1. Introduction 2. Pre-zygotic selection 3. Meiotic Drift 4. The Cytogenetic Basis of pre-zygotic sex determination 5. Sexual dimorphism of spermatogenesis and ovogenesis 6. Population functions of gender 7. The Mechanism of negative reverse connection in sex
ratio regulation 8. Variations in the rhythm of sexual activity 9. The importance of the frequency of male ejaculation 10. Ideas about the relationship of the level of sexual
desire to the rate of sexual activity 11. Clients' genealogical trees
Human reproductive behavior is studied by specialists of
many disciplines. Until now, however, there has been no
convincing explanation of the fall in birth-rate in developed
countries. Demographic investigations show that many modern
couples are limiting themselves to one child, even as men
and women express in opinion surveys the desire for larger
families. This discrepancy has been explained by the fact
that more than 50% of respondents said they would prefer
a family with two children, one boy and one girl. That is
to say that spouses would be more willing to have a second
child, on condition that they could be assured of having
either a son or a daughter. The impossibility of determining
the sex of a future baby has thus proved a negative influence,
decreasing the likelihood that couples will decide to have
a second child.
The possibility of regulating the gender
of a child before conception has been of interest to human-
kind since the dawn of time. We know of many recommendations,
drawn from the sexual cultures of many nations, for how
a woman might choose the sex of her baby. Of course, many
of these recommendations should be met with skepticism –
they are based more on mysticism than on scientific knowledge.
The fact remains, however, that they are taken seriously
by many people even today.
Unfortunately, the current theme has not
been the subject of broad scientific investigation, and
any progress towards its resolution has invariably led to
heated discussions, reflecting the polarity of opinions
on the only 100%-effective means of controlling the birth-rate.
Some people have worried that artificial regulation of a
child’s gender may lead to social and demographic problems.
Some authors felt that the disruption of the more-or-less
stable proportion of male to female births could harmfully
affect the rate of reproduction of the population (4.c.
140), or even lead to social up-heaval (5). The counter
to this view is the confirmation (on the basis of sociological
studies of reproductive attitudes) that an effective method
of gender-determination will not lead to a disruption in
the secondary sex ratio (6, c. 75). Perhaps this is really
the case, because the majority of respondents express a
preference for families with one boy and one girl. So, if
we provide parents with the opportunity to realize their
reproductive rights, there will not be any great change
in the ratio of the sexes within the population. The population
itself, however, may well be affected, increasing in countries
where couples had previously limited themselves to one child,
and decreasing in those where people usually have more than
two.
Few specialists doubt that the gender of
a child is at least partly determined by non-random factors
(in fairness, it must be noted that some have disputed this
in doctoral dissertations - 7). Investigations in various
branches of science have provided data on the planning of
a child's gender, and methods for gender planning have been
proposed (8, 9, 10). None of these theories or methods,
however, gives a convincing explanation of why the process
of pre-zygotic determination should exist in nature.
The data show that
this process has an effect on the population, and that it
is a natural consequence of the division of a species into
two genders. No single scientific discipline can provide
sufficiently exhaustive evidence to convincingly demonstrate
the biological advantage of this phenomenon. As a result,
a multi-disciplinary investigation is necessary. First,
we will clarify the influence of immunological factors.
Immunological factors doubtlessly have a great effect
on conception. We have evidence of this fact from the
investigation of rabbits, immunized with spermatozoid
antigens. The effect of the antigens drastically altered
the gender-ratio among descendents along the female line.
When mating took place after the introduction of X-sperm
antigens, more males were born, and when Y-sperm antigens
were introduced, more females.
In the immunology of reproduction it is well established
that significant differences exist in the characteristics
of sperm carrying the different chromosomes (references
12,13,14). The protein on the surface of male sex-cells
has different characteristics in X- and Y-carrying sperm.
The particular characteristics of this membrane are genetically
controlled, as indeed are all the other characteristics
of spermatozoids. On the other hand, some factors, such
as sperm's speed of motion are dependant on the specifics
of the surrounding environment. On the basis of the functional
and morphological differences between X- and Y-carrying
sperm cells, some methods have been proposed for distinguishing
between the two, with the goal of determining the sex
of a baby by artificial insemination.
The movement of sperm along the sexual channels before
and after ejaculation are accompanied by complex immunological
phenomena which are known as 'pre-zygotic selection'.
Pre-zygotic selection is seen as the combination of two
processes which occur in the woman's sexual tract after
ejaculation. Firstly (while sperm move through the cervical
filter), genetically defective sperm are eliminated by
immunological reactions. After this 'rejection of the
defective,' there follows 'selection of the fittest.'
The essential feature of this last process in that from
the pool of genetically viable sperm, only the 'best'
(according to certain functional characteristics), are
allowed to move towards the egg for fertilization.
Diagram 1: Pre-zygotic selection:
1 - "rejection of the defective"; 2 - "selection
of the fittest"
(by N.N. Zhukov-Verezhnikov, et al.,1979)
It is by no means impossible that
the chromosome carried by a sperm-cell (i.e. X or Y),
could have an effect on its selection or rejection. The
theoretical positions of reproductive immunology, however,
do not explain how exactly X- or Y- carrying sperm could
acquire such a characteristic. To find the explanation
we must turn to ideas about the regulation of spermatogenesis,
and especially to the genetic phenomenon of meiotic drift.
