Today we see innumerable varieties of insects, birds and animals besides human beings on Earth; there are various kinds of trees, plants and bushes, too. All of them come under the category of living beings. Do you know how life started on the Earth? To study the origin of life on the Earth, the scientists study the fossils of those animals, trees and plants, which lived millions of years ago. Excavations carried out at various places on the Earth have made available fossils, rocks and bones that throw a significant light on the existence of living beings of ancient times. There are many theories about how life began on Earth. Almost all religions teach that all forms of life were created by some divine or supernatural power or force. Another theory states that life originally came to Earth from outer space through micro-organisms. Many biologists and biochemists believe that life developed from non-living matter. However, scientific studies have revealed that life on Earth started with a unicellular organism called amoeba. This happened some 570 million years ago. From this unicellular amoeba evolved the multicellular life on Earth. The first 345 million years saw the development of the marine life, the subsequent 160 million years saw the development of reptiles, and in the last 65 million years, the evolution of mammals took place. Man’s birth is approximately one million year old. After a lot of research, scientists found that the cells of plants and animals are made of proteins, carbohydrates, fats and many other substances. All these substances must have existed on the earth much before the origin of the unicellular life. This perplexed the researchers. They wondered how did these substances, which are so essential for life come on earth? Then they found that these were formed by electric discharge. Around 3500 million years ago, the Earth’s atmosphere was full of ammonia, methane, hydrogen, water vapour, etc. At that time, the Earth was very hot and the sky was overcast with clouds. Lightning and thunder were common occurrences. The electric discharge during the lighting led to the chemical combination of molecules of these gases, resulting in the formation of proteins, carbohydrates, etc., which finally gave birth to the unicellular amoeba. Even though we have been able to solve many mysteries relating to the origin of life on the Earth, there are many more aspects, which we still need to look into. For example, atoms and molecules have no life, then how come their combination creates life? What is it that enables a unicellular amoeba to produce multicellular creatures? Scientists are still studying to find answers to many such complex questions.