The morphogenic development of an egg cell into a living creature
is full of inherited baggage that constrains the possible variety of its
potential descendants. Overall, materials that constitute bodies impose
physical constraints that limit what kind of animals can be formed.
There'll be no elephants with legs as thin as an ant's. Genetic
constraints -- the physical nature of genes -- likewise narrow what kind of
animals can be formed. Each hunk of genetic information is a protein
that must physically move to communicate. As general as DNA is, some
messages will be difficult or impossible to code in a complex body
because of the physical constraints of the genes.
Because genes have their own dynamics independent of the organism, they
dictate what can be birthed from them. Inside the genome, genes are
interconnected to the point that the gene can become grid-locked -- A is
waiting on B, B is waiting on C, and C is waiting on A. This internal
linkage raises a conservative force within the genome that pushes on
itself to keep the genome unchanged -- regardless of what body it makes.
Like a complex system, the genetic circuitry tends to resist
perturbations by restricting allowable variations. The genome seeks to
persist as a cohesive unity.
When artificial or natural selection moves a genotype (say, of a pigeon)
out of one stability toward a preferred character (say, white color),
the interlinked character of the genome kicks in to produce multiple
side effects (say, nearsightedness). Darwin, pigeon breeder that he was,
noticed this and called it "the mysterious law of correlation of
growth." Ernst Mayr, the grand old man of neodarwinism, states, "I do
not know of a single intensive selection [breeding] experiment during
the past 50 years during which some such undesirable side effects have
not appeared." The single-point mutations that traditional population
genetics are built upon are rare. Genes usually work in complexes, and
are themselves a complex, adaptive system. The genes harbor their own
wisdom and their own inertia. This is why even monsters follow
The genome must stray far enough from its usual arrangement before it
can create a substantially different outward form. When the genome is
"pulled" by competitive pressures outside its usual orbit, it must
materially rearrange its patterns of linkage in order to remain stable.
In cybernetic terms, it must settle into a different basin of
attraction, one that has its own unity and cohesion, its own
Before an organism takes a stand in the world, before it directly meets
the natural selection of competition and survival, it has already been
subjected to two degrees of internal selection -- first by the internal
constraints of the genome, and secondly by the laws of bodily form.
There is yet a third degree of internal selection that affects an
organism before it can truly deal with natural selection. A change
accepted by the genome, and then accepted by the bodily form, must then
be accepted by the population at large. A single individual with a
brilliant mutation will bury that innovation when it dies unless those
genes are spread throughout the population. Populations (or demes)
exhibit their own cohesive drive toward unity, contributing to an
emergent behavior of the whole, as if they were one large,
homeostatically balanced system -- the population as an individual.
That anything novel ever surmounts these hurdles to evolve is
astounding. Mayr writes in Toward a New Philosophy of Biology: "The most
difficult feat of evolution is to break out of the straight-jacket of
this cohesion. This is the reason why only so relatively few new
structural types have arisen in the last 500 million years, and this may
well also be the reason why 99.999 percent of all evolutionary lines
have become extinct. They did so because the cohesion prevented them
from responding quickly to sudden new demands by the environment."
Stasis, long a major riddle in a constantly changing, coevolving world,
now has a alibi.
I delve into these matters deeply because the constraints on biological
evolution are the hope of artificial evolution. Every negative
constraint within the kinetics of evolution may be viewed in the
positive. The power of constraints that retain the old also assemble the
new. The delicate gravity that holds organisms in their places,
preventing them from casually drifting off to other forms, is the same
gravity that pulls in organisms to certain forms in the first place. The
self-reinforcing aspect of a gene's internal genetic selection -- which
makes leaving its stability so difficult -- acts as a valley drawing in
random arrangements until they rest in that basin of the possible. Over
millions of years, the multiple stabilities of genome and body keep a
species centered, overriding the action of natural selection. When a
species does break away by a radical jump, the same cohesion -- again
beyond influence of natural selection -- lures it into a new homeostasis.
It seems odd at first, but constraints create.
Therefore what is said about extinctions -- that constraints caused
them -- may be equally true about origins. The emergent cohesion at various
levels of biology, and not natural selection per se, may well be the
reason why 99.999 percent of life forms originated. The role of
constraints to assemble life -- what some call self-organization -- is
unmeasured, but probably immense.