Blute Blog

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

Posts Tagged ‘sexual selection

The Potential Role of Centrioles in Active or Passive Female Choice

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In animals and some other groups in which centrioles are inherited through males, good centrioles may be what females/ova are commonly choosing for or being manipulated with sexually to provide offspring or the expectation of offspring with the ability to escape difficult conditions by dispersing in time, space and/or niche, hence yielding grand offspring. These are the 3M’s – maintenance, motility and mutability. Centrioles as cellular organelles provide maintenance (the aster which emerges from them nucleates the cytoskelton), hence the choice for more mature, healthier males. They provide motility (they form the base of flagella), hence the choice for songs, dances and nuptial flights. They also provide mutability (in the sense of differentiation in development because they determine the planes and directions of cell divisions affecting cytoplasmic heredity), hence the choice for complex, symmetrical ornaments – for example those peacocks’ tails. The dramatic colour patterns sometimes observed in complex, symmetrical ornaments may make the latter more likely to be noticed by females in active or passive choice. And since it may be unclear whether flagella actually contribute to motility at the organismic level, it may be that songs, dances and nuptial flights are simply another form of complex, symmetrical ornament, one in space and time outside the body instead of inside it.

Written by Marion Blute

August 15, 2021 at 9:47 am

Feminist Views on a Theory of Sexes, Sex and Sexual Selection

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In an article in Biological Theory in 2019 on mating markets and in two posts here, one in September 2019 on the two-fold cost of sex and in May 2020 on mating markets, together I hope made clear that a single premise, if justified, could solve the three major evolutionary puzzles about sex. The premise is that in a dioecious population for example, i.e. one composed of males and females, the two are ecologically, i.e. naturally selected, to be somewhat different. That would solve:

a) the puzzle of what compensates for the two-fold cost of sex because of the advantages of specialization

b) the puzzle of why they engage in sex at all because such trade is a form of bet hedging which produces diversity reducing the risk of extinction, and

c) the puzzle of why they engage in sexual competition and selection and why it takes the form that it does because sexual competition and selection are conflict over the profits of the sexual trade and the form it takes depends on what the naturally-selected differences are.

However, there is one thing not discussed in any of the three (possible feminist views of such a theory) and one briefly discussed in the article (the potential role of centrioles) but not in the posts. The former is discussed here and the latter will be in a subsequent post.

As noted in the article and in the most recent post, if the naturally-selected sex allocation is with males/male gametes at high frequency but low quality, i.e. low per capita cost, and females/female gametes at low frequency but high quality, i.e. high per capita cost, then sexually males/male gametes would compete intrasexually for female mates/female gametes and females/female gametes would compete intersexually choosing high quality male mates/male gametes. Feminists might find both something to both dislike and to like about this explanation of “conventional” sex roles. On the one hand, one can imagine some people reacting, “I see, on this view the sexes are naturally different, well then that justifies etc.” On the other hand, in this scenario, females/female gametes choose not just as a side effect of high male/male gamete frequency, nor even necessarily because they invest more in each offspring, both of which theories are popular. They can choose because they are of higher quality, i.e. have more invested in them than do males/male gametes, and hence they can afford to choose. Of course, where the naturally-selected strategies are different – sex role reversed, or both sexes high quantity but low quality, or both high quality but low quantity, then sex roles would be different than the conventional ones. And as previously noted, if the naturally-selected population were for some reason completely out of sex allocation equilibrium, then sexual selection could restore it as, or perhaps even more easily than by Fisher’s principle.

Written by Marion Blute

August 15, 2021 at 9:39 am

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