flatt head

Recently I started cutting my hair very short and noticed that I have this peculiar flat area at the back of my scull,it is almost flatt not too big.I observed other people also have similar thing(mostly bald guys)but theirs is much worse.In their case looks like whole back scull is flatt(.very scary.)
My co-worker (who is from Jamaica) on the other hand has most beautyfull shaped head, simply awesome!
Is this genetic problem in my case or maybe during babyhood I was sleeping too much in one position?