It would seem unlikely that evolution should discriminate against sinistral snails if sinistral and dextral snails are exact mirror images, for any disadvantage that a sinistral twist in itself could confer on its possessor is almost inconceivable. But left- and right-handed snails are not actually true mirror images of one another
But this evolutionary mechanism combining dissymmetry, anatomy, and chance does not provide an adequate explanation of why right-handedness should have become predominant
Here, the evolutionary theory must defer to a theory based on an explicit developmental mechanism that can favor either right- or left-handednessThus, the path to a solution to the puzzle of handedness in all snails appears to be as twisted as the helix itself。
是什么样的原因致使自然界中的螺旋体呈现出右旋或左旋?这是形态科学中一个最引人入胜的不解之谜....。。究竟是一些什么样的机制控制着旋转方向,并使左旋的比例为数稀少呢??
假如左旋和右旋蜗牛呈完全一致的镜像对称的话,那么进化对左旋蜗牛不利,这近乎不太可能。几乎无法想象左旋本身会给左旋者带来任何不利之处。然而,左旋与右旋蜗牛彼此间实际上并不呈真正的镜像对称....
但是,这种结合不对称、解剖学和偶然性的进化论机制并未提供一种充分的解释,以说明蜗牛的右旋何以会成为主要的旋向....
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