The disastrous economic policies of Mao’s Great Leap Forward caused the single deadliest famine in the history of the world. Between 1958 and 1961, an estimated 15 to 45 million people died of malnutrition in China. And during this period, according to a new study, a strangely high proportion of babies born were female.
China has had a long cultural tradition of favoring sons over daughters, and boys outnumber girls every year in this data from 1940 to 1980. But from one year after the famine’s beginning to two years after its end, the proportion of males drops sharply, as you can see in the graph above.
This study may bolster the Trivers-Willard hypothesis, which suggests that poor maternal condition, such as famine, would favor giving birth to more girls. Since the reproductive success of males tend to be more variable—a reproductively successful male can father many children, whereas a unfit one fathers none—girls are a “safer” evolutionary investment in risky times. The birth sex ratios of mammals such as ground squirrels and red deer follow this pattern. Lab experiments where the male blastocytes of cows survive better in glucose-rich environments identified a possible mechanism.
Robert G. Edwards.
Edwards’ work creating in vitro fertilization led to the birth of four million babies, and now it has garnered him the Nobel Prize.
Dr. Edwards, a physiologist who spent much of his career at Cambridge University in England, spent more than 20 years solving a series of problems in getting eggs and sperm to mature and successfully unite outside the body. His colleague, Dr. [Patrick] Steptoe, was a gynecologist and pioneer of laparoscopic surgery, the method used to extract eggs from the prospective mother. Dr. Steptoe, who presumably would otherwise have shared the prize, died in 1988. [The New York Times]
DNA may dictate your development, but you also wouldn’t be you without the unique mix of bacteria that make their home on your body. This week in the Proceedings of the National Academy of Sciences, researchers say that the very moment of your birth can decide for a lifetime what kind bacteria live in your body, and even whether you’ll be at a higher risk for conditions like asthma.
The uterus is a sterile environment. So, in the womb, babies don’t have any bacteria to call their own. It’s only once they enter the world that they begin to collect the microbes that will colonize their bodies and help shape their immunity [Scientific American].
How babies enter the world is the key, the team says. The studied surveyed the bacterial colonies of 10 mothers just before birth; four of those women gave birth traditionally and six did through cesarean section. When the scientists then checked up on the bacteria living in the newborns, they found that the difference in birth method decided what microbes the baby would get. Those born vaginally tended to pick up the bacteria from their mother’s vagina, while those born via C-section harbored bacterial colonies that tend to come from skin.