Showing posts with label disaster biology. Show all posts
Showing posts with label disaster biology. Show all posts

Monday, September 13, 2021

#72. Why There is Sex [evolution]

EV

Red, theory; black, fact.

The flower Coronilla varia L.

Sex is 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 3 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, he dies, ha ha, 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. 2020;10, 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. Male promiscuity can therefore be seen as a necessary part of this system, which 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. 

Now all I have to do is reconcile all this with the laws of Mendelian inheritance. 

Mechanistic reconciliation with Mendel's laws

09-16-2021: This reconciliation seems to require an exemption mechanism built into the postulated chromosome inactivation process that operates on genes present in only one copy per parent. The effect of this mechanism will be to double the penetrance of dominant alleles at that gene. Therefore, in males, at single-copy genes, evolution of the machinery of sex is driven by the favorable mutations.

A lovers' heart drawn in dust






Sunday, May 23, 2021

#69. Storming South [Evolution]

EV

Red, theory; black, fact.

This is a theory of the final stages of human evolution, when the large brain expansion occurred.
At least, we did.

Homo sapiens: created by ice

H. sapiens appears to have arisen from Homo erectus over the last 0.8 million years due to climate instability in the apparent origin area, namely East Africa. During this time, Europe was getting glaciated every 0.1 million years because of the astrophysical Milankovitch cycle, a rhythm in the amount of eccentricity in the Earth's orbit due to the influence of the planet Jupiter.
However, I am thinking of the poor slobs who had settled in Europe (or Asia, it doesn't matter for this argument) during the interglacial periods (remember that H. erectus was a great disperser) and when the ice began advancing again, were now facing much worse cooling and drying than in Africa, and thus much greater selection pressures. At least during the last continental glaciation, the ice cap only extended to the Baltic Sea at the maximum, but long before the ice arrives, the land is tundra, which can support only a very thin human population. In any given glaciation, the number of souls per hectare the land could support was relentlessly declining in northern Europe/Asia, and eventually the residents had to get out of Dodge City and settle on land further south, almost certainly over the dead bodies of the former owners. This would have selected Europeans or Asians for warlike tendencies and warfaring skills, which explains a lot of human history. 

Our large brains

However, our large brains seem to be great at something else besides concocting Games of Thrones: that is, environment modification. It's a no-brainer that the first thing someone living in the path of a 2-km wall of ice needs is to keep from freezing to death, and this would have been the first really good reason to modify environments. Unlike chipping a stone axe, environment modification involves fabricating something bigger than the fabricator. Even a parka has to be bigger than you or you can't get into it. This plausibly would have required a larger brain to enable a qualitatively new ability: making something you can't see all at once when it is at working distance.

Our rhythmic evolution

After parkas, early northerners might have evolved enough association cortex (maybe on the next glaciation cycle) to build something a little bigger, like a tent or a lean-to. On the next cycle, they might have been able to pull off a decent longhouse made of wattle. On the next, a jolly good castle surrounded by cultivated lands and drainage ditches. These structures would have delayed the moment of decision when you have to go and take on the Pleistocene-era Low-brows to the south. This will buy you time to build up your numbers, and I understand that winning battles is very much a numbers game. Therefore, environment modification skill would have been selected for in tandem with making like army ants.

Where is the fossil evidence for this theory?

Why do we not find fossil evidence of all this in Europe or Asia? <05-19-2022: Actually, we do: the Neanderthals and Denisovans, who have been difficult to account for in terms of previous theories of human origins.> My scenario can be defended against the inconvenient fossil evidence for a human origin in East Africa in general terms, by citing the well known incompleteness of the fossil record and its many biases, but, of course, I want details. Note, however, what else is in East Africa: the Suez, a land bridge to both Europe and Asia via the Arabian tectonic block, which was created by plate tectonics near the end of the Miocene, thus antedating both H. sapiens and H. erectus. Not only can hominins disperse through it to other continents during interglacials, but they can come back in, fiercer and brainier than before, when the ice is advancing again, to then deposit their fossil evidence in the Rift Valley region of East Africa. The Eurasian backflow event of 3000 years ago may be a relatively recent example of this. The Isthmus of Suez is low-lying and thus easily drowned by the sea, but the probability of this was minimal at times of continental glaciation, when sea levels are minimal. I assume that early hominins expanded like a gas into whatever continent they could access. Increasing glaciation/tundrafication of that continent would have recompressed the "gas" southward, causing it to retrace its path, partly back into Africa. 

