The number phi (ϕ ), often known as the golden ratio, is a mathematical concept that people have known about since the time of the ancient Greeks. Many of the bones in the human body use The Golden Ratio. Our fingers have three sections. The proportion of the first two to the full length of the finger gives the golden ratio (with the exception of the thumbs). We can also see that the proportion of the middle finger to the little finger is also a golden ratio. Using the index finger as an example we notice that every segment of the finger gets larger as we move from the tip to the wrist. The segments of your index finger are in a ratio of 1.618 which also means that the numbers tie in with The Fibonacci Sequence.
The proportion of index finger in Geogebra