The Fibonacci ratio shows up a lot in naturally evolved designs.
The length of the bones in the hand and fingers show the Fib ratio in
their lengths. Also the length of the hand compared to the length of
the forearm. The distance from the floor to a human's naval as
compared to the distance from the naval to the top of the head is
Fib. The placement of the F holes on a violin are determined using F.
And, it's not just the ratio, it's the actual numbers that also
recur. The number of rows on a seed head of wheat and the number of
seeds per row.
Livio's book, "The Golden Ratio," can be dense reading. Here's a
quick entertaining read loaded with examples. "Fascination Fibonaccis
- Mystery and Magic in Numbers," by Garland. You can get a used copy
for as little as $1.62
(Amazon.com product link shortened)