 Although the roots of careful observation and experimentation of the natural world go back to ancient times, study of animal behavior remained largely anecdotal until long after the scientific revolution. Animals were, of course, widely used in pursuit of answers to anatomical, physiological, and embryological questions. Vivisection was carried out by such ancient luminaries as Galen and there was a resurgence of the practice in early modern times (Bertoloni Meli 2012). Descartes himself practiced and advocated vivisection (Descartes, Letter to Plempius, Feb 15 1638), and wrote in correspondence that the mechanical understanding of animals absolved people of any guilt for killing and eating animals. Mechanists who followed him (e.g. Malebranche) used Descartes' denial of reason and a soul to animals as a rationale for their belief that animals were incapable of suffering or emotion, and did not deserve moral consideration — justifying vivisection and other brutal treatment (see Olson 1990, p. 39–40, for support of this claim). The idea that animal behavior is purely reflexive may also have served to diminish interest in treating behavior as a target of careful study in its own right.