Thursday, December 6, 2007

University of Albany Researchers Discover that a Handshake Could Signal High Quality Genes

ALBANY, N.Y. (November 16, 2007) -- Handgrip strength is an important measure of health and reproductive fitness, according to findings of University of Albany researchers Andrew C. Gallup, Daniel D. White and Gordon G. Gallup published in the November 2007 issue of Evolution and Human Behavior.

Although it can be influenced by nutrition and exercise, handgrip strength is highly heritable. In addition, grip strength is a ubiquitous measure of health and vitality in both men and women, and as grip strength increases so does a person's overall health status, speed of postoperative recovery, and longevity. People with higher grip strength scores experienced reduced disability, reduced morbidity, and more rapid recovery from injury, and also have higher bone mineral density and greater fat free body mass.

The authors also report that handgrip strength is an honest signal of genetic quality in males. Male college students with stronger grip strength scores had more masculine physical features, reported being more aggressive in middle and high school and had more reproductive opportunities than their peers.

In a sample of more than 140 college students, the researchers obtained measures of handgrip strength using a hand-held dynamometer. In addition to recording left and right handgrip strengths, they recorded particular body morphological measurements. The college students were also asked to fill out brief surveys about their sexual history and their social experiences in middle and high school.

The study concluded that male handgrip strength scores predicted aggression and social dominance in adolescence, broader shoulders and narrower hips, and an increase in reproductive opportunities. Grip strength accounted for more than 10 percent of the variance in promiscuity among college-age males. Although handgrip strength predicted many of the same health variables in females, it did not predict any of the behavioral or morphological features measured in the study.

Study author and UAlbany evolutionary psychologist Gordon Gallup surmises that the relevance of handgrip strength to health in humans may be embedded in our evolutionary past. "Unique to the evolutionary history of humans and all primates were complex adaptations to life in the trees. As a result, handgrip strength was featured prominently in patterns of brachiating, or moving through the canopy, as well as in minimizing the chances of falling," he said.

The researchers found nearly non-overlapping distributions between male and female grip strengths, stating, "Whereas handgrip strength is a powerful indicator of health and vitality in both men and women, in the present study we found that its relationship to sexual behavior and body morphology was restricted almost exclusively to men."

The authors conclude that the dramatic sex differences between males and females might be the consequence of primitive division of labor that emerged after early humans came down out of the trees and put a premium on the maintenance of grip strength in men. The authors suspect that one of the leading factors in accounting for handgrip strength among males is testosterone levels.

Courtesy: University at Albany

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