Natural Selection Image Map

Selection Forces on Humans

What is the selection force that gives humans the best brain on earth?

Clearly, early humans had a major selective advantage if they could occupy many niches, compete with other species for food, and avoid becoming food for other species. Their better brains made these things possible. 

Another somewhat frightening thing to consider is that humans have always killed each other, sometimes for food, but more often out of just plain meanness. No other species does that against its own kind on the scale that humans have. All this killing may have created selective forces for being smart because being smart gives advantages in war.
But humans also are smart enough to cooperate and work together to help the species survive. Early hunter-gatherer cultures left plenty of evidence that they worked as teams to find food.  

We cannot be certain of the selective forces acting on humans today because we can't look back from a million or so years from now. But let us consider some possibilities:

  • Worldwide famine could act as a selective force that favors the survivors whose bodies used food more efficiently or who were so aggressive that they took food resources from the  less fortunate.
  • Worldwide disease epidemics could favor people who were more resistant to disease.
  • Worldwide pollution could favor people who resist the damaging effects of environmental hazards  (But remember, that cancer develops late in life, after successful reproduction has occurred).
  • World war could favor people with traits that lead to success in war (such as intelligence or aggressiveness).

Can you think of others?


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