Pleistocene selection pressures

To reiterate, this process would have been accompanied by great mortality and therefore, potentially, much selection. Moreover, during the period we are considering, temperatures were declining most of the time; the plot of temperature versus time has a saw-tooth pattern, with long declines alternating with short warming events, and it is the declines that would have been the times of natural selection of hominins living at high latitudes.

A limestone block in Canada showing scratches left by stones
embedded in the underside of a continental glacier.
The rock has also been ground nearly flat by the same process. Scary.

Glaciated boulder by night. Have a nice interglacial.


Tuesday, June 16, 2020

#66. Neuromodulators as Peril Specialists [Neuroscience]

NE

Red: theory; black, fact.



“Life is Difficulty”


The basic theory

I conjecture that the primordial function of any type of transmitter substance acting on the g-protein-coupled cell-surface receptors or nuclear receptors of neurons was to coordinate the whole-organism response to some class of perils.
 

Complications

Glutamate, GABA, and acetylcholine are usually considered neurotransmitters, not neuromodulators, but all three have G-protein-coupled receptors in addition to ionotropic receptors and are thus both.
In thermoregulation, hypothalamic glutamate and GABA act on the body via the serotonergic raphe pallidus nuclei. The implied connection with predation (See table) would be due to the fact that animals become torpid at extremes of temperature and thus easy prey. The larger predator would have a smaller surface to volume ratio and thus slower warming and cooling after leaving its refugium to hunt. The predator thermal advantage would have been the selection pressure for thermal sensitivity in the anti predation system, which eventually became upstream of temperature regulation effectors generally. 
The functional assignments suggested in Table 1 would pertain to a very primordial brain. The implication is that any modern biological function of the neuromodulator substance other than organizing the response to a specific type of peril was elaborated out of the primordial function over long-term evolution, which can act opportunistically to confer new functions on preexisting adaptations.

Table 1.

 Peril  Substance  Failure mode
Extremes of heat and cold glutamate and GABA  ?
Predator serotonin depression
Parasite histamine phobia
Rival conspecific noradrenaline paranoia
Starvation dopamine addiction
Non-reproduction testosterone and estrogen overpopulation 
Change per se acetylcholine positive symptoms of schizophrenia 

<10-30-2020: human failure modes added.>

Complex instincts

A network of neuromodulator interactions exists, which may serve to implement the more complex innate behaviors such as migration, nest building, and care of the young. The chemically information-rich peptide neuromodulators such as oxytocin, orexin, and cholecystokinin may organize the fine details of such behaviors.

Mosaic model

Thus, all human-characteristic behaviors will be made of the same primordial behavioral components, but in different combinations and sub serving different functions. For example, there seems to be at least a bit of the male-female interaction mixed into all our fraught dyadic interactions of whatever biological purpose; if operant learning helps to shape the behavior, you can be sure that dopamine is involved; the perception of any existential threat will call up serotonin, and so on.

Notes on serotonin

07-06-2020: The assignment of serotonin to the organization of anti-predation defenses may require some explaining because this chemical is usually thought of as some kind of happy juice due to evidence from SSRI-type drugs that elevating its concentration in the brain can often produce a mood elevation in clinically depressed patients. I propose that the anti-predation defenses organized by serotonin have a short-term part and a long-term part (called phasic and tonic, respectively, when referring to individual neurons). One predator emergency would trigger only the short-term part, organized by a single burst of serotonin release in the brain and spinal cord. (Four of the eight serotonin-releasing brain nuclei innervate the spinal cord.) Multiple predator emergencies happening within too short a time would induce the long-term part. Paradoxically, this part would be organized by a long-term reduction in the release of serotonin to below its normally non-zero baseline level, probably due to upregulation of the inhibitory 1B serotonin autoreceptors on the serotonergic presynaptic terminals. Depressed mood would ensue, which we know involves little physical activity. This can now be interpreted as the patient moving slowly or not at all to escape the notice of the local predator—the sloth strategy. SSRIs increase the long-term serotonin levels in the brain, thereby suppressing the long-term anti-predation adaptations, thereby producing a mood elevation—while increasing rates of all-causes premature death in patients by 33%! (See: The Mortality and Myocardial Effects of Antidepressants Are Moderated by Preexisting Cardiovascular Disease: A Meta-Analysis. Maslej MM, Bolker BM, Russell MJ, et al. Psychother Psychosom. 2017;86:268-282.) Apparently, the present environment contains real existential threats for some people (dominance contests leading to social hierarchies?) equivalent to the presence of a predator. Some of the social, occupational, and physical impairments associated with depression may be pre-existing and causative of the depressive symptoms, which can be read as a withdrawing from the fray that confers a net survival benefit.

