The EvolutionModern scientists estimate that the earth is 5 to 6 billion years old. Life is thought to have begun 3 to 4 billion years ago. By comparison, most of the evolution of human like creatures has taken place in a very short time – the first mammals began to evolve from reptiles perhaps 200 million years ago, and the first placental mammals (i.e., that give birth to live young.
As opposed to the egg bearing platypus or marsupials such as kangaroo) date back about 130 millions years.
Monkey like mammals with relatively large brains and tendencies toward social behavior have existed for roughly 30 million years, while terrestrial primates who engage in some hunting as well as gathering have been around only about 15 million years.
The first human like animals appeared some 3 million years ago, around the beginning of the epoch known as the Pleistocene. This was the time of the great ice ages, when drastic changes in climate affected life throughout the world.
This climate change may account for more rapid evolution that produced modern human beings in such a short period; that is the pace of natural selection may have been quickened because of environmental changes and the resulting pressures on our ancestors.
The Evolution
