[rlanday]

Citation needed on both points. Most evidence points to IQ scores being valid measures of intelligence, in that they have some predictive power, especially for average life outcomes for groups of people, and are mostly stable throughout life. For example, look up the Study of Mathematically Precocious Youth, which examines life outcomes based on SAT scores at age 12.

[david927]

valid measure ... some predictive power

I'm not sure if those two belong in the same sentence. If we were to come up with a point system that measured beauty in women, for example, you could measure pronouncement of cheekbones and thickness of lips, etc. While Angelina Jolie would score well, so would Jocelyn Wildenstein, and Emma Watson would score poorly. Such a system might have "some predictive power" for large population sizes, but could never measure "beauty".

Intelligence is qualitative, like beauty, not quantitative, and therefore could never be expressed individually as a number. We would do well to bear that in mind.