It is well established in cyto-genetics, that there is
an active process which leads to genetic drift within
a population. This happens during meiosis as a result
of crossing-over, when during the exchange of chromosomes,
factors distribute themselves in ratios different from
those postulated by Mendel's laws. Experiments on fruit-flies
have shown how meiotic drift can be induced (for example,
by spirochaeta infection, and by certain mutagens), and
to what extent it can lead to a change in the ratio of
genders (in some cases, the percentage of female descendents
along the male line can be as high as 95%).
Crossing-over occurs at those phases of meiosis where
cell-division is declining - in the stage where spermatocyte-1
transforms into spermatocyte-2 (diagram 2). It is well
known that these very spermatocytes are the target cells
for testosterone. Crossing-over, then, is a testosterone-dependant
process.
The level of testosterone production by Glandulocytes
(Leidig cells), which have direct functional links to
cells of the sperm-generating epithelium, is determined
by genetic factors and by the intensity of sexual life.
Diagram 2: The Cytogenetic
Mechanism of pre-zygotic sex determination
In accordance with the above, the cyto-genetic basis
of pre-zygotic gender determination can be seen as a testosterone
dependant process - crossing-over during the course of
meiosis. During this process, the distribution and exchange
of sex-chromosomes occurs according to Mendel's laws,
but the determination of the functional characteristics
of X- and Y-carrying spermatozoids does not. As a result
of meiotic drift, the surface membranes of X- and Y-carrying
sperm acquire special characteristics which are realized
during immunological reactions after the sperm enter the
woman's genital tract.
In the male organism, then, there is a biological 'tool,'
the purpose of which is to determine the functional characteristics
of X- and Y- carrying sperm cells so that one pool of
sperm gains an advantage over others during the movement
towards the egg-cell, and another pool of sperm does not
gain such an advantage. Clearly, this is a universal mammalian
biological mechanism which is regulated by hormones, and
can be the subject of external manipulation.
Note that the above-defined cyto-genetic
phenomenon occurs in the male organism. In this connection,
we should turn our attention to the sexual dimorphism
of spermatogenesis and ovogenesis.
The two sexes differ fundamentally in gametogenesis.
The basic difference is that spermatogenesis is a dynamic,
strictly ordered process of forming new cells, whereas
in a woman an already formed cell is induced to develop
further. The male organism, therefore, can be influenced
by outside forces, and the female can transfer these influences
to successive generations.
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spermatogenesis |
ovogenesis |
is a dynamic, strictly
ordered process of forming new cells |
is induction of one
cell development from already once formed pool |
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"operative
memory" of a species |
"constant
memory" of a species |
The sexual dimorphism of gametogenesis
allows for the realization of the so-called 'population'
functions of gender
Differences in gametogenesis are necessary in nature
to ensure the realization of the population functions
of the sexes. According to our current understanding,
the female sex represents 'long-term memory' and the male
'operating memory' (25, c.108).
This idea helps to understand the phenomenon by which
the level of stress in a population influences the rate
of male births.
The idea of the population functions explains the difference
in average life expectancy for males and females. More
accurately, these differences are a consequence of the
population functions.
A difference in the average life expectancy of males
and females indicates a critical situation for a population,
especially in cases where male life-expectancy is on the
decline. This indicates that the population is under the
influence of negative factors. The influence of these
factors is even more apparent if the rate of male births
increases.
The secondary sex ratio and the difference in average
life expectancy provide the clearest evidence for the
population functions of gender. The functions have an
adaptive purpose and are responsible for the continued
existence of a population and its adaptation to the environment.
Well known in the field of demographic statistics is
the so-called 'war phenomenon,' whereby the rate of male
births rises in the years during and after a war. One
of the proposed explanations for this is the natural increase
in marriages after wars and other social upheavals. Clearly
the ratio of the sexes is dependant on specific human
behavior.
It is well established that in the normal course of the
reproductive process, neither male nor female embryos
are selectively eliminated (the primary sex ration does
not change). Therefore 'the change in the secondary sex
ratio in favor of male births is conditioned by the selective
fertilization of eggs by Y-carrying sperm' (28,
c.38).
The sex ratio of a population
is a typological characteristic, usually characterized
by stability. Under the influence of extreme factors,
however, it can shift significantly, returning to its
normal level only after the disappearance of these factors.
All this is evidence in favor of the theory that the mechanism
for regulating the sex ratio is consistent and non-random.
The hypothesis that males and females are conceived with
equal probability was refuted long ago. The intensity
of sexual life plays an important role in the mechanism
of sex determination.
More than 30 years ago, specialists postulated that intensity
of sexual activity is a mechanism of negative reverse
linking between the secondary and tertiary ratios of a
population. This is easy to explain. When there are more
males than females in a population, then the rate of male
sexual activity decreases, and conversely, when there
are more females then males, it rises. All this follows
common logic, and does not require further explanation.
