Are humans taller than chimpanzees

Primates: why chimpanzees are stronger than humans

Since the 1920s, anecdotal reports and individual scientific studies have repeatedly demonstrated the outstanding muscular strength of chimpanzees. Despite the relatively close relationship, the animals are even five times as strong as humans, it is still often said today. But what is the monkey's secret? Researchers have already made various assumptions about this. A team led by Matthew O'Neill from the University of Arizona in Phoenix now believes they have found the answer.

The scientists first looked at the previous literature on the topic. In doing so, they discovered that the difference in strength between humans and chimpanzees is apparently not as great as previously assumed. In fact, the animals prove to be only 1.5 times stronger than humans in various tests that determine, for example, the jumping or pulling force.

This article is included in Spectrum - The Week, 26/2017

The chimpanzees owe this still considerable lead to two factors, as the comparison of monkey and human muscle fibers revealed: On the one hand, the muscle fibers of the animals are somewhat longer, the researchers write in the Proceedings of the National Academy of Sciences of the United States of America "(PNAS). However, differences in the myosin of the muscles are even more important. Myosin is a group of motor proteins that play a crucial role in muscle contraction. Functional myosin usually consists of two different components: a heavy amino acid chain and a variable number of light chains.

This heavy chain, as O'Neill and his colleagues have now been able to prove, seems to differ between chimpanzees and humans. While three different isoforms of the heavy chain are used equally in chimpanzee muscles, one of the variants predominates in humans. According to a computer model by the researchers, this means that the chimpanzee muscles can perform around 1.35 times more and is therefore responsible for a large part of the difference in force between humans and monkeys.

The scientists suspect that the differences in myosin and muscle fiber length result primarily from the different lifestyles of humans and chimpanzees. While higher muscle strength would allow the monkeys to climb trees more easily, building muscle in humans would be more energy-efficient and would also ensure that the muscles do not tire so easily even with repeated strain.