Complex sentence: In the 19th century, the advances in cell theory in biological science encouraged this view and the evolutionary theory of Charles Darwin (1859) promised a mechanistic explanation for the origin of species on account of natural selection.
Split into simpler sentences: In the 19th century, the advances in cell theory in biological science encouraged this view. The evolutionary theory of Charles Darwin (1859) is a mechanistic explanation for the origin of species by means of natural selection.