D.F. Swaab

A child’s first language isn’t determined by its genetic background, only by the surroundings in which it grows up during that critical period of language acquisition. Not only does acquiring language have a very marked effect on the brain, it’s also crucial to many other aspects of a child’s development. In 1211, the Holy Roman Emperor Frederick II of Germany, Italy, Burgundy, and Sicily tried to establish what language God spoke to Adam and Eve. He believed that children would spontaneously speak it if they were not exposed to other languages and set up a rigorous experiment in which dozens of children were brought up by nurses ordered never to speak to them. However, his hopes were met with disappointment. The children couldn’t speak at all, and they all died at a young age.

Labor starts when the baby’s blood sugar level starts to drop—a sign that the mother can no longer provide the growing child with sufficient nourishment. Michel Hofman has calculated that labor is triggered at a stage when the child accounts for around 15 percent of the mother’s metabolism. That point is reached earlier by twins, triplets, and so on, which is why they are born prematurely. While still in the womb, the brain cells in the child’s hypothalamus respond to a drop in blood sugar level in the same way that they later respond to a lack of food in adulthood, by stimulating the stress axis. This induces a series of hormonal changes, making the uterus contract (fig. 3). The contractions, stimulated by oxytocin, make the baby’s head press against the cervix. This in turn triggers a reflex, via the mother’s spinal cord, which causes the release of yet more oxytocin. The baby’s head then exerts more pressure, triggering the same reflex. The child can only escape from this chain reaction by being born.

Various psychiatric disorders are associated with a difficult birth. It has long been known that a high percentage of patients with schizophrenia experienced problems at birth, such as delivery by forceps or vacuum pump, low birth weight, premature birth, premature breaking of the waters, or time spent in an incubator. It was once thought that difficult births caused brain damage, leading to schizophrenia. We now know that schizophrenia is an early developmental brain disorder largely caused by genetic factors (see chapter 10). So a difficult birth can be seen as a failure of interaction between the brains of mother and child and thus as the first symptom of schizophrenia, even though the disease doesn’t develop fully until puberty. The same applies to autism, another early developmental brain disorder (see chapter 9) that also often goes hand in hand with birth-related problems. Recent studies have shown that girls who suffer from the eating disorders anorexia and bulimia nervosa often had problems at birth, including low birth weight. The more numerous such problems are, the earlier eating disorders manifest themselves in young adults. One wonders whether their hypothalami started out unable to deal well with glucose levels, given that a decrease in them signals the start of labor. So here, too, birth-related problems of this type could be seen as the first symptoms of a malfunction of the hypothalamus, later taking the form of an eating disorder.

Children who are seriously neglected during their early development also have smaller brains (fig. 7); their intelligence and linguistic and fine motor control are permanently impaired, and they are impulsive and hyperactive. Their prefrontal cortices can be particularly undersized. Studies have shown that orphans adopted before the age of two go on to develop normal IQs (averaging 100), while children who are not adopted until between the ages of two and six attain average IQs of 80.

Both brains play a role in speeding up labor by secreting a hormone, oxytocin, into the bloodstream that makes the uterus contract. The mother’s biological clock imposes a day-night rhythm on the birth process, which explains why most children are born during the quiet phase, at night and in the early hours of the morning. That’s also the time when birth progresses fastest and requires the least assistance.

When a mother is fearful during pregnancy, she can permanently activate her baby’s stress axis, thus increasing the risk of phobia, impulsiveness, ADHD, and depression later in life.

Brain cells are created with incredible rapidity in the womb and shortly after birth, and this process continues, somewhat more slowly, until around the fourth year of life. Brain maturation goes on much longer; in the case of the prefrontal cortex, it continues right up to the age of twenty-five.

It is curious that a genetic predisposition for homosexuality should persist in populations over the course of evolution, given that this group reproduces so much less. One explanation for why homosexuality persists is that the involved genes don’t just increase the likelihood of homosexuality but also promote fertility in the rest of the family. Heterosexual individuals with the same genes produce a larger than average number of offspring, causing the genes to remain in circulation.

ll the research indicates that our sexual orientation is programmed in the brain before birth, determining it for the rest of our lives

While the adolescent PFC is still immature, parents have to be responsible for a child’s planning, organization, moral framework, and limits. These functions are gradually taken over by the slowly maturing PFC.