The ratio of, or difference between, your arm-span and your height is your Ape index. According to the climbing oriented site ( the scale is measured in inches.

Measure yourself against a wall, or tall friend. Then perform your best yogic side-bend touching the floor keeping your shoulders nice and perpendicular. Note the position of your top hand.

If you have an arm span less than your height, you have a negative ape index. If they are similar, you are normal. If you have a wider arm span than you are tall, you have a positive ape index.

Positive differences of a hand or more are significant gibbon evidence and you may receive cruel, yet possibly deserved, pet-names like monkey-boy. Compare this to the predatorial (T-Rex) -- or is that rodent-like? -- features of the very negative ape indexed individuals.