behavior is allowed and produced by physical matter. Fight/flight, love, mate preference, incest avoidance, motherly love, etc etc are all just as physical as kidney function. Parts of our brains are dedicated to producing and directing behavior. Almost any behavior requires complex, unique interactive brain activity, many with distinct but overlapping chemical and neurological structures.
Facial detection happens in the fusiform gyrus, an adaptation that produces specialized behavior. the only thing known to create Specialized and functionally complex machinery is evolution by natural selection, or GENETIC. hundreds of human behaviors are universal, like smiling, thats genetic too.
infact we likely share behaviorial genes with other apes AND mammals, well, not likely we do.