- The origin of life on earth can be understood only against the background of origin of universe especially earth.
- Most scientists believe chemical evolution, i.e., formation of biomolecules preceded the appearance of the first cellular forms of life.
- The subsequent events as to what happened to the first form of life is a conjectured story based on Darwinian ideas of organic evolution by natural selection. Diversity of life forms on earth has been changing over millions of years.
- It is generally believed that variations in a population result in variable fitness.
- Other phenomena like habitat fragmentation and genetic drift may accentuate these variations leading to appearance of new species and hence evolution.
- Homology is accounted for by the idea of branching descent. Study of comparative anatomy, fossils and comparative biochemistry provides evidence for evolution.
- Among the stories of evolution of individual species, the story of evolution of modern man is most interesting and appears to parallel evolution of human brain and language.
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