Rachel Caspari has been doing some amazing work with micro-CT scans of Neandertal teeth. The work got profiled this week by Elizabeth Culotta in the Science “Findings” blog:
Caspari analyzed a trove of 120,000-year-old Neandertal fossils from the site of Krapina in Croatia. Excavated more than 100 years ago, the assemblage contains bones of 75 to 83 individuals, which apparently accumulated within 10,000 to 20,000 years. Caspari estimated their age at death from the teeth; in young people, teeth are generally pristine, while the enamel is worn away in older people. And over time, a tooth's pulp cavity shrinks as additional dentine is deposited into it. In a new method, Caspari used nondestructive micro CT scans to measure pulp cavities.
After aging each specimen, she found that the Krapina Neandertals died before the age of 30. "There were very few old Neandertals, if any," she said. For every 10 young adults found, only four older Neandertals were found.
This method is more complicated to carry out than Caspari and Sang-Hee Lee’s earlier work using dental wear categories. So it’s very heartening that it leads to the same result. That’s significant because it further documents the substantial difference in adult mortality rates: Neandertals had a much greater annual chance of death than early Upper Paleolithic Europeans.
I’ve been giving talks lately that touch on the possible causes of this big difference in life history, and the likely demographic and evolutionary consequences of it. Caspari and Lee’s earlier work points to Upper Paleolithic cultural innovations as the probable cause of their lower mortality rates, and that may have been one of the most important drivers of recent human evolution.