#65. Why There is Sex [evolution, genetics]

EV  GE

Red, theory; black, fact

The flower Coronilla varia L.

Sex as an evolvability adaptation

There are always two games in town: reproduction and evolution. Since we live on an unstable planet where the environment can change capriciously, species here have been selected for rapid evolvability per se to enable them to adapt to the occasional rapid environment changes and not go extinct. Apparently, mutations, the starting point for evolutionary adaptation, become more common when the organism is stressed, and stress may partly be a forecast of loss of fertility due to a developing genome-environment mismatch. Bacteria exhibit the large mutation of transformation under stress conditions, and three types of stress all increased the meiotic recombination rate of fruit flies (Stress-induced recombination and the mechanism of evolvability. Zhong W, Priest NK. Behavioral ecology and sociobiology. 2011;65:493-502). Recombination can involve unequal crossing-over in which changes in gene dose can occur due to gene duplication or deletion. However, since most mutations are deleterious (there are more ways to do something wrong than to do it better) many mutations will also reduce fertility, and at precisely the wrong moment: when a reduction in fertility is impending due to environment change. The answer was to split the population into two halves: the reproduction specialists and the selection specialists, and remix their respective genomes at each generation.

The roles of the two sexes

Females obviously do the heavy lifting of reproduction, and males seem to be the gene testers. So if a guy gets a bad gene, so long, and the luckier guy next to him then gets two wives. The phenomenon of greater male variability (Greater male than female variability in regional brain structure across the lifespan. Wierenga LM, Doucet GE, Dima D, Agartz I, Aghajani M, Akudjedu TN, Albajes‐Eizagirre A, Alnæs D, Alpert KI, Andreassen OA, Anticevic A. Karolinska Schizophrenia Project (KaSP) Consortium. Hum. Brain Mapp., doi:10.1002/hbm.25204, and I have never seen so many authors on a paper: 160.) suggests that mutations have more penetrance in males, as befits the male role of cannon fodder/selectees. What the male brings to the marriage bed, then, is field-tested genetic information. This system allows many mutations to be field tested with minimal loss of whole-population fertility, because it is the females who are the limiting factor in population fertility.

Chromosomal mechanisms of greater male variability

Chromosomal diploidy may be a system for sheltering females from mutations, assuming that the default process is for the phenotype that develops to be the average of the phenotypes individually specified by the paternal and maternal chromosome sets. Averaging tends to mute the extremes. The males, however, may set up a winner-take-all competition between homologous chromosomes early in development, with inactivation of one of them chosen at random. The molecular machinery for this may be similar to that of random x-inactivation in females. The result will be greater penetrance of mutations through to the phenotype and thus greater male variability. 

Quantitative prediction

This reasoning predicts that on a given trait, male variability (as standard deviation) will be 41% greater than the female variability, a testable prediction. 41% = [SQRT(2) -1] × 100. Already in my reading I have found a figure of 30%, which is suggestive. 

Mechanistic reconciliation with Mendel's laws

The postulated chromosome inactivation process may feature an exemption mechanism that operates on genes present in only one copy per parent. The effect will be to double the penetrance of dominant alleles at that gene. 

# 54. Disaster Biology [evolution, evolutionary psychology]

EP    EV 

Red, theory; black, fact

The habitat may have been a unit of selection in early hominins, leading to group selection, and much of our evolution may have proceeded by an accumulation of founder effects.

Opportunities for colonization of recently-emptied habitats are ephemeral. Under disaster-prone conditions, this plausibly leads to selection pressure for migrant production and evolvability (i.e., a high rate of evolution, especially founder-effect evolution).

Language diversification in humans may be an evolvability adaptation. Language diversity would work by preserving genetic founder effects from dilution by late-coming migrants, whose reproduction would be held back by the difficulties of learning a new language. Xenophobia and persistent ethnicity markers can be explained in the same way. The spread of linguistic and cultural novelties in a hominin population is predicted to be especially fast in newly colonized, previously empty habitats. Alternatively, the linguistic novelties may start as a thick patois developed by an oppressed group in the home habitat prior to becoming refugees, as a way to make plans "under the noses" of the oppressing group.

