 According to the same biology that embraces natural selection, however, behavior has muscular causes, which in turn have neural causes. Barring neural events that are inexplicably in violation of biological constraints on their conditions of activation, there must be an adequate physical cause of every link in the causal chain leading to behavior. Thus, it is easily understood how certain kinds of neural events can be selected for. Epiphenomenalists hold that conscious events are effects of (certain) neural events. Thus, it fits well in their view that we have the conscious events we do because the neural causes of these events have been selected for. Indeed, if neural causes of behavior are selected for, and are sufficient causes, there cannot be any further effect attributed to natural selection.