the necessities of life

I learned that most basic human activities that are necessary for life are the 3 S's:

• Sex: to propagate the genes.
• Sleep: to recharge the mind and body.
• Sustenance: food and water to keep you alive.

All other human activity serves only to achieve at least one of these goals. For example, working lets a person buy sustenance. Art can either be work (which eventually leads to sustenance) or creative (which is necessary for sleep). Etc.

I'm skeptical. I don't know if this is really true or just a clever trick with alliteration.