Natural dyes from plant and animal products have been used since ancient times.

VOA: special.2010.08.02

We can think about this in an evolutionary way, as I've alluded to a lot, but if you think about it from a completely Darwinian point of view, and you think about these food conditions where food would be scarce in ancient times.

我们可以从生物演化的角度来看这个问题,我已经提到过很多了,但是如果你完全从达尔文学说的角度思考,从食品条件想想,在古代,哪里可能出现食物短缺

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选