Scientists believe that chemical evolution occurred around 3.5 billion years ago.

Scientists test ideas about chemical evolution by using computer models.

Chemical evolution: the evolution of the elements (building blocks of matter)

biological evolution: the small scale change in a population that can be passed from generation to generation

Both of these are changes that occur to gradually create a new species or substance

Heinrich D. Holland has written:

'Mineral Deposits and the Evolution of the Biosphere - Dahlem Workshop Reports -'

'The chemistry of the atmosphere and oceans' -- subject- s -: Atmospheric chemistry, Chemical oceanography, Molecular evolution

'The chemical evolution of the atmosphere and oceans' -- subject- s -: Molecular evolution, Atmospheric chemistry, Chemical oceanogrpahy, Atomospheric chemistry, Chemical oceanography

This is a sign of a chemical reaction.