Wealth of info in the tiniest of fossilised teeth

The fossilised teeth of species found by paleontologists may be tiny, but they’re a Pandora’s box of information – not only about how the species looked, but also how it lived and ate.

Added to that is the fact that linear enamel hypoplasia can tell us what sort of stress they had in their lives. So what exactly is linear enamel hypoplasia?

Simply put, it is the band-like dental defects in a child’s tooth that show some form of disruption to the child’s health. It basically means the enamel thickness has been affected by a stressful event such as disease.

In a study just published in the SA Journal of Science, new information has come to light about the species, Homo naledi, which has been defying conclusive answers since its discovery at the Rising Star cave system in the Cradle of Humankind in 2015.

When the species was discovered, it was in a similar area to another great find – Australopithecus africanus – which meant scientists could compare and contrast the two to learn more about the environment in which they lived and how it affected them.

This latest study compares the linear enamel hypoplasia in both species and compares it to apes from equatorial regions.

Author of the study, Mark Skinner, from the University of York’s archaeology department, says: “The discovery of a new hominin [Homo naledi] in the same geographical area as Australopithecus africanus creates the opportunity to compare developmental dental stress in higher-latitude hominins with that in lowerlatitude apes.”

In the case of the modern apes, linear enamel hypoplasia recurs seasonally at about six or 12 months. In contrast to equatorial Africa, a single rainy or dry cycle occurs annually in noncoastal southern Africa, so it was predicted that perhaps the disruptions to health (related to the weather) would show up annually (as revealed by the teeth).

But this isn’t what showed up: the species were experiencing disruptions to their health every 1.6 to 7.6 months, indicating disease and malnutrition were playing a role.

Skinner says this particular study had an unexpected result.

“Because of the innate way that enamel is deposited, the timing of stress in the childhood of apes, modern humans and their fossil ancestors can be measured with a precision of about one week,” he explains, and this particular study revealed, unexpectedly, “that both forms show semi-annual stress”.

This is likely attributable to “two independent stressors – possibly disease and malnutrition”. – Times Select

The timing of stress in the childhood of apes, modern humans and their fossil ancestors can be measured precisely