Kluge

is an excellent book by Gary Marcus (isbn 978-0-571-23652-7). As usual I'm going to quote from a few pages:

The best science, like the best engineering, often comes from understanding not just how things are, but how else they could have been.

One molecule of DNA polymerase does its job in a perfectly straight-forward fashion, but the other does so in a back-and-forth, herky-jerky way that would drive any rational engineer insane. Nature is prone to making kluges because it doesn't "care" whether its products are perfect or elegant. If something works, it spreads. If it doesn't, it dies out.

What can evolve at any given point in time is heavily constrained by what has evolved before.

The vast majority of our genetic material evolved in the context of creatures who didn't have language, didn't have culture, and didn't reason deliberately.

What is recent is rarely fully debugged.

Our memory is organized to focus primarily on our own experiences.

Other studies have showed that people are more likely to accept falsehoods if they are distracted or put under time pressure.

Organisms tend to value the present far more than the future.

That which is clumsy is rarely reliable.

In physics, they have laws; in biology, we have gadgets [Francis Crick]

The value of imperfections extends far beyond simple balance, however. Scientifically, every kluge contains a clue to our past; wherever there is a cumbersome solution, there is insight into how nature layered our brain together; it is no exaggeration to say that the history of evolution is a history of overlaid technologies, and kluges help expose the seams.