How did life on earth originate?
By chemical reactions made of meteorites
According to the best current hypothesis it all started about 3,7 billion years ago when meteorites chrashed on the surface of the earth. The fragments from the meterorite got heated up by geothermal activity underneath the surface. This caused some reactions to occur, creating some of the most important molecules for life to form. These molecules combined and created some really primitive cells.
These cells got mutated in different ways while being exposed to high levels of radiaton or when dividing, changing the properties of the cell, making it better or worse. The cells who got mutated for the better lived on while those who got mutated for the worse died faster. This is called evolution and it's what made us, billions of years later.