So it's not too much of a stretch to claim that pre-human forms of laughter may exist.
所以我们就不难延伸，人类初期也可能存在着表示笑声的方式。
2
And he has a theory about early life and perfectly appropriate as far as one can tell of what pre-human form he studied.
他有一个有关早期生命的理论，一般人都会觉得很正常，他研究人类之前的生命形式没有什么不合适。
3
One model 'envisions the pre-human ancestor as a terrestrial knuckle-walker, a behavior frequently used by our closest living relatives, the African apes,' the report said.