Most people associate big brains with intelligence—and at first glance it’s true, at least when comparing different species of mammals. But upon further investigation, the relationship between brain size and intelligence levels is more complicated. For example, biologists point out that brain size relative to body mass (also called the encephalization quotient, or EQ) is a better reflection of cognitive capacity because as an animal’s body gets larger, more of its brain must be devoted to maintaining and controlling the body.
A new study on Neanderthal brain structure indicates that, in addition to EQ, brain organization is also important for determining cognitive capacity.1 Neanderthals possessed nearly the same brain size as modern humans. (They also had a greater body mass and, consequently, a smaller EQ compared to modern humans.) However, Neanderthal brain structure—such as the shape of the parietal lobe—varied from that of modern humans (see my book Who Was Adam?). Moreover, as discussed in a past episode of our Science News Flash podcast, the development of modern human and Neanderthal brains after birth also differs.
Researchers from the UK have identified other differences. They measured the orbit size (eye socket) of 32 anatomically modern human and 12 Neanderthal skulls from Europe and the Near East. These remains date between 27,000 and 75,000 years in age. The researchers used orbit size as a proxy for eye size, noting that a tight relationship exists between primate eye size and the cortical primary and downstream visual areas of the brain. Neanderthals possessed larger eye sockets than modern humans. This means that a greater portion of their brain area was devoted to vision.
Additionally, the researchers note that Neanderthals had a much larger body size than modern humans, which would have required that a greater area of their brain be devoted to body maintenance and control, leaving a much smaller part of the brain devoted to other processes and activities. Based on these two observations the researchers concluded that a limited volume of this hominid’s brain was used for forming social networks.
Among primates, scientists have discovered a relationship between brain volume and bonded group size. The rationale for this phenomenon is that when an individual is part of a bonded group, he/she must keep track of other individuals in the group—requiring brain activity. The greater the amount of brain area available, the bigger the social network in which the individual can take part.
Thus, it is no surprise that the social networks employed by modern humans must be much larger and more elaborate than those of Neanderthals. Smaller networks would have limited Neanderthals’ ability to trade for resources outside the region they occupied, restricted their foraging range, and reduced their capacity to retain newly learned innovations.
This research helps support a key prediction of RTB’s human origins model by demonstrating a fundamental difference between humans and Neanderthals. Instead of viewing hominids as evolutionary transitional forms, RTB’s biblical model holds that hominids, including Neanderthals, were animals made by God. They possessed intelligence and emotional capacity, but lacked the image of God—a quality associated only with anatomically modern humans (Genesis 1:26–27). Therefore, we expect that Neanderthals would have displayed behavior that is qualitatively different from, and inferior to, that of modern humans. This study provides confirmation of this expectation.