What Happened to the Hominids Who May Have Been Smarter Than Us?

A now-extinct race of humans - the Boskop - had big eyes, child-like faces, and an average intelligence of around 150, making them geniuses among Homo sapiens. From http://discovermagazine.com/2009/the-brain-2/28-what-happened-to-hominids-who-were-smarter-than-us/article_view?b_start:int=0&-C=

We’re drawn to the idea that we are the end point, the pinnacle not only of the hominids but of all animal life.

Boskops argue otherwise. They say that humans with big brains, and perhaps great intelligence, occupied a substantial piece of southern Africa in the not very distant past, and that they eventually gave way to smaller-brained, possibly less advanced Homo sapiens—that is, ourselves.

We have seen reports of Boskop brain size ranging from 1,650 to 1,900 cc. Let’s assume that an average Boskop brain was around 1,750 cc. What does this mean in terms of function? How would a person with such a brain differ from us? Our brains are roughly 25 percent larger than those of the late Homo erectus. We might say that the functional difference between us and them is about the same as between ourselves and Boskops.

[...]

There is another, again poignant, possible explanation for the disappearance of the big-brained people. Maybe all that thoughtfulness was of no particular survival value in 10,000 B.C. The great genius of civilization is that it allows individuals to store memory and operating rules outside of their brains, in the world that surrounds them. The human brain is a sort of central processing unit operating on multiple memory disks, some stored in the head, some in the culture. Lacking the external hard drive of a literate society, the Boskops were unable to exploit the vast potential locked up in their expanded cortex. They were born just a few millennia too soon.

Or perhaps they were simply hunted to extinction by our ancestors.

Should be noted that John Hawks take great issue with this:

The portrayal of "Boskops" in the Discover excerpt is so out of line with anthropology of the last forty years, that I am amazed the magazine printed it. I am unaware of any credible biological anthropologist or archaeologist who would confirm their description of the "Boskopoids," except as an obsolete category from the history of anthropology.

 See http://johnhawks.net/weblog/reviews/brain/paleo/return-amazing-boskops-lynch-granger-2009.html 

He goes on to note at http://johnhawks.net/weblog/reviews/brain/paleo/lynch-granger-big-brain-boskops-2008.html

what happened is that a small set of large crania were taken from a much larger sample of varied crania, and given the name, "Boskopoid." This selection was initially done almost without any regard for archaeological or cultural associations -- any old, large skull was a "Boskop". Later, when a more systematic inventory of archaeological associations was entered into evidence, it became clear that the "Boskop race" was entirely a figment of anthropologists' imaginations.

[...]

there has been a reduction in the average brain size in South Africa during the last 10,000 years, and there have been parallel reductions in Europe and China -- pretty much everywhere we have decent samples of skeletons, it looks like brains have been shrinking. This is something I've done quite a bit of research on, and will continue to do so, because it's interesting. But it is hardly a sign that ancient humans had mysterious mental powers -- it is probably a matter of energetic efficiency (brains are expensive), developmental time (brains take a long time to mature) and diet (brains require high protein and fat consumption, less and less available to Holocene populations).