Other researchers agree that the precocious immunity of the La Braña individual is especially intriguing.
"The most surprising and interesting part is that the authors detected derived alleles in pathogen resistance genes," commented Albert Zink, director of the Institute for Mummies and the Iceman in Bolzano, Italy. "This can shed new light on the evolution and interaction of diseases in human populations. This is of particular interest as we know from other studies that some infectious diseases, such as tuberculosis, most probably have been present long before the Neolithic and doesn't necessarily have a (animal) origin."
The blue eye color was just as unexpected, but less problematic, said Carles Lalueza-Fox.
"We tend to think both things (skin and eye color) are related, but they are different genes," Carles Lalueza-Fox explained.
It's also not clear if there's any evolutionary advantage to blue eyes. It could just be from random genetic drift and not have any purpose. Skin color, on the other hand, is thought to be an adaptation to different amounts and intensity of sunlight.