The length of your arms relative to your height. Typically:

Da Vinci’s classic Vitruvian man has an arm span equal to his height and therefore an ape index of 1. An ape index greater than 1 (arm span longer than height) seems to be helpful for rock climbers, swimmers (Michael Phelps = 1.06), boxers, professional basketball and goalkeeping.

It’s also known as the gorilla index though I couldn’t actually find a measure for gorillas remarkably. A quick calculation shows for an average male gorilla at 1.75m tall and arm span of 2.45m that the gorilla index for a real gorilla would be = 2.45 / 1.75 = 1.4. I’d definitely fancy the gorilla in rock-climbing and boxing…

It’s sometimes calculated as arm span minus height, that would give gorillas a ridiculous: +70

I have not been able to figure out if your ape index changes from a child to adult though it seems like it might.

Sketchplanations tagged with gorilla