The simplest life forms were in existence for a few billions of years as they very gradually developed into intermediate forms. With the progression of time, organisms gradually accelerated in their degree of complexity.

If the entire history of the universe were compressed into a single year, then the origin of life on earth would have occurred around the last of September and the entire recorded history of man would occupy the last 10 seconds of the year. The first worms would have appeared on approximately December 15, the first fish and vertebrates on December 19, first insects on December 21, first reptiles on December 23, first mammals on December 26, first primates on December 29, and the first humans on December 31.⁵...(See Figure 1.)

The non-linear upward evolution of intelligence is also manifested by tracing the continued increase in information as seen during the history of life on earth. This can be plotted on a graph in two ways, as suggested by Carl Sagan. The solid curve represents the number of bits of information contained in the genes of various taxa, whose time of origin in the geological record is also roughly indicated. The dashed curve represents an approximate estimate of the evolution in the amount of information in the brains and nervous systems of the same organisms.⁶...Both curves are clearly non-linear. (See Figure 2.)

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