Why do some guys have stronger, defined jawlines and chins than others?

Because they do, OP.

Next question.

Thyroid

Are you an incel, R1? Incels are concerned about jawlines in order to become "Chads".

Whoops, I meant OP. Sorry R1!

And why are some people tall, yet others short? Is it genetic?

And is it the same with the whole blue eyes vs. brown?

Eyebrow ridges and jawlines are among what's known as secondary male characteristics.

In sexually dimorphic species, the onset of puberty and secretion of hormones results in the development of these characteristics (the mane on a lion and plumage on peacocks are also examples). It results in the deepening of the voice, growth of testicles and penis, facial hair among other changes.

Steroid abuse among bodybuilders results in the classic "lantern jaw" and is commonly seen.

OP has a 3rd grade education.

Jowls, or the fat stored under the chin is the first place I lose weight and the first I put it on. I’ve noticed if I lose enough weight, my facial features become more prominent. That and the muscular tone from

The picture at R3 is vomit inducing. They give themselves that "jaw" on purpose?

Yes R10. Read the linked article if you have time. It's amazing (the entire incel culture), sad and disgusting all at the same time.

Wow.

The terminology that they've invented really reveals their true character or lack thereof. They clearly have no coping skills whatsoever and are possibly more superficial than anyone who has ever accessed the DL.

I don't feel sorry for them at all.