The modal-brain theory 

03-27-24: Neuromodulators are here postulated to shift the brain between the default mode in which reproduction occurs to one of six peril-addressing functional states or modes. Shifts between modes are postulated to be all-or-nothing. Variations in personality and the causes of mental illnesses would inhere in variations in the lifetimes of the modal states. Some of the complexity of sleep states may stem from the presence of multiple waking functional modes requiring distinct maintenance processes during sleep.


Schizophrenia may be a combination disorder with comorbid solitariness enhancing disregulation related to dopamine and rigidity-loss disregulation related to acetylcholine, simultaneously caused by an aversive social positive feedback. Loss of sociality would remove social controls on behavioral variability, thus synergizing with runaway rigidity loss controlled by acetylcholine. See my post #61,“Stress and Schizophrenia.”

Wednesday, March 25, 2020

#64. The Drill Sergeants of the Apocalypse [evolutionary psychology, population]

EP     PO     

Red, theory; black, fact.



A drill hall of the Apocalypse?
If you are:
  • amused by abuse of trust
  • amused by subversion
you may have what might be called "subversion complex" (SC). Other evidence of this may be:
  • hacking
  • pedophilia
  • enjoyment of sick jokes
  • trust issues


Social role of  the trickster

I conjecture that the evolved role of SC (tricksterism) is to harden a population against natural disasters such as famine and pestilence. In this regard, persons with SC are analogous to white-hat hackers, or penetration testers, that the military or a large corporation may keep on staff to harden their systems against hacking for real by outsiders. Spontaneously formed, cooperating groups of persons with SC would be analogous to corporate "red teams" or "tiger teams."

Tricksterism as a subroutine of the human swarm intelligence

SC is probably transmitted intergenerationally by child abuse. The prevalence of SC in a population may rise with increasing population density because of adult carriers encountering and victimizing solitary children more frequently. If the SC prevalence rises high enough, carriers encounter each other often enough to form social groups ("red teams") that cooperate in subversion to amplify their social effect. This is adaptive, because the risk of famine and pestilence to a population increases with population density. <06-19-2020: this can be called a "macro-homeostatic effect," or maybe a "population homeostatic effect," but is usually called "the hand of God.">

There may also be a complimentary subversion-victim complex (SVC), also induced by childhood abuse, but involving a milder disturbance that spares the victim's ability to influence and harden a network of friends against adversity. <03-27-2020: This may be where priests come from.>

An SC carrier or red team of same will appear to the victim to:

  • accurately imitate the essential features of microbial pathogens
  • accurately imitate the essential features of a famine
  • "not be doing a very good job" of killing the victim, because their evolved role is essentially instructional.

Of value would be a psychometric test to detect SC and SVC, but the test authors will need to do much field testing to bullet proof the SC test against cheating.

Schizophrenia may be a disease of persons with SVC who fail to learn fast enough to defeat the threats posed by their local "red team." 

The evolved emotional reactivities underlying tricksterism

05-14-2020: The toxic factor that induces the SC/SVC may be unavoidable stress experienced in childhood. This factor is also linked to depression. In adulthood, the dynamic would be between the Till Eulenspiegels (SC) and the control freaks (SVC). The angrier the control freaks get because of the tricks of the Tills, the more fearful the Tills get because the control freaks signal their desire for disproportionate retribution. However, the Tills have learned that by cleverly subverting the control freaks, thus making them look feckless and by implication, no real threat, they can reduce their own anxiety levels, resulting in negative reinforcement of the subversion behavior (and a vicious interpersonal cycle). <05-17-2020: These emotional reactivities underlying full-blown SC may also underlie the cultural phenomenon of humor.>

06-09-2020: The victims of Till Eulenspiegel's tricks were often craftspersons, which supports the present theory because such people are in the best position to devise technological solutions to external threats to society, which are one possible output of the SC/SVC adaptation that led to its selection in evolution. Recall that both Jesus of Nazareth and Paul the Apostle were craftspeople (carpenter and tent maker, respectively). However, the worst mass murderer in Canadian history to date was also a craftsperson (denturist). Keep calm and make something.

