Are iron chins born or bred?

Iron chins, are you born with them or are they developed through training and fighting style?

Could it be that fighters that dont get accostumed to get punched in the face since they're kids are destined to become glass jawed frauds in the pro stage?

Examples:


Mexican fighters are famous for the quality of their chins, they're also famous for their agressive style that disregards defense for attack, the typical mexican fighter gets hit a lot, yet he also posseses a great chin so he can be succesful with that style. Mexicans barely spend time in the amateurs so they get accostumed to get punched in the face since an early age in the pro stage.

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mexican chin in display

On the other hand you have the cubans, most of them seem to possess fragile glass mandibles in the pro stage, they also tend to have very, very extensive amateur bgs, so they're accostumed to be protected by headgear most of their boxing lives. Cubans are proud of their skills, they dont like to get hit, and they dont get hit very often in the pros, but the moment they do, stuff like this happens:

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cuban chin in display


So what do you think? are solid chins a genetic trait? are they a by-product of getting used to get punched in the face since an early age? or maybe a combination of both factors? what's the secret behind the Haglers, Chuvalos, McCalls of the world?

 

So let's assume Marvin Hagler was a cuban amateur who was boxing with headgear until his 30's, then becomes a pro in the U.S. Do you think his punch resistance would have been the same?

 

It protects it partially, and it makes taking hits to the head overall much easier, the gloves and the padding are smaller in the pros too. But this is not only about headgear and gloves. There's also the amateur mentality, they're more concerned about defense and technical aspects than the pros. Pros know a good punch can reverse the result in any fight and the matches are much longer so even if they lose some rounds they know they can turn the tide, not the same with amateurs. You dont see guys trying to grind down their opponents to KO them late or taking two punches to land a good one, etc in the amateurs.