Neanderthal brains measure up to ours—literally

Source: Ars Technica

Intelligence and brain size

When we talk about “intelligence,” we’re describing something complex and, frankly, nebulous; it’s impossible to really quantify, but that hasn’t stopped generations of scientists from trying. Researchers who study cognition break it down into specific areas:

• attention
• inhibition
• cognitive flexibility
• speech production and speech comprehension
• working memory
• episodic memory

Some of those abilities are associated with particular sections of the brain, but those relationships are often complicated.

So, when looking at brain size and intelligence, the differences among human brains are relatively small compared to the differences between a human brain and any other great ape brain. For example, our closest relatives, the chimpanzees, have brains that average just 400 cm³; the average adult human brain takes up about 1,350 cm³ (with a wide range from about 1,100 to 1,500 cm³).

Total brain volume is “empirically the best predictor of behavioral and cognitive abilities among primates,” but only when comparing different primate species. Within a species, the differences aren’t pronounced enough to matter.

Comparing species

If you’re comparing, say, crows to dolphins, you have to factor in the size of the brain relative to the size of the whole animal, which scientists call the encephalization quotient. According to Schoenemann and his colleagues, that metric is less relevant for primates, where absolute brain size is the dominant factor.

Early hominins

A group of early hominins called Australopithecus afarensis, who lived about 3.2 million years ago, had brains of about 500 cm³. That difference is large enough to suggest they were cognitively more like chimpanzees than like modern humans.

In contrast, the average Neanderthal had a brain capacity consistent with scoring about the same on cognitive tests as their Homo sapiens neighbors.