Evolution

An organism has two type of cells:  Somatic cells that will
form the basis for tissues and organs, and Germ cells that are
able to form a complete organism generations after generations.
In most cases, germ cells are set aside from somatic cells during
embryogenesis.  In time, they will migrate through the embryo,
associate with somatic gonadal cells and form the gonad.

When somatic cells divide, the daughter cell will be an
exact copy of the parent cell.  Occasionally, though, a
transcribing error can occur.  The new cell is somewhat
different; this is what we call a mutation.  The mutation can be
of a minor nature and have little or no impact, or the effect
could be substantial.  A mutation could be harmful or beneficial.
If it’s harmful, the odds are that the new individual and his
descendants will not survive for long.  Take the case of a brown
mouse giving birth to an albino mouse.  The new mouse will be
readily spotted by predators, and that will be the end of that.
Even if it manages to reproduce, the descendants are still
doomed.  It doesn’t always work that way though; the albino mouse
may only come out to forage at night when it is practically
invisible.

[To the best of my knowledge, there is signalling as between
the somatic cells and the germ cells.  Thus, if errors occur when
somatic cells divide, there may be equivalent changes in the germ
cells of that individual.  These changes in turn can be passed on
to future generations].

Beneficial mutations is what clued Darwin on the
evolutionary nature of life and started the evolution revolution.
His now famous finches had different beaks (generated through
mutations) which allowed them to rely on different food sources.

Beneficial mutations took us from the mouse to the elephant
over millions of years!  For a long time it was thought that this
happened by increments.  We didn’t move from the mouse to the
elephant overnight!  It was later found out, that while this was
largely true, evolution at time skipped a few steps, there was a
big mutational “jump.”  A major shortcut may for example have
been taken to take us out of the Simian Species and move us to
the Human Species.  I am not aware that science has ever provided
an explanation for these abrupt evolutionary changes; if so, let
me provide an epigenetic one.

Epigenetics tells us that we can pass some of our
experiences to future generations.  This “accumulated knowledge”
could be saved, and eventually when it is meaningful passed on to
our descendants.  Thus we get a sudden change.  For instance, the
epigenetic accumulation in a pony could suddenly give rise to a
horse.  A stronger and faster animal.  Did it happen exactly this
way?  We can’t know for sure.  We were not there!  But
archaeological discoveries have shown that there has, at times,
been sudden evolutionary changes.  At any rate, the accepted view
of evolution (by gradual increments) would have been too slow to
bring us from unicellular organisms to humans.

Source

Germ Cells are Forever:  a lecture by Ruth Lehmann. Ph.D.
May 2007
http://cas.nyu.edu/object/as.news.lehmann_lecture.html

A Final Word

If this is the first you’ve heard of epigenetics, rest
assured that you will be hearing a lot more in the years to come.
By the same token, don’t ever assume that epigenetics is the
final frontier; in your lifetime, if you’re young enough, you
will find out that the human genome holds more surprises for us.

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