Theory of Asynchronous Evolution


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The Evolutionary Theory of Sex

Sex represents the most important challenge to the modern theory of evolution...
the queen of problems... t
he main question is —why sex?”
Bell (1982)

V. Geodakyan’s theory can be summarized in one sentence:
Males are the experimental animals of the Nature.

It appears that sex is more likely a way of asynchronous evolution
rather than a way of reproduction as it was considered before.
V. Geodakyan (1991)

Answers the main question—What two sexes are for?
Substitutes Darwin’s theory of sexual selection.
Explains and predicts differences between sexes (sexual dimorphism).
Applies to plants, animals and humans.
Applies to all levels of organization: cell, organ, population, social and psychological.

Ways of Reproduction, Reproduction analysis

Dioecism involves two fundamental phenomena: mating and sex differentiation. Genetics considers only the results of mating but not differentiation; therefore the phenomena related to the differentiation itself cannot be explained.

A new theory suggested considers sex differentiation as a useful for population form of informational contact with the environment, as evolutionary specialization by two main information currents: genetic (from preceding generations) which realizes stabilizing, conservative trends of evolution, and ecological (about changes in environment) which carries out  operative trends of evolution.

For the case of sexual differentiation, the sequence of arrival of the controlling information from the environment to the subsystems is as follows:

                                     environment male sex female sex.

In panmictic and polygamous populations where each male can fertilize many females the number of mothers always exceeds that of fathers. Therefore hereditary information obtained by the offspring from their mothers is more representative, better reflects genetic distribution in population/preceding generation. Information obtained from fathers is more selective; it reveals the genotypes suitable for the environmental conditions.

Broader reaction norm of females makes them more flexible, adaptive in Ontogeny so they can move within the ecological niche from the zones of discomfort and elimination to the comfort zone. It narrows their phenotypic variation thus better preserving their genetic one. The narrow reaction norm of males preserving wide phenotypic variation subjects them to greater elimination. It means that males are the first to be affected by evolutionary transformations.

The raised death rate and damageability of males is a general biological phenomenon. It is favorable to a population form of information contact with environment, a payment for the new (ecological) information. The higher male death rate and more intensive sexual selection among males combined with their potential opportunity to impregnate many females (the wide liaison channel cross-section with posterity), lead to that the hereditary information on distribution of genotypes in a population, transferred to the following generation by a female sex, is more representative (better reflects distribution in previous generation), and the information transferred by a male is more selective (better reflects the environment requirements).

Therefore genotypic distribution (variation) of the female individuals participating in a reproduction, is wider, than male's. Hence, in Phylogeny, contrary to Ontogeny, male sex is more plastic (changeable), therefore the evolutionary transformations of a population reflect males first. The new view on appearance of sexual dimorphism as a consequence not only sexual selection (as Darwin thought), but natural and artificial selection as well.

Hence males can be considered as evolutionary “vanguard” of population, and sexual dimorphism for a character - as a “compass” indicating the evolution of this character (“phylogenetic rule of sexual dimorphism”). Therefore the characters which more often appear and are more pronounced in females ought to be of the “atavistic” nature, and those more often manifested in males - of the “futuristic” one (search). Maximal sexual dimorphism must be observed by evolutionary young (new) characters.

Consequently, when different forms are mated in reciprocal hybrids paternal breed must dominate over the maternal one by divergently acquired new characters (“paternal effect”), closer relationship of males with heterosis must be also observed. The “paternal effect” predicted by the theory is really observed for many economically valuable (breeding) characters.

The theory connects three main characteristics of dioecious population: sex ratio, variation and sexual dimorphism, with the ecological conditions and evolutionary plasticity of the species. These characteristics decrease under stable environmental conditions thus reducing the plasticity; under varying conditions - they increase raising the plasticity.

The new theory enables to reveal some earlier unknown regularities related to sex, to explain many known phenomena from a single standpoint and to predict new ones.

New view on the evolutionary role of sex differentiation leads to a proper understanding of all sex-associated derivatives: differentiation of sexes, sex ratio, sex variation (SV), sexual dimorphism (SD), sex chromosomes (SC), sex hormones (SH), psychological differences associated with sex, and all other sex-related phenomena.

The sex ratio, variation and sexual dimorphism—are regulated variables closely related to environmental conditions, contrary to traditional view of them as constants specific to a species. In stable conditions (the optimum environment) they should decrease thus reducing the evolutionary plasticity of the species and in changeable conditions (the extreme environment)—grow, raising the plasticity. The mechanism of stress serves as a transmitter of the ecological information and a regulator of evolutionary plasticity at animals. The quantity of pollen getting on a pistillate flower serves the same purpose at cross-pollinating plants.

Sexual dimorphism is the “distance” between sexes during evolution of any character. It’s the genetic information which due to sex specialization at the population level has already come into the male subsystem, but not to the female one. This interpretation allows answering many questions which Darwin's theory of sexual selection failed to explain.

Sex chromosomes serve the purpose of separating male and female subsystems. New genes first appear in the Y-chromosome and stay in the male subsystem for a long time. Only after many generations they are transferred via X-chromosome into female subsystem. More …

Sex hormones: New generalized concept of estrogens as compounds that widen the norm of reaction, move the female subsystem away from the environment, and slow down evolution. Contrary, androgens narrow the reaction norm, bring male subsystem closer to the environment, and speed up the evolution. More …

Medicine: Sexual dimorphism on many diseases can be explained. More …

Congenital anomalies: Female congenital anomalies are considered as a consequence of excessive conservatism, as a return to a near past (in ontogenetic and phylogenetic sense). They are of the "atavistic" nature. Male congenital anomalies are the attempts of the evolution to try new things and can be viewed as "futuristic" ones (search). More …

Anthropology: Sexual Dimorphism in different ethnoses can be explained. More …

Effects related to differentiation of sexes


More about the Evolutionary Theory of Sex:

First publication:  Mal’shik ili devoska (A boy or a girl. Sex ratio—value regulated by Nature?) (Geodakyan V.). Nauka i Zhizn (Science and Life)., 1965, № 1, p. 55–58. [in Russian]
Rol' polov v peredace i preobrazovanii geneticeskoj informacii (Role of sexes in the transmission and transformation of genetic information). Geodakjan V.A. (1965) Probl, Peredaci Inform. 1: 105-112. [in Russian]

Popular version: Why Two Sexes? Geodakyan V. Nauka i Zhizn (Science and Life). 1966, N 3, с. 99–105. Translated from Russian by B. Lubachevsky

Most complete scientific version:
The Evolutionary Theory of Sex. Geodakyan V. A. “Priroda (Nature)” 1991, N 8, p. 60–69.
Sexual dimorphism. Geodakyan V. A. In: Evolution and morphogenesis. (Mlikovsky J., Novak V. J. A., eds.), Academia, Praha, 1985, p. 467–477.

Most recent publication: Мужчина и женщина. Эволюционно-биологическое предназначение. (Man and woman. Evolutionary-biological purpose) Геодакян В. А. Межд. Конф.: Женщина и свобода. Пути выбора в мире традиций и перемен. Москва, 1–4 июня 1994, с. 8–17. [in Russian]


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


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