It's important to realize that evolution does NOT work by
systematically marching off toward 'better' organisms. Populations
change because different genes from them are reproduced at different
rates. (There can also be some slow drift due to random changes in
genes.) Is there any evidence that under current human social
conditions genes that make people 'stronger..faster..smarter' cause
them to have more offspring? I really doubt it.
There does seem to be some world-wide tendency for people with
less schooling to have more children. So perhaps we are evolving toward
a species that's less likely to be comfortable going to school, for a
variety of emotional and intellectual reasons.
Then maybe new social conditions will arise, in which other types
reproduce best. This coupled social-biological system seems way too
complicated to predict.
I'd disagree with Mike about whether a sample of people who are
less schooled are actually genetically disposed to be uncomfortable
with going to school. The schooling of people in different countries
has a lot more to do with the availability of schools rather than with
the willingness of people to attend. Some people may be unable to
attend school because they are needed to do work, but this again seems
not heritable to me.
Evolution depends on natural selection as well -- there must be
population variation and natural selection is the name we give to the
fact that some people with some genes reproduce more than others (at
least for many cases this is because individuals who survive to
reproductive age are able to reproduce). A strong force in natural
selection is disease. We have evolved intricate defense mechanisms to
fight against disease, and we continue to be amazed each time we learn
more about it. But we are also getting better and better at preventing
disease and in curing people once they have disease. Disease may no
longer be a significant force in evolution.
The diseases that cause the most mortality in our modern, affluent
society in the United States tend to be those that strike after
reproductive age, and thus also have little effect on which individuals
reproduce. If junk food caused young people to have heart attacks, you
might imagine that humans may evolve to be more resistant to heart
disease at an early age (but heart disease, cancer, and stroke are rare
in young people, even those with poor diets). Diabetes strikes younger
and younger people, but it is controllable, so it won't be a pressure
(published on 10/22/2007)