Some of these species are thought to be smarter than us, so you better be careful or you will end up the specimen in the zoo.
Contrary to pop media, there is also literally no clear evidence they even engaged in the most basic of symbolic behavior such as self adornment or even primitive art. [1] Now mostly disregarded efforts to show such were highly optimistic. This included things like bird bones being laid near a corpse = self adornment, or scratches on a cave floor = art. Even in what they did do - hunt, despite engaging in hunting for hundreds of thousands of years there are extremely high rates of traumatic injury among neanderthal corpses which suggests they never even managed to refine their hunting ability.
And the brain size : intelligence correlation is just so broken in so many ways. If you go based on raw size sperm whales should be, by far, the most intelligent species there is. If you go based on the ratio of brain matter to mass, ants should be, again by far, the most intelligent species there is. Suffice to say you're probably not too worried about being put in zoos by sperm whales or ants.
The point is that even in a time frame of a single century you're looking at very radical changes in intellectual ability between populations that would appear, on the surface, to be practically 100% identical. When you start talking about tens of thousands of years ago, it's impossible to do even begin to intelligently speculate based on anything other than achievement. And what did we achieve? As you mention, not much. And so the only justifiable explanation is that we probably didn't have that much going on upstairs until relatively recently.
I think the most interesting question is a direct spin off of yours. What triggered the intellectual spike? Was it in any way related to whatever caused the more contemporary spikes in intelligence? Why are IQs now decreasing and can global intellect fade away as rapidly as it emerged? Probably the most depressing possible solution to the Fermi paradox!
"You don't get anatomically modern humans until 30,000-50,000 years ago."
And this is wild speculation without any basis:
"And so the only justifiable explanation is that we probably didn't have that much going on upstairs until relatively recently."
Economic development is complex, it depends on a lot more than IQ. As a point of comparison, we could ask why did the Industrial Revolution only happened 200 years ago? If, as you suggest, homo sapiens have had high IQ for 50,000 years, then why didn't we have the Industrial Revolution much sooner?
But more so, you seem to imply, in response to the original article, that the mixing of homo species helped us develop a certain kind of IQ. But according to that theory, the most advanced people on Earth should be the aborigines of Australia, as they were the first group to mix with all the different homo species, as sapiens moved from Africa to Australia. But in fact, the aborigines of Australia were quite content with their lives, and felt no need to build civilizations, even though they certainly have high IQ, and they have the mix of genes you'd expect of humans outside of Africa.
About this:
"What triggered the intellectual spike?"
There was no spike in IQ. You have no reason to believe that. The development of culture and civilization have nothing to do with IQ. Large parts of the world remained completely primitive until recent centuries, even though those regions were full of high IQ homo sapiens.
I can't tell if you are trying to build a racial theory of history, but if you are, that idea has been debunked many times. All I can do is recommend that you read some of that debunking.
But most importantly of all this is where you find the first clear evidence of intelligence which rapidly expand outward: art, ceremonial burials, clear evidence of fishing, and much more. Some time after that you start to see the beginning of modern civilization with bladed weapons, pottery, agriculture, and so on. This is also one of the most likely time periods for the development of language, though that is something that is hotly debated.
I'm going to dodge the second part of your post for the sake of trying to keep the conversation on the up and up. If you have some clear message you'd like to convey, I'd be happy to get into that. It's a fun topic. However, please do drop the ad hominem.
"There are some other types of argument, similar to yours, that I've run into online. Some people insist that humans were genetically engineered by aliens. That argument is based on no evidence, though it does have the nice property that is not raced based. Some other people make a religious and/or spiritual argument, arguing that there is a universal consciousness and that it spread across the world 50,000 years ago. That has all the problems of any religious argument -- it could be true, but there is no evidence and no way to prove it."
There is nothing ad hominem about trying to clarify what sort of argument someone is making. So I am curious why that previous comment was downvoted?