Why is the idea of innate IQ still taken seriously if there's so little evidence for it? If intelligence is just the ability to think in a structured abstract way, doesn't it make sense to think of it as a skill developed over time? I mean, it's not hard to think of spending most of your time in a different mode of thought. I'd say that for most people their normal day to day tends to require concrete or social/emotional information processing.

If it seems that intelligence (specifically abstract structured thought) seems to stabilize early in life, maybe it's something that starts developing even earlier. A strategy for prioritizing, filtering, and processing information from a world of endless stimuli (of which abstract/structured would be only one such strategy) would start developing the moment we're born. By the time you're 10, you'd already have 10 years of "practice".