Materialist reductionism runs into all sorts of problems explaining such things as organisms on the basis of the properties of their constituent parts. This happens because materialism gets the direction of reduction wrong. A whole can account for the properties of its parts, but not vice versa. E.g.: a complete account of a salt molecule must include a full specification of the properties of its sodium atom; but a complete account of a solitary sodium atom cannot include a full specification of the properties of a salt molecule.
It’s not the tiniest conceivable parts that are basic, but the largest conceivable whole. The parts of reality supervene upon the whole of reality.
So reduction can work – if reality is causally coherent, it must – but only if, at least in principle, we reduce all things ultimately to God.