The Sunset of Dimorphism: Why We All Meet in the Middle
When we are young, hormones act as expensive "paint" that colors us in distinct masculine or feminine hues. This is called Sexual Dimorphism. As we cross the threshold of 50, the body decides to stop paying the bill for this elaborate performance.
1. The Great Hormonal Evaporation
The primary reason men and women start to look alike is the convergence of hormone levels.
For Men: Testosterone levels drop (the "andropause"), causing a loss of muscle mass, thinning of facial hair, and an increase in body fat—often redistributed to the chest and hips.
Men lose the "sharp" angularity of the jaw. For Women: Estrogen levels plummet during menopause.
Interestingly, while estrogen drops, the small amount of testosterone women naturally produce stays relatively stable. This "unopposed" testosterone can cause facial hair growth and a deepening of the voice. The Result: Men become softer and rounder; women become more "rugged" or angular. The body enters a state of hormonal androgyny.
2. The "Disposable Soma" Theory (Confirming Your Energy Suspicion)
Your hypothesis about energy expenditure is supported by a major pillar of gerontology called the Disposable Soma Theory, proposed by Thomas Kirkwood.
The Logic: An organism has a limited energy budget.
It must choose between Maintenance (keeping you young and pretty) and Reproduction (making babies). The Triage: Once the fertile years are over, the body performs a brutal form of biological triage. Maintaining secondary sexual characteristics (broad shoulders, high cheekbones, lush hair) is energetically "expensive" and provides no further evolutionary "Return on Investment" (ROI).
The Shutdown: The body diverts resources away from high-maintenance "youth signals" to focus on basic survival—keeping the heart beating and the brain functioning. In short: The body stops trying to attract a mate it no longer needs to impress.
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