12-24-2020: Evolution has raised up a number of supporting roles for the builder-trickster interaction: the humorist, the madman, and the suicide. The humorist makes the trickster role appealing to young people and serves as recruiter. The madman runs to the police with tales of nonexistent persecution, thereby obfuscating attempts by the tormented builder to explain his problem and be believed, and get help, due to a poor signal-to noise ratio, thereby allowing the tricksters to do their work unimpeded by social controls. The suicide obfuscates the question of whether someone has been murdered. If the tricksters decide that some builder must be murdered to keep the party going, they just have to pin a suicide note on the body to get away scot-free.

12-25-2020: The final stage in the builder-trickster program is making public the findings of the builder, for which an attention-getting emotional explosion will be needed, e.g., the crucifiction of Jesus, or the Gabriel Wortman massacre. However, this is probably simplistic. <01-26-2022: Other mechanisms for propagating design improvements can be imagined, such as the emulation of high-status individuals.>

A biological precedent for penetration testing?

Evidence for a biological precedent may be the many retroviruses integrated into the human genome. Presumably, one of these becomes active now and then at random and kills the host cell if the anti-viral defenses of the latter have become weak due to some somatic mutation. The red team-blue team strategy seems to be too good a trick for nature to miss (TGTNM).

A field observation

06-18-2020: Don't assume that all persons with SC are necessarily grinning and leering all the time. I strongly suspect that the ones who have done time are unsmiling, taciturn, and given to complaint--and still up to their tricks.

Evolution of the trickster

09-27-2020: Modern human populations may have two (independent?) axes of political polarization: oppressor-oppressed and trickster-control freak. The first may sub serve dispersal by generating refugee groups and the second may sub serve building. Any built thing must serve in a complex world in which many constraints must be simultaneously observed. Thus, after the initial build, a long period of tweaking must typically follow. The role of the tricksters is to powerfully motivate this tweaking before the complacency of the control-freak builders leads to disaster. <03-12-2021: This may have been how engineering was done by an archaic version of Homo sapiens.><12-02-2022: The tricksters can also make mistakes, causing damage that cannot have a silver lining in any possible world, and moving to correct this is a natural role of the builders. If you are a builder, ask this: “What is the best use of my indignation?” It is to keep to a strict harm-reduction approach.>


A tangent about our evolutionary context

Our evolutionary forebears may have been champion dispersers for a long time <12-21-2020: i.e., Homo erectus*> before the ice age** forced some of them to become champion builders (initially, of shelters and warm clothing). <12-31-2020: "champion environment modifiers" may be closer to the mark than "champion builders"> It is an interesting fact that physically, humans exceed all other animals only in long-distance running, which can be read as dispersal ability. Our carelessness with preserving the local environments and our propensity for overpopulation can be read as typical r-selected disperser behavior. <12-21-2020: The r-selecting niche was probably big game hunting. H. erectus sites indicate consumption of medium and large meat animals. Overhunting would have occurred routinely, due to the slow reproduction rates of large animals and the high hunting efficiency of H. erectus due to tool use, so that dispersal of the hunters to new habitats would likewise have been routine.>

* H. erectus: lived 2 million years ago to 100,000 years ago. H. sapiens: earliest fossils, 300,000 years old. Evidence of behavioral modernity: 100,000–70,000 y ago.

** that is, the Pleistocene ice age, itself a sequence of 5 successive continental glaciations (by oxygen isotope evidence) separated by temperate periods, starting 2.6 million years ago and thought to be not over yet. Over the past 800,000 y, continental glaciation has happened rhythmically on a 100,000-y cycle due to astronomical factors (Milankovitch cycle). Selection for building skill may therefore have occurred in multiple successive episodes over the course of the Pleistocene.