Refugee-producing adaptations sub-serving dispersal can be called "tough altruism." Populations producing more refugees are more likely to colonize further empty habitats, a selective advantage.

Disaster biology may be what is conceptually missing from theories of the origin of life (abiogenesis). i.e., the forerunners of the first cells may have been spores that formed by budding from the surface of bodies of water.

Photo by Purnomo Capunk on Unsplash

#46. Body-mod Bob's [evolution, evolutionary psychology]

EP   EV

Red, theory; black, fact

Techno-evolution 

Evolution may be operating in cooperation with a general capacity for technology. Natural selection would operate on the brain pathways underlying our aesthetic preferences concerning our own appearance and that of possible reproduction partners, and then a technology would automatically be developed to satisfy the new preferences.

In the Past

As a first example, consider the oil and brush technology previously assumed for differentiating women from men by hair smoothness. A further step in this direction is to posit that hair color may have been used to code gender. The first step would have been selection for a blond(e) hair colour in both women and men. Since this is a very light colour, it will show the effect of dyeing maximally. Concurrently with this, the aesthetic preferences of men and women would have been differentiated by selection, resulting in blonde women who experience a mild euphoria from being blonde and blond men who experience a mild dysphoria from the same cause. The men would predictably get busy inventing hair-dyeing technologies to rectify this. The necessary dyes are readily obtained from plant sources such as woad and walnut shells. The result would be an effective blonde-female/nonblond-male gender code.

Theory

This style of evolution could be very fast if the brain pathways of aesthetic preferences require few mutations for their modification compared with the number required for the equivalent direct modification of the body. If technologically assisted evolution has general advantages, then we can expect its importance to grow with increases in the reach of technology. 

In the Present

Today, we seem to be at a threshold, with male-to-female and female-to-male gender transitions becoming well known. Demand for this service is probably being driven by disordered neural development during fetal life due to contamination of the fetus by environmental pollutants that have estrogenic properties (e.g., bisphenol A, PCBs, phthalates, etc.). The result would be the birth of individuals with disordered and mutually contradictory gendered aesthetic preferences. 

In the Future 

With further development of cell biology in the direction of supporting body-modification technology, who knows what bizarre hankerings will see the light of day on demand from some customer? Remember that in evolution, the mutation comes first, and the mutation is random. Most such cases will be punished by reduced employability and reduced reproductive success, doubtless exacerbated by prejudice on the part of the normal, normative majority.

However, the very occasional success story is also to be expected, involving the creation of fortuitously hyperfunctional individuals, and thus the technologically assisted creation of a new pre-species of human.

If the engineering details learned by the body-modification trade during this process are then translated into germ-line genetic engineering, then a true artificial humanoid species will have been created.

Photo by Levi Stute on Unsplash

#39. The 1950 Ramp [population, evolutionary psychology, engineering, neuroscience]

PO   EN   EP   NE

Red, theory; black, fact

A schematic of a simple rate-of-increase controller mechanism

Historical 

Since about 1950, the world population has been increasing along a remarkably steady ramp function with no slackening in the rate of increase yet apparent, although one cycle of oscillation in the slope occurred during the Sixties. Malthusian reasoning predicts an exponential increase, which this is not. Several lines of evidence point to the idea that humans have a subconscious population controller in their heads, and yet such a controller would have leveled out the increase by now. Until now, no theory has sufficed to explain the facts.

