Evolution of Intelligence on the Earth

Abstract

Life started on the earth about 3.8 billion years ago, but the emergence of animals with simple nervous systems had to wait until about 580 million years ago. The brain is an organ to receive various kinds of information, assess them, and make decisions to produce adaptive behavior. The cost of having a large brain is quite high, and evolution of large brains seems to be a rather rare event. There is only one species with a brain the size of which amounts to 2% of its body size, namely, modern humans. A species that is intelligent enough to discover and utilize electromagnetic waves must have large brains, organs to manipulate objects, a means to communicate ideas about the external world, and a method to verify or refute hypotheses about nature. During the evolution of life on earth, at least one such species, modern humans, has evolved. As we do not know of any life forms other than those on our earth, we have only one evolutionary system within which to investigate the possibility of the evolution of intelligent species. Conclusions remain tentative until we have other examples of the evolution of life forms on planets other than our earth.