Sex_Theory

The Evolutionary Theory of Sex: Mechanisms of Regulation of the Population Parameters

Since there are many different environmental factors (temperature, pressure, humidity, amount of food, numbers of enemies and pests etc.) it is natural to think that evolution could not combine each environmental factor directly with the population parameters by means of independent mechanism. Evolution must have produced some “generalizing lever” by means of which any environmental factor could affect the population parameters.

A definite range of values exists for each factor which corresponds to comfort conditions. Discomfort and elimination zones adjoin the comfort one on both sides. Similar zones can be distinguished in the population habitat where in a stable environment the comfort conditions are more often in the habitat center, the discomfort ones—in the periphery; and the elimination zones correspond to the territories outside of the habitat.

The control mechanisms of population parameters are switched on as a result of ecological information received by the organisms in the discomfort zones. They get the information because of their contact with the front of the environment factor. Particular nature of the environmental factor which causes the discomfort of the organism seems to have no significance for starting up these mechanisms. The cause of the discomfort (frost, dry periods, famine or enemies) makes no difference. The “generalized” ecological information has one dimension only (“good” or “bad”) and its cause is unimportant.

Stress as a transmitter of ecological information between the animals

Such a “generalizing lever”, a non-specific factor which transmits ecological information from the environment to population in animals is the mechanism realized through the stress. Animals actively “move and communicate” with each other (fight, look after etc.) and thus receive the ecological information. For example, if a population of animals luck females, males more often need to fight for the female, or experience a sex starvation longer.

All the unfavorable environmental factors regardless of their specific nature bring about stress. Stress, initiated as a result of discomfort conditions, transforms ecological information into the physiological one, which is coded by concentrations of various hormones in the organism. Further control in the organism is performed by the hormones.

Consequently, frequent stresses in animals and man must enlarge phenotypic (and, probably genetic) variation of the offspring, increase the quota of male offspring and produce more pronounced sex dimorphism in the progeny. The data of demographic statistics show that during long wars and other social or climatic shifts (famine, people migrations etc.) the secondary sex ratio grows statistically significant.

Chronic stress can create steady changes of hormonal balance which may lead to sharp raise of the form modification process. This can be due to modifying influence of hormones on regulatory processes in Ontogeny, and it is also possible, by virtue of a mutagen role of hormones.

Sex Hormones

It is well-known that male and female sex hormones androgenes (An) and estrogenes (Es), which are chemical antagonists, are developed and are present in both sexes, but in different proportions. Androgen concentration in man is approximately hundred times higher, and estrogen—hundred times higher at women.

Sex hormones form phenotypical realization of sex, therefore they should determine the relation of an organism and environment in Ontogeny. Androgene/estrogene ratio in the body regulates its information contact with the environment. This leads to a new interpretation of androgens as an environmental hormones “bringing the system closer” to the environment, while their antagonists, estrogens, insulate or protect the system from the environment.

By analogy to a sex ratio (M/F), ratio An/Es is a regulator of a “distance” from the environment, and evolutionary plasticity as well. The evolutionary plasticity should decrease in optimum environment, and increase in extreme one.

Previously described phenomenon of the increased male mortality represents that total price which the male sex has to pay to the environment for the new information. This price develops of many components: at animals brighter, appreciable coloring and plumage, more risky behavior, in humans—a choice of dangerous professions, the higher susceptibility to “new” illnesses (the illnesses of a “century” or “civilization”) and to social defects (smoking, alcoholism, drug addiction, crime and gambling).

Pollen as a carrier of ecological information in plants

What is the plant's source of ecological information? How the plants “know” about ecological situation? Of course, plants can get information about temperature or humidity directly. But how, for example they can get information about sex ratio changes?

The application of the ideas which have been developed to the plant populations, the distinctive trait of which is an immobile form of life, an attachment to a place, makes it possible to disclose certain new regularities. When analyzing the habitat of a plant species it is clear that in the average more optimal comfort conditions are in the center of the habitat (in its depth), while more the extreme, the discomfort ones exist in its periphery (on its borders). The existence of the habitat boundary itself indicates that in its natural expansion, the species came upon a “wall” of the ecological niche at this place because of one environmental factor or another. Such factors may be either low or high temperature, or various concentrations of moisture, nutritive substances, enemies, parasites, etc. It is evident that in the center of the area the density of the population is maximal, and at the periphery, minimal.

In realizing the informational connection between plants, the principal role may belong to the amount of pollen. In dioecious or cross-pollinated species in otherwise equal circumstances, the falling of a large amount of pollen on a female plant means that there are many male plants in the area. Conversely, a small amount of pollen means that there are few male plants in the vicinity. In the center the amount of pollen getting on female flower is always on the average greater than that on the periphery due to different population density. Male plants are first who die from the extreme environmental conditions. This also decreases pollen count.

The pollen amount gives information to the female flower about population density, tertiary sex ratio around it, about its location in the habitat center or periphery, and about optimal or extreme environmental conditions. Reception of the great amount of pollen always carries on the information about favorable environmental conditions and requires increased production of females with small phenotypic variation. On the contrary, the reception of small amount of pollen carries on the information about unfavorable conditions. This can occur either at the periphery where the density of the population drops sharply, or at the center, but when extreme conditions occur at the center, they eliminate the male individuals first. Both require higher production of male offspring with higher phenotypic variation to speed up the search of evolutionary pathways (leading selection).

So, in any optimal environmental conditions female flower receives more pollen than in extreme conditions. In other words, small amount of pollen always mean “bad”, and big amount of pollen always mean “good”.

Consequently, the statement of classical genetics should be reconsidered, that pollen carries only genetic information and the pollen amount which gets on the female flower is of no importance, since one pollen grain is sufficient for fertilization. The pollen transmits not only genetic information, but also the ecological one, which controls the ratio between stabilizing and leading selection. The information is coded by the pollen amount.

Center	←	Location	→	Periphery
		↓
Optimal	←	Environmental conditions	→	Extreme
		↓
Max	←	Density of population	→	Min
		↓
Max	←	Pollen amount	→	Min
		↓
Min	←	Pollen of other species	→	Max
		↓
Min	←	Dispersion of offspring Sex Ratio Sexual Dimorphism	→	Max
		↓
Min	←	Evolutionary plasticity	→	Max