Speciation, Origin and Evolution of Man

Formation of one or more new species from an existing species is called speciation. Speciations are of two types-

1.0Divergent Speciation

When one or more new species are formed from an ancestor species.

(a) Allopatric speciation: When a species split into two or more geographically isolated populations and these populations finally form a new species, It is called allopatric speciation e.g. Darwin finches.

(b) Sympatric speciation: In this type of speciation a sub population becomes reproductively isolated from its parental population. It is the formation of species without geographical isolation. 

e.g. mainly present in plants due to polyploidy.

2.0Transformation Speciation

When an ancestor species changes into a new species.

(a) Phyletic speciation: Ancestor species changes into new species by gradual changes in thousands of years. 

e.g. Eohippus → Mesohippus → Merychippus → Pliohippus → Equus

(b) Quantum speciation: In this process suddenly, major changes appear in ancestor species and ancestor species immediately changed into new species. No connective links are present in this type of speciation. It is caused by major mutation.

3.0Origin and Evolution of Man

• Human is a member of order Primata of class Mammalia.
• First real primate ancestors were tree shrews.

Evidences for common origin of human & apes:

Skull comparison of adult modern human being, baby chimpanzee and adult chimpanzee

(1) Banding pattern of chromosome no. 3 & 6 of human and chimpanzee is 100% similar.

(2) The skull of baby chimpanzee is more like adult human skull than adult chimpanzee skull.

(3) Composition of Hb is same in both human and chimpanzee. Only one amino acid is different in human and gorilla.

(4) Blood group of AB series is present in both and plasma protein is also same.

(5) Menstrual cycle is present in females of both.

(6) Tail is absent in both and have grasping hands with opposable thumbs.

Differences between Human and apes:

4.0Human Evolution

(I) About 15 mya, primates called Dryopithecus and Ramapithecus were existing. They were hairy and walked like gorillas and chimpanzees.

(II) Few fossils of man-like bones have been discovered in Ethiopia and Tanzania. These revealed hominid features leading to the belief that about 3-4 mya, man-like primates walked in eastern Africa. They were probably not taller than 4 feet but walked up right.

(III) Ape man fossils - Australopithecus

2 mya, Australopithecines probably lived in East African grasslands.

- Evidence shows they hunted with stone weapons but essentially ate fruit.

- It is also considered as connecting link between apes and man.

(i) Ape-like characters:

- Less cranial capacity (600 c.c.)

- Thick growth of hair

- U shaped jaw (prognathous face)

- Larger and sharper teeth

(ii) Man-like characters:

- Complete erect posture and Bipedal locomotion (first man who stood erect)

- Forelimbs shorter than hind limbs

- Vertebral column with distinct lumbar curve 

• Prehistoric Man

These extinct species of Homo are called as prehistoric species of man.

(1) Homo habilis

- First human-like being.

- First tool maker man or Handy man, they lived in caves.

- They probably did not eat meat.

- The brain capacities were between 650-800 cc.

- Its fossils were discovered from 2 million years old rocks in Africa.

(2) Homo erectus

- They existed about 1.5 million years ago.

- They had large brain with a cranial capacity around 900 cc.

- They were cave dwellers and probably ate meat. 

- Many subspecies are discovered of Homo erectus as given below 

(a) Java man (Homo erectus erectus/ Pithecanthropus erectus)

- Its fossils discovered in Java in 1891.

- First man who used fire for hunting, protection and cooking.

- They used tools of bones and stones.

- Their cranial capacity was 800-1000 cc (avg. 900 cc)

- They were omnivorous and cannibalism was also found.

(b) Peking man (Homo erectus pekinensis):

- W.C. Pei discovered the fossils from China.

- They used fire for cooking meat and protection.

- Their cranial capacity was 850-1300 cc (avg. 1050 cc)

- They were omnivorous and cannibalism was also found.

(3) Homo sapiens:

- Many subspecies are discovered of Homo sapiens as given below 

(a) Neanderthal man (Homo sapiens neanderthalensis)

- They lived near east and central Asia between 1,00,000 - 40,000 years back, fossil was discovered in Neanderthal valley of Germany.

- They had a brain size of 1400 cc (similar as modern man).

- They buried their dead and probably believed in immortality of soul.

- They used hides (skin of animals) to protect their body.

- They lived in huts and were omnivorous by nature.

- Development of speech centre and language started.

(b) Cro-Magnon man (Homo sapiens fossilis)

- Origin and evolution 50,000 to 10,000 years ago.

- Fossils discovered from Cro-Magnon rocks of France.

- Cranial capacity: 1650 c.c.(maximum)

- They lived in caves and Omnivorous by nature.

- They had Semi-circular jaw and orthognathous face with larger forehead and well-developed chin.

- Speech and language centre were well developed in them.

- They wore clothes of animal skin.

- This man was hunter and used domesticated dogs in hunting, hence domestication was started by this man.

- They also painted beautiful paintings on cave walls. Pre-historic cave art developed about 18,000 years ago, which can be seen at Bhimbetka rock shelter in Raisen district of Madhya Pradesh.

(c) Modern man (Homo sapiens sapiens): 

- During ice age between 75,000-10,000 years ago modern Homo sapiens arose.

- It arose in Africa and moved across continents and developed into distinct races. 

- This is the man of today having a brain capacity of 1300 - 1600 cc (avg. 1450 cc).

- This man has well developed chin, well developed speech centre, smaller forehead and reduced body hair.

- Semi-circular jaw and orthognathous face.

- It is omnivorous by nature.

- Agriculture was also started by this man. Agriculture came around 10,000 years back and human settlements started.

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