regarding mutations, perhaps they are just confined to certain physical systems. The reason I bring this up is my mother-in-law has brownish hair with not a sin

regarding mutations, perhaps they are just confined to certain physical systems. The reason I bring this up is my mother-in-law has brownish hair with not a single grey hair, she does not dye her hair and is about to turn 70. Her mother also has barely any grey hair and is in her 90's, this to me is extremely strange as people in my family get alot of grey in their 40's and most get grey at least by 50ish.