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MHT-CET : Biology Entrance Exam

MHT - CET : Biology - Human Evolution Know More

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Early Primates

In the late Cretaceous, 70 million years ago, two varieties of primates existed:

1.      The Strepsherinni, a nocturnal beast.

2.      The Haplorini, a diurnal variety from which the hominids evolved.

Some Differences Between Ape and Man

 

Ape (Pongid)

Man (Hominid)

1.

Arboreal

Terrestrial

2.

Number of chromosomes - 48

Number of chromosomes - 46

3.

Quadrupedal locomotion

Bipedal locomotion

4.

Low forehead

High forehead

5.

Lots of hair

Little hair

6.

Reduced chin

Prominent chin

7.

Large jaw

Small jaw

8.

U-shaped dentition

Crescentic dentition

9.

Long arms

Short arms

10.

Thumb not opposable

Opposable thumb

11.

Flat nose

Elevated nose

12.

Eyebrow ridges elevated

Eyebrow ridges flat

 

Stages in Human Evolution

Class: Reptilia

Class: Mammalia

 

Order: Primata

Suborder
Prosimii

Suborder
Anthropoidea

 

 

 

Lemur

Shrew

 Tarsier

 

 

Family

 

Ceboldea

Cercopithecoidea

Pongidae

Hominidae

New world
monkey

Old world
monkey

Apes

  • Gibbon
  • Gorilla
  • Chimpanzee
  • Orang-utan

Man

  • Dryopithecus (Miocene)
  • Ramapithecus (Miocene)
  • Australopithecus (Pliocene)
  • Java Man (Pleistocene)
  • Peking man
  • Heidelberg man
  • Neanderthal (Pleistocene)
  • Cro-magnon man (Pleistocene)
  • Modern man(Holocene)

 

Lemurs and tarsiers were ancestors of apes mainly because of the following reasons:

1.      Primates, the order to which lemurs and tarsiers belong to along with apes and monkeys, were nocturnal (active in the night) in the beginning of their evolution.

2.      The hands of these animals underwent a number of changes during the progress of evolution. For example, the thumb became opposable, which helped these insect-eating primates in holding their prey.

3.      Lemurs, tarsiers and apes all developed sensitive fingers with nails instead of claws.

4.      The eye sockets in these primates were shifted to the front of the head, thereby providing better vision and ability to judge distance.

5.      From tarsiers, the early arthropods, i.e. monkeys and apes evolved. It is well exhibited by the fossil of Parapithecus discovered from a 36 million-year-old Miocene rock.

Lemurs

1.      Lemurs are primitive mammals.

2.      Lemurs are characterised by the presence of hair on their body.

3.      The eyes of Lemurs are directed forward. They have flat nails and an opposable thumb.

4.      Lemurs evolved from tree shrews that existed 70 million years ago and their limbs are modified for tree dwelling.

How did the pre-human ancestors adapt to the change in habitat?

  • They started standing on two feet instead on four (bipedal habit), with an erect posture, making their hands free to do work.
  • Opposable great toe became parallel to other toes. This helped them walk efficiently on the ground.
  • Opposable thumb was developed, which helped the human beings do more skilled work. Since, human brain is well developed, he can think better, associate things and integrate his thoughts, thus helping him take better decisions.
  • Human eyes are located uniquely on the head, giving stereoscopic vision, i.e. they are able to perceive depth and distance.
  • The retina of human eyes has cones, which provide coloured vision to human beings, i.e. the ability to distinguish various colours.
  • A salivary amylase named ptylene helps in digestion of starch.
  • The erect position of the body is maintained by a special set of muscles.
  • Human beings are capable of reproduction throughout the year.

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