鈥淣ature teaches beasts to know their friends,鈥 wrote Shakespeare. In humans, nature may be less than half of the story, a team led by 葫芦娃视频 researchers has found. In the first study of its kind, the team found that genetic similarities may help to explain why human birds of a feather flock together, but the full story of why people become friends 鈥渋s contingent upon the social environment in which individuals interact with one another,鈥 the researchers write.