It is an ancient sense in evolution: even the simplest single-celled organisms can feel when something brushes up against them and will respond by nudging closer or pulling away.

• 触感是仍在演化的古老感觉：连最简单的单细胞有机体，也能在有东西拂过它们时感觉到，而出现轻轻推近或拉开的反应。