Was this small brain able to think big?

Jay Ingram, Toronto Star
Remember Flores man (actually a woman)? Flores "person" is a skeleton that was found last year on the island of Flores in Indonesia. It was a sensational discovery then, but has been made even more exciting this week with revelations about his brain.

This new species appeared to live as recently as 13,000 years ago and stood only about a metre tall. There hadn't been a hominid that small on the Earth for millions of years. But despite its small brain, it appeared to have used stone tools and controlled fire. In other words, small-brained or not, it was smart.

The discovery raised all kinds of questions. Where did this creature come from? The only sensible idea seemed to be that it had descended from Homo erectus, an ancestor of ours practically as big as we are. The theory was that some Homo erectus individuals migrated to the island, and over time shrank due to the well-known effect that tends to reduce the size of mammals that are island-bound.

But if that was the case, how was Flores man able to retain its intelligence in the face of a dramatic reduction in brain size? Does that mean it's possible to stay smart with less brain?

That wasn't the only controversy. Teuku Jacob, the grand old man of Indonesian archeology, examined the skull and immediately proclaimed it to be a fully modern human suffering from microcephaly, a disorder of development that leaves the skull, and the brain within, shrunken and deformed. According to Jacob, it was anything but a new species.

The report, published Thursday, addresses this very criticism and concludes that Jacob was wrong, that Flores man was not a microcephalic and does indeed bear a strong resemblance to Homo erectus, but with some surprising differences.

Dr. Dean Falk of Florida State University came to those conclusions by analyzing virtual endocasts of a variety of skulls, including a microcephalic, Homo erectus, modern human and Flores. Endocasts are usually made by pouring liquid rubber into a skull. When the rubber hardens, it bears the imprint of marks on the inside of the skull that were left there by the brain. The endocast is a surrogate for the original brain.

In this case, the Flores skull was so fragile that the researchers were forced to resort to a virtual endocast made by scanning the inside of the skull. Falk says the resulting "brain" was one of the most surprising she has ever seen (see image at right).

First, and most important, it is radically different from the microcephalic specimen she compared it to. This isn't a conclusive denial of Jacob's claim that Flores is nothing new — one skull isn't enough — but Flores and the microcephalic are so different it's hard to imagine how they could be one and the same.

What's more interesting is the comparison of Flores with Homo erectus, the species that was suggested to have been its ancestor. The two brains are worlds apart in size: Flores's brain is less than half the volume of the Homo erectus brain (and less than a third as big as a modern human brain). Even so, Falk was shocked to discover that this tiny brain had very well developed frontal lobes, parts of the brain that are, at least in us, associated with complex thinking and planning.

So, although the Flores brain was small, even by the standards of hundreds of thousands of years ago, it looks modern. Not as modern as our brains, but more advanced in some ways than Homo erectus, the species from which it is supposed to have evolved.

But did it? In the light of these new insights into the brain, Falk and the Australian archeologists who discovered Flores are stressing that there is another possibility: Flores man and Homo erectus might both have descended from an as-yet-undiscovered small-brained, small- bodied ancestor. That creature's descendants would have split into the two species, one small, one tall.

There's talk of searching on other Indonesian islands for the remains of that hypothetical ancestor, or for more Flores man. It's an exciting time, partly because the human family tree is branching out wildly in all directions, partly because these new fossils are raising new questions about brain size and intelligence.

How smart can a small brain be?