Evolution’s Arrow

Cosmic Timeline, from Chandra X-Ray Observatory

Does evolution have a direction?


Scientists have gathered a great deal of evidence showing that the universe began around 13.8 billion years ago and that time flows in one direction.  We know know that the universe moves in a direction toward greater entropy and size.   And in certain areas, the universe also flows toward more complexity.

Some call this direction “Evolution’s Arrow.”

But people have only had evidence of this in the past century.  In 1929 Edwin Hubble discovered that our universe is expanding.  Hubble found that light emitted from galaxies shifted toward the red part of the spectrum the more distant that galaxies were.   In 1964, scientists Arno Penzias and Robert Wilson discovered cosmic microwave background (CMB) radiation,  which provided more compelling evidence that the universe had a beginning.

Evolution’s arrow explains why there is such a thing as time, why stars form, why cells cooperate to become organisms, why people congregate into complex societies, and even, why we love.

But what causes the universe to have a direction?

At the most basic level, the arrow of evolution is caused by the flow of energy.   For more information, check out physicist Eric Chaisson’s article, Energy Rate Density as a Complexity Metric and Evolutionary Driver.

In what seems like a paradox, the same energy flow that is adding entropy to the universe, can,  at the same time, create areas of local complexity, and thus drive the emerging complexity that we see in evolution.

It may be that the expansion of the universe causes these local areas of complexity is the expansion of the universe itself.

By showing us where we have come from, Evolution’s arrow shows where we may be going.