Fifteen million years ago yet another brain growth spurt happened. Marino and her colleagues speculate that changes in social ecology-essentially the dolphin's social lifestyle-probably contributed to the process. For example, the more a dolphin needed to communicate, benefiting its survival, the more its brain evolved to permit that interaction.
而1千5百万年前,(海豚的)大脑又经历了一次突然的进化.马里诺和她的同事推测，社交环境的改变-特别是海豚生活方式的改变,很可能是造成这次进化的原因。比如，海豚越是需要沟通以利生存，它们的大脑就越会朝着这个方向进化。
Moving to the present, dolphins have brains that are about "five times larger for their body size when compared to another animal of similar size," Marino said. "In humans, the measure is seven times larger-not a huge difference."
回过头来说，现如今，与体型相近的动物相比，海豚的大脑要上大5倍.马里诺说，“人类大脑是同体型动物的7倍--(和海豚的相比)差别并不是很大。”
She concluded, "Essentially, the brains of primates and cetaceans arrived at the same cognitive space while evolving along quite different paths."
她总结说，“灵长类动物和鲸类的大脑的认知能力基本上处在同一是水平，只是进化方式截然不同。”