About 700 million years ago, the basic chemicals in the earth’s atmosphere, namely Hydrogen and Carbon combined to form life in the water. This slowly evolved into primitive water plants. They began to grow and occupy the shallow and warm seas. The water plants gradually adapted themselves and began to encroach on to the land.

About 500 million years ago, Protozoa originated in water. It is considered to be the first form of animal life. Then single-cell beings became multicellular. The primitive life forms like photosynthetic bacteria released oxygen into the atmosphere as they evolved, which made earth more habitable for higher life forms to originate.

Water creatures appeared. Insects and Amphibians came into existence. The Amphibians were capable of existing on land and water as well. Then the reptiles appeared and some of the species among them adapted to become birds. All this diversified life forms took about 400 million years to evolve.

Mammals evolved about 200 million years ago. Horses, Camels, Dogs, etc. evolved around 50 million years ago. Primates made their appearance 36 million years ago. Hominoids evolved and human-like creatures came upon earth’s surface about 5.6 million years ago.