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The clever design of crypts is a direct consequence of how tissues are renewed by stem cells, the “parent cells” in the body. This is particularly important because, given how much material we digest, the lining of the colon is forever being replenished. A few stem cells sit at the base of the crypt and divide once per week to produce colon tissue cells. As these cells become more differentiated and move up the crypt, their progeny divide more and more quickly. By the time they reach the top of the crypt they are dividing around once per day, until they eventually die at the hands of apoptosis, a self-destruct program built into every cell.

My later work showed how this cellular structure, with a few slowly dividing stem cells at the base of a pocket, and the fastest dividing cells at its top and closest to death, puts a brake on evolution. This is precisely why the colon is populated with crypts. Mother Nature has honed their design to provide fewer opportunities for tumors to evolve. You can actually prove that these structures, which are seen in tissues with high turnover, have optimal anticancer properties. By washing out the mutations from the fastest-dividing cells as quickly as possible, cancer is delayed. That leaves only the rare and relatively slowly dividing stem cells to be really vulnerable to cancer causing mutations.

Excerpted from page 148-149 of ‘Super co-operators ’ by Martin Nowak