The pattern of evolutionary causality is a web of astonishing complexity. Happenstance may play a powerful role in biology, as it does in history.
Were the Earth to be started over again with all its physical features identical, it is unlikely that anything closely resembling a human being would ever again emerge.
In fact, there is a powerful random to the evolutionary process. A solitary cosmic ray striking a different gene, producing a different mutation, can have small consequences early but profound consequences late.
The father back the critical events occur, the more powerfully can they influence the present.
For example, we have five fingers, including one opposable thumb. These five fingers serve us quite well.
But we would be served equally well with six fingers including, or four fingers including a thumb, or five fingers and two thumbs. There is nothing intrinsically best about our particular configuration of fingers.
We use base ten arithmetic only because we have ten fingers on our hands (the arithmetic based on the number 5 or 10 seems to be so obvious that the ancient Greek equivalent of “to count” literally means “to five”.
We have five fingers because we have descended from a Devonian fish that had five phalanges or bones in its fins. Had we descended from a fish with six our four phalanges, we would have six or four fingers on each hand and would think them perfectly natural.
Even more, had the arrangement been otherwise, we would use base eight or base twelve arithmetic. The same point applies to other essential aspects of our being – our hereditary material, our internal biochemistry, our stature, form, organ systems, loves and hates, passions and despairs, tenderness and aggression, even our analytical processes – all of these are, at least in part, the result of minor accidents in our immensely long evolutionary history.
Perhaps if one less dragonfly had drowned in the Carboniferous swamps, the intelligent organisms on our planet today would have feathers and teach their young in rookeries.
Everything would depend on what ancient findings we had accidentally been told about, and how accurate the account was. Image: © Megan Jorgensen