21th Century Humans are the Weakest Ever

Writer Peter McAllister in his book Manthropology, claimed that men are physically weaker than our ancestors. McAllister does not say "people" he says "men," maybe to be provocative, or maybe because Australians are not so politically correct.  

McAllister says "for some reason our muscle fibers got weaker over time."  He argues primarily for nurture rather than nature, saying that  a lifetime of hard work induces stronger muscles and bigger bones.  For example, he points out the Nepalese hill porters are much stronger than "modern men."  Seems racist to me; aren't Nepalese guys modern? I suppose he means Nepalese porters are stronger than journalists from Western Australia.

Normally I favor nurture over nature in debates like this, but nature has alot on its side. There are three factors, smaller arms, and  two disabled genes.

First, chimps have relatively bigger arms than humans. Anyone can see their arms nearly reach to the ground. Longer arms mean they can have longer muscle fibers, and they can work over a longer range of motion. This alone could double the strength of the arm.

Second, chimps have two genes that are deactivated or relatively rare in people, one codes for weaker jaw muscles. Speculation ties this to the development of cooked food. Chimps literally spend hours a day chewing.

Third is the ACTN3 gene which has been found to be enriched in Olympic sprinters. Most people have a non-functional version of this gene. This gene makes the muscle react faster. Africans are most likely to carry the gene, and Asians are the least likely.

It is unclear why ACTN3 is mainly deactivated.  Alan Walker, of Penn State, suggest we are wired for fine muscle control instead. He sites differences in the spinal cord as seen by Ann MacLarnon. 

This all reminds me of devolution, and an old favorite song, Jocko Homo by Devo. People are deevolving in that we are physically weaker, but we are evolving to adapt to other traits too.