Uhh given that an
elephant's gestation period
is almost two years long
and females don't reach
sexual maturity until about
ten years old, it is a little
naive to assume that
elephants being born
without tusks is due to
selective pressure by
poachers in the past 50
years.
Think about it this way - for
elephants to evolve to not
have tusks, there doesn't
have to be a reason for
them not to have tusks, per
se, only a reason that
HAVING tusks is bad. Well
that is easy, right? If you
have big tusks, the
poachers kill you for them.
Here's the tricky bit though -
african elephants (the ones
that are being killed for
tusks, for the most part;
asiatic elephants have
much smaller tusks) don't
really get really big or grow
really large tusks until
they're around 30 - so we
asume that most of the
ones being killed for tusks
are being killed around
then, right? But elephants
are physically able to
reproduce around 10 years
old - the males just don't
because it's the big males
with the big tusks that are
getting all the females.
Even if the poachers are
killing every single big male
with big tusks and every
single big female with big
tusks, there are still
younger animals whose
tusks haven't grown big
enough to be worth
poaching but who are still
going to be able to
reproduce. There's nothing
saying that if these animals
grow larger their tusks
wouldn't grow in.
It is EXTRAORDINARILY
unlikely that poaching
pressure even if it has been
happening for the past
thousands of years would
cause elephants to lose
their tusks entirely ("be born
without them" - elephants
are born without real tusks
so I imagine you refer to the
teeth that will grow into
tusks); it is more likely that
either the tusks would
evolve to become greatly
reduced in size (this doesn't
seem likely to me) or MOST
likely that elephants would
evolve such that the growth
of the tusks was greatly
delayed. It is much easier
for adaptations to occur on
the TIMING of the growth of
structures (you don't get big
tusks until you are 50, as
opposed to getting them at
30) than it is for it to make
structures entirely
disappear.
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