Jaw size = granite chin

Big neck traps and thick skull sure helps. It always helps to be big for the weight, frame wise not pumped up muscle.

 

Mahmoud Charr has a massive but weak jaw.

 

Neck training for sure improves somehow your chin.

 

Juan Manuel Marquez massive head, Loma tiny head and skinny jaw

 

If you have a pathetic looking mandible, it's over for you in life let alone the ring.

 

Inoue. He absorbed some seriously spiteful nukes from Nonito and never went down.

 

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That's a skinny ass jaw. He should be packing glass.

 

To be fair he fights at 118. Like with the other guy who pointed out that Charr has a weak chin despite his being large, he's a heavyweight. Likely the more exceptions the higher and lower in weight you go

 

Devin Haney massive head and squared jaw, chinny.

Regis tiny jaw, good chin

I think Crawford has a small chin but he always has that beard, suspect chin

Canelo has a boulder head and short neck, good chin

GGG's head and chin look pretty regular but he has an iron chin

Erislandy Lara has a small chin, suspect chin

Gamboa angular chin, glass chin

Charlo brothers big square heads and jaws, good chins

Felix Cash small recedded chin, packing glass

Eubank Jr square big jaw, good chin

George groves regular head and jaw, glass chin

Jaime Munguia regular head, good chin

Demetrius Andrade pointy chin, glass chin

Gilberto Ramirez square jaw, good chin

Marcus Browne small pointy chin, glass chin

Jean Pascal rounded block head, good chin

Kovalev pointed out jaw, suspect chin

 

You are 100 percent correct. Neck and jaw muscles must play a part

Here's an interesting paper not saying its gospel and it has its critics but worth a read about fighting in humans from archaic humans till now.

https://carrier.biology.utah.edu/Dave's PDF/Protective buttressing of the face.pdf

A few quotes

""The most sexual dimorphic part of the human body, in terms of muscular strength, may be the neck. Maximum moments produced by the muscles of the neck are 100–150% greater in men than in women (Vasavada, Li & Delp, 2001).""

Probably one of the reasons why we women suffer more concussions in sports.

""However, as discussed above, energy absorption by the muscles of the neck can protect against concussion when the head is struck. Thus, humans do show very high levels of sexual dimorphism in the parts of the postcranial musculoskeletal system that appear to be most important in fighting (Lassek & Gaulin, 2009; Puts, 2010; Carrier, 2011; Sell, Hone & Pound, 2012; Morgan & Carrier, 2013).""

""(3) Human jaw muscles

Given that humans have relatively small canine teeth, exhibit low canine sexual dimorphism (Frayer & Wolpoff, 1985; Wood et al., 1991; Plavcan & van Schaik, 1997) and rarely bite during fighting (Shepherd et al., 1990; Boström, 1997), it is puzzling that humans exhibit significant sexual dimorphism in the strength of their jaw adductor muscles. Five studies that measured maximum bite force in men and women indicate that, on average, men produce 34.3±10.5% (mean±S.D.) greater forces than women (Klatsky, 1942; Waltimo & Könönen, 1993; Braun et al., 1995; Raadsheer et al., 2004; van der Bilt et al., 2008). This level of sexual dimorphism is only 7–20% below estimated sexual dimorphism in bite force of gorillas and orangutans (Demes & Creel, 1988; Eng et al., 2013); species in which biting is an important male fighting behaviour. The human masseter muscle also exhibits substantial gender differences in the proportion of fast-twitch (type II) muscle fibres. The average cross-sectional area of type II fibres in the masseter muscle averages 66.9% in males and only 8.3% in females (Tuxen, Bakke & Kenrad, 1992; Tuxen, Bakke & Pinholt, 1999). Type II muscle fibres shorten faster and generate force more quickly when stimulated than type I fibres (Close, 1967). Although human sexual dimorphism in adductor muscle strength and fibre type cannot be explained by aggressive biting behaviour during fighting or by mastication, because diets of human males and females are largely similar, the observed human dimorphism is consistent with the hypothesis of protective buttressing of the face. If the jaw adductor muscles do function to protect against mandibular dislocation and fracture, as suggested above, greater muscle strength and shorter force activation times in males would be expected because of their higher incidence of fighting and facial injury.""


There is no reason any boxer should not be training neck muscles....

 

Joe Smith Jr. Has one of the strongest jaws I've ever seen in my life. And it's been literally broken twice.