Human Population is Being Controlled for Endless Trouble

The natural population curve for humans in good times may be a saw-tooth waveform, with population ramps alternating with political convulsions that result in a large group being expelled permanently, resulting in the precipitous but limited drop in local population density that ends the saw-tooth cycle. This cycle accomplishes the ecological dispersal function. The population must ramp up for a time to sustainably create the numbers needed for the expulsions. The WHO population curve shows only a ramp because it is a worldwide figure and therefore population losses in expelling regions are balanced by population increases in welcoming regions. This also implies that human population has been increasing in a way unrestrained by food or resource availability or any other external constraint since 1950, to now.

Clearly, human population is being controlled; not to a constant absolute density, but to a constant rate of increase. Population density would go up along the much faster, steeper, and more disastrous exponential curve of Malthus if there were actually no controller.

Neuroscience Aspects

Researchers should look first for such a controller in the hypothalamus, already known to control other variables, such as temperature, by feedback principles.

"Nature does not reinvent the wheel" [quote from my old Professor], which I understand to mean that once a brain structure evolves to serve a particular computational function, it will be tapped for all future needs for such a calculation. This process may make it grow larger or develop sub-nuclei, but additional, independent nuclei for the same computation will never evolve.

Engineering Aspects 

The population controller may contain a conventional PID controller. To make it control rate of increase rather than absolute population density, you put a differentiator in the feedback pathway. If you are of the opinion that human population control is urgent, then you must knock out this differentiator and replace it with a simple feed-through connection. 

Back to Neuroscience 

Fortunately, one common way for evolution to implement differentiation in mammals is to begin with such a feed-through connection and supplement it with an inhibitory, slow, parallel feed-forward connection. If this is the case here, then you  inhibit the feed-forward pathway pharmacologically with sufficient specificity and the job is done. Subjectively, the effect of such a drug would be to take away people's ability to get used to higher population density in deciding how many children to have. An increased propensity to riot should not occur.

The political convulsions that produce dispersal would be triggered by the value on the integrator of the PID controller rising above a threshold. The amygdala of the brain may mediate this. Consistent with this, bilateral removal of the amygdala and hippocampus in monkeys is known to have a profound taming effect accompanied by hypersexuality, known as the Kluver-Bucy syndrome.

#38. Can Irreducible Complexity Evolve? [genetics, evolution]

EV   GE

Red, theory; black, fact

2 x 2

The Key Insight

Sexual reproduction may allow the evolution of irreducible complexity by increasing the intrinsic complexity of the basic building block of change, the mutation.

Irreducible Complexity 

Influential biologist Richard Dawkins wrote in "The God Delusion" that a genuine case of irreducible complexity will never be found in biology. A case of irreducible complexity would be some adaptation that would require an intelligent designer because it could never evolve one mutation at a time, and Dawkins believes there is no such intelligent designer in biology.

In classic natural selection, each mutation must be individually beneficial to its possessor in order for selection to increase its prevalence in the population to the point where the next incremental, one-mutation improvement becomes statistically possible. In this way, all manner of wondrous things are supposed to evolve bit by tiny bit. You have irreducible complexity if an advantageous evolutionary innovation requires two mutations,  but neither confers any advantage in isolation and so cannot be selected up to a sufficiently high frequency that the second mutation is likely to happen in the background of the first.

However, I am seeing irreducible complexity everywhere these days. 

Possible Cases of Irreducible Complexity

For example, your upper-jaw dentition must mesh accurately with that of your lower jaw or you can't eat. Thus, the process of evolutionary foreshortening of the muzzle of the great apes to the flat human face could never have happened, assuming that a single mutation affects only the upper or lower jaw. 

Furthermore, how can any biological signaling system evolve one mutation at a time? At a minimum, you always need both the transmitter adaptation and the receiver adaptation, not to mention further mutations to connect the receiver circuit to something useful.

The evolution of altruism presents a similar problem. The lonely first altruist in the population is always at a disadvantage in competition with the more selfish non-mutants unless it also has a signaling system that lets it recognize fellow altruists (initially, close relatives) and a further mutation that places the altruistic behavior under the control of the receiver part of this system. Thus, altruists would only be altruistic to their own kind, the requirement for altruism to be selected in the presence of selfishness. Finally, the various parts of this system must be indissolubly linked in a way that the non-altruists cannot fake.

