It has always been assumed that chimps are much stronger than humans, despite the fact that on average they are smaller than us. A new study by Dr. Matthew O’Neill from The University of Arizona College of Medicine set out to find out exactly what gives chimps such super-strength.

Skeletal muscle fibers were sampled from three young male chimps and compared to those of humans. The big difference was found to be in the way those muscle fibers are distributed.

Chimps climbing

Having faster twitch muscle fiber than humans give chimps the strength to climb. (Eric Kilby/Wikimedia Commons)

In chimps, one-third of their muscles are slow twitch fibres and the other two thirds are made up of two types of fast twitch muscle fibres. Fast twitch muscle contracts more quickly and provides more force in quick bursts, but fatigues faster. This accounts for a chimp’s ability to climb and jump rapidly over short distances.

On average, humans have 70 percent slow twitch and 30 percent fast twitch muscle fiber. This gives us greater endurance, but less strength in bursts.

Chimp muscle fiber was found to be 1.35 times more powerful that that of humans. It may be that humans traded strength for endurance when the lineages separated millions of years ago, giving us the ability to travel farther to find food.

Paper in the journal PNASChimpanzee super strength and human skeletal muscle evolution

Credits: CBC Radio

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