Greenbeard effect

The Greenbeard effect is a genetic phenomenon where an individual with a visible trait (like a green beard) can recognize and help others with the same trait. This recognition promotes cooperation among these individuals, even if they are not close relatives. Essentially, it's a mechanism where a gene causes both a noticeable trait and the ability to identify and favor others with that trait, increasing the chances that those sharing the trait will pass on the gene. This helps explain how altruistic behavior can evolve based on specific shared characteristics.