To a man who makes shoes, the whole world
is made of leather.
That proverb, Chinese in origin
if I remember correctly, came to mind tonight as I read more
of Addy Pross’ What is Life. This is one of those beautiful little books
that bare the soul of a complex science to amateurs like me. Pross clearly intends to answer the question
in a reductionist fashion. Biology, he
dares to say at one point, is just another branch of chemistry. Well, the whole world is made of chemicals. Is
biology really reducible to chemistry?
No.
In chapter 4: ‘Stability and
Instability’, Pross gives us a tour of basic chemistry. Chemical reactions move “downhill,” i.e.,
from states of higher free energy to states of lower free energy. Sometimes, I gather, they have to get over a “hump,”
and in those cases a catalyst is required.
To employ my own analogy, an
avalanche occurs when an unstable sheet of snow begins to slide downhill. The catalyst may have been some fool
yodeling. The result is a ton of snow on
top of a group of helpless skiers, at which point the situation is distressingly
more stable than the original state.
Similarly, a mixture of
hydrogen and oxygen gas is higher in energy than water. It requires a spark (the catalyst) to get the
former to combine into the latter, but once the combination has happened water
is relatively stable. Good thing,
that. Two cheers for the second law of
thermodynamics.
Pross then makes a distinction
between two kinds of stability: static and dynamic. Water molecules are statically stable. Once
formed, a molecule of water remains materially what it is pretty much
forever. A river, by contrast, is dynamically stable. The Thames River has been flowing, he tells
us, for around thirty million years—longer than there has been an England. Yet the water in it is constantly
renewed. As Heraclitus famously
observed, you can’t step in the same river twice.
Self-replicating molecules (e.g.,
RNA) are capable of achieving dynamic stability. They form and decay by a constant exchange of
basic building blocks. In one experiment,
more robust RNA chains emerged from less robust versions. All populations of living organisms achieve
some measure of dynamic stability.
Cyanobacteria have been in business for more than two billion
years! That makes geography look short
sighted.
Pross goes all in by arguing
that the stability achieved by such populations of organisms is more than
analogous to the chemical stability governed by the second law of
thermodynamics (which just states that isolated molecular systems always go
from less stable to more stable states).
He proposes a version of the second law for dynamic stability:
Replicating chemical systems will tend to be transformed
from (dynamically) kinetically less stable to (dynamically) kinetically more
stable.
So the elegant symmetry of
chemical reactions is reproduced at the level of organic systems. Thus is biology consumed by chemistry.
Color me underwhelmed. Granted, I am only half way through the book;
however, it seems to me that dynamic stability just isn’t another version of
static stability. It is a whole ‘nuther’
animal, as we would say down South. To
be sure, everything going on in living organisms has to obey the laws of
thermodynamics. Organisms, however, obey
rules that are not derived from those chemical laws. The stability of populations in a given
ecosystem incorporates chemical stability but it is not reducible to the laws
of chemistry. Biology is a more comprehensive
science than chemistry. Sorry.
Nonetheless, I am very grateful
to Pross for this argument. I think that
he has conceded all the ground he hoped to occupy. I also think that his dynamic stability is
pretty much what Aristotle was aiming at in his treatment of the soul. Aristotle’s soul is precisely the communication
of organic form over time by means of a constant exchange of matter (and I
would add, energy) with the outside world.
Aristotle was a vehement opponent of reductionism. Pross’ reductionism isn’t reductionism at
all, thus confirming the Philosopher’s point.
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