Disappearing blonde gene
The "disappearing blonde gene" refers to a hoax that emerged in parts of the Western world in the early 2000s, claiming that a scientific study had estimated that blonds would become extinct within the next two centuries. More specifically, it claimed that, because the alleles for blond hair genes are recessive, people with natural blond hair would become less common as people with dominant non-blond hair alleles had offspring with them, even though such a pairing would retain one copy of the blond allele in the genome of said offspring.