Genetic hitchhiking

Gene hitchhiking is like when somebody got a ride in a car. If a gene is "hitchhiking," that means it is being carried along with another gene. There are two kinds of gene hitchhiking. The first kind is called genetic drift. Genetic drift is when a gene randomly becomes very common and spreads out. The second kind of gene hitchhiking is called a selective sweep. A selective sweep is when a gene becomes very common because it is helping the organism survive, like a super strong gene. So the gene gets carried along with other genes and spreads out. That's gene hitchhiking!