Ecology: Biology of Interaction. VI-04. Biological Features of Humans

VI-4. Biological features of humans
Which medical school specialisations are hardest to get into? Gynaecology, dentistry, and surgery. Specialists in these fields are most in demand, since they ensure the functioning of systems that were restructured in the final stages of human biological evolution. For the intensification of cultural inheritance, a flexible, reprogrammable brain was necessary, and to house it — a capacious skull. Developmental restructurings occur in evolution through the action of regulators that suppress certain parts of the developing system and accelerate others. In the course of human evolution, the development of the facial part of the skull was suppressed, while that of the braincase was accelerated. Disproportions arose in the facial skull, as a result of which the chin appeared (anatomists and physiologists long tried to establish the functions of this part of the body). The chin has no functions; it appeared because the growth of the base of the lower jaw turned out to be better regulated and was suppressed less than the part bearing the teeth! Unfortunately, as a result of these restructurings, the development of the teeth turned out to be substantially deregulated, leading to a sharp increase in the frequency of dental diseases. With the increase in brain and skull size, childbirth became much more difficult. The transition to bipedalism led to the pelvis, which had covered the abdominal organs from the sides, becoming bowl-shaped and supporting them from below. As a result, the pelvic outlet became narrower and childbirth even more difficult. The vertical position of the spine led to changes in the loads acting upon it. These are partly compensated by the spinal curves that develop during the formation of the support system; but the spine is still a source of many health problems. It is likely that compression of one or another nerve by vertebrae is most often the true cause of many illnesses.
So, the human is 'made' with many defects. Their elimination has been slowed: carriers of biological defects can survive and leave offspring thanks to cultural adaptations. A serious problem has become the increase — as a result of advances in medicine — in the number of carriers of more or less serious anomalies.
The need to extend the period of receptivity to cultural inheritance has led to a delay in human maturation and a lengthening of childhood. A human cannot be born with a ready-made structure of neural networks in the brain: it must be formed during interaction with the surrounding environment and other people. Naturally, the hereditary component plays a very important role in this process. Presumably, certain hereditary predispositions can substantially alter the brain's capacity for learning. An example is Turner syndrome — a genetic anomaly in which patients have only one sex chromosome (the female one) and develop as short-statured, infertile women. The mental development of such patients is normal, but with a characteristic impairment of spatial thinking. The disruption of brain function due to genetic causes turns out to be highly specific!
Incidentally, humans are also characterised by another remarkable biological feature. Humans are the only permanently sexual animal. The reproduction of other animals is in one way or another tied to a particular period of time. Thus, female mammals are characterised by an oestrous reproductive cycle. In it, at the moment of ovulation (the release of an egg cell) — that is, when the female is capable of becoming pregnant — oestrus (heat) occurs, accompanied by the shedding of the uterine epithelium and characteristic discharge. These external manifestations serve as a signal for males, stimulating competition for a sexual partner and mating. Humans have a menstrual cycle, in which ovulation occurs concealed, between menstruations. Armed with modern knowledge, people calculate the moment of ovulation (for example, for contraceptive purposes) and miscalculate! Contrary to the value structure of contemporary society, the biological goal of the organism is to leave offspring. The menstrual cycle compels the male (that is, the man) to regularly engage in sexual relations with the female (the woman), 'catching' the moment when she is capable of conceiving. This means he must live with her constantly!
It is now difficult to say precisely at what stage of human evolution this trait arose, but its close connection with the establishment of a relatively stable family — a social structure that creates favourable conditions for cultural inheritance — is clear.
If a male cares for the offspring of the woman with whom he lives, he must ensure that they are his offspring (men who raise other people's children leave fewer of their own descendants and disappear from the population). Consequently, he must prevent her relations with other men! For a woman, conjugal infidelity is biologically permissible, since she will in any case raise her own child. If the child's external father is more viable than the permanent cohabitant, this will only increase the child's chances of survival. And for a man, an outside relationship is entirely acceptable too. His biological costs for a child are small (unlike a woman's!). If, in addition to children raised with a permanent partner, he has offspring 'on the side', his contribution to future generations will only increase. That is precisely why in male-dominated societies there is a persistent double moral standard: a woman's infidelity is vileness, while a man's is a prank or even a feat of valour.