Hey SF1900, you do realize that cultures have had "professional athletes" for as long as we have recorded history. Many of the best Roman Gladiators were paid very well, and treated like superstars (much like boxing and mma today)
Have you ever heard of the Hippodrome?

It was a stadium mainly used for chariot races during the Roman Empire. There were replicas built across the empire. They had teams/factions, which included lots of bets being made by "fans". The best of the best chariot racers were some of the richest, and most adored people of the Roman Empire.
Not to mention the Olympics, which were invented by the ancient Greeks, and to this day, is the pinnacle of professional athletics, worldwide.
Sports are as human as it gets.