Where did the gay "lisp" some from?

Back in the stone age a gay caveman found that more gay cavemen noticed him if he spoke with a lisp. It is an acquired behavior just like twitching the hips back and forth or wearing pink hot pants and lavender shirts. The lisp immediately gets one noticed as a gay guy and removes any doubt. This seeming speech impediment immediately increases the chances of two gay guys hooking up. It's like wearing a neon sign that say's GAY on it in BIG LETTERS. No offense to any gay folks, just making an observation.