What Makes These Dominican Children Grow Penises at Puberty?

BBC via Youtube
BBC via Youtube

In the Dominican Republic, the phenomenon of children who were raised female appearing to swap sexes at puberty is so common it even has a name. Guevedoces roughly translates to "penis [or "balls"] at 12," and it’s the result of a rare enzyme deficiency that delays crucial steps of male sexual development until puberty.

When guevedoces are born, they appear to have external female genitalia even though their genes and internal reproductive organs are male. Parents assume their children are girls and raise them as such. But when these children begin producing large amounts of testosterone at puberty, their testes descend and they grow a penis—in addition to all the other changes that come along with male adolescence. 

Sexual development normally begins in the womb, and the same is true for guevedoces. Whether the fetus has one X chromosome or two, for the first several weeks of development its genes follow the same blueprint for both sexes. Then, sometime around the eight-week mark, the sex chromosomes get to work. For males, the undeveloped gonads become testicles and they start to release male hormones, including testosterone. In a structure called the tubercle, an enzyme called 5-alpha-reductase converts the testosterone to a stronger hormone called dihydrotestosterone (DHT), which is necessary to develop external genitalia. It's this hormone that turns the tubercle into a penis; without it, it develops into a clitoris.

The rare enzyme deficiency found in guevedoces leaves them unable to develop external male genitalia in the womb. They still produce plenty of testosterone, which triggers the development of internal structures like the epididymis and vas deferens, but the lack of DHT makes the babies appear female at birth. It’s not until the second surge of testosterone these children receive at puberty that they grow testes and a penis. 

The condition is thought to be genetic, tracing back to the female founder of a small village in the Dominican Republic's mountainous hinterland. Outside of the nation, it’s incredibly rare.

For some guevedoces, being raised as female wasn’t an easy experience. “I never liked to dress as a girl, and when they bought me toys for girls, I never bothered playing with them,” Johnny, who had grown up as Felicita, told BBC Two, which features these kids in the second episode of the series Countdown to Life: The Extraordinary Making of You. “When I saw a group of boys, I would stop to play ball with them.” When Johnny, now 24, began to undergo physical changes, he was taunted at school and called nasty names by his classmates. He’s had a number of short-term girlfriends since going through puberty and dreams of one day getting married and starting a family. Another child named Carla began the process of transitioning to Carlos at age 9; he can be seen receiving a smile-inducing haircut in the photo above. 

Most people with this condition live out their adult lives as men, but some choose to undergo surgery and remain female. The discovery of this disorder in the 1970s led to the development of a best-selling drug called finasteride, which is commonly prescribed to treat benign enlargement of the prostate and male pattern baldness. (You may know it by the brand name Propecia.) The drug mimics the enzyme deficiency by blocking the action of 5-alpha-reductase.

You can learn more about this rare condition and the people who have it on the BBC Two series Countdown to Life: The Extraordinary Making of You

[h/t: BBC]

Why Does Humidity Make Us Feel Hotter?

Tomwang112/iStock via Getty Images
Tomwang112/iStock via Getty Images

With temperatures spiking around the country, we thought it might be a good time to answer some questions about the heat index—and why humidity makes us feel hotter.

Why does humidity make us feel hotter?

To answer that question, we need to talk about getting sweaty.

As you probably remember from your high school biology class, one of the ways our bodies cool themselves is by sweating. The sweat then evaporates from our skin, and it carries heat away from the body as it leaves.

Humidity throws a wrench in that system of evaporative cooling, though. As relative humidity increases, the evaporation of sweat from our skin slows down. Instead, the sweat just drips off of us, which leaves us with all of the stinkiness and none of the cooling effect. Thus, when the humidity spikes, our bodies effectively lose a key tool that could normally be used to cool us down.

What's relative about relative humidity?

We all know that humidity refers to the amount of water contained in the air. However, as the air’s temperature changes, so does the amount of water the air can hold. (Air can hold more water vapor as the temperature heats up.) Relative humidity compares the actual humidity to the maximum amount of water vapor the air can hold at any given temperature.

