Pec lines. Some are round and some are slanted.

[LovingtoLift]

Looking at photos of Andy Haman for example. His pecs are full but slanted. They are not round at the bottom.

Genetics or training? Could be age maybe?

 

[BeastFitness]

Could be their genetic insertion and attachment points, could be if they're depleted or carbed up, could be improper training

 

[LovingtoLift]

Could be their genetic insertion and attachment points, could be if they're depleted or carbed up, could be improper training

Depletion or too many carbs? Which one would create this shape?

 

[MBZ]

I think it could potentially be either. So many variables to take into account that it would be hard to pinpoint what exactly gives a muscle shape at a given point in time without knowing more details of that individual.

 

[Aleksandar37]

Could be their genetic insertion and attachment points

I would say mostly this.

 

[BeastFitness]

Depletion or too many carbs? Which one would create this shape?

Completely depends on the person TBH…one person's flat pecs might be another's full…to hard to pin down specifically without everything out in front of you ya know?