Did Neanderthals die out because they suffered from chronic ear infections? That’s the possibility raised by a new study that has attempted to reconstruct the structure of the Neanderthal inner ear.
Today middle ear infections are usually a minor hazard of childhood that clear up quickly following a course of antibiotics. Untreated though ear infections can lead to a suite of nasty complications including infections of the surrounding ear bones, hearing loss and even bacteria meningitis.
Ear infections can strike at any age but they are much more common in children because their Eustachian tubes are typically much shorter and straighter than those of an adult. The Eustachian tube is a short vessel that connects the throat and inner ear; it’s small, even in adults it’s usually only around 35mm long, and it performs a couple of important functions. For our purposes the most important is to allow the drainage of mucus that builds up inside the ear, this removes dirt and germs but if the tube gets clogged it can lead to an infection.
This new study attempted to reconstruct the structure of the Neanderthal Eustachian tube for the first time. In modern humans, and Neanderthals, the Eustachian tube is a cartilaginous structure and so it is not readily fossilised. Instead this study used measurements of the associated skull bones, and the known ratios between them, to calculate the probable size and shape of the Eustachian tube. The results were fascinating. They suggested that in adult Neanderthals the Eustachian tube was much shorter and straighter than those of adult humans. Instead they were much more similar to those of a human children. This suggests that Neanderthals could have been much more susceptible to middle ear infections than adult humans are.
Ear infections are rarely fatal, even untreated and this new study is not suggesting that Neanderthals all died from serious ear infections. Instead the study suggests that it was the chronic nature of these infections that was key. Even if a disease doesn’t kill you it can reduce your chances of survival. It can make you sick, tired, less able to feed yourself or to raise as many children. This is described by biologists as a cost to your fitness. You might not die, and you might still reproduce but you might have fewer offspring than your rivals. Over time this effect adds up and makes your genetic line less likely to survive. For Neanderthals this cost to fitness could have made it harder to compete against their Homo sapiens cousins, newly arrived into Europe.
The idea is definitely intriguing, and of course it’s impossible to know if Neanderthals really did suffer from ear infection. It does however, highlight an issue sometimes overlooked in palaeopathology. That which doesn’t kill you doesn’t necessarily make you stronger.
Anthony Santino Pagano, Samuel Márquez, Jeffrey T. Laitman. Reconstructing the Neanderthal Eustachian Tube: New Insights on Disease Susceptibility, Fitness Cost, and Extinction. The Anatomical Record, 2019