Theory of Asynchronous Evolution

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The Evolutionary Theory of Sex: Hormonal Sex

“The sexes were not two as they are now, but originally three in number;
there was man, woman, and the union of the two, having a name
 corresponding to this double nature, which had once a real existence,
but is now lost, and the word "Androgynous"…”
                                                                                       Plato “Symposium”

“… there are many gradations running from female to male; and …  one can argue that along that spectrum lie at least five sexes and perhaps even more.”
                                         
                     A. Fausto-Sterling “The Five Sexes”

“… since the beginning of humankind, a man's voice could have
functioned as a testosterone advertisement.”

Sex is an alternative character that distinguishes male and female individuals from each other, allows them to produce different gametes and participate in sexual reproduction. We will consider female an individual that produces large usually immobile gametes (as eggs). Accordingly male is an individual that produces small usually mobile gametes (as spermatozoids). Sex of an individual, as any other character, is defined by a genotype and environment.

According to chromosomal theory, sex chromosomes determine the sex at the moment of fertilization. Without Y-chromosome “asexual” rudiment of a gonad turns into ovaries producing estrogen. Y-chromosome transforms gonad into testes producing androgen.

Sex chromosomes define sex of a zygote only at the level of genes, its homo- or hetero-gamety (XX or XY). Further realization of sex in Ontogeny, i.e. phenotypic sex, is influenced by sex hormones. While chromosomal sex is discrete (intersexual dimorphism), hormonal sex is continuous (inter- and intrasexual polymorphism).

 

Sex hormones along with the other features change the harmonics of the voice that occur during male and female puberty. In the female, the impact of estrogens produces the characteristics of the female voice, with a fundamental frequency one third lower than that of a child. In the male, androgens released at puberty are responsible for the male vocal frequency, an octave lower than that of a child. Testosterone, the hormone that elongates the vocal cords during puberty, is also responsible for other manly features - such as broad shoulders and hairy faces. And as indicators of sexual maturity, these traits may play a large role in the process of finding a mate for reproduction. This means that since the beginning of humankind, a man's voice could have functioned as a testosterone advertisement.

To consider the differences caused by sex hormones we shall allocate for simplicity inside of man's and a female on three gradation of "a fractional sex": modal, feminine, and masculine. Since sex hormones define the tone (height) of voice in humans, these forms can be presented as average frequencies of voices (in hertz). For women it is a soprano (340 hz), mezzo-soprano (250 hz) and contralto (160 hz). For men — a tenor (200 hz), baritone (140 hz) and bass (80 hz).

 

Hormonal Sex and Homosexuality ►                              Evolutionary role of cancer

References:

Vocal range Wikipedia < http://en.wikipedia.org/wiki/Vocal_range >
Plato “Symposium”. < http://classics.mit.edu/Plato/symposium.html >

A. Fausto-Sterling The Five Sexes: Why Male and Female Are Not Enough The Sciences March/April 1993, p. 20-24. < http://www.mtsu.edu/~phollowa/5sexes.html >

 

Copyright 2005-2009 S. Geodakyan. All rights reserved.

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