“普遍共同祖先”是說所有陸地生命在基因上都是相關聯(lián)的,，用達爾文的話說就是,，都來自某種“溫暖的小池塘”,。這種觀點已成為現(xiàn)代進化論的中心思想。關于“普遍共同祖先”的經典證據很多,，但大都是定性的,，而且該理論也很少接受正式的、定量的驗證,。
“普遍共同祖先”觀點（簡稱“UCA觀點”）因很多生物中大量橫向基因轉移的存在而受到質疑,。Douglas Theobald將“UCA觀點”稱之為一個正式假設,，并利用對普遍保守蛋白的序列所做的Bayesian統(tǒng)計分析對其進行了驗證，同時還將所獲得的結果與其他模型（在這些模型中,，基因相似性并不被假設能夠反映系統(tǒng)發(fā)生上的相關性）進行了對比,。
最后的結果是，“UCA觀點”勝出,。生命的單一起源的可能性要遠遠大于任何其他假設,。（生物谷Bioon.com）
生物谷推薦原文出處：
Nature doi:10.1038/nature09014
A formal test of the theory of universal common ancestry
Douglas L. Theobald 1
1 Department of Biochemistry, Brandeis University, Waltham, Massachusetts 01778, USA
Universal common ancestry (UCA) is a central pillar of modern evolutionary theory1. As first suggested by Darwin2, the theory of UCA posits that all extant terrestrial organisms share a common genetic heritage, each being the genealogical descendant of a single species from the distant past3, 4, 5, 6. The classic evidence for UCA, although massive, is largely restricted to ‘local’ common ancestry—for example, of specific phyla rather than the entirety of life—and has yet to fully integrate the recent advances from modern phylogenetics and probability theory. Although UCA is widely assumed, it has rarely been subjected to formal quantitative testing7, 8, 9, 10, and this has led to critical commentary emphasizing the intrinsic technical difficulties in empirically evaluating a theory of such broad scope1, 5, 8, 9, 11, 12, 13, 14, 15. Furthermore, several researchers have proposed that early life was characterized by rampant horizontal gene transfer, leading some to question the monophyly of life11, 14, 15. Here I provide the first, to my knowledge, formal, fundamental test of UCA, without assuming that sequence similarity implies genetic kinship. I test UCA by applying model selection theory5, 16, 17 to molecular phylogenies, focusing on a set of ubiquitously conserved proteins that are proposed to be orthologous. Among a wide range of biological models involving the independent ancestry of major taxonomic groups, the model selection tests are found to overwhelmingly support UCA irrespective of the presence of horizontal gene transfer and symbiotic fusion events. These results provide powerful statistical evidence corroborating the monophyly of all known life.
