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Anisogamy - Wikipedia
Anisogamy is a fundamental concept of sexual dimorphism that helps explain phenotypic differences between sexes.[3] In most species a male and female sex exist, both of which are optimized for reproductive potential. Due to their differently sized and shaped gametes, both males and females have developed physiological and behavioral differences that optimize the individual’s fecundity.[3] Since most egg laying females typically must bear the offspring and have a more limited reproductive cycle, this typically makes females a limiting factor in the reproductive success rate of males in a species. This process is also true for females selecting males, and assuming that males and females are selecting for different traits in partners, would result in phenotypic differences between the sexes over many generations. This hypothesis, known as the Bateman’s Principle, is used to understand the evolutionary pressures put on males and females due to anisogamy.[4] Although this assumption has criticism, it is a generally accepted model for sexual selection within anisogamous species. The selection for different traits depending on sex within the same species is known as sex-specific selection, and accounts for the differing phenotypes found between the sexes of the same species. This sex-specific selection between sexes over time also lead to the development of secondary sex characteristics, which assist males and females in reproductive success.

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Since this process is very energy-demanding and time consuming for the female, mate choice is often integrated into the female’s behavior.[3] Females will often be very selective of the males they choose to reproduce with, for the phenotype of the male can be indicative of the male’s physical health and heritable traits. Females employ mate choice to pressure males into displaying their desirable traits to females through courtship, and if successful, the male gets to reproduce. This encourages males and females of specific species to invest in courtship behaviors as well as traits that can display physical health to a potential mate. This process, known as sexual selection,[3] results in the development of traits to ease reproductive success rather than individual survival, such as the inflated size of a termite queen. It is also important for females to select against potential mates that may have a sexually transmitted infection, for the disease could not only hurt the female’s reproductive ability, but also damage the resulting offspring.[7]

Although not uncommon in males, females are more associated with parental care.[8] Since females are on a more limited reproductive schedule than males, a female often invests more in protecting the offspring to sexual maturity than the male. Like mate choice, the level of parental care varies greatly between species, and is often dependent on the number of offspring produced per sexual encounter.[8]

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Since females are often the limiting factor in a species reproductive success, males are often expected by the females to search and compete for the female, known as intraspecific competition.[4] This can be seen in organisms such as bean beetles, as the male that searches for females more frequently is often more successful at finding mates and reproducing. In species undergoing this form of selection, a fit male would be one that is fast, has more refined sensory organs, and spatial awareness.[4]

Darwinian sex roles confirmed across the animal kingdom: http://advances.sciencemag.org/content/2/2/e1500983.full
Since Darwin’s conception of sexual selection theory, scientists have struggled to identify the evolutionary forces underlying the pervasive differences between male and female behavior, morphology, and physiology. The Darwin-Bateman paradigm predicts that anisogamy imposes stronger sexual selection on males, which, in turn, drives the evolution of conventional sex roles in terms of female-biased parental care and male-biased sexual dimorphism. Although this paradigm forms the cornerstone of modern sexual selection theory, it still remains untested across the animal tree of life. This lack of evidence has promoted the rise of alternative hypotheses arguing that sex differences are entirely driven by environmental factors or chance. We demonstrate that, across the animal kingdom, sexual selection, as captured by standard Bateman metrics, is indeed stronger in males than in females and that it is evolutionarily tied to sex biases in parental care and sexual dimorphism. Our findings provide the first comprehensive evidence that Darwin’s concept of conventional sex roles is accurate and refute recent criticism of sexual selection theory.

Coevolution of parental investment and sexually selected traits drives sex-role divergence: https://www.nature.com/articles/ncomms12517
Sex-role evolution theory attempts to explain the origin and direction of male–female differences. A fundamental question is why anisogamy, the difference in gamete size that defines the sexes, has repeatedly led to large differences in subsequent parental care. Here we construct models to confirm predictions that individuals benefit less from caring when they face stronger sexual selection and/or lower certainty of parentage. However, we overturn the widely cited claim that a negative feedback between the operational sex ratio and the opportunity cost of care selects for egalitarian sex roles. We further argue that our model does not predict any effect of the adult sex ratio (ASR) that is independent of the source of ASR variation. Finally, to increase realism and unify earlier models, we allow for coevolution between parental investment and investment in sexually selected traits. Our model confirms that small initial differences in parental investment tend to increase due to positive evolutionary feedback, formally supporting long-standing, but unsubstantiated, verbal arguments.

Parental investment, sexual selection and sex ratios: http://www.kokkonuts.org/wp-content/uploads/Parental_investment_review.pdf
The second argument takes the reasonable premise that anisogamy produces a male-biased operational sex ratio (OSR) leading to males competing for mates. Male care is then predicted to be less likely to evolve as it consumes resources that could otherwise be used to increase competitiveness. However, given each offspring has precisely two genetic parents (the Fisher condition), a biased OSR generates frequency-dependent selection, analogous to Fisherian sex ratio selection, that favours increased parental investment by whichever sex faces more intense competition. Sex role divergence is therefore still an evolutionary conundrum. Here we review some possible solutions. Factors that promote conventional sex roles are sexual selection on males (but non-random variance in male mating success must be high to override the Fisher condition), loss of paternity because of female multiple mating or group spawning and patterns of mortality that generate female-biased adult sex ratios (ASR). We present an integrative model that shows how these factors interact to generate sex roles. We emphasize the need to distinguish between the ASR and the operational sex ratio (OSR). If mortality is higher when caring than competing this diminishes the likelihood of sex role divergence because this strongly limits the mating success of the earlier deserting sex. We illustrate this in a model where a change in relative mortality rates while caring and competing generates a shift from a mammalian type breeding system (female-only care, male-biased OSR and female-biased ASR) to an avian type system (biparental care and a male-biased OSR and ASR).

LATE FEMINISM: https://jacobitemag.com/2017/08/01/late-feminism/
Woman has had a good run. For 200,000 years humankind’s anisogamous better (and bigger) half has enjoyed a position of desirability and safety befitting a scarce commodity. She has also piloted the evolutionary destiny of our species, both as a sexual selector and an agitator during man’s Promethean journey. In terms of comfort and agency, the human female is uniquely privileged within the annals of terrestrial biology.

But the era of female privilege is ending, in a steady decline that began around 1572. Woman’s biological niche is being crowded out by capital.

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Strictly speaking, the breadth of the coming changes extend beyond even civilizational dynamics. They will affect things that are prior. One of the oldest and most practical definitions for a biological species defines its boundary as the largest group of organisms where two individuals, via sexual reproduction, can produce fertile offspring together. The imminent arrival of new reproductive technologies will render the sexual reproduction criteria either irrelevant or massively expanded, depending upon one’s perspective. Fertility of the offspring is similarly of limited relevance, since the modification of gametes will be de rigueur in any case. What this looming technology heralds is less a social revolution than it is a full sympatric speciation event.

Accepting the inevitability of the coming bespoke reproductive revolution, consider a few questions & probable answers regarding our external-womb-grown ubermenschen:

Q: What traits will be selected for?

A: Ability to thrive in a global market economy (i.e. ability to generate value for capital.)

Q: What material substrate will generate the new genomes?

A: Capital equipment.

Q: Who will be making the selection?

A: People, at least initially, (and who coincidentally will be making decisions that map 1-to-1 to the interests of capital.)

_Replace any of the above instances of the word capital with women, and you would have accurate answers for most of our species’ history._

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In terms of pure informational content, the supernova seen from earth can be represented in a singularly compressed way: a flash of light on a black field where there previously was none. A single photon in the cone of the eye, at the limit. Whether … [more]
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january 2018 by nhaliday

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