Theissen Günter
Department of Genetics, Friedrich Schiller University Jena, Jena, Germany.
Theory Biosci. 2009 Mar;128(1):43-51. doi: 10.1007/s12064-009-0058-z. Epub 2009 Feb 18.
Since 150 years it is hypothesized now that evolution always proceeds in a countless number of very small steps (Darwin in On the origin of species by means of natural selection or the preservation of favoured races in the struggle of life, Murray, London, 1859), a view termed "gradualism". Few contemporary biologists will doubt that gradualism reflects the most frequent mode of evolution, but whether it is the only one remains controversial. It has been suggested that in some cases profound ("saltational") changes may have occurred within one or a few generations of organisms. Organisms with a profound mutant phenotype that have the potential to establish a new evolutionary lineage have been termed "hopeful monsters". Recently I have reviewed the concept of hopeful monsters in this journal mainly from a historical perspective, and provided some evidence for their past and present existence. Here I provide a brief update on data and discussions supporting the view that hopeful monsters and saltational evolution are valuable biological concepts. I suggest that far from being mutually exclusive scenarios, both gradual and saltational evolution are required to explain the complexity and diversity of life on earth. In my view, gradual changes represent the usual mode of evolution, but are unlikely to be able to explain all key innovations and changes in body plans. Saltational changes involving hopeful monsters are probably very exceptional events, but since they have the potential to establish profound novelties sometimes facilitating adaptive radiations, they are of quite some importance, even if they would occur in any evolutionary lineage less than once in a million years. From that point of view saltational changes are not more bizarre scenarios of evolutionary change than whole genome duplications, endosymbiosis or impacts of meteorites. In conclusion I argue that the complete dismissal of saltational evolution is a major historical error of evolutionary biology tracing back to Darwin that needs to be rectified.
150年来，人们一直假设进化总是以无数个非常小的步骤进行（达尔文在《通过自然选择的物种起源，或在生存斗争中对有利种族的保存》，默里，伦敦，1859年），这种观点被称为“渐变论”。很少有当代生物学家会怀疑渐变论反映了最常见的进化模式，但它是否是唯一的模式仍存在争议。有人认为，在某些情况下，生物体可能在一代或几代内发生了深刻的（“跳跃式”）变化。具有深刻突变表型且有可能建立新进化谱系的生物体被称为“有希望的怪物 ”。最近，我主要从历史角度在本期刊上回顾了“有希望的怪物”的概念，并提供了一些关于它们过去和现在存在的证据。在这里，我简要更新一下支持“有希望的怪物”和跳跃式进化是有价值的生物学概念这一观点的数据和讨论。我认为，渐变进化和跳跃式进化远非相互排斥的情况，两者都是解释地球上生命的复杂性和多样性所必需的。在我看来，渐进变化代表了通常的进化模式，但不太可能解释所有关键创新和身体结构的变化。涉及“有希望的怪物”的跳跃式变化可能是非常罕见的事件，但由于它们有可能产生深刻的新事物，有时会促进适应性辐射，所以它们相当重要，即使它们在任何进化谱系中出现的频率可能不到百万分之一。从这个角度来看，跳跃式变化并不比全基因组复制、内共生或陨石撞击等进化变化的奇特情况更离奇。总之，我认为完全摒弃跳跃式进化是进化生物学可追溯到达尔文的一个重大历史错误，需要加以纠正。
