Speciation :
- Formation of new species of plants and animals is the effect of evolution.
- Species is the group of organisms that can produce fertile individuals through natural reproduction.
- Genetic variation is responsible for formation of new species from earlier one.
- Besides, geographical and reproductive changes are also responsible.
- Similarly, geographical or reproductive isolation also leads to speciation
Human Evolution :
- Last dinosaurs disappeared approximately seven crore years ago.
- At that time, monkey-like animals are said to be evolved from some ancestors who were more or less similar to the modern lemurs.
- Tail of these monkey-like animals of Africa is said to be disappeared about 4 crore years ago.
- They developed due to enlargement in brain their hands were also improved and thus ape-like animals were evolved.
- Meanwhile, these ape-like animals reached the South and North-East Asia and finally evolved into gibbon and orang-utan.
- Remaining ape-like animals stayed in Africa and from them, gorilla and chimpanzee evolved about 2.5 crore years ago.
- Evolution of some of the 2 crore year old species of apes seems to be occurred in different way. They had to use their hands more for eating food and other work.
- These first human--like animals with erect posture which were using their hands have evolved abou11t 2 crore years ago.
- Afterwards, this ape grown up in size and became more intelligent and thus the ape of South Africa evolved about 40 lakh years ago.
- The morphology of these human-like animals started to appear [genus Homo] about 20 lakh years ago and thus skilled human developed.
- About 15 lakh years ago, human walking with erect posture was evolved.
- It may have existed in China and Indonesia of Asian continent.
- Evolution of upright man continued in the direction of developing its brain for the period of about 1 lakh years and meanwhile it discovered the fire.
- Brain of 50 thousand year old man had been sufficiently evolved to the extent that it could be considered as member of the class- wise-man (Homo sapiens).
- Neanderthal man - first example of wise-man.
- The Cro-Magnon man - 50 thousand years ago and afterwards, this evolution had been faster than the earlier.
- About 10 thousand years ago, wise-man started to practice the agriculture.
- Art of writing - 5000 years ago
- Modern sciences emerged - 400 years ago
- Industrial society - 200 years ago
- Now we have reached at this stage, and still we are searching the details of roots of human ancestry.