Evolutionary biology: The butt boggles the mind: Nature explores evolution of the anus

Darkfrog submitted, created time 2 months 4 days (www.nature.com)

It might not make for stellar dinner conversation, but it's a relevant question. When did multicellular organisms develop an anus? The first organisms to use guts--like modern cnidarians (formerly called coelenterates, meaning "one hollow cavity")--got by with just a mouth. (Feeling like you need to barf? They did too!) However, as the guts get longer, one hole becomes impractical.

"Just punch another hole in it" might seem like an obvious answer to anyone who's survived a kindergarten art class, but, from an evolutionary standpoint, it's pretty darn unlikely

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