Sex Differences in the Brain

(revisited) A comment that was complementary led me to add this:

Ideas about evolutionary processes that automagically led to sex differences in cell types can be dissmissed in the light of experimental evidence of biologically-based cause and effect.

Since 1996, for example, serious scientists have known about the role of Xist in chromosome inactivation. See also, from 2015:An Xist-activating antisense RNA required for X-chromosome inactivation

In our Hormones and Behavior review we (TB) wrote:

“Genomic-imprinting is also manifest in specific parts of the X-inactivation region’s related XIST gene. Here male- and female-specific methyl-group patterns participate in X-inactivation in females and also in the preferential inactivation of the paternal X in human placentae of female concepti (Harrison, 1989; Monk, 1995). This process indicates that tissues of the early conceptus can sense and react differentially to epigenetic sexual dimorphisms on the female conceptus’ own two X chromosomes. Furthermore, variations of X-inactivation patterns often account for traits discordance in monozygotic twin females. In other words, they are often found to have nonidentical patterns of X-inactivation, yielding differing expression of noticeable X-linked traits (Machin, 1996).”

The methyl-group patterns, which lead to increasing organismal complexity, are RNA-directed and they link nutrient-dependent fixation of RNA-mediated amino acid substitutions to the differentiation of all cell types in all individuals of all living species via the physiology of reproduction. (It’s not just about sex differences, Peg.)

Evolutionary theorists seem to think that cell type diferentiation automagically occurs outside the context of the biophysically constrained physiology of reproduction. That leads some of them to conclude that the differences between asexual reproduction and sexual reproduction arise in the context of their definition of “mutation” and assumptions about how long it would take a new species to emerge.

In the context of sex differences in cell types, there is no such thing as the automagical emergence of males and females, which suggests it is unlikely that any new species that reproduces sexually has ever emerged. For comparison, see this example of what happens when ecological variation appears to be on the verge of leading to ecological adaptations manifested in differences in morphological and behavioral phenotypes that are directly attributed to ecological speciation without the pseudoscientific nonsense of evolution.

Estrogen receptor α polymorphism in a species with alternative behavioral phenotypes


Once everyone has realized that sex difference in cell types do not automagically emerge, someone can address the “re-evolution” of the bacterial flagellum, which “emerged” over-the-weekend. See: Evolutionary Rewiring.

If the molecular mechanisms of biophysically constrained nutrient-depenendent cell type differentiation are conserved in all living genera, microbes are linked to humans via the physiology of reproduction and ecological speciation. If others think the molecular mechanisms are not conserved, they may be from another planet.

SARCASM ALERT (2) Alternatively, they may be emergently-evolved mutants who automagically arose to conquer the Earth in an epic of Biblical proportions.

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