根据一项新的基因研究，之前并不为人所知的人类物种——丹尼索万人——可能在亚洲游荡了数千年，大约偶尔与像你和我一样的人类杂交。
A previously unknown kind of human—the Denisovans—likely roamed Asia for thousands of years, probably interbreeding occasionally with humans like you and me, according to a new genetic study.
然而，糙皮病在当时的美洲几乎还不为人所知，甚至在主要以玉米为生的人之间也是如此。
Pellagra was virtually unknown at that time in the Americas, however, even among people who subsisted primarily on maize.
地面上的人们听到了云中的声音，而这声音说的什么却可能因为纸草书上的一道撕口而永不为人所知。
People on the ground hear a voice from the cloud, though what it says may be forever unknown due to a tear in the papyrus.
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