From this insight, we can draw some conclusions. In the
case of a preponderance of males, the rate of female births
should rise, so that in the next generation the sexes
will balance out. In the case of a preponderance of females,
the male birth rate will rise, and the sexes will also
balance out.
Diagram 3. The regulation
of tertiary and secondary sex ratio through the intensity
of sexual activity
Diagram 4. Sex hormones
in man during increasing sexual activity rhythm
Since the general intensity of
sexual activity in a population is an aggregate of the
sexual lives of many individuals, the study of individuals
should be of particular interest, all the more so considering
that significant variability between individual sexual
behavior has already been established. In men, the rhythm
of sexual life is determined by the specifics of the system
of sex-hormones, and the influence of the above-mentioned
cyto-genetic mechanism of pre-zygotic determination, including
glandulocyte, a link in the process of spermatogenesis
at the stage of the transformation of spermatocyte-1 to
spermatocyte-2, and the mechanism of crossing-over.
We must turn our attention to the condition of the human
organism at various levels of sexual activity. It has
been established that with frequent ejaculations, several
of a man's sperm indexes change.The fertilizing abilities
of the sperm are not, however, reduced.
Some well known studies have shown that the incidence
of infertility in prostitutes is linked to high levels
of spermicidal anti-bodies in their blood serum.
It is well known that periods of sexual abstinence encourage
the conception of female children, and that frequent sexual
activity leads to the conception of more males. To quantify
the categories of 'frequent' and 'infrequent' we use the
theory of sexual constitution. We understand sexual constitution
as the aggregate of stable biological mechanisms, arranged
under the influence of hereditary factors, and conditioned
during the pre-natal period and in early stages of ontogenesis.
Sexual constitution fixes the individual sex-drive at
a certain level, and determines a subject's resistance
to pathogenic factors which have a selective role in the
sexual sphere.
Using the algorithm for determining sexual constitution
(by G.Vassiltchenko), we can calculate the genotype index
(Kg), the index of sexual activity (Ka), and also their
ratio (Ka/Kg). The ratio of the two indexes allows us
to quantify the rhythm of ejaculation as shown below:
1. Ka/Kg between 0.90 - 1.09 is evaluated as an "optimal"
rate of sexual activity.
2. Ka/Kg higher than is evaluated as "over-active"
sexual life.
3. Ka/Kg lower than 0.89 is evaluated as "relative
abstinence".
The use of the algorithm of sexual
constitution, then, helps to evaluate and to classify
the rate of sexual activity. In general, the rhythm of
sexual life is a product of libido, and it is worthwhile
to examine the causes of variations in the level of sexual
activity.
We assume that there exists a "basic," genetically
determined level of sexual desire, and that this level
can change under the influence of personal factors,
sexual partners, and the micro- and macro-social environment.
The various levels of a subject's sexual activity can
therefore be classified as belonging to one of three
states.
In the first state the rate of sexual activity corresponds
to the level of libido, in the second case it is higher,
and in the third it is lower.
Continuing the theme, let's take the example of a man
whose basic level of libido is classified as 'low,'
but who is driven by personal factors towards an intense
rhythm of sexual life - a result of his acceptance of
the social stereotype that in the first year of marriage
sexual intercourse should be "frequent".
As a result of this man's high rate of sexual activity,
the cyto-genetic mechanism of pre-zygotic determination
produces an elevated level of testosterone, and the
pool of Y-carrying spermatozoids have a selective advantage,
which is realized in the process of pre-zygotic selection,
leading to the conception of a male child.
There are some families where the genealogical tree
along the male line shows only men (and vice versa)
for several generations. >>>
It is possible that in these cases, the limited level
of sexual desire is inherited, as are the specific personal
factors which lead to "frequent" sexual activity.
We will now examine the second case - where the man
has a 'low' or 'moderate' level of libido, but the personal
factors are situation-dependant, and not genetically
determined. The man's partner has a strong sexual drive,
and the couple's sexual life reflects this. The man
again produces high levels of testosterone, leading
again, through the familiar process, to the conception
of a male child.
In this case, the subject's genealogical tree does
not have the characteristics described above. In the
next example, the genetically determined level of libido
is 'high,' but personal and social factors (for example,
a religious world-view) limit the level of sexual activity.
As a result the cyto-genetic mechanism produces less
testosterone, and the X-carrying pool of sperm gains
a selective advantage, which is realized in the process
of pre-zygotic selection, leading to the conception
of a female child.
We will not continue to enumerate all the possible
variants, but note merely that, even though the factors
influencing the basic level of libido and the rate of
sexual activity are extremely numerous and varied (these
factors include the influence of the sexual partner,
somatic condition, marital status, social conditions,
and so on), the modulations of the cyto-genetic mechanisms
of pre-zygotic determination lie within certain clear
boundaries.
Yours sincerely,
Yuriy Zharkov
Picture 1: Genealogical
tree of couple A-N
Picture 2: Genealogical
tree of couple V-M
Picture 3: Genealogical
tree of couple N-A
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