A Solution   

Consider the crossing-over events that occur during meiosis as complex mutations: two changes to the genome from a single event, each corresponding to one end of the DNA segment that translocates. In crossing over, two homologous chromosomes pair up along their length and swap a long segment of DNA, a process requiring two double-chain breaks on each end, and their corresponding repairs. A very far-reaching change to the genetic information can occur during crossing-over that is termed unequal crossing-over. This form of the process arises because of inaccuracies, sometimes major, in the initial alignment of the homologous chromosomes prior to crossing-over. When the process is finished, one chromosome has been shortened and the other has been lengthened. This is the major source of gene duplication, which, in turn, is a major source of junk DNA, the part that is classified as broken genes.

A Mechanism for the Evolution of Complexity 

Anatomical features such as jaw length and axon targets may be controlled by variations in gene dose that originate in unequal crossing-over.

In this way, a concerted change affecting multiple distinct sites becomes possible. The two ends of the recombinant segment can in principle be functionally unrelated initially. They become related if both are affected by the same complex mutation and the entire change increases fitness and is thus selected.

A single complex mutation could in principle produce a communication channel at one stroke because of the number of simultaneous changes involved. 

Statistical Issues

The probability of a combination of simultaneous local changes being beneficial to the organism is much smaller on mathematical grounds than is the probability of a given single-nucleotide change being beneficial. However, these unfavourable statistics are at least partly offset by the existence of a dedicated system for producing complex mutations in large numbers, namely meiosis, part of the process of maturation of egg and sperm cells.

The Big Picture 

Complex mutations provide a way for a species to discontinuously jump into new niches as they open up, possibly explaining how a capacity for this kind of mutation could spread and become characteristic of surviving species over time. This idea also provides another explanation for the lack of transitional forms in the fossil record.

#33. Emotions [evolutionary psychology, genetics, neuroscience]

EP   NE   GE

Red, theory; black, fact

A Genetics Theory 

All sexually reproducing species may have a long-range guidance system that that could be called proxy natural selection, or preferably, post-zygotic gamete selection (PGS). This is basically a fast form of evolution in which particular body cells, the gametes, are the units of selection, not individuals. Selection is conjectured to happen post-zygotically (i.e., sometime after the beginning of development, or even in adulthood) but is retroactive to the egg and sperm that came together to create the individual. 

Each gamete is potentially unique because of the crossing-over genetic rearrangements that happen during its maturation. This theory explains the biological purpose of this further layer of uniqueness beyond that due to the sexual mixing of chromosomes, which would otherwise appear to be redundant.

Emotions Represent Fitness 

Our emotions are conjectured to be programmed by species-replacement group selection and to serve as proxies for increases and decreases in the fitness of our entire species.

The Corresponding Mechanistic Theory 

A further correlate of an emotion beyond the cognitive and autonomic-nervous-system components would be the neurohumoral component, expressed as chemical releasing and inhibiting factors that enter the general circulation via the portal vessels of the hypothalamus, blood vessels which are conventionally described as affecting only the anterior pituitary gland. These factors may reach the stem-like cells that mature into egg and sperm, where they set reversible epigenetic controls on the level of crossing-over that will occur during differentiation. 

Large amounts of crossing-over are viewed as retroactively penalizing the gametes leading to the individual by obfuscating or overwriting with noise specifically the genetic uniqueness of said original gametes. In contrast, low levels of further crossing-over reward the original gametes with high penetrance into the next generation. 

Here we have all the essential ingredients of classical natural selection, and all the potential, in a process that solves problems on an historical timescale.

