Materialism claims that everything is physical; everything can be exhaustively described and explained in principle by physics. For over half a century challenges to materialism have focused on mental phenomena such as consciousness, reason, and value. The tacit assumption among most materialists – one shared by most of their critics – has been that more basic biological phenomena, such as metabolism and reproduction, do not pose a serious obstacle to the materialist program, that these can be easily accommodated within a materialist framework. But there is reason to think that this assumption is false. Thomas Nagel has recently argued that materialism cannot countenance biological phenomena at large. Like so many anti-materialist arguments, however, his focuses on mental phenomena. After explaining why this is a liability for him and other would-be critics of materialism, I advance an anti-materialist argument that appeals directly to biology. Materialism is false, it says, because our best empirical descriptions and explanations of biological phenomena appeal to biological organization or structure, and there is good reason to think that these appeals cannot be eliminated, reduced to, or paraphrased in favor of descriptions and explanations framed in exclusively physical terms. As a result, not everything can be described and explained exhaustively by physics. Materialism must be false. The reason, however, has nothing to do with mental phenomena specifically.