Tell the doneness of red meat

We don't eat any red meat at MM house but I found this is fascinating.

""Put the tips of your first finger and thumb together lightly, then use your opposite hand to squeeze the fleshy bit of the palm just below the base of the thumb. That is the consistency of rare meat. If you switch to thumb and second finger, the pad of your hand actually feels more solid, and that's the texture of medium-rare. Thumb and third finger is medium; thumb and pinky is well done. Clearly this is what they are talking about when they say opposable thumbs are a sign of our evolution (Link).""