[Serious] Why defecation?

[John 6IX Breezy]

First, pollution. Second, waste. Third, farts.

I think the place to begin is with a proper understanding of the digestive system, ingestive behavior, and fecal composition. For example, something like 50% of fecal matter is composed of bacteria; that's an important number. And other plants and animals, including other bacteria, tend to reuse our waste for their own benefit.

Nature tends to be is very conservative. It rarely lets anything go to waste. Whatever isn't used at the individual level is accounted for at the ecological level.

So I'm not sure I see the same problem you see.