The Limited Scope of Crossing-over

Crossing-over happens only between homologous chromosomes, which are the paternal and maternal copies of the same chromosome. Human cells have 46 chromosomes because they have 23 pairs of homologous chromosomes. 

The homologous-chromosome-specificity of crossing-over suggests that the grand optimization problem that is human evolution has been broken down into 23 smaller sub-problems for the needs of the PGS process, each of which can be solved independently, without interactions with any of the other 22, and which involves a 23-fold reduction in the number of variables that must be simultaneously optimized. 

In computing, this problem-fragmentation strategy greatly increases the speed of optimization. I conjecture that it is one of the features that makes PGS faster than classical natural selection.

Do Chromosome-specific Signaling Pathways Exist?

However, we now need 23 independent neurohumoral factors descending in the bloodstream from brain to testis or (fetal) ovary, each capable of setting the crossing-over propensity of one specific pair of homologous chromosomes. Each one will require its own specific receptor on the surface of the target oogonia or spermatogonia. In the literature, I already find a strange diversity of cell-surface receptors on the spermatogonia. I predict that the number of such receptors known to science will increase to at least 23. None of this is Lamarkism, because nervous-system control would be over the standard deviation of traits, not their averages.

Naively, this theory also appears to require 23 second messengers to transfer the signals from cell surface to nucleus, which sounds excessive. Perhaps the second messengers form a combinatorial code, which would reduce the number required by humans to log₂ (23) = 4.52, or 5 in round numbers. This is much better. Five second-messenger systems are known, these being based on: cyclic AMP, inositol triphosphate, cyclic GMP, arachidonic acid, and small GTPases (e.g., ras). The AND-element that would be required for decoding could be implemented straightforwardly as a linear sequence of transcription-factor binding sites along the DNA strand. However, many mammalian species have many more than the 32 chromosome pairs needed to saturate a 5-bit address space. If we expand the above list of second messengers with the addition of the calcium/calmodulin complex, the address space expands to 64 pairs of homologous chromosomes, for a total ploidy of 128. This seems sufficient to accommodate all the mammals. Thus, a combinatorial second-messenger code representable as a five- or six-bit binary integer in most organisms would control the deposition of the epigenetic marks controlling crossing-over propensity.

It Gets Bigger

If the above code works for transcription as well as epigenetic modification, then applying whatever stimuli it takes to produce a definite combinatorial second-messenger state inside the cell will activate one specific chromosome for transcription, so that the progeny of the affected cell will develop into whatever that chromosome specifies, be it an organ, a system, or something else. And there you may have the long-sought key to programming stem cells. You're welcome.

The requirement that the evolution of each chromosome contribute independently to the total increase in fitness suggests that a chromosome specifies a system, like the nervous system or the digestive system. We seem to have only 11 systems, not 23, but more may be defined in the future.

Illustration credit: By Edmund Beecher Wilson - Figure 2 of: Wilson, Edmund B. (1900) The cell in Development and Inheritance (2nd ed.), Category:New York: The Macmillan Company, Public Domain, https://commons.wikimedia.org/w/index.php?curid=3155599

#26. Why Organized Religion? Theory Two [evolutionary psychology]

EP

Red, theory; black, fact

Emotions are an "endophenotype," a term from functional magnetic resonance imaging, that provides a useful stepping stone from evolutionary arguments to explanations of our daily lives. 

Starting with the Emotion 

What is the mood or feel as you enter a place of worship and participate in the ceremonies conducted there? More than anything else, the mood is one of great reverence, as though one is in the presence of the world's most powerful king. Kings are supposed to "represent their race." 

Problem

If the emotional outline of people's behaviour is being partly randomized in each generation by recombination-type mutations, a consistent moral code seems impossible if we assume that morality comes mostly from peoples' inborn patterns of emotional reactivity, that is, the sum total of everyone's preferences. The purpose of a king may be to find and coincide with societies' moral center of gravity, around which a formal, if temporary, moral code can be constructed. In a complex society, everyone must be "on the same page" for efficient interaction. 

