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The bodies that genes wear play an incredible role in the
gene's evolution. When two chromosomes recombine in sex they do so not
in nakedness but clothed inside a gigantic egg cell. The overstuffed egg
has a great deal of say in how the genes are implemented. The yolky cell
is chock-full of protein factors and hormonelike agents, and controlled
by its own nonchromosomal DNA. The egg cell directs the chromosomal
genes as they begin to differentiate, guiding them, orienting them, and
orchestrating the construction of their baby. It is no exaggeration to
say that the final organism reproduced is partly under the control of
the egg cell, and out of the control of the genes. The state of the egg
cell can be affected by stress, age, nutrition, etc. (There is one claim
that Down's Syndrome, common in babies born to older women, happens
because the two chromosomes responsible for the birth defect become
physically entangled by lying so close to each other for so many years
in the mother's egg cell.) Even before you are born -- indeed from the
moments of conception onward -- forces outside of your genetic information
form you genetically. Hereditary information does not exist
independently of its embodiment. The origin of an organism's inheritable
body, or morphogenesis, is due then to a partnership of nongenetic cell
material and hereditary genes -- body and genes. Evolution theory, and in
particular evolutionary genetics, cannot understand evolution in full
unless it remembers the complicated morphology of life. Artificial
evolution will only take off when it is embodied.
Each biological egg cell, like most nucleated cells, carries several
libraries of DNA information outside of the chromosomes. Most disturbing
to standard theory, the egg cell may be constantly swapping bits of code
within itself, between the files of its in-house DNA and the files of
inherited chromosomal DNA. If information in the house DNA could be
shaped by the experience of the egg cell, then transmitted to the
chromosomal DNA, it would transgress the stern Central Dogma, which
states that in biology information can only flow from the genes to the
cellular body -- not vice versa. That is, there is no direct feedback from
the body (phenotype) to the gene (genotype). We should be suspicious of
any rule such as the Central Dogma, Darwinian critic Arthur Koestler
pointed out, because "it would be the only example found in nature of a
biological process devoid of feedback."
There are two lessons in morphogenesis for creators of artificial
evolution. The first is that changes in an adult organism are triggered
in embryos indirectly through the environment of the mother's egg, as
well as directly by genealogy. There is plenty of room in this process
for unconventional information flow from the cell (the mother's cell) to
the genes via control factors and intracellular DNA swap. As German
morphologist Rupert Riedl puts it, "Neolamarckism postulates that there
is direct feedback. Neodarwinism postulates that there is no feedback.
Both are mistaken. Truth lies in the middle. There is feedback but it is
not direct." One major route for indirect feedback to the genes is the
very early stages of embryonic growth, the hours of incarnation when the
genes become flesh.
During these hours, the embryo is an amplifier. Hence the second lesson:
Small changes can be magnified as development unfolds. In this way,
morphogenesis skips Darwinian gradualism. This point was made by the
Berkeley geneticist Richard Goldschmidt, whose ideas on nongradual
evolution were derided and scorned throughout his life. His major work,
The Material Basis of Evolution (1940), was dismissed as near-crackpot
until Steven Jay Gould began a campaign to resurrect his ideas in the
1970s. Goldschmidt's title mirrors a theme of mine here: that evolution
is an intermingling of material and information, and that genetic logic
cannot be divorced from the laws of material form in which it dwells.
(An extrapolation of this idea would be that artificial evolution will
run slightly differently from natural evolution as long as it is
embedded on a different substrate.)
Goldschmidt spent a unrewarded lifetime showing that extrapolating the
gradual transitions of microevolution (red rose to yellow rose) could
not explain macroevolution (worm to snake). Instead, he postulated from
his work on developing insects that evolution proceeded by jumps. A
small change made early in development would lead to a large change -- a
monster -- at the adult stage. Most radically altered forms would abort,
but once in a while, large change would cohere and a hopeful monster
would be born. The hopeful monster would have a full wing, say, instead
of the half-winged intermediate form Darwinian theory demanded.
Organisms could arrive fully formed in niches that a series of partially
formed transitional species would never get to. The appearance of
hopeful monsters would also explain the real absence of transitional
forms in fossil lineages.
Goldschmidt made the intriguing claim that his hopeful monsters could
most easily be generated by small shifts in developmental timing. He
found "rate genes" that controlled the timing of local growth and
differentiation processes. For instance, a tweak in the gene controlling
the rates of pigmentation would produce caterpillars of wildly different
color patterns. As his champion Gould writes, "Small changes early in
embryology accumulate through growth to yield profound differences among
adults....Indeed, if we do not invoke discontinuous change by small
alterations in rates of development, I do not see how most major
evolutionary transitions can be accomplished at all."
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