Humans do it, chimpanzees do it, even polar bears do it.
人类这样做，黑猩猩这样做，甚至北极熊也这样做。
And now a study has shown that kissing likely evolved about 21 and a half million years ago.
现在的一项研究表明，接吻可能在大约2150万年前进化而来。
The mouth-on-mouth kiss is actually something of a biological puzzle, with no obvious survival or reproductive benefits, so the Oxford University-led team gathered evidence of animals that kiss each other on the mouth and worked out their evolutionary relationship to each other and to humans.
嘴对嘴的接吻实际上是一个生物学谜题，没有明显的生存或繁殖益处，因此牛津大学领导的团队收集了动物相互嘴对嘴接吻的证据，并计算出了它们之间以及与人类的进化关系。
This revealed that kissing probably evolved in the last common ape ancestor of humans, chimps and bonobos.
这揭示了接吻可能进化自人类、黑猩猩和倭黑猩猩最后的共同猿类祖先。
The study suggested that Neanderthals probably kissed too, and that they may have smooched with modern humans when the two species lived alongside each other.
该研究建议尼安德特人可能也接吻，并且当两个物种相互共存时，他们可能与现代人类亲吻过。
The researchers hope that the insight will encourage more scientists to gather data that could finally help solve the evolutionary mystery of why we and many other animals kiss.
研究人员希望这一见解将鼓励更多科学家收集数据，最终帮助解决我们和许多其他动物为何接吻的进化之谜。
