The Evolutionary Theory of
Sex: Rules
“
“Ecological rule of sexual differentiation”: Major
population parameters—sex ratio, variation and
sexual dimorphism—are not constant but rather closely
linked with environment defining evolutionary plasticity of
a species. In stable environment they reveal decreasing
plasticity, while in extreme environment they show opposite
trend. Some species, like Crustacean, switch from one
reproduction style to another (from parthenogenesis in
optimal conditions to dioecious in extreme conditions). Most
of the species with separate sexes have smoother transition:
in optimal conditions the main characteristics are low
(fewer men are being born, their dispersion narrows, and the
sexual dimorphism decreases) and in extreme conditions they
grow.
Stress acts as a regulatory mechanism
of evolutionary plasticity. Since the ecological stress
brings to the rise of these parameters, they can be
considered indicators of the ecological niche. In this
regard it is explicable that the rate of boy births in
Kara-Kalpak for the past 10 years grew 5%. According to the
ecological rule, the main parameters have to grow when
natural or social disasters happen (earthquakes, wars,
hunger,
and
resettlement).
Criterion of character’s evolution:
monomorphic characters are stable while dimorphic characters
undergo evolution.
“Phylogenetic rule of sexual dimorphism”: Evolution of a
trait is directed from its female form to the male. The
characters which 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).
The rule is easy to verify on the farm animals and plants
that were artificially selected and induced into evolution
by a human being. The selection features must be more
dominant in males. The examples are numerous: with the meat
producers such as pigs, sheep, cows, birds, the males grow
faster, gain weight and provide better meat than females,
the stallions are better than mares in sporting and physical
labor features, the fine-fleeced rams provide 1.5-2 times
more fleece what the sheep produce, among the fur producers
males have better fur than females, the male silkworm
produces 20% more silk, etc.
The
phylogenetic rule of sexual dimorphism was also successfully
verified up on a large group (173 species) of lower
Crustaceae (Geodakian V. A., Smirnov N. N., 1968).
“Phylogenetic rule of
variation”:
If the
variation of a trait is larger in males — the phase
of its evolution is divergent; if
variations are
equal – the phase is parallel; if
variation is
higher in females — the phase is convergent.
Rule to define average speed of character’s evolution (V):
V= dimorphism/dichronism
“Ontogenetic rule of sexual
dimorphism”: In individual development a character
evolves from its female form to the male one.
If there is population sexual
dimorphism according to a certain trait, then during
ontogeny (with age), this trait changes, as a rule, from the
female form to the male, i.e., the female form of a trait is
more characteristic of the initial, juvenile stage, while
the male form is more characteristic of the definitive stage
(mature, adult). In other words, female forms of traits
should, as a rule, weaken with age, while male forms should
intensify.
Verification of this rule in two dozens of anthropometrical
features fully corroborates with the theoretical prediction.
Clear example – the development of horns in different deer
and antelope species: the larger the horns, the lower in
Ontogeny males acquire them before females. The same
dependency is proved by the age latency in the functional
asymmetrical brain development among women, as discovered by
S. Vitelzon (1976). She explored the skills of 200
right-handed children to recognize the subject based on its
shape by touching it with right and left hands and came to
the conclusion that boys at age 6 have right-brain
specialization, while girls are symmetric until 13.
About twenty anthropological characters for which the data
on both sexual dimorphism and ontogenetic dynamics were
obtained prove completely the regularity predicted by the
theory. These characters are: relative length of legs,
forearm, fingers, head index, tooth arch, epicanthus,
aquiline nose, erythrocyte concentration in the blood, pulse
frequency, brain asymmetry, norm and time of reaction,
olfaction, perception of bitter taste of phenylthiourea and
others (Roginskij Ja.Ja., M.G.Levin, 1963; Harrison G.A.,
e.a. 1964)
“Rule of reciprocal effects”:
Hybrids show paternal dominance (“paternal effect”)
in divergent characters and maternal dominance in the
convergent one. In particular, the paternal effect should
exist on all economically valuable traits at agricultural
animals and plants.
“Teratological rule of sexual
dimorphism”: Atavistic anomalies are more frequent in
females while “futuristic” ones occur in males.
The teratological rule of sexual dimorphism easily
explains a different spectrum of congenital anomalies of
development of heart and the main vessels, observed at
children of a different sex. Elements of defects with which
girls are born more frequently, have the “atavistic” nature
(ostium secundum and patent ductus arteriosus). They can be
found as a norm at human phylogenetic predecessors and at
human embryos at last stages of development. Elements of
man's defects (stenoses, coarctations, transpositions of the
main vessels) have the “futuristic” nature (search). Usage
the sex of a patient as a diagnostic character increases the
probability of right diagnosis on all congenital heart
anomalies by 14%, and on some congenital anomalies—up to
32%. The advantage of character “sex”—stability and
simplicity.
Another pathology—congenital hip
luxation is four times more frequent in girls, and the left
side is the most frequently affected (60%). We shall note
that children with this defect can crawl and climb on trees
better, than normal children. Anencephaly can be two times
more often is found at girls (WHO reports, 1966). Darwin
mentioned above permitted standard muscles, which are 1.5
times more often found out in men corpses. He also listed
the data on frequency of occurrence newborns with 6-th
finger. Here also the number of boys exceeds the number of
girls 2 times (Darwin, 1953).
“Epidemiological rule of sex ratio”: Juvenile
diseases are more frequent in females and vice versa for
adult diseases.
These
regularities explain a number of enigmatic phenomena, e.g.,
differential mortality of sexes, increased proportion of
male newborns at the time of high juvenile mortality,
distribution pattern of congenital developmental anomalies,
such as heart diseases as well as psychological
differences between sexes and occupational preferences etc.
References:
Geodakian V. A., Smirnov N. N. (1968). Sexual Dimorphism and
Evolution Lower Crustacea “Problemy Evolutsii” Novosibirsk,
"Nauka" '''1''' 30-36.
Roginskij Ja.Ja., M.G.Levin (1963)
Antropologija (Anthropology). Moskva: Vyssaja Skola.
Harrison G.A., Weiner J.S., Tanner J.M., Barnicot N.A.
(1964) Human biology. Oxford: Oxford
University Press.
Witelson S. F. Sex and the single hemisphere. Science,
1976, v. 193, N 4251, p. 425–427.
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