Evidence of early boat and ship structures beyond the level of log canoes and rafts indicates that they shared comparatively simple shapes across cultures, time, and geography. From Egyptian (ca. 2400 B.C.), Roman, or East Asian (reported during the Dark Ages) times to present, there is a basic geometry of bottoms that are flat across and curved up fore and aft (that is, parallel to the midline of the boat) and sides vertical to flaring outwards 30° or more. These simple shapes typically did not reflect an absence of understanding of how to build more complex shapes, but allowed for more affordable ships that could be built quickly.