Institute of Psychology, University of Debrecen, P.O.B. 28, Debrecen, H, 4010, Hungary.
Biol Direct. 2012 Jul 12;7:22. doi: 10.1186/1745-6150-7-22.
The overwhelming majority of animal species exhibit bilateral symmetry. However, the precise evolutionary importance of bilateral symmetry is unknown, although elements of the understanding of the phenomenon have been present within the scientific community for decades.
Here we show, with very simple physical laws, that locomotion in three-dimensional macro-world space is itself sufficient to explain the maintenance of bilateral symmetry in animal evolution. The ability to change direction, a key element of locomotion, requires the generation of instantaneous "pushing" surfaces, from which the animal can obtain the necessary force to depart in the new direction. We show that bilateral is the only type of symmetry that can maximize this force; thus, an actively locomoting bilateral body can have the maximal manoeuvrability as compared to other symmetry types. This confers an obvious selective advantage on the bilateral animal.
These considerations imply the view that animal evolution is a highly channelled process, in which bilateral and radial body symmetries seem to be inevitable.
绝大多数动物物种都表现出两侧对称。然而，两侧对称的确切进化重要性尚不清楚，尽管几十年来科学界一直存在对这一现象的理解元素。
在这里，我们用非常简单的物理定律表明，在三维宏观世界空间中的运动本身足以解释动物进化中两侧对称的维持。改变方向的能力，运动的关键要素，要求产生瞬时的“推动”表面，动物可以从中获得在新方向上离开所需的力。我们表明，双边是唯一可以最大化这种力的对称类型；因此，与其他对称类型相比，主动运动的双边身体可以具有最大的机动性。这赋予了双边动物明显的选择优势。
这些考虑表明，动物进化是一个高度定向的过程，其中双边和放射状身体对称性似乎是不可避免的。
