Billionaire Elon Musk aired his controversial ideas on population decline and reproduction in the second of a series of meandering interviews with Fox News' Tucker Carlson that aired Tuesday. 

During the discussion, Musk claimed that the human urge to procreate had been "subverted," leading to population decline. 

Carlson then asked the Tesla and SpaceX billionaire to expand on the idea.

"Why is that? I mean, the urge to have sex and to procreate is – after breathing and eating – the most basic urge. How has it been subverted?" said Carlson. 

"Well, it's just, in the past we could rely upon, you know, simple limbic system rewards in order to procreate. But once you have birth control and abortions and whatnot, now you can still satisfy limbic instinct, but not procreate," Musk replied. 

Musk then went on to claim humans haven't yet evolved to deal with that because abortion and birth control are fairly recent developments.

"I'm sort of worried that hey, civilization, if we don't make enough people to at least sustain our numbers, perhaps increase a little bit, then civilization's going to crumble," Musk added.

"The old question of like, will civilization end with a bang or a whimper? Well, it's currently trying to end with a whimper in adult diapers, which is depressing as hell."