There is no need to assume the supernatural.
They are machines based on what?
By definition, a machine is something build by humans, or any intelligent life form (because we extend the definition from our own experience as self defined 'intelligent life forms').
Living organisms and machines do share traits under our current frame of reference in modern science. But that doesn't mean cells are machines. The right framing would be 'cells exhibit behavior and certain internal relations that we can conceptualize them as machines', which is different from 'cells are machines'.
replyBy what definition?
replyAnyway, seems like an argument over said definitions rather than the underlying characteristics. The relevant question is whether they're purely physical objects behaving according to rules, which is being described as "machine," or whether there is something beyond that. Current understanding is contradictory: all indications are that cells and bodies are purely physical objects, except that there is this phenomenon of subjective experience which doesn't fit with that at all.