Others have mentioned using fictional positing etc, but if you want to rely on dice mechanics the Fudge system (which Fate descends from) kinda works like that. Every attribute or ability is on the same scale, and set the difficulty for a task on that scale. You roll with 4dF, where a dF is a custom die that has -1, 0, and 1. These are Fudge/Fate dice, and are actually fairly easy to find (unlike e.g. Genesys dice), easy to make yourself from blank dice, and it's also easy to convert from a standard d6 (1,2=-1, 3,4=0, 5,6= 1). Typically, you'll get a result somewhere from -2 to 2, so you'll achieve something that's similar in difficulty scale to your base skill/attribute, but you can sometimes get up to -4 or 4, so there's a chance of getting something beyond your capabilities by chance, just a rare one. This kind of mechanic, if you have a big enough range of values for an attribute, means that some characters will routinely succeed at tasks that other characters will never be able to accomplish.

I don't have the book on me right now, and I don't recall the exact numbers, but you can kinda do it how you like. You can set 0 for "baseline human", and a task of difficulty 0 is therefore something that is a challenge for a regular person but one they'll accomplish more often than not. "Smartest person in the universe" might be like level 6 on the scale - a level 3 task that a normal human could pass would be difficult for you to fail. "Very small" might take you to -2 or -3 where it's relevant. Overall, you can assign these values to any attributes you like - they don't have to be traditional statistics and skills, you can have them as Fate-style "aspects", just with a score assigned to them.