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I believe that this is generally true, and provable.

One of the hardest things to learn, for example, is a foreign language. If the language is drastically different from one's mother tongue, then it generally takes adults about 10 years of casual study, or three years of intense study. I think this qualifies learning a second language as an outstanding achievement. Many adults try and give up, and the vast majority never progress past fluency to native-level (partly for lack of trying). By many objective measures too, it's a difficult task; I have probably stored many dozens of thousands of unique pieces of information in my brain related to my chosen language of study. Languages are complex in ways we don't even know we understand; Clifford is a big red dog, not a red big dog.

And yet, for the most part, every single person ever born learns language. Even people born with severe cognitive disabilities generally succeed at learning language.

So while I accept there is a strong correlation between genetics and measures such as IQ, I really do find it hard to believe that there is anyone who is truly incapable of learning basic calculus, or Python, or how to play the guitar. In practice, it doesn't seem this way, but every time I think about this issue I can't help but consider that out of a sample size of 1 billion people randomly born in China, pretty much 1 billion of them successfully learned Chinese.