Noticed a correlation today between guys with completely shaved heads and the little roll of fat between the back of their heads and the top of their necks that bulges out with a little crease in the middle when they tilt their head back, like a little mini-bum between the shoulders.

Is it a medical condition that arises from excess UV penetration of the scalp, or is voluntary baldness a mental thing caused by something excreted by the roll of fat, like aluminium in your deodorant gradually causing Alzheimer's?

What came first? The chicken, or the guy with the egg-shaped head?