Biology. The original Chuck D: it's Charles Darwin. The father of natural selection knew a thing or two about the origin of species, and he also knew a badass beard could attract a mate.
Physics. Roentgen, the dude who discovered X-Rays. People talk about "x-ray specs", but it turns out if you want to see what's under a woman's clothes you just need an epic beard and she'll be ready to show you.
Chemistry. August Kekulé was a chemist who always kept his beard in a French fork, so I guess you could say he knew about frenchin', forkin', and chemistry.
Art. Leonardo da Vinci was known as the master. Artist, inventor, scientist. You know he had a million good reasons for growing such a kick-ass beard. And the ladies surely didn't mind that he was good with his hands.
Literature. Leo Tolstoy is best known for writing a book few read but everyone name drops when they want to sound smart (War and Peace, if you didn't know). But he had a major influence on Gandhi and Martin Luther King Jr., and had a pretty awesome beard, too.
Journalism. He loved it when you called him Big Poppa. It's Ernest Hemingway, who brought journalistic style to literature and literary themes to journalism. A man's man who punched his way through the world as much as he wrote.
Economics. Karl Marx. Forget the Communist Manifesto and just think about the manifesto he could've written about growing a beard. "From each according to his ability" when your beard is this prodigious.