Estrogenic: Consumption of Certain Plants May Be Linked to Aggression in Monkeys

Red colobus monkeys in Uganda.
Image by Duncan (Wellington, NZ). CC By-S.A. 2.0.

Munching on large amounts of phytoestrogen-rich leaves from the Milletia dura tree appears to alter hormone levels and behavior among red colobus monkeys, according to a study published in the journal Hormones and Behavior.

Studying a group of male red colobus monkeys in Uganda, scientists from the University of California-Berkeley found that levels of estradiol and cortisol rose with seasonally higher consumption of estrogen-like compounds. In addition, the monkeys fought and mated more, and indulged less in the social-bonding activity of grooming.

“It’s one of the first studies done in a natural setting providing evidence that plant chemicals can directly affect a wild primate’s physiology and behavior by acting on the endocrine system,” said study lead author Michael Wasserman, who conducted the research as a graduate student at UC Berkeley’s Department of Environmental Science, Policy and Management. “By altering hormone levels and social behaviors important to reproduction and health, plants may have played a large role in the evolution of primate — including human — biology in ways that have been underappreciated.”

via Eating estrogenic plants alters hormones in monkeys, may increase aggression and sex.

Researchers warned against assigning too much influence to phytoestrogens, however, explaining that diet is just one factor in behavior. Others include the hormones already produced inside the body as well as the amount of competition for food and mates.

Body Language: “Fake It Til You Become It”

Low-power poses can decrease testosterone and raise cortisol, says researcher Amy Cuddy.
“Young Girl Holding a Letter” (circa 1665), Caspar Netscher-PD

Just try to watch this TED talk by Harvard Business School professor Amy Cuddy without sitting up straighter.

A few tweaks in body language, argued Cuddy, “could significantly change the way your life unfolds.” In her she recommended that people try “power poses” before entering stressful situations where they feel evaluated by others—whether it’s the high-school lunchroom, a date, or a job interview. The point is not to change how you talk to other people, but how you “talk to yourself,” she said.

In a study with Berkeley professor Dana Carney, Cuddy showed that adopting “power poses” for two minutes changed people’s hormonal levels and behavior. They divided subjects into two groups—those told to engage in expansive, high-power poses (think Wonder Woman, with hands on hips, or someone sitting with their feet up propped on a desk)—and those told to do low-power poses, hunching over and taking up as little space as possible.

Of the subjects who did the high-power poses, 86 percent chose to “gamble” when given the opportunity, compared to 60 percent in the low-power poses group. The high-power group also had a 20 percent increase in testosterone level (the dominance hormone) and a 25 percent decrease in the stress hormone cortisol. In contrast, the low-power pose group experienced a 10 percent decrease in testosterone and a 15 percent increase in cortisol.

“Two minutes lead to these hormonal changes that can configure your brain to be assertive, confident, and comfortable, or really stress-reactive and feeling sort of shut down,” Cuddy said.

Next the researchers brought more people into the lab to do the poses and then go through a stressful five-minute job interview, knowing they were being judged and recorded. Afterward, coders evaluated the videos. With no knowledge of the experiment hypothesis or different conditions, they chose to “hire” the people who had practiced the high-power poses over those from the low-power group.

The power-pose research was partly inspired by Cuddy’s own experiences as a student and professor. When Cuddy was 19, she suffered a serious head injury in a car accident. Though she was not expected to finish college, she pressed on and eventually went to graduate school. But when she got there, she felt like a fraud. An advisor urged her to keep going: to “fake it.”

Years later, she found herself giving a struggling student that same advice. “I told her, ‘Tomorrow you’re going to fake it. You’re going to make yourself powerful. You’re going to go into the classroom and you’re going to give the best comment.’ And she gave the best comment ever … ” Months later, when the student came back to see her, Cuddy was amazed by how much she’d internalized this new, confident persona, and actually changed.

“I want to say to you: Don’t fake it til you make it,” she told her TED audience. “Fake it til you become it.”