Red, theory; black, fact.
2-06-2017
As promised, here is my detailed and hypothetical description of the entity responsible for compensating for the fact that our microbial, insect, and rodent competitors evolve much faster than we do because of their shorter generation times. In these pages, I have been variously calling this entity the intermind, the collective unconscious, the mover of the zeitgeist, and the real, investigable system that the word "God" points to. I here recant my former belief that epigenetic marks are likely to be the basis of an information storage system sufficient to support an independent evolution-like process. I will assume that the new system, "proxy natural selection" (PNS) is DNA-based.
11-20-2017
The acronym PNS is liable to be confused with "peripheral nervous system," so a better acronym would be "PGS," meaning "post-zygotic gamete selection."
2-06-2017
First, a refresher on how standard natural selection works. DNA undergoes point mutations (I will deal with the other main type of mutation later) that add diversity to the genome. The developmental process translates the various genotypes into a somewhat diverse set of phenotypes. Existential selection then ensues from the interaction of these phenotypes with the environment, made chronically stringent by population pressure. Differential reproduction of phenotypes then occurs, leading to changes in gene frequencies in the population gene pool. Such changes are the essence of evolution.
PNS assumes that the genome contains special if-then rules, perhaps implemented as cis-control-element/structural gene partnerships, that collectively simulate the presence of an objective function that dictates the desiderata of survival and replaces or stands in for existential selection. A given objective function is species-specific but has a generic resemblance across the species of a genus. The genus-averaged objective function evolves by species-replacement group selection, and can thus theoretically produce altruism between individuals. The if-then rules instruct the wiring of the hypothalamus during development, which thereby comes to dictate the organism's likes and dislikes in a way leading to species survival as well as (usually) individual survival. Routinely, however, some specific individuals end up sacrificed for the benefit of the species.
Here is how PNS may work. Crossing-over mutations during meiosis to produce sperm increase the diversity of the recombinotypes making up the sperm population. During subsequent fertilization and brain development, each recombinotype instructs a particular behavioral temperament, or idiosyncratotype. Temperament is assumed to be a set of if-then rules connecting certain experiences with the triggering of specific emotions. An emotion is a high-level, but in some ways stereotyped, motor command, the details of which are to be fleshed out during conscious planning before anything emerges as overt behavior. Each idiosyncratotype interacts with the environment and the result is proxy-evaluated by the hypothalamus to produce a proxy-fitness (p-fitness) measurement. The measurement is translated into blood-borne factors that travel from the brain to the gonads where they activate cell-surface receptors on the spermatogonia. Good p-fitness results in the recombination hot spots of the spermatogonia being stabilized, whereas poor p-fitness results in their further destabilization.
Thus, good p-fitness leads to good penetrance of the paternal recombinotype into viable sperm, whereas poor p-fitness leads to poor penetrance, because of many further crossing-over events. Changes in hotspot activity could possibly be due to changes in cytosine methylation status. The result is within-lifetime changes in idiosyncratotype frequencies in the population, leading to changes in the gross behavior of the population in a way that favors species survival in the face of environmental fluctuations on an oligogenerational timescale. On such a timescale, neither standard natural selection nor synapse-based learning systems are serviceable.
2-07-2017
The female version of crossing over may set up a slow, random process of recombination that works in the background to gradually erase any improbable statistical distribution of recombinotypes that is not being actively maintained by PNS.
7-29-2017
Here is a better theory of female PNS. First, we need a definition. PNS focus: a function that is the target of most PNS. Thus, in trees, the PNS focus is bio elaboration of natural pesticides. In human males, the PNS focus is brain development and the broad outlines of emotional reactivity, and thus behavior. In human females, the PNS focus is the digestive process. The effectiveness of the latter could be evaluated while the female fetus is still in the womb, when the eggs are developing. The proxy fitness measure would be how well nourished the fetus is, which requires no sensory experience. This explains the developmental timing difference between oogenesis and spermatogenesis. Digestion would be fine tuned by the females for whatever types of food happen to be available in a given time and place.
8-18-2017
Experimental evidence for my proposed recombination mechanism of proxy natural selection has been available since 2011, as follows:
Stress-induced recombination and the mechanism of evolvability
by Weihao Zhong; Nicholas K. Priest
Behavioral Ecology and Sociobiology, 03/2011, Volume 65, Issue 3
permalink:
Abstract:
"The concept of evolvability is controversial. To
some, it is simply a measure of the standing genetic variation in a population
and can be captured by the narrow-sense heritability (h2). To others,
evolvability refers to the capacity to generate heritable phenotypic variation.
Many scientists, including Darwin, have argued that environmental variation can
generate heritable phenotypic variation. However, their theories have been
difficult to test.
Recent
theory on the evolution of sex and recombination provides a much simpler
framework for evaluating evolvability. It shows that modifiers of recombination
can increase in prevalence whenever low fitness individuals produce
proportionately more recombinant offspring. Because recombination can generate
heritable variation, stress-induced recombination might be a plausible
mechanism of evolvability if populations exhibit a negative relationship
between fitness and recombination. Here we use the fruit fly, Drosophila
melanogaster, to test for this relationship.
We exposed females to mating stress, heat shock or
cold shock and measured the temporary changes that occurred in reproductive
output and the rate of chromosomal recombination. We found that each stress
treatment increased the rate of recombination and that heat shock, but not
mating stress or cold shock, generated a negative relationship between
reproductive output and recombination rate. The negative relationship was
absent in the low-stress controls, which suggests that fitness and
recombination may only be associated under stressful conditions. Taken together, these findings suggest that
stress-induced recombination might be a mechanism of evolvability."
However, my theory also has a macro aspect, namely that the definition of what constitutes "stress," in terms of neuron interconnections or chemical signaling pathways, itself evolves, by species-replacement group selection. Support for that idea is the next thing I must search for in the literature. &&
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