Scientists study families a lot, because it’s an extremely important human unit both socially and genetically. How different or alike are siblings? How does birth order affect your life? Studies like this help to determine which traits are genetic and which are learned. Sometimes those things are hard to separate, since families not only share genes, but also learn from each other. We also have new research about how families have changed over time. John Green has some really interesting findings about families this week’s episode of the mental_floss List Show.