Impact of Evolution on Human Thought. Testosterone
Farid Gazizov
Impact of evolution on human thought
Testosterone
For a long period of time humans could not answer the question of what
makes a man, a man, and a women, a women. As was recently found main
difference is not just in presence of genitals. Probably one will ask why?
The answer is that genitals themselves are indirect products of another
matter. The name of this matter is testosterone.
“Testosterone is a hormone that stimulates sexual development in male
human beings. It belongs to a family of hormones called androgens.
Primarily the testicles, a part of male sex glands, produce androgens.
The ovaries in females and the adrenal glands in both sexes also
yield small amounts of testosterone and other androgens (The world
book encyclopedia).”
In its earliest crucial functions, in developing embryo, testosterone
play the key role in telling the cells of the genetically male embryo to
develop as a male. It is amazing, but all human embryo begins as females
for the first few weeks of an embryo’s life, a small group of cells have
potential to develop either as ovaries or testes. About one million of
genes that are needed to direct the development of a human being, one
single gene (the “SRY” gene), which is carried on the Y chromosome, is
responsible for determining the sex of the embryo. If the embryo’s cells
contain the “SRY” gene, the embryo will develop testes, which at some point
and for a limited period of time early in its development produce and
release a big amount of testosterone. It turn, testosterone then signal
the cells of other parts of the embryo to develop as a male.
As shown in the study by a Stanford research group namely testosterone
is responsible for formation of genitals. An experiment was held on
newborn female rats. They were injected with testosterone. Surprisingly,
but the female rats developed male genitals, and female genitals began
disappearing. Later “converted” female rats started revealing purely male
behavior, and they were fully aware of usage of their “new” male genitals.
The same experiment was performed with male newborn rats. It is amazing,
but their penises withered and later completely disappeared. This
experiment is not ethical to perform on humans, but random facts suggest
that all most the same can be done with humans. For instance, in lesbian
couple, butches (female that represents male) use testosterone injections
to develop male features such as deep voice, facial hair and muscles (“The
He Hormone,” Andrew Syllivan)
In girls, the adrenal glands begin to produce testosterone earlier
than in boys. That’s is how and why girls mature earlier, as a rule, than
boys. It was testosterone that stimulated the growth of girls pubic hair
and underarm hair (there are testosterone receptors in the skin of the
pubic area and the skin of the underarm that are genetically programmed to
react to testosterone by producing hair). And testosterone stimulated
girls skin to produce more oil, contributing to the acne of girls early
teenage years, but also to the healthy glow of the skin and the shine of
the hair.
The medical book Reproductive Endocrinology by Drs. Samuel Yen and
Rovert Jaffe, states; “Testosterone and other androgens have some
biological activity o virtually every tissue in the body.” Among the most
important functions listed are “anabolic actions, such as stimulation of
linear body growth, nitrogen retention, and muscular development.” This
statement means that testosterone works to keep the cells of the body
functioning efficiently, making the best use of nourishment of growth and
maintenance, and particularly contributing to the health of bones and
muscles.
Having knowledge of the way testosterone function in the body, artificial
testosterone injections can be used for variety of purposes. One of the
purposes of artificial use of testosterone is to stimulate sex drive. The
balance of this hormone is responsible for initiating and maintaining the
production of sperm from early puberty throughout adulthood in male body.
During childhood and adolescence, these hormones are responsible for:
1) Growth of genitals
2) Depth of pitch of the voice, increase muscle mass, and growth of bones.
3) Appearance of the body and facial hair.
Overproduction of testosterone caused by testicular, adrenal, or
pituitary tumors in the young male may result in precocious puberty.
Overproduction of testosterone in females, caused by ovarian and adrenal
tumors, can result in muscessation of the menstrual cycle and excessive
growth of body hair. Level of testosterone are low before puberty; they
begin to increase at the onset of puberty and continue to increase during
adulthood. Production begins to diminish at about age of 40, eventually
dropping to about one-fifth of the peak level by age of 80 (“Hormone of
desire,” Susan Rako). Scientifically established men’s testosterone, level
is at least ten times higher than any of the women. According to the last
available date, even male population accounts for less than 50 percent of
the world’s population, major part of violence is perpetrated by men.
Currently many males use testosterone shots or gel for the purpose of
body-building. Testosterone shots trigger imbetterment of appetite and
muscles growth. Besides, testosterone can have effects on the function of
several brain areas. One additional surprising effect of testosterone is
that it can not only affect the function of the brain but also its
development and anatomy. Study in laboratory of Roger Gorskis at the
University of California, Los Angeles, has revealed that the sex difference
in the brain anatomy appears to be due to the presence of male sex hormones
at a certain stage of brain development in male rats. Later work has shown
a similar effect of testosterone at other brain areas: for example, the
spinal nerve cells that control the muscles of the genital area are more
numerous in male rats (cross sections through the hypothalamus of a male
and female rats (male, (thinner and longer)).
Below is a human life example how hormone level can influence human health,
and behavior brought by John K. Young in his book “Hormones; molecular
messenger.”
“Bridget was divorcing Bob, her husband of tem years, so she was not
terribly surprised when she started to feel anxious and upset upon
awakening in the morning. She grew worried, however, when these
anxiety attacks became more frequent and stronger, coming upon her at
all times of the day. She went to see a psychiatrist. The doctor
also assumed the problem was stemming from her divorce proceedings and
prescribed an antidepressant. After two weeks of more anxiety and no
relief coming from the dedication, Bridget felt like committing
herself to a institution. Her nervousness was now even making her
hair fall out; her skin began to feel thin and bruised. She was not
eating properly either, but was surprised to see she had lost over
twenty pounds.
One night Bridget’s best friend Virginia invited her to a dinner
party. Over the meal, someone mentioned how traumatic divorce was;
Bridget laughingly said that it was not making her thin and anxious,
it was also thinning out her skin and hair. One of the other guests,
a young woman, asked her to elaborate, and Bridget shyly told her the
symptoms she had been suffering from. The young woman then introduced
herself as a doctor. She asked Bridget to come down to her office for
a few tests. Bridget did and these tests revealed what the doctor had
first suspected; that Bridget was not suffering from a psychiatric
disorder, but rater a hormonal one. Her thyroid gland was
overworking, giving her the symptoms of thinning hair, thin skin,
excessive weight loss, and anxiety. Afte4r treatment all of Bridgets’
symptoms disappeared.”
The example described above suggests that level of testosterone
influence not only physical development of the body, but also is
responsible for emotions and behavior. One researcher, curios about the
fact that only male canaries sing during mating season, gave a testosterone
shot to female canaries. The result was amazing, the female canaries
“burst into song.” The same experiment was performed on zebra finches.
Dr. Christina Wang’s study reveals that men with low testosterone level are
irritable and aggressive than those with high-normal level. “When their
testosterone level was increased during hormone-replacement therapy, their
anger diminished and their sense of well-being increased.”
Robert M. Sapolsy, in his book “The trouble with testosterone,” takes
opposite opinion side to scientists who think that increasing testosterone
level leads to changes in behavior (such as becoming more aggressive). He
holds an opinion that changes in surrounding environment trigger change in
the level of testosterone.
“Okay, suppose you note a correlation between levels of aggression and
levels of testosterone among these normal males. This could be
because (a) testosterone elevates aggression; (b) aggression elevates
testosterone secretion; (c) neither cause the other. There is a huge
bias to assume opinion (a), while (b) is the answer. Study after
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