进化偶然性论题是美国生物学家古尔德（Stephen Jay Gould）提出的关于进化趋向的一种理论。传统达尔文主义认为生物进化是以自然选择为根本动力，在适应的作用下渐进演化。古尔德则认为，生物进化模式是间断平衡，即物种更多是在偶然因素作用下呈现长期的稳定不变与短暂的巨变交替的态势。进化并不全然是达尔文言说的累积渐进，进化是无方向性和不可预测的，在路径上不同于线性进化模式，会受到环境等事件的影响而呈现不可预测的趋向。进化偶然性论题是古尔德在20世纪70年代提出的，他从新的视角分析了进化的模式和趋向。在古尔德看来，基于物种累积性的演化模式不利于解释环境巨变造成的进化异常。根据布尔吉斯页岩所表现的寒武纪大爆发后物种的骤然变化，他提出：物种是在“间断平衡”下进化的，即大部分时间物种保持性状不变，随后在突然的环境事件之后，物种出现大规模的突然的变化。因为间断平衡发生的一个重要条件是偶然的环境事件，所以古尔德提出了一个重要的命题：进化偶然性论题，即进化是在偶然的大规模环境事件的影响下发生的；不同的环境事件将产生不同的进化结果。因此，如果“重播生命进化磁带”，物种将进化出完全不同的结果。 古尔德的进化偶然性论题提出后，得到了一定程度的认可，但同时也有很多学者反对。比如，偶然性进化因素能否说进化就是偶然的？进化偶然性论题是确定的理论还是假说？进化是适应性选择的结果还是偶然性变异的结果？进化是进步的还是非进步的？基于讨论，重播生命进化磁带的思想实验存在很大不确定性，这种论题模型与进化史实不完全相符，尚且不能论定进化的偶然性。 本文认为，古尔德进化偶然性论题虽然在一定程度上为进化中化石的断缺提供解释效力，但是并不能说明整个进化都是在偶然因素为主导下展开的。古尔德的进化理论自身存在着理论缺陷，并不足以取代既有的进化理论。他将进化的动力归之于历史中的偶然大事件，没有意识到整体偶然性与过程偶然性的不对等， 不同概率事件的叠加不能简言为整个生物群体进化的偶然。生物进化存在偶然变异，但进化中也有诸多非偶然因素。受环境及物种自身的影响，在微观程度上还会受到发育的限制，如物理限制、形态发育限制和发育史的限制，等等。此外，“环境——进化——发育”之间存在非单向制约关系，整个生态系统是一个网络系统，物种与环境之间是互动的，自然选择使物种能在变异过程中提升适应度，同时也会在适应环境的同时施加力量于环境，环境的变化会受到物种变异的影响。因此，断言一切进化具有偶然性是不成立的。

The evolutionary contingency thesis is a theory of evolutionary tendency put forward by American biologist Gould. It is generally assumed that natural selection is the fundamental motive for Darwinism.But American biologist Gould proposed that the evolutionary state of life was Punctuate Equilibrium,the species were largely affected by occasional factors and presented a long-term stability and short-term change. Evolution was not all the way Darwin's idea of gradual accumulation, but undirected and unpredictable. For the path, it is different from the linear evolution mode. It may be unpredictable due to the influence of environment and other big events. Gould's evolutionary contingency is based on a series of paleontological discoveries, mainly emphasizing evolution is contingency and non-directional. The topic of evolutionary contingency was put forward by Gould in 1970s. He analyzed the patterns and trend of evolution from a new perspective. In Gould's view, Evolutionary patterns based on species accumulation are not conducive to explaining evolutionary anomalies caused by environmental changes. According to the abrupt change of species after the Cambrian outbroke in the Burgess shale, he proposed that the state of species evolution was "Punctuated Equilibrium": that is, most of the time, species remain unchanged,then,after sudden environmental events, species suddenly appear on a large scale. As the accidental environmental events is an important condition for the Punctuated Equilibrium, Gould put forward an thoughtful proposition: the evolutionary contingency thesis. That is, evolution happens under the influence of occasional large-scale environmental events; Different environmental events can produce different evolutionary results. Therefore, if "replay the tapes of life", the species will evolve a completely different outcome. However, there are a lot of controversies on Gould's theory of chance evolution. For example, can we say evolution is accidental because of chance evolutionary factors ? Is the theory of evolutionary contingency a definite theory or a hypothesis? Is evolution the result of adaptive selection or the result of accidental variation? Is evolution progressive or non progressive? Accidental environmental events do not make evolution limited by laws. And Gould's thought experiment of rebroadcasting the tapes of life evolution has great uncertainty, besides, this model is not consistent with the history of evolution, so we can not regard evolution as contingent. Gould's evolutionary contingency thesis, though, to some extent, provides explanation for the breaking up of fossils in evolution, it doesn't mean that the whole evolution is based on accidental factors. And Gould's theory of evolution has its own theoretical defects, which is not enough to replace the existing theory of evolution. He attributed the power of evolution to the accidental events in history, and did not realize the inconsistency between the whole contingency and the process contingency. The superposition of different probability events can not be simply an accident of the whole biological group evolution. There are occasional variations in biological evolution, but there are also many non accidental factors in the process of evolution. Under the influence of environment and species, it will be constrained by development, such as physical constraint, morphological development constraint and phylogenetic constraint.In addition, the modern development of evolution also shows that the relationship between ecology, evolution and development is not unilateral restriction, but interaction,the whole ecological system is a network system. Natural selection enables species to enhance their fitness in the process of variation,at the same time, it will react to the environment while adapting to the environment. Changes in the environment are affected by the variation of the species. Therefore, it is inaccurate to assert that all evolution is accidental.