POWER POINT ABSTRACT, ARE HUMANS STILL EVOLVING?
In order to discuss this fundamental question, we need to clarify some
basic concepts that pertain to evolution in general. Evolution depends
on individual genetic variability. However, the main selective force
that drives evolution in a specific direction is natural selection.
Darwin described natural selection as "the great battle of life".
Hereditary traits that lead to a survival advantage in a particular
situation along with differential reproductive success is evolution.
Without differential reproductive success, the advantageous genes of the
fittest individuals mean nothing, as they do not influence the gene pool
of a specific population. Another key ingredient of evolution is
isolation, as the influence of a successful individual's genetic
contribution is far more pronounced in an isolated population with a
relatively small genetic pool.
We can now investigate the various elements in more detail and apply it
to the modern human. The main mechanisms that generate genetic
variability (genetic mutation and genetic exchange) remain intact.
However, the real question is whether natural selection is still
operational as a selective force. Is modern life still enough of a
battle, with a sufficient number of casualties along the way, for it to
act as a strong selective force? Our large brain and dextrous behaviour
has allowed us to overcome most of the environmental challenges faced by
our ancestors, by artificial manipulation. Modern agricultural
practices have ensured levels of food security that were previously
unknown. Modern humans build houses and manufacture clothes that keep
them warm, even in some of the most hostile environments on earth.
Modern medicine has led to a drastic reduction in early deaths and the
lifespan of the average person in the developed world extends far beyond
the reproductive period. The unprecedented population explosion
witnessed during the past century demonstrates how the major driving
force of evolution, "the battle of life" has lost its bite.
In addition, individuals who are deemed to be most successful in
developed countries rarely have the most children. This indicates that
even if limited natural selection is still taking place, it does not
translate into differential reproductive success. Many factors
contribute to this, but two of the most important influences are
probably the practice of monogamy and the liberal use of artificial
birth control in the developed world. Globalization has also shrunk our
world to such an extent, that in practical terms we all share one
massive, and therefore static, gene pool.
Are humans still evolving? I think we can say with a fair amount of
certainty that the selective forces required for evolution to occur,
have been eroded in the modern developed world. However, this does not
imply that evolution is non-existent. In fact, the basic evolutionary
mechanisms are still in place and it only requires a strong selective
force, like a worldwide outbreak of bird flu, for evolution to awaken
from its present slumber.
BCB Hons NISL student
University of the Western Cape
Private Bag X17