Whose idea was the heat index?

While the notion of humidity making days feel warmer is painfully apparent to anyone who has ever been outside on a soupy day, our current system owes a big debt to Robert G. Steadman, an academic textile researcher. In a 1979 research paper called, “An Assessment of Sultriness, Parts I and II,” Steadman laid out the basic factors that would affect how hot a person felt under a given set of conditions, and meteorologists soon used his work to derive a simplified formula for calculating heat index.

The formula is long and cumbersome, but luckily it can be transformed into easy-to-read charts. Today your local meteorologist just needs to know the air temperature and the relative humidity, and the chart will tell him or her the rest.

Is the heat index calculation the same for everyone?

Not quite, but it’s close. Steadman’s original research was founded on the idea of a “typical” person who was outdoors under a very precise set of conditions. Specifically, Steadman’s everyman was 5’7” tall, weighed 147 pounds, wore long pants and a short-sleeved shirt, and was walking at just over three miles per hour into a slight breeze in the shade. Any deviations from these conditions will affect how the heat/humidity combo feels to a certain person.

What difference does being in the shade make?

Quite a big one. All of the National Weather Service’s charts for calculating the heat index make the reasonable assumption that folks will look for shade when it’s oppressively hot and muggy out. Direct sunlight can add up to 15 degrees to the calculated heat index.

How does wind affect how dangerous the heat is?

Normally, when we think of wind on a hot day, we think of a nice, cooling breeze. That’s the normal state of affairs, but when the weather is really, really hot—think high-90s hot—a dry wind actually heats us up. When it’s that hot out, wind actually draws sweat away from our bodies before it can evaporate to help cool us down. Thanks to this effect, what might have been a cool breeze acts more like a convection oven.

When should I start worrying about high heat index readings?

The National Weather Service has a handy four-tiered system to tell you how dire the heat situation is. At the most severe level, when the heat index is over 130, that's classified as "Extreme Danger" and the risk of heat stroke is highly likely with continued exposure. Things get less scary as you move down the ladder, but even on "Danger" days, when the heat index ranges from 105 to 130, you probably don’t want to be outside. According to the service, that’s when prolonged exposure and/or physical activity make sunstroke, heat cramps, and heat exhaustion likely, while heat stroke is possible.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

This article has been updated for 2019.

Chimpanzees Bond by Watching Movies Together, Too

Windzepher/iStock via Getty Images
Windzepher/iStock via Getty Images

Scientists at the Wolfgang Kohler Primate Research Center in Germany recently discovered that, like humans, chimpanzees bond when they watch movies together, the BBC reports.

In the study, published in Proceedings of the Royal Society B, researchers stationed pairs of chimpanzees in front of screens that showed a video of a family of chimps playing with a young chimp. They found that afterward, the chimps would spend more time grooming and interacting with each other—or simply being in the same part of the room—than they would without having watched the video.

They gave the chimps fruit juice to keep them calm and occupied while they viewed the video, and they chose a subject that chimps have previously proven to be most interested in: other chimps. They also used eye trackers to ensure the chimps were actually watching the video. If you’ve ever watched a movie with friends, you might notice similarities between the chimps’ experience and your own. Drinks (and snacks) also keep us calm and occupied while we watch, and we like to watch movies about other humans. Since this study only showed that chimps bond over programs about their own species, we don’t know if it would work the same way if they watched something completely unrelated to them, like humans do—say, The Lion King.

Bonding through shared experiences was thought to be one of the traits that make us uniquely human, and some researchers have argued that other species don’t have the psychological mechanisms to realize that they’re even sharing an experience with another. This study suggests that social activities for apes don’t just serve utilitarian purposes like traveling together for safety, and that they’re capable of a more human-like social closeness.

The part that is uniquely human about this study is the fact that they were studying the effect of a screen, as opposed to something less man-made. The chimps in question have participated in other studies, so they may be more accustomed to that technology than wild apes. But the study demonstrates that we’re not the only species capable of social interaction for the sake of social interaction.

[h/t BBC]

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