I agree with Sour, Those hormones can kick in at a very early age. And it's that cascade of T that starts the whole enlarging of comb and wattles that can often be distinguished at a VERY early age. I had a cockerel who was a complete jerk starting at 2 weeks of age. However, I was able to work him out of his jerkiness. He was human aggressive. If he had been aggressive to his pullet flock mates, I doubt that I could have "fixed" his jerkiness.