The bow and arrow, being the oldest type of weapon, has undergone a long evolution over the millennia. The bow has gone (in ascending order) from primitive, simple, compound to complex. At each of these stages, there were continuous searches for their optimal sizes, and, therefore, arrows in order to obtain maximum effect. The article describes the functional features of onions and indicates the reasons for the appearance of various types of onions. The experimental and functional analysis of the bow carried out in the article indicates that with the optimal ratio of bow and arrow, that is, its range, the speed of flight of the arrow, and its penetrating ability depended on the correct distribution and combination of composite materials, sizes and shape of the bow. All these properties were superbly combined in the complex Mongolian bow.