We tend to think of the atomic grain of human life as the individual. Realistically we are made of cells that live and die, and interact in a community of scarce resources - they have a life of their own.
Perhaps cells are to humans as humans are to x. x then is a single life form, made of cells (individual humans) that live and die, and interact in a community of scarce resources.
Moreover, x meets the biological criteria of a living organism. Reproduction is satisfied by evolution.
