Meeting life's necessities is all about maintaining homeostasis at many levels. For example, cells continually use ATP to do work, so we need to renew our food supply through consumption of food, and waste must be excreted. Failure on one end leads to starvation, failure on the other leads to toxicity or infection. Then there are emotional needs and wants; the need for safety and security, the need for self-confidence, the need for relationships, and so on.

Failure to accommodate needs on any level will lead to imbalance, whether detrimental or fatal.

See also Maslow's Hierarchy of Needs.

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.