The Small but Complex Brain of Victoriapithecus Revealed
Researchers from Duke University, North Carolina, announced this month that they have successfully reconstructed the brain of a 15 million year old monkey. The brain shows an unexpected level of complexity, despite its small size, and is changing our ideas about how brain size and intelligence are linked.
Victoriapithecus was first identified from fossils recovered from Maboko Island, Lake Victoria, Kenya in the 1990s. It lived 15 million years ago and belongs to the lineage that eventually gave rise to apes and ultimately us. In fact the evolutionary history of the Old World Monkeys has been one of consistent growth in brain size and complexity but deciding which came first has long been something of a chicken-and-egg problem for palaeontologists. Calculating brain volume from fossils is hard enough but judging complexity is almost impossible. Now new techniques are allowing us to glimpse the brains of extinct animals like Victoriapithecus.
By micro-CT scanning the fossilised brain case of the monkey the researchers were able to create a computer-generated reconstruction of the skull. This included impressions within the skull which hinted at the size and shape of the brain. What it revealed was that Victoriapithecus actually had a far smaller brain than modern monkeys of a similar body size, about half the volume in fact at only 36 cubic cm. However, its olfactory bulb, the part of the brain responsible for processing smells, was nearly three times larger then expected. The brain surface also showed a complex pattern of wrinkles suggesting that despite its small size it was still highly complex. This is fascinating because in most primates the sense of smell has been severely reduced to make way for other brain development, meaning that Victoriapithecus may well have had a better sense of smell then any living monkey.
The other major conclusion that can be drawn from this study is that brain size alone is not always an accurate predictor of complexity. This ties in well with another debate currently raging in anthropology about the mysterious ‘hobbit’, Homo floresiensis which had a relatively tiny brain volume and yet used tools and made fire. Now it seems that there is a precedent in the primate fossil record for a small but highly developed brain and no reason to think that a smaller volume alone makes for a less intelligent animal.
Reference: Gonzales, L.A., et al. 2015. Cerebral complexity preceded enlarged brain size and reduced olfactory bulbs in Old World monkeys. Nature Communications. 6. doi:10.1038/ncomms8580
Featured Image: Wikimedia Commons