Tom Walker:
>A differential equation approximating the sigmoidal growth curve of an
ideal population is:
>dN/dt = rN(K - N) / K where r is the intrinsic rate of population growth, K
is the carrying
>capacity of the environment, N is the number of individuals present in a
population, and t
>is time.
>An organism which is particularly well adapted to an exponential increase
in population
>size is know as an r strategist. r strategists are characterized by great
rapidity in their
>developmental programs combined with an ability to produce large numbers of
offspring.
>(example): weeds
>In contrast to r strategists, many organisms show extreme potential to
survive and prosper
>at or near carrying capacity, though often at the expense of their ability
to display rapid
>population increases under most circumstance. Such organisms are called K
strategists
>example: gorilla:
All of which has me wondering whether we are weeds or gorillas. We are
probably both. Hunters and gatherers, particularly those who live in colder
and less biologically productive climates, are undoubtedly k strategists.
The have existed as small populations at the limit of the carrying
capacities of their environments. Ancient agricultural populations may
initially have been r strategists, but had to settle for being k strategists
as agricultural lands filled up. However, there were occasional
breakthroughs, as when people harnessed water power and horses replaced oxen
in pulling plows. Reversions to r strategy would then be possible. And of
course r and k strategists have often met in history. Who won out probably
depended on numbers more than anything else. When k strategist Asiatic
tribes swept into Europe they encountered agricultural populations who were
probably in their r phase, and knowing a good thing when they saw it, often
stayed. When r phase Europeans swept into the Americas, they completely
overwhelmed the then k strategist aboriginal populations. They remained r
strategists for a very long time, but are now, alas, probably having to
revert to being k strategists.
The foregoing has been written with something bordering on tongue in cheek
(Eva please take note), and is probably a terrible misapplication of
biological science. Nevertheless, it does suggest that human beings are more
flexible than both weeds and gorillas. But it might also suggest the
ultimate triumph of k strategists as the opportunities for exercising r
strategies become fewer and fewer. If only those gorillas could hang on a
little longer!
Ed Weick
