[AmericaUnited]

The human back, with its rather appalling record of longevity and its predilection to failure;

Do you mean the backs of overweight Americans who don't exercise, eat crap, and have back trouble by the time they're 45, or the backs of older Okinawans who do tough manual labor well 100?

[Junior]

Not just them. I pulled my back at age 22 while partaking in a Navy working party. I was young, skinny and in great shape. Eighteen years later and my back hasn't been the same.

As pointed out earlier, the human back is pooorly engineered.

[atlaw]

I see. So again, the designer is absolved because humans abuse their backs. That's two where you find the design itself to be blameless, and where you seem to be contending that proper care necessarily equals non-failure (a contention I'm sure a great many patients and doctors would find peculiar, especially with respect to colon cancer).

How about eyes? Do humans abuse their eyes too, thereby causing vision failures and the common need for corretive lenses?