American biologists have found out why, in the course of evolution, people stopped turning their pelvis when walking. This is stated in a study published in the Journal of Experimental Biology.
Chimpanzees, the closest relatives of humans, turn their pelvis with each step when they walk, which makes their movement seem awkward, while for humans an even gait is considered the norm. Scientists have conducted experiments with human volunteers and monkeys standing on two legs, and found that turning the pelvis helps lengthen the stride. Despite the fact that human legs are much longer, chimpanzees have a stride-to-height ratio of 26 percent.
When walking, these monkeys rotate their hips 30-60 degrees, and humans - no more than 8. "I think chimpanzees use pelvic rotation to get the most out of each step, otherwise their steps would be too small," says Nathan Thompson, study author at the New York Institute of Technology. He explains that monkeys usually walk on bent legs, which naturally shortens their steps, and this must be somehow compensated.
The authors suggest that people have moved away from long strides in favor of a more agile and lighter gait, which saves strength and puts less stress on the muscles.