I thought you meant that you suspect 200-300 year old humans. I would suspect them too of some weird practices that allow them to live so long.
Wrong there likely a subraces of homo sapiens.
Humans have been aware of gene inheritance for 100's of thousands of years.
It's a common myth that people in the past were completely unaware of genes this is flat out wrong.
If there is a group of high breed humans, they likely originated in the middle east.
Over 100-200 generations it's very possible for selective breeding to result in a group of people that are truly superior to us low breeds.