I now believe Neanderthals had an IQ of at least 85, not 70 as I had estimated earlier.

Why at least 85?

According to this article, until about 50,000 years ago, Neanderthals were more technologically advanced than AMH (Anatomically Modern Humans).

This suggests their IQs were higher than the AMH who lived before the upper Paleolithic.

Before the upper Paleolithic, I suspect all AMH resembled Bushmen, pygmies, and Australian Aboriginals, and I would guess these have a genetic IQ of 80, so Neanderthals were likely at least 85 to have had better tools

But why did Neanderthals suddenly fall so far behind?

It seems the shape or position of their larynx prevented fully modern speech so they never acquired the advanced language that AMH enjoyed.

This also may explain why AMH was also so primitive before 50,000 years ago, yet suddenly so advanced after 50,000 years ago, despite no noticeable change in brain size. Perhaps prior to around 50,000 years ago, the AMH larynx resembled that of Neanderthal’s in its form or position.

Perhaps scholar Richard G Klein was right about a genetic mutation causing behavioral modernity, but instead of a mutation in the brain, as Klein argues, it was a mutation in the neck.  This mutation produced fully modern speech allowing us to pool our huge brains and share ideas, creating a collective intelligence that was far smarter than any one individual.

It would also explain why Neanderthals stayed so primitive, despite having such big brains. It may even explain why shortly after the Upper Paleolithic Revolution, brains suddenly started shrinking after millions of years of explosive growth.  Advanced language and the huge cultural knowledge it had produced, had made individual genius redundant, and huge metabolically expensive brains, a pointless and expensive liability.

Seldom has one theory so parsimoniously explained so many mysteries.

In order to test my hypothesis, we would need to see neck bones from AMH prior to the Upper Paleolithic Revolution, to see if they resemble Neanderthal’s.

For more on this, start watching at 6:48 in the below video

And at 3:30 of next video: