“That shouldn’t be there.” I was sitting in front of my computer, staring at a 3D model of a fossil called Krapina 17, the right side of the skull of an infant Neandertal that lived in Croatia 130,000 years ago. I was interested in what this and other fossils from the Krapina site could tell us about brains and growth in these extinct humans. Although I was initially concerned with the size and shape of this poor child’s brain, it was a small groove on the bone that grabbed my attention.
The inner surface of the skull reflects the size and shape of the brain it surrounds—brains themselves do not fossilize, but fine details like blood vessels and the brain’s wrinkly convolutions leave their imprints on the bony surface of the skull, like signatures scrawled on the sidewalk. Scientists have studied these impressions in humans, our fossil forebears and other animals for over a century, and so we have a decent idea of which wrinkles represent which brain structures, and where different amounts of blood get ferried into and out of the skull (there is so much blood in there). The groove I saw was too long and smooth to have been made by a wrinkle in the underlying parietal lobe of the brain, and too deep and wide to be scar of the middle meningeal artery that meanders through this area. It looked more like a dural sinus—one of the large channels that drains blood from the head (again, so. much. blood.). Spotting a sinus is not unexpected when studying fossil skulls: After all, all animals have to get spent blood out of their crania. What’s bizarre is that this is not where a sinus is supposed to be.
This seemingly mundane groove raises a host of questions to be answered: if this is in fact a sinus, what caused it to develop in this unusual place? How common is this feature in humans today? What can its etiology tell us about Neandertal life 130,000 years ago? Did a certain experience in the short life of this child necessitate this new blood vessel, and were there any associated impacts on brain function?
This is an exciting finding for several reasons. For one thing, this fossil was discovered among a hoard of Neandertal bones over 120 years ago, and to the best of my knowledge no one has noticed this groove in all this time. In addition, modern technology allows new ways to analyze bones and features like this. With 3D models of over 100 other Krapina fossils and cutting-edge software programs in my lab, what other surprises await?