字幕列表 影片播放 列印英文字幕 Chimps can be three to five times stronger than humans. That means a really strong chimp could, in theory, lift around sixteen people over its head. But, can eating bananas and swinging around in trees really account for this difference? After all, aren't we supposed to share 99% of our genes? Studies have shown differences in the way our muscles are built but muscle control may be a much more important factor Chimps seem to have less control over how much muscle they use at once. While this may sound counter-intuitive, this can account for the difference in strength. Let's take a look at why. Compared to humans, chimps have less gray matter relative to body weight. Gray matter is the part of the nervous system that contains the nerves responsible for controlling motion. These branch out from the spine into the muscles to control individual muscle fibers. Some neurons can contact many muscle fibers at once. Activating these neurons causes all of the muscle fibers that touches to contract at once. Creating a lot of force. This combination of neurons and muscle fibers is called the large motor unit. And these are used for gross motor skills like jumping and climbing. Some neurons contact only a few fibers making a small motor unit. These don't have a lot of power but they are a lot more precise. Small motor units let us do delicate complex tasks like playing a video game or plucking a ukulele. Things that we can do and chimps can't. So chimps who have less gray matter have fewer motor neurons. Therefore, their motor neurons are more likely to be dedicated to large motor units. This means when they do engage their muscles it's an all-or-nothing response which we see as strength. Unlike chimps, our neurons control smaller bundles so we have more specific muscle control. So keep this in mind the next time you think of challenging a chimp in a pub; You might want to try thumb wrestling instead. For Scientific American, I am Yasmin Tayaq.