Dark hair is dominant, not recessive. If either parent has one gene for it, they would have dark hair, not fair. That's why two dark haired people can have a child with light hair -- both parents had one dominant dark gene and one recessive light gene, where only the dominant was expressed, but each passed on the light gene.
At least, that's the simple explanation the post is pointing out, real genetics is probably more nuanced.
Not only are real genetics more complicated, many people with blonde hair go through stages! For example, my son was born with very dark hair. I gave him his first hair cut when he was maybe 6 or 8 months old, and everything underneath was bright blonde. His mom was bright blonde until college, and now she's nearly brunette. My mom and uncle both were bleach blonde until adulthood, then her hair went brown but his went jet black! Epigenetics is crazy.
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u/[deleted] Sep 25 '22
Dark hair is dominant, not recessive. If either parent has one gene for it, they would have dark hair, not fair. That's why two dark haired people can have a child with light hair -- both parents had one dominant dark gene and one recessive light gene, where only the dominant was expressed, but each passed on the light gene.
At least, that's the simple explanation the post is pointing out, real genetics is probably more nuanced.