It Gets Bigger

The same problem no doubt recurs each time organisms come together to form a colony, or super-organism: the conflict between the need of a colony for coordination of colonists and the need of evolution for random variability. Such variability will inevitably affect the formulation and interpretation of the coordinating messages that the colonists exchange, like all their other inborn characteristics. 

A Social Solution 

With kingship comes the corrupting influence of personal power and  tyrannical government. Replacing a real king with a pretend-king named "God" would seem to be the solution that accounts for organized religion, but then one loses the flexibility that goes with having a flesh-and-blood king who can change his predecessor's laws based on current popular sentiment.

Mechanistic Interpretation 

However, human nature may well have a core-and-shell structure, with an "unchanging" core surrounded by a slowly changing shell. The former would be the species-specific objective function and produced by species-replacement group selection within the genus, and the latter would be due to selection of smaller units, and would represent the stratagems hit upon by our ancestors to meet the demands of the objective function in our time and place. This shell part may account for cultural differences between countries. The core may be implemented in the hypothalamus of the brain, whereas the shell may be implemented in the limbic system. The core, being very slow to change, could be managed by organized religion, whereas the shell could be codified by the more flexible institution of government. Though the core is unchanging overall, specific individuals will harbor variations in it due to point mutations, necessitating the standardizing role of religion. Synaptic plasticity would then be used to cancel the point-mutational variation in the objective function.

The Big Picture 

The core may consist of four pillars, or regulatory themes: regulation of genetic diversity, memetic diversity, altruism, and dispersal. Our energetic investment in obtaining each item is to be optimized.

#22. Proxy Natural Selection: The God-shaped Gap at the Heart of Biology [genetics, evolution]

EV   GE

Red, theory; black, fact

The Problem and My Solution 

Some entity must be 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, "post-zygotic gamete selection" (PGS) is DNA-based.

Background 

First, a refresher on how standard natural selection works. DNA undergoes various mutations 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.

My Solution, Big Picture 

PGS 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.

The PGS Mechanism 

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 oligo-generational timescale. On such a timescale, neither standard natural selection nor synapse-based learning systems are serviceable.

Female PGS Is Different 

However, egg cells mature in utero and therefore face a selection disconnect or delay. 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 PGS.

A Better Theory of Female PGS 

First, a definition. PGS focus: a function that is the target of most PGS. Thus, in trees, the PGS focus might be bio-elaboration of natural pesticides. In human males, the PGS focus might be brain development and the broad outlines of emotional reactivity, and thus behaviour. In human females, the PGS focus might be 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.

Experimental evidence for the proposed recombination mechanism of PGS 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

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 signalling pathways, itself  evolves, by species-replacement group selection.

#16. The Intermind, Engine of History? [evolutionary psychology]

EP

Red, theory; black, fact

Statue of Samuel de Champlain, explorer

A Mechanism of Rapid Evolution 

A plausible reason for having a mechanism of rapid evolution is that it permits evolutionary enlargement of body size without loss of evolvability; larger size leads to more internal degrees of freedom and therefore access to previously impossible adaptations. For example, eukaryotes can phagocytose their food; prokaryotes cannot. However, larger body size comes at the expense of longer generation time, which reduces evolvability. A band of high frequencies in the spectrum of environmental fluctuations therefore develops where the large organism has relinquished evolvability, opening it to being out competed by its smaller rivals. 

What I call the intermind would be a proxy for classical evolution that fills the gap, but it needs an objective function to provide it with its ultimate gold standard of goodness of adaptations. Species-replacement group selection could ensure that the objective function is close to optimal. This group selection process takes place at enormously lower frequencies than those the intermind is tracking, because if the timescales were  too similar, chaos would result. For example, in model predictive control, the model is updated on a much longer cycle than are the predictions derived from it.

