossile of Shivapithecus was discovered from the middle and late Pliocene rock of Shivalik hills of India.
Characteristics
Its forelimb, Skull, and brain resembled the monkeys.
Its face, jaws, and teeth had a resemblance with those of apes.
Ramapithecus
Discovery
Edward Lewis (1932) obtain the fossil of Ramapithecus from rocks of Shivalik hills of India.
Fossile was represented by a few teeth and some fragments of the jaw.
Kenyapithecus (Kenyapithecus wicker) similar to Ramapithecus was discovered by LSB Leakey (1955) from Pliocene rocks of Kenya in Africa, but Ramapithecus was older than Kenyapithecus.
Characteristics
Ramapithecus survived about 14-15 million years ago during the Late Miocene to Pliocene.
Ramapithecus walked erect on its hind legs.
It was similar to ape, which lived on the treetops but also walked on the ground.
It eats hard nuts and seeds like modern man. Its jaw and teeth were similar to humans.
Its canine teeth were small but molar teeth were broad and flattened with thicker enamel.
Dryopithecus gave rise to Ramapithecus , which is on the direct line of human evolution.
Ramapithecus became extinct about 7-8 million years back.
There is a fossil gap of about 9-10 million years in Ramapithecus and Australopithecus.
The fossil record of man's ancestor from the Pliocene are completely blank and once again reappear in the Pleistocene.
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