those are just issues in how intelligence is measured. As far as Neanderthals, its my opinion they were smarter than us. we just came from down south (not effected by sudden surge in ice age) and higher birth rates. The intelligence of neanderthals keeps getting revised up every time we learn something about them.

I've heard that there's archeological evidence that ancient sapiens engaged in long-distance trade, objects brought to places they shouldn't have been. Nothing like that was found with neanderthals. Not sure if this is due to having fewer samples of neanderthals, nor whether this reflects intelligence or something else (I think Harari or someone may have argued that it might be about eusocial myths enabling coordinating larger armies) but that's one contraindication.

Do you base your opinion on anything?

I'm no where near a subject matter expert, but I thought there was a mild correlation within humans?

https://en.wikipedia.org/wiki/Neuroscience_and_intelligence#...

I take your point on ravens and chimps, but surely whales are more intelligent than shrimps.

Are big people smarter than small people?

"I have no doubt that I am very stupid; but I must confess that I am unable to follow you. For example, how did you deduce that this man was intellectual?" For answer Holmes clapped the hat upon his head. It came right over the forehead and settled upon the bridge of his nose. "It is a question of cubic capacity," said he; "a man with so large a brain must have something in it."

> Some epidemiological research on the subject has shown that there is a small but statistically significant positive correlation between height and intelligence after controlling for socioeconomic class and parental education

[0]: https://en.wikipedia.org/wiki/Height_and_intelligence

General health is still a probable shared cause here, they're going to need to control for more than just socioeconomic class and parental education.

What happens, for instance, if they control for stamina (I'd predict the effect goes away)

As a rule of thumb, yes.

(children vs adults)