The Reproductive Imperative 1
For most biologists, it seems that life is defined by reproduction.
If it reproduces, it's alive. Life = reproduction. Death = non-reproduction.
But this idea of life doesn't square with a more general view that
a creature (an animal, a human) has died when it stops breathing,
or its heart stops beating, or it ceases moving and turns blue.
No-one asks whether it has stopped reproducing.
Not even the paramedics who show up at the scene of death.
The result is a mismatch between what biologists regard as alive,
and what more or less everyone else regards as alive. And when
biologists insist that the essential characteristic of living creatures
is that they reproduce, everyone else has to shrug and accept.
After all, they should know. They're biologists. They study life.
But there may be a simple explanation of why this mismatch has
arisen. And it grows from the way that biologists (or rather
microbiologists) determine whether bacteria are alive.
Discussing how to determine what proportion of a bacterial
population is alive, the microbiologist John Postgate wrote:
To discover how many cells in a bacterial population are dead (if any)
the microbiologist has to take a sample of that population, count the
cells in it, place it on the surface of a medium in which all living
cells can divide, incubate it for a few hours - usually overnight in
a Petri dish - and see how many cells have taken advantage of the
situation and multiplied to form colonies. Those which have not done
so are presumed to be dead.
(John Postgate. The Outer Reaches of Life. ch.16 Canto. 1994)
What's interesting about this is the last sentence: bacteria which
have not reproduced to form colonies are presumed to be dead.
Given the right environment and nutrients, living bacteria reproduce
every half hour or so, which is why, over a 12 hour night, a
single bacteria which divides and then divides again every half
hour will generate a population of 224 bacteria.
That's about 17,000,000 bacteria, and even though individual
bacteria are invisible to the naked eye, that number of them
produces a visible growth on the surface of the Petri dish.
It's very convenient for microbiologists that bacteria reproduce
so rapidly. If bacteria reproduced once a day, it would take 24 days
to get the same population. If bacteria reproduced once a year,
then it would take 24 years. In that circumstance, microbiologists
would have to find some quicker way of determining whether bacteria
were alive or not. They can't wait 24 years to find out whether
something is alive or not. They'd quite likely be dead themselves
by the time the results were produced.
Using bacterial reproduction rates is a convenient way of
determining whether bacteria are alive, because they reproduce so
rapidly. It is probably the case that it is
not possible to tell, even looking through a microscope, whether
a single bacterium is 'alive' in the sense of showing some sign
of activity. So instead microbiologists use one of the characteristics
of life - reproduction - to test whether any members of a bacterial
population are alive, because this is the most convenient way to
determine the fact. And yet there are pitfalls in using this
method , as Postgate points out:
Would they have survived and divided if the microbiologist had chosen
a different culture medium?
Maybe not. In which case the microbiologist would state that they
were all dead because they were not reproducing.
But, it seems, once having become accustomed to determining
life status this way, biologists slip into the habit of
thinking that the only way of telling whether something is
alive - rather than one way - is to see whether it reproduces
or not. If it reproduces, it's alive. If it doesn't, it's dead.
And the insistence by biologists that the essential
characteristic of life is that it reproduces simply reflects
standard laboratory practice.
But it gets worse. Once biologists have begun to equate life
with reproduction, they then go on to start thinking that the
primary purpose of life is reproduction, that the creatures
exist simply so as to produce more creatures, to make as many copies
of themselves as they possibly can. And the next thing you know
they're on TV saying:
Everyone in a sense knew that what animals work for is not their own
survival but their own reproduction.
(Richard Dawkins. Darwin: The Legacy. BBC TV. 29 Mar 98)
'Everyone' here refers to the closed biological community. And
'in a sense knew' refers to the habitual way biologists think about
life.
A habit of thought, which arose from using just one of the
characteristics of life to test for life, has been elaborated into
the fully-fledged sociobiological dogma, with living creatures vying
to reproduce and pass on their genes to subsequent generations, and
absolutely everything they do is explained as assisting, in one way or
other, this imperative.
The individual organism is only the vehicle (of genes), part of an
elaborate device to preserve and spread them with the least possible
biochemical perturbation.. The organism is only DNA's way of making
more DNA."
(Sociobiologist E.O. Wilson)
If the explanation offered here of the equation of life with reproduction
- that it is a habit of thought peculiar to microbiologists -
has any validity, it is unlikely that the mentality will ever pass
into general use, simply because most non-biologists have never
acquired this habit of thought, and are never likely to.
Most people will probably continue to think that their pet cat has
died when it stops breathing and turns cold, not when it stops
having kittens.
But since (if Richard Dawkins is right) the entire biological
community is now infected with the idea that life is reproduction,
it now requires non-biologists to muster arguments that
re-emphasize the other characteristics of living creatures, of
which reproduction is just one.
Niles Eldredge, a palaeontologist, is one who has stepped into
the argument.
Fitness to Darwin meant something like overall vigor. Those
individuals best suited to cope with life's exigencies were
the more 'fit'. The more 'fit' were more likely to to be the ones
to produce more offspring, thus leaving more copies of their
genes to the next generation. But following the lead of Ronald
Fisher and other early population geneticists, the definition of
fitness became elided - now simply meaning 'reproductive success'.
(Niles Eldredge. Re-Inventing Darwin. 1995)
Although it is unfashionable these days to think of organisms as
machines, to me, [a] fox is a matter-energy transfer machine that needs
to catch and devour [a] rabbit merely to continue to exist. Williams
thinks that the fox eats the rabbit on order to pass on its genes.
I see ... reproduction as a physiological luxury rather than an
imperative that is necessary for that fox to go on living. In my
view, if and only if that fox's economic life is going well can
it afford to reproduce.
(Niles Eldredge. Re-Inventing Darwin. 1995)
A re-assertion that living creatures actively induct and expend
energy (metabolize) is needed, that they eat and breathe and grow
and move.
They hate to admit it, but the life scientists, whether the natural
historians of the 19th century or the biologists of the 20th,
cannot explain what life is in scientific terms. They all know what
it is, as we have done since childhood; but in my view no one has
yet succeeded in defining life.
(James Lovelock. The Ages of Gaia)
Lovelock outlines 3 scientific approaches to life:
- Molecular biology - understanding information-processing chemicals
that are the genetic basis of all life on earth.
- Physiology - the science of living systems seen holistically.
- Thermodynamics - the branch of physics that deals with time and
energy, and connects living processes to the fundamental laws of
the universe.
Thermodynamics is Lovelock's choice, but "so far it has made the
least progress".