This genetic intelligence may construct our sociobiology in an ad hoc fashion, by rearranging a knowledge base, or construction kit, of rules of conduct into algorithm-like assemblages. This rearrangement would be blindingly fast by the standards of classical Darwinian evolution, which only provides the construction kit itself, and presumably some further, special rules equivalent to a definition of an objective function to be optimized. The ordinary rules translate experiences into the priming of certain emotions, not the emotions themselves, 

Its Properties 

The set of ordinary rules or intermind would be intermediate in speed between classical evolution and learning by operant conditioning. (All three depend on trial-and error.) The name is also appropriate in that the intermind would be a distributed intelligence, acting over continental, or a least national, areas. Its objective function, which is simply whatever produces survival, will be explicitly encoded into the genes specifying the intermind. (For more on multi-tier, biological control systems with division of labor according to time scale, see "Sociobiology: the New Synthesis," E. O. Wilson, 1975 & 2000, chapter 7.)

Evil Explained

The intermind may account for evil because it is only concerned with survival of the entire species and not with the welfare of individuals.

Evolutionary Mechanisms 

The intermind will have been created by group selection of species. Higher taxonomic units such as genus or family will scarcely evolve because the units that must die out to permit this are unlikely to do so, because they comprise relatively great genetic and geographical diversity. However, we can expect intermind-related adaptations that facilitate the creation of new species, the units of selection. Imprinted genes may be one such adaptation, which might enforce species barriers by a lock-and-key mechanism that kills the embryo if any imprinted gene is present in either two or zero active copies. Species-replacement group selection need act only on the objective function used by trial-and-error processes.

What Are Its Objectives?

In these times, we have come to know that species survival is imperiled by loss of range and by loss of genetic diversity. Thus, the objective function will tend to produce range expansion (exploration in humans) and optimization of genetic diversity. 

However, all this is insufficient to explain the creativity of humans, starting at the end of the last ice age with cave paintings, followed shortly thereafter by the momentous invention of agriculture. The hardships of the ice age must have selected genes for a third, novel component, or pillar, of the species objective function, namely optimization of memetic diversity. Controlled diversification of the species memeplex may have been the starting point for cultural creativity and the invention of all kinds of aids to survival. Art forms may represent the sensor of a feedback servomechanism by which a society measures its own memeplex diversity, measurement being necessary to control.

#1. The Origin of the Eukaryotes [evolution]

EV

Red, theory; black, fact

A fossil (oncoid or stromatolite) of a colony of prokaryotes. Photographed in situ.

The eukaryotic cell may have arisen from a clonal array of prokaryotes that selectively lost some of its internal partition walls while following the colony path to complexity. The remaining partitions gave rise to the internal membrane systems of present-day eukaryotes. Those prokaryote colonists specializing in chemiosmotic processes such as oxidative phosphorylation and photosynthesis could not lose any of their delimiting walls because of the need to maintain concentration gradients, so they remain bacterium-like in morphology to this day. This is an alternative to the phagocytotic theory of the origin of mitochondria and chloroplasts. Modern blue-green algae genetically resemble the DNA in chloroplasts, and modern aerobic bacteria have genetic resemblances to the DNA in mitochondria, but this is not necessarily differential support for the phagocytosis theory. The resemblances can be accounted for by convergent evolution or by the existence of an ancestor common to the modern organisms and the ancient colony formers I suppose here.

These prokaryote colonies would have originally reproduced by sporulation, not mitosis, which would have come later. The "spores" would be actively-metabolizing prokaryotes and before growing into further colonies, would be subject to natural selection. In the spore phase, the rapid evolvability of typical prokaryotes would have been recovered, allowing the formation of large, slow-growing colonies without sacrifice of the high evolvability of the original solitary prokaryotes. Modern-day eukaryotes often secrete tiny bodies called exosomes containing all the macromolecules of life. Exosomes may be the evolutionary vestige of the sporulation phase of the original eukaryotes.