Challenges have been proposed to the classical theory of origin cells of glioma, since the successful researches on neural stem cells and tumor stem cells.

神经干细胞和胶质瘤干细胞的研究成功，对早有定论的胶质瘤起源细胞学说发出了挑战。

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Whoever formulated the theory of the origin of the universe, it is just hypothetical and needs proving.

无论谁提出了宇宙起源的理论，它都只是一个假设，需要证明。

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Darwin had been working on his theory for over twenty years when he published " On the Origin of Species."

VOA: special.2009.12.01

Mother's Day marks the halfway point of Lent, and one theory of its origin is that it was marked by visiting the region's "mother church" or cathedral.

BBC: How much Christianity is hidden in British society?

Another theory of the origin of modern humans, known as the multiregional hypothesis, holds that earlier forms of humans originated in Africa and then slowly developed their anatomically modern form in every area of the Old World.

WSJ: Study Points to a Single, Original Language for All Humans

He landed, camped there, left and returned, studied, researched and conceived his earth-shaking theory of evolution, On the Origin of Species, in 1859.

FORBES: Connect