translation.en: If we look across many, many different species of animals, not just us primates, but also including other mammals, birds, even marsupials like kangaroos and wombats, it turns out that there's a relationship between how long a childhood a species has and how big their brains are compared to their bodies and how smart and flexible they are.
translation.zh: 如果我们观察各种不同种类的动物， 不光是灵长类， 包括其它哺乳动物和鸟类， 还有有袋目哺乳动物 比如像袋鼠和袋熊， 结果是 动物的孩童时期长度 和它们的脑部大小与身体的比例 还有它们的智慧和灵敏是存在关系的。