The eye is a complex sensory organ that allows us to see the world around us. The eye works by gathering light from the environment and converting it into electrical signals that can be interpreted by the brain. The basic structure of the eye includes the cornea, iris, pupil, lens, retina, and optic nerve. The cornea is the transparent outer layer of the eye that helps to focus incoming light. The iris is the colored part of the eye that regulates the amount of light that enters the eye through the pupil, which is the black circular opening in the center of the iris. The lens is a clear, flexible structure located behind the iris that helps to focus light onto the retina. The retina is a thin layer of tissue that lines the back of the eye and contains photoreceptor cells called rods and cones. These cells convert light into electrical signals that are sent to the brain via the optic nerve. The rods are responsible for the low light vision and detecting motion, while the cones are resp
When we start to talk about the human evolution, the first line which appear in our mind is hat the human is evolve from monkey or monkey is our ancestor, you also hear about this from most of the people that monkey is our ancestor but this is not true. Monkey and human was originated from common ancestors, so monkey are similar to human but when we talk about similarities the apes were more closer to human than monkey because apes and humans share there ancestors for very recent times.
Some evidences for common origin of human and apes :
- Banding pattern of chromosome no. 3 and 6 of human and chimpanzee is 100% similar.
- Number of chromosomes are approx same in human (46) and apes (48).
- DNA content and DNA matching is same in both. This similarity is more than 99% with chimpanzee, 94% with Gibbon, 88% with Rhesus monkey.
- The skull of baby chimpanzee is more like adult human skull than adult chimpanzee skull.
- Composition of Hb is same in both. Only one amino acid is different in human and gorilla.
- Blood group of AB series is present in both and plasma protein is also same.
- Menstruation cycle is present in females of both.
- Tail is absent in both and have grasping hands.
HUMAN EVOLUTION
(A) Ape Fossils :
About 15 million year ago, primates called Dryopithecus and Ramapithecus were existing. They were hairy and walked like gorillas and chimpanzees.
(1) Dryopithecus : It is considered as common ancestor of man and apes and it is considered as direct ancestors of modern day apes. They had semi erect posture, thick hair, U shaped jaws, larger and sharper teeth and were vegetarian. They walked on four legs and their forelimbs were longer than hind limbs and they were forest dwellers and spent most of the time on the trees.
(2) Ramapithecus : Fossils discovered from Shivalik hills in India.
(3) Shivapithecus : Fossils discovered from Shivalik hills in India.
(4) Kenyapithecus : Fossils discovered from Kenya. They are considered as ancestors of human, similar in characteristics to Dryopithecus, but spent most of the time on the land.
(B) Ape man fossils : Australopithecus
Prof. Raymond Dart discovered a fossil of skull of 5-6 years old baby from the Pliocene rocks of Tuang region (S. Africa) and named it Tuang baby. Later he renamed it as A. africanus (African apeman). About 2 million years ago, Australopithecines probably lived in East African grasslands. Evidences shows that they hunted with stone weapons but essentially ate fruit. It is also considered as connecting link between apes and man because they had some ape like character and some man like character, Ape like character such as Less cranial capacity (600 c.c.), Thick growth of hair, U shaped jaw and large and sharper teeth, and man like characters are complete erect posture and bipedal locomotion (first man who stood erect), Forelimbs shorter than hindlimbs and Vertebral column with distinct lumber curve.
(C) Prehistoric Man :
A number of other species of Homo appeared and became extinct from time to time on the evolutionary sense before the origin of Homo sapiens. These extinct species are called as prehistoric species of man.
(1) Homo habilis : These are first human like being. Its fossils were discovered by Dr. Leakey from 2 million years old rocks in Africa. These are the first man who made tools of stones for hunting animals only for defence, because they probably did not eat meat, hence called as first tool maker man or Handy man. Their cranial capacities were between 650-800 c.c. and they lived in caves.
(2) Homo erectus : They existed about 1.5 million years ago and were cave dwellers and probably ate meat. They had large brain with a cranial capacity around 900cc. Many subspecies are discovered of Homo erectus as given below :
(1) Homo habilis : These are first human like being. Its fossils were discovered by Dr. Leakey from 2 million years old rocks in Africa. These are the first man who made tools of stones for hunting animals only for defence, because they probably did not eat meat, hence called as first tool maker man or Handy man. Their cranial capacities were between 650-800 c.c. and they lived in caves.
(2) Homo erectus : They existed about 1.5 million years ago and were cave dwellers and probably ate meat. They had large brain with a cranial capacity around 900cc. Many subspecies are discovered of Homo erectus as given below :
- Java man (Homo erectus erectus) : Its fossils discovered in java in 1891. These are the first man who used fire for hunting, protection and cooking. They used tools of bones and stones and they were omnivorous and cannibalism have also found and their cranial capacity was 800-1000cc (avg. 900cc)
- Peking man (Homo erectus pekinensis) : Its fossils was discovered by W. C. Pei from China.They were omnivorous and cannibalism have also found and their cranial capacity was 850-1300cc. (avg. 1050cc.). They used fire for cooking meat and protection and they used sharp chisel shaped tools of stones/ bones for cutting and killing animals.
- Heidelberg man : Its fossil was recovered in form of lower jaw from Heidelberg in Germany. It is believed that this man was evolved as a branch from main line of evolution and got extinct after some time.
(3) Homo sapiens : Many subspecies are discovered of Homo sapiens as given below :
- Neanderthal man (Homo sapiens neanderthalensis) : Their fossil was discovered by Fulhrott in Neanderthal valley of Germany. They lived near east and central Asia between 1,00,000 - 40,000 years back. They had a brain size of 1400cc (same as modern man). They used hides (skin of animals) to protect their body. They started buried their dead and probably believed in immortality of soul. They lived in huts and omnivorous by nature. Development of speech and language centre started.
- Cromagnon man (Homo sapiens fossilis) : Their origin and evolution is around 50,000 to 10,000 years ago. Their fossils was discovered by Mac Gregor from Cromagnon rocks of France. They had a cranial capacity of 1650cc (maximum) and they have large forehead and well developed chin. They live in caves and omnivorous by nature. They have semi circular jaw and orthognathous face. Speech and language centre were well developed in them and they also painted beautiful paintings on cave walls. Pre-historic cave art developed about 18,000 years ago. They wore clothes of animal skin and these man were hunter and used domesticated dogs in hunting, hence domestication was started by this man.
- Modern man (Homo sapiens sapiens) : Modern homo sapiens arose during ice age between 75,000 - 10,000 years ago. It arose in Africa and moved across continents and developed into distinct races (Caucasoid, Negroid, Mongoloid and Australoid). This is the man of today having a brain capacity of 1300 - 1600cc (avg. 1450cc), 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 in nature. Agriculture was also started by this man. Agriculture came around 10,000 years back and humans settlements started.
Comments
Post a Comment