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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 rules.

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 homeostasis.

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.