Margulis L
Symp Soc Exp Biol. 1975(29):21-38.
The purpose of a scientific theory is to unite apparently disparate observations into a coherent set of generalizations with predictive power. Historical theories, which necessarily treat complex irreversible events, can never be directly tested. However they certainly can lead to predictions. The 'extreme' version of the serial endosymbiotic theory argues that three classes of eukaryotic organelles had free-living ancestors: mitochondria, basal bodies/flagella/cilia [(9 + 2) homologues] and photosynthetic plastids. Many lines of evidence support this theory and can be interpreted in relation to one another on the basis of this theory. Even if this theory should eventually be proved wrong it has the real advantage of generating a large number of unique experimentally verifiable hypotheses.
科学理论的目的是将明显不同的观察结果统一为一套具有预测能力的连贯的概括。历史理论必然要处理复杂的不可逆事件，永远无法直接进行检验。然而，它们肯定能够产生预测。连续内共生理论的“极端”版本认为，三类真核细胞器有自由生活的祖先：线粒体、基体/鞭毛/纤毛[（9+2）同源物]和光合质体。许多证据支持这一理论，并且基于该理论可以相互关联地进行解释。即使这一理论最终被证明是错误的，它也有一个真正的优势，即能产生大量独特的、可通过实验验证的假设。
