There's plenty of evidence for those who want to learn instead of split hairs.
I'd start with a search on "general intelligence factor".
Is this the 'g' factor? What studies do you find compelling? Any done after the early 1900s or on adults?
So you've got nothing to offer?
I answered your question clearly and in good faith.
The rest of your diatribe is US styled epistemic theatre I don't feel the need to engage with, so I didn't.
What exactly did your posts contribute?
You provided nothing but unsupported claims. Nobody else is doing your research for you.
It's the scientific consensus not somebody's pet theory. So you don't need to get answers from here, you can get them from Google.
It's the consensus among g-theorists. "The scientific consensus" on cogntive function is Not A Thing.
Are you really lmgtfy-ing on Hacker News?
Again, any evidence? What exactly is 'cognitive ability'? A hallmark of the lack of substantive argument is vague terms that can mean anything the speaker likes, and by not defining the term they prevent any substantive critique - nobody really knows what they're talking about (and usually, not the speaker either).
I highly doubt it's all or nothing. While there are likely variations in anything, they can be quite insignificant. For example, everyone, with tiny exceptions, can learn to speak & understand language, and write & read - highly sophisticated cognitive abilities. And they can improve those abilities through education.
These baseless generalities don't show much 'cognitive ability'.