Genetic Drift

Captions are on! Click the CC button at bottom right to turn off. So here’s a question for you. Have you ever compared the candy you get on Halloween with your friends? My sister and I---a bit competitive in the sport of Halloween candy hunting---we both have preferences of what kind of candy we hoped to get in our buckets each year. As for me, I LOVE gummy bears. And every once in a while, someone would have them mixed in a big bucket and I remember watching—with intense focus--- the hand that picked out the candy hoping for gummy bears. Getting those gummy bears was always total luck. Total chance. Well unless of course the entire bucket they had was actually gummy bears---but that would not be luck---no, that would be pure bliss. But that’s never happened to me. Yet. So why bring this up? Well, what if instead of candy, we were talking about insects? And they weren’t in a Halloween bucket because that’d be kind of gross. They’re on the sidewalk. And when you’re scooter riding through the neighborhood on Halloween to collect candy---because scooters may or may not be our super awesome childhood mode of transportation---you squash some. Accidentally, of course, because you like insects overall. Were the ones that survived better adapted? Did they have some special ability to foresee events or to move your scooter away from them? Assuming they all were just there on the sidewalk in the path of your trick-or-treating, no, in this random event example---the survivors were not better adapted. They were lucky. It was chance. And the ones that were squashed were, in this case, at the wrong place at the wrong time. And that’s what genetic drift is. Genetic drift can change allele frequencies in a population. Remember, alleles are a form of a gene.