Manthropology: The Science of Why the Modern Male Is Not the Man He Used to Be - by Peter McAllister

Wolff's law, named after German military surgeon Julius Wolff, states that bone carries a record of the muscular load placed upon it because it grows larger over time in response to mechanical stress.

It is widely acknowledged, among arm-wrestling champions, that a short forearm is a serious advantage. This is because the forearm is a third-class lever. Levers generally increase the amount of work that can be done as they grow longer, but third-class levers don't--they decrease it. This is called the lever's "mechanical disadvantage," and its number rises as the lever lengthens. A short forearm, therefore, means a lower mechanical disadvantage.

This then is the real secret of the Ice Age Australian runners and the Athenian trireme rowers: their incredible athleticism was not genetic, but ontogenetic. Ontogeny is the process by which an organism grows by interaction with its environment. While genes might fix the limits of its potential development, whether or not it reaches them is governed by the environmental stresses placed upon it. Effectively, therefore, those historic and prehistoric men were superb athletes because of the working toughness they had developed over harsh and demanding lives.

Examples of how much working toughness historical men had compared to Homo masculinus modernus are available even closer to home. Laborers in the rip-roaring early days of the Industrial Revolution, for example, often performed feats unthinkable today. One New Scientist correspondent reported that bridge builders in the mid-nineteenth century toiled all day with forty-pound sledge-hammers; today's hammers weigh fourteen pounds. English railway navvies in the 1850s were expected to shovel, by hand, twenty tons of earth daily.

Why should male muscularity be so sexy? It's not just because it signifies physical strength in the hunt and war, though that principle does operate. Big male muscles are also what is called an "honest" sexual signal, similar to the male peacock's tail--an unfakeable indicator of how good the male's genes are because they show he can afford their cost. Big muscles are expensive not just because of their energy cost, but also because the testosterone that builds them suppresses the immune system. This means that the disease-fighting system of any healthy, muscular male must be exceptionally strong, simply to remain functional in spite of such high testosterone. Thus, it makes perfect sense, from a mating-strategy point of view, for women to prefer muscular men for short-term liaisons, simply to access those genes. But therein lies the modern rub: thanks to contraception, those liaisons no longer have as many reproductive consequences. Sure, women's instincts may still drive them to steal away for illicit pleasures with the occasional passing beefcake, but they save their reproductive potential for their tamer, less attractive but thoroughly-better-with-the-kids partner waiting patiently at home. Sexual selection by modern women really might, therefore, be acting to remove male muscularity from the human gene pool.

[An example of] the distinction between proximate and ultimate causes in evolutionary theory: the proximate cause of young men's bravado, besides instinct, is their mistaken belief that it appeals to women; but the real, ultimate, cause is probably its role in establishing male-male coalitions.)

Herding societies tend to be quite violent ones. The fact that so much wealth is tied up in a mobile, easily stolen resource means herders often have to employ extreme violence as a deterrent.

The male body is most responsive to the mechanical stresses that stimulate growth between the ages of eight and fourteen.