If you made it past 10, you had a decent chance of hitting 60 no matter who you were for centuries.
Unless you were the kind of daredevil who went hunting for large dangerous animals down at the water hole with a switch and mud balls? That's where natural selection came in.
"I double dog dare you hit a leopard with a mud clod, Gurk."
"Oh yeah? Watch this!"
"Whoa! Wait until we climb this big tree so we can get a clear view of you doing it. I'm not having you come back with muddy hands claiming you did. You're not getting our females that easy."
"Climb up to watch and weep, Dork!"
"Arghh!" "Aiyeee!" "Kee-runch!"
"Hmm...Who knew leopards were that fast, Ack? Heh, heh, heh, that dumb rock pounder! Settle in and nap until the leopard gets it's fill and does the same. We'll climb down from this tree to head back to camp while the leopard is snoozing. Say, don't you need a new rabbit stick? If the leopard doesn't eat it, you're in luck! I've got dibs on his hand-axe. 50-50 on the female split?"
"Sounds good to me, Uncle Dork."