Blute Blog

Blute's blog about evolutionary theory: biological, sociocultural and gene-culture.

Archive for May 2020

Mating markets

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Darwinian Sociocultural Evolution Chpt. 4 was on social interaction within a population – competition, conflict and cooperation. After general discussions of relevant evolutionary principles, these were applied to gender differences and relations. The latter discussion was expanded on in Blute (2019).

Rather than males as reproductive parasites of females (as has often been thought, most likely at high densities relative to resources where the most common female ‘quality’ strategy would be most beneficial) or even females as reproductive predators of males (most likely at low densities where the most common male ‘quantity’ strategy would be most beneficial), the approach suggested that the sexes have somewhat different naturally-selected frequency and/or quality ecologically-oriented strategies and that sex is trade in these. The sexes have what economists call different “comparative advantages” compensating for the up to two-fold cost of sex. Males and females (or male and female functions in hermaphrodites) have sex i.e. then trade because males including females among their offspring and females including males among their offspring bet-hedges under uncertainty – reducing the risk of extinction for families, populations or species. Protecting the portfolio is the same reason why humans invest in index funds rather than trying to pick stocks or dollar cost average rather than trying to time markets. Sexual competition and selection on the other hand is conflict over the profits of that trade.

Because natural selection comes logically, historically and developmentally before sexual selection, the table in the 2019 article (see below) more clearly illustrates the consequences of the results of natural for sexual selection than did Table 2. on p. 100 of the book. For example, in line 1 below, if males are naturally selected to be more frequent and females to be higher quality (i.e. have a higher per capita cost), then the results for sexual selection would be males intrasexually selected (male-male competition for mates and/or gametes) and females intersexually selected (active choice for a male mate and/or gametes). Table 1 as a whole illustrates how combining quantity and quality approaches based on natural selection can explain the resulting conventional sex roles, the sex-role reversed, inter as well as intra sexual selection, and passive as well as active choice. As well, the approach implies that sexual selection could equilibrate the sex allocation instead of Fisher’s sex allocation principle and that Mayr’s species definition could be made explanatory. The latter can be restated as “a species is a biological, specifically a mating market, one isolated from other such markets”.

Table 1. Ecologically oriented, naturally selected frequency and mean quality of males and females and their implications for the directions and forms of sexual selection*

Males          Females      Direction and forms of sexual selection

M     Qm      F     Qf            

h      l          l      h          Males intrasexually selected, Females intersexually selected (active choice)

l       h         h     l           Females intrasexually selected, Males intersexually selected (active choice)

h      l          h     l          Both sexes mate multiply, Little or no sexual selection

l       h         l      h         Pair bonded, Little or no sexual selection

h      h         l      l          Males intra & intersexually selected (female passive choice)

l       l          h     h         Females intra & intersexually selected (male passive choice)

*M frequency of males, Qm mean quality of a male, F frequency of females, Qf mean quality of a female, h high, l low
Blute, Marion. 2019. “Mating markets: A naturally selected sex allocation theory of sexual selection.” Biological Theory    14(2) 2019: 103-111.

Written by Marion Blute

May 10, 2020 at 2:53 pm

Density-dependent natural selection may have implications for the coming decline side of the COVID-19 pandemic

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Chapter 3 of Darwinian Sociocultural Evolution on “Necessity: why did it evolve” discussed principles of evolutionary ecology, notably density dependence relative to resources in section 3.3.1., and applied them illustratively to the sociology of science. Subsequently Blute (2016) reviewed the history of, and greatly extended the theory. The extensions included its applicability to selection in space and/or time, to somatic functions as a cause and not just an effect (as in Fisher’s sex allocation theory for example), and to selection within and between, not just growing populations, but also declining ones. These may have implications for the coming declining side of the COVID-19 pandemic.

Where/when density measured in cost per capita relative to resources is low within a population, or in growing populations with a history of catastrophes, natural selection favours spending on consumption (eating and excreting) whereas where/when it is high or in declining ones with a history of bonanzas, selection favours investing in digestion (breaking down and building up). What should be built up? In a homogeneous environment it is mechanisms of social interaction whether cooperative, antagonistic or a mixture of both but in a patchy environment it is mechanisms of dispersal in time (maintenance), in space (motility), and/or in niche (mutability) – the 3 M’s. Similarly, low density measured in frequency or in growing populations with a history of catastrophes, natural selection favours production (many small offspring) whereas high densities or in declining ones with a history of bonanzas, selection favours “reproduction” (fewer larger offspring, ones capable of social interaction or their own 3M’s).

Both these somatic and reproductive distinctions are quantity versus quality ones with the former in each case depleting and degrading the external environment while the latter depletes and degrades the internal environment. As well, the former in each case is associated with a small size because of the disproportionate surface to volume ratio there and the latter of each associated with a large size because of the disproportionate volume to surface ratio there. Under the simplest set of conditions if both somatic and reproductive functions utilize the same or positively correlated resources and the two functions interact synergistically, then at low densities the more one consumes the more one can produce and vice-versa whereas at high densities the more one digests the more one can reproduce and vice-versa.

What then of COVID-19? Our culture is coevolving in interaction with their genes (gene-culture or culture-gene coevolution, between species in this case) and our culture has evolved favouring social distancing etc. in some places – depleting viral resources and causing a levelling off and decline in the viral population(s).  But our culture is now on the edge of reversing itself at least somewhat. What are the implications of that for the virus? Given that surely humans are a heterogeneous environment, selection on the viruses should then favour:
i) maintenance: those which live longer (e.g. making the recovered or infected but symptom free contagious for longer)
ii) motility: those which move further (e.g. placing themselves in small droplets which disperse further rather than just in large drops which tend to fall) and/or
iii) mutability: those which increase their blind mutation rate seeking a new niche (e.g. infecting organs other than respiratory systems such as kidneys, nervous systems etc.)

It is at least possible therefore that changes in their genes and not just in our culture will in the future be contributing to one or more further spikes in the pandemic until a vaccine is widely available or until the 70 or 80% infection rate required for herd immunity is reached.

Blute, Marion. 2016. “Density-dependent selection revisited: Mechanisms linking explanantia and explananda.” Biological Theory 11(2) 113-121.

Written by Marion Blute

May 3, 2020 at 4:22 pm