Reductionists would answer that a horse isn’t ultimately different in kind from a chunk of granite; the horse is just a more complicated effect of the moving and material causes that physics investigates. This view flattens life down to more general facts about patterns of matter and energy.
Likewise, reductionists will say that human beings aren’t irreducibly different from horses: politics, music, money and romance are just complex effects of biological phenomena, and these are just effects of the phenomena we observe in nonliving things. Humans get flattened down along with the rest of nature.