(from Musings and Rants 1985-2016, Marcus Everett 2017, CKCPC3 Publishing, p173, written in 2007)
Several
years ago a friend was telling me about a book she had read about the
Blue Crab. The life cycle of the Blue Crab begins in bays and
marshes along the East Coast from the Mid-Atlantic States to the Gulf
States. The mature female can only mate during a 'shed', when she
discards an old shell and before the new shell hardens. If she is
fertilized during this event, under her 'apron' she will grow a large
egg mass, which looks like a big orange sponge. She will then make
her way to the inlet of the bay where she has been living to release
her eggs into the outgoing tide.
The
eggs hatch and the baby crabs spend the first half of their life at
sea. When they reach about half of their adult size, they return to
the bays to mature and mate. The question of interest, then, is what
percentage on average of the thousands of eggs released by a female
make it back to successfully mate?
Most
people would guess that the percentage is small, and they would be
right. But it is possible to be more precise. For a stable
population, each successfully breeding female must, on average,
produce exactly one successfully breeding female. If the average
success rate is greater than 1, the population will grow
exponentially; if the rate is less than 1 it will decrease
exponentially. An average success rate of 2 would result in the
population doubling every generation, a success rate of 0.5 would
result in it halving every generation.
One
might ask about the poor males, but as long as the survival rate of
males is sufficient to fertilize a sufficient number of females, the
population growth rates depend almost entirely on the success rates
of the females.
The
above consideration holds for any sexually reproducing species,
whether it's crabs, birds, whales or humans. If the average female
success rate differs from 1, the population will either grow or decay
exponentially. This fact has rather profound implications for modern
humanity.
For
most of known human history, the long-term female success rate has
been greater than 1, but only barely. Estimates of population growth
over the 10,000 years before about 1700 put the average success rate,
assuming 20 years for a generation, at about 1.01. This rate of
success implies that each generation was about 1% larger than the
previous, and that the population doubled about every 1500 years.
Wars had little effect, since as was pointed out above only a
sufficient number of males are required. (This fact is borne out by
the baby boom after WWII - losing a half million males didn't even
keep the growth rate flat!) Disasters that affect both sexes cause a
short-term stutter, but usually this just makes it easier for the
next generation or so to make up lost ground.
The
problem is that, over the last 200 years, the industrial revolution
together with modern medicine and agriculture has greatly increased
the survival rate and therefore the potential female success rate. I
say potential rate, since some cultures have voluntarily reduced the
rate even below 1. China, in fact, has recently implemented a one
child per couple rule which, together with a cultural bias against
female offspring, has apparently resulted in an effective female
success rate of something like 0.4. This is a drastically low rate,
and will result in economic and social chaos in even one generation
if not eased. A more reasonable target might be one female child per
couple.
Unfortunately,
much of the third world is reproducing at a rate significantly
greater than one. The world population growth rate is currently such
that the population has been doubling about every 35 years. If we
assume a 20-year generation, this is an average success rate of about
1.5, or in other words each generation is about 50% larger than the
previous. The third world rate must be considerably higher than this
since the industrial nations (minus certain minority groups) now have
rates lower than 1. If the human density on the planet were still
insignificantly small, this might be a good thing. However, we are
already depleting our natural resources such as fossil fuels, water,
oceanic fish stocks and everything else you can think of. Our
waterways are polluted, our air is polluted, and there MAY be some
increase in global warming over and above the interglacial effect due
to human activity such as deforestation and production of excess
carbon dioxide and methane.
What
is depressing is that, although there seem to be unlimited cries for
more laws against SUVs, coal fired power plants, etc., there is never
a discussion or even a suggestion about reducing the human
population. Doing so would not only help solve all these problems,
but may well be the only long-term solution. No laws and no amount
of technology can long compensate for the current rate of exponential
growth of the human population on Earth. We must control our numbers
or face the inevitable catastrophic reduction that reality will
impose upon us. This fact especially must become a part of any
intelligent discussions about subjects such as global warming, as
well as contraception and abortion.
It
should also be noted that, although the human female success rate is
considerably greater than 1, the blue crab is obviously suffering a
current female success rate significantly below 1. The friend that I
referred to above recently paid over $60 a DOZEN for jumbo crabs at a
restaurant near Baltimore. H. L. Mencken would be aghast.
