Brains - big and little

Of course, Brett's big brain didn't do him much good. But, in the normal course of events, isn't a big ole brain the way to go? We humans are certainly proud of our large reasoning organs - couldn't be biased, could we? A new paper in the online journal BMC Biology (and referenced at ScientificAmerican.com) takes a look at brain/body sizes over primate history and concludes that evolution hasn't always trended toward the giant economy size.

That conclusion is particularly significant in our interpretation of one little guy - the hobbit. No, not Frodo. And actually, not a guy either. The small female hominid discovered in Indonesia in 2004 and christened Homo floresiensis by her finders and the "hobbit" by the popular media has a brain size about 1/3 that of a modern human. Since the fossils are only about 13,000 years old, the tiny-brained hobbit and her ilk would have had to coexist with their big-brained cousins for almost 200,000 years. A number of ideas have been advanced to explain the find, with some contending that H. floresiensis had adapted toward a smaller size because of their island habitat and others claiming that the specimen simply represents a malformed individual. Still others have suggested that the little lady is the culmination of an ancient lineage that, for whatever reason, had evolved toward smaller brain and body size.

The researchers, led by Cambridge's Stephen Montgomery, examined sizes of bodies and brains of 50 primate species, 35 living and 23 extinct, and concluded that, while there has been an overall trend toward increased brain size, there are certainly exceptions in some lineages. The earliest primate brains were little more than a tenth of a gram. The Cadillac today, of course, is the human brain which averages around 1.3 kg, and over the extent of primate history there has been an average increase in brain size in the neighborhood of 2.5% per million years. However, this is by no means universal, and decreases are the rule along some lines. In fact, the researchers conclude that the decrease in brain size seen in our little hobbit friends are "not unusual in comparison to these other primates."

So, good news for the little lady. Still in the club. Take your little hat off and take a bow.