True, things go wrong with our bodies, with results that range from the tragic to the merely expensive or inconvenient.
“The human eye is a well-tread [sic] example of how evolution can produce a clunky design,” writes Professor Lents.
In a physical world there will be design constraints, so it is only realistic to expect tradeoffs.
Vertebrate eyes work reasonably well, Richard Dawkins conceded, but “it is the principle of the thing that would offend any tidy-minded engineer!”
The key lies in a triple-layered structure and a protein called osteopontin.