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Vestigial genes can go hand in hand with vestigial structures. We mammals evolved from reptilian ancestors that laid eggs. With the exceptions of the “monotremes” (the order of mammals that includes the Australian spiny anteater and duck-billed platypus), mammals have dispensed with egg-laying, and mothers nourish…
One of my favorite cases of embryological evidence for evolution is the furry human fetus. We are famously known as “naked apes” because, unlike other primates, we don’t have a thick coat of hair. But in fact for one brief period we do—as embryos. Around sixth months after conception, we become completely covered with…
For evolutionary reasons, human babies were never meant to be born and raised in isolation from a group. Psychotherapist Ruth Josselson believes it is especially important for young mothers to create and maintain an active social tribe after giving birth. There are two big problems with this suggestion: 1) Most of us…
Researchers have isolated three toxic types. Their common characteristic: that you feel out of control over the bad stuff coming at you. As stress moves from moderate to severe, and from acute to chronic, this loss of control turns catastrophic and begins to affect baby. Here are the bad types of stress: • Too…
Two types of cells are important here. The first type, glial cells, make up 90 percent of the brain cells inside your child’s head. They give the brain its structure and help the neurons correctly process information. It’s a good name; glial is a Greek word for glue. The second type of cell is the familiar neuron…
The opening cast members of the baby-making play are simply a sperm and an egg and a saucy Marvin Gaye song. Once these two cells are joined, they begin producing lots of cells in a small space. The human embryo soon looks like a tiny mulberry. (Indeed, one early development stage is called the morula, Latin for…
Believe it or not, no commercial product has ever been shown in a scientifically responsible manner (or even in an irresponsible non-scientific manner) to do anything to improve the brain performance of a developing fetus. There have been no double-blind, randomized experiments whose independent variable was the…
In fact, some evolutionary biologists believe this is why morning sickness still persists in human pregnancies. Morning sickness, which can last the entire day (and, for some women, the entire pregnancy), makes a woman stick to a bland, boring diet—if she eats much at all. This avoidance strategy would have kept our…
As a scientist, I was very aware that watching a baby’s brain develop feels as if you have a front-row seat to a biological Big Bang. The brain starts out as a single cell in the womb, quiet as a secret. Within a few weeks, it is pumping out nerve cells at the astonishing rate of 8,000 per second. Within a few months…
Like many other areas of development, memory generally matures more rapidly in girls than boys. Beginning in the womb, female fetuses are known to habituate to auditory stimuli about two weeks earlier than males. After birth, they are more advanced at visual habituation. Toward the end of the first year, girls are…
Because it develops so early, this brain asymmetry appears to be largely innate. It is possible, however, that environmental factors begin operating even before birth. One hypothesis is that the right hand becomes more skillfull because it has greater freedom to move in the womb. About three-quarters of all fetuses…
Olfactory recognition may also be the first step toward human bonding and attachment. As we've seen, newborns quickly learn and prefer the scent of their own mother or other caretaker. Nursing babies clearly have the richest olfactory experience, being bathed several times a day in the odors of their mother's milk and…
There are two main reasons for concern about exercising during pregnancy. One is that it may reduce the baby's oxygen supply, since exercise, like other sources of stress, reduces blood flow to the uterus. Another risk is overheating. As we have already seen, fetal development is highly sensitive to temperature, and…
In the case of a mother's more general nutritional status—her tota caloric intake—the brain is actually less sensitive during the first three to four months of gestation. In spite of its massive developmental changes, the fetus grows surprisingly little in size during this period, so its growth is not very dependent…
Caffeine crosses the placenta and may even concentrate in the fetal circulation. Concern about its effect on fetal development stems from animal studies, where it has been found to be teratogenic when fed to pregnant rats in high doses; a dose equivalent to 150 cups of strong coffee per day causes malformations in…
Most women also realize that smoking is bad during pregnancy. Unfortunately, it can be a very hard habit to give up, even for the best-intentioned parent. Smoking is not as detrimental to fetal brain development as heavy alcohol drinking, but it acts on many other organ systems. like the heart and lungs, that…
It is from a public health standpoint, rather than from knowledge of indipercent of pregnant wompr. i^ percent of pregnant women in the United States reported drinking alcohol in the month preceding the survey, and 3 percent admitted to at least one binge. (Alcohol consumption is notoriously underreported in this kind…
The similarity between different vertebrate embryos is indeed remarkable. Since the early 1800s, embryologists have been struck by the parallel between early development in various animal species and their evolutionary relationship, a resemblance conveniently abbreviated by the saying "ontogeny recapitulates…
Another experiment, however, proves that babies really do imprint on auditory experiences while still in the womb. In this case, mothers were asked to read a particular story aloud, twice a day, during the last six weeks of pregnancy. The story was by Dr. Seuss again, this time The Cat in the Hat, and it was estimated…
Other, less tragic kinds of evidence also support this idea. Most people have a much more difficult time learning a second language late in life than they do in childhood. Immigrants may try to learn the language of their new country, only to be outdone by their own children. When we visit a foreign country for a…