From: jjh00@diag.amdahl.com (Joel Hanes)
Newsgroups: talk.origins
Subject: Re: Next?
Date: 17 Dec 92 18:29:10 GMT
Reply-To: jjh00@diag.amdahl.com
Organization: Amdahl Corporation  Sunnyvale California


 m23364@mwunix (James Meritt) writes:
>
>What is next?
>
>talk.origins:  On the evolutionary side, 
> homo sapiens is seen as merely the most recent
> step in a series of rungs in a ladder. 
>  What do you see as the "next rung"? 

oooh, damn.
 
I'm sorry to see a t.o regular like Jim Meritt even hint
at the "ladder of progress" or "great chain of being"
view of evolutionary succession.  Humans aren'e in any
way the penultimate step in a long directed journey --
they're one of the few flourishing twigs on a sparse bush
of ape species, a lineage that's been notably unsuccessful
since the Miocene.  Bats have done much better than apes;
so have the ungulates.

So, our evolution wasn't linear or directed; the question
remains: what next?

It's hard to extrapolate very far these days -- the rate of
change in human institutions continues to accelerate.

These days, I think that contingency is far more important
than selected-for competitive advantage 
in determining the genetic composition
of posterity.  Certainly the AIDS pandemic raging in central
Africa and the inner cities of the US, and beginning to catch
fire in Thailand and India, will more-than-decimate whole
populations.  The collapse of societies in Eastern Europe
and Western Asia, coupled with a hard winter, could likewise
depopulate a province or two, greatly reducing the overall
occurence of alleles common in those populations.

Speciation from human stock is not to be expected, at least
until self-supporting colonies on other worlds have existed
for some time.  No population of humans today has adequate
reproductive isolation from other populations to stray very
far from the rest of us in genetic composition.  In fact,
I'd say the opposite is occurring -- that we are living in
a period of great genetic exchange between formerly-more-isolated
populations, and that the geographic distribution of genes
in humans is becoming more uniform.

So what selective pressures might be acting on humanity as
a whole?  Although the ability to withstand famine is undoubtedly
being brutally selected for in many areas of the world, this is
nothing new, and I think represents the a frequent condition
of much of human history.

I think that the truly new features in the human condition,
at least in the developed world, that might produce new
kinds of selection pressures are:

      Accelerating change in all aspects of life; in family
      structure, in social structures, in the economies of
      societies, in technology -- the high rate of change I
      think produces chronic stress, which seems to me likely
      unprecedented as a long-term condition of many people.

      Perhaps we see the selective effects of change-stress
      in the new constellation of human diseases that show
      up in the developed nations: cardio-vascular disease,
      depresssion and other affective diseases, suicide,
      certain kinds of cancer -- these are all at historic
      highs.  They must have *some* differential effect on
      reproductive success.

In the developing and undeveloped countiries, the unprecedented
condition is the sheer number of people -- the population density.
It's hard for me to see what the consequences of this will be --
maybe repeated decimation from epidemic and from surviving 
repeated ecological catastrophes will selectively cull 
the unfortunate denizens of these regions.

Physically, humans haven't changed much since the development
of Neolithic culture, nearly a hundred thousand years ago.
I wouldn't expect the pace of biological change to be rapid
any time soon.

---
Joel Hanes
Newsgroups: talk.origins