11.3 Life’s History
Pre-Cambrian DUMMY
Hadean: the Earth we live on is approximately 4,6 billion years old. The conditions that
allowed for the emergence of life lasted approximately 500 million years. It was an environ-
ment in which the Earth’s crust cooled and the oceans and atmosphere began to form. In this
environment, a variety of complex chemical reactions occurred, resulting in the production
of the earliest molecules capable of making copies of themselves at a rate that was faster than
that at which they were destroyed. However such self-replication required energy, space and
smaller building blocks which soon become limited. This resulted in competition for these
resources, and natural selection favoured those molecules that were best at self-replication.
Chapter 11. History of Life on Earth 323