Fingers are meat stripes?

Well, kinda.

Much thanks to this video.

You, presumably, know that tigers have stripes, leopards have spots, and so on. You never see a tiger that is spotted or ticked instead of striped, for example. So, why is that? How do the cells in a tiger’s skin “know” to form stripes instead of some other pattern?

Well, Alan Turing figured that one out. Basically, it’s a matter of an “activation diffusion system”. Essentially, you need two components. One, the activator, turns on the feature (pigmented skin cells, when you’re talking about stripes), and the other, the inhibitor, turns the feature back off. The substance or cell type that makes the “turn on” component also makes the “turn off” component. And the “turn off” component can only stop *new* “turn on” components, not existing ones.

So, depending on how fast and in what ways the “turn on” and “turn off” components spread through (in the case of stripes and spots) the developing skin, you will, mathematically, get different patterns. If the “turn off” components spread fairly fast, for example, you’ll get fairly small spots, while if they move more slowly, you are more likely to get larger patterns like long stripes.

And fingers? Work more or less the same way. It’s a little more complex–there is more than one set of activators and inhibitors involved–but, essentially, your body makes fingers about the same way that a tiger makes stripes in its skin.