Apparently humans used to have penis spines...

[Mister Obvious]

Did sex in this species get too wild and too many dicks were getting broken??

I think this might be why...

Sex in the animal kingdom is probably pretty standard, it probably doesn't differ very much from its own norm.

But it seems like the more aware humans are, the more whack and wild their sexual activities become...

So maybe broken dicks were becoming too common as mankind got "smarter" and more aware and they had to be done away with.