Got it? No doubt it's painfully obvious; hairy leaders give way to bald ones. And bald leaders are replaced by hirsute ones. It's a male-pattern baldness pattern!*
Steve Jones of University College, London is credited with making this insight public with NPR's science guy, Robert Krulwich. Jones started with Lenin, so this blog scores one for beginning with Czar Nicholas II. Oh, and remember Boris Yeltsin? He had a partially-amputated finger on his left hand. At a White House dinner, Yeltsin once dipped his stump into a mustard pot and then used it to smear the mustard onto his bread.
* In order: Czar Nicholas II, Vladimir Lenin, Joseph Stalin, Nikita Khrushchev, Leonid Brezhnev, Yuri Andropov, Konstantin Chernenko, Mikhail Gorbachev, Boris Yeltsin, Vladimir Putin, and Dmitry Medvedev.