A few years back, a team of scientists combed through the records for a million births in New York City. They noted women who had developed gestational diabetes during their pregnancy, and they also noted the women’s ethnic backgrounds. Women of European descent, the scientists found, had the lowest risk for gestational diabetes, with only 3.6% of them developing the disorder. African Americans had a somewhat higher risk of 4.3%. South Asian women, by contrast, face a far higher risk of 14.3%, with Bangladeshis running the highest risk of all: one out of every five Bangladeshi mothers in New York developed gestational diabetes.

Another risk that pregnant women run is giving birth to babies with deformed spinal columns. The pattern of these so called neural-tube defects is quite different from that of gestational diabetes. Dark-skinned women–in Africa, as well as Asia and Australia–are at low risk, while European women are the ones more likely to encounter this trouble.

Continue reading “What To Expect When You’re Expecting, By Charles Darwin” →

I’ve written about a lot of parasites over the years, but for some reason I haven’t gotten around to one that’s intensely familiar to suburbanites: the tick. Recently, Outside asked me to write a feature about these blood-sucking creatures–exploring their chilling sophistication as blood-suckers and their disturbing ability to spread pathogens. Fortunately (if that’s how you want to think about it) I live in Tick Central, otherwise known as Connecticut. To report on Lyme Disease, I can drive up the road to Lyme. My story is in the June issue of Outside. Check it out.

Originally published April 30, 2013. Copyright 2013 Carl Zimmer.

Cities may not seem like hotbeds of evolution. Tropical rain forests, maybe. The Galapagos Islands, certainly. But Central Park?

Yes, even Central Park. Wherever there is life, there is evolution. Organisms reproduce, passing down their genes to their offspring. Some variants of those genes may become more common over the generations thanks to lucky rolls of the genetic dice. But they can also become more common thanks to natural selection–because they make individuals better able to survive and reproduce than others. That advantage depends in large part on their particular environment. If the environment changes dramatically–if, for example, people cut down forests and put up skyscrapers–then a new set of mutations may give organisms an evolutionary advantage.

Continue reading “The Evolution of the Country Mouse and the City Mouse” →