Evrim Yazgin
Cosmos science journalist
A tooth from a 1.77-million-year-old fossil child has given new insights into the process of how a unique aging process evolved in humans.
Analysis of the teeth from Georgia in Eastern Europe shows that ancient human ancestors aged in a combination of ape-like early maturity, and human-like delayed development.
The research, published in Nature, looked at the fossilised remains of a hominin who died at about 11 years old – before reaching dental maturity.
It’s not clear which species the ancient child belonged to, but it was from the genus Homo.
Some of the earliest Homo remains outside Africa have been found at the site in Dmanisi, Georgia, close to the Armenian border. Around the time, several species of hominin were around, including H. habilis and H. erectus.
The Dmanisi individual dates to a period before significant increase in brain size in humans.
Modern human lifespans are relatively unusual among animals. We have prolonged childhoods and delayed maturation compared to our closest living relatives, the great apes.
Developmental stages can be understood through changes in teeth.
Human teeth mature slower than great ape teeth. This is especially true of the permanent molar teeth. This correlates to the pace of brain development and maturing of the body across primates.
Using synchrotron phase-contrast tomography, the researchers analysed microscopic structures in the teeth.
They found the tooth growth rates were high, like in great apes. But the individual also showed delayed development, like in modern humans, of the back teeth relative to the front teeth.
“The unique combination of great-ape-like and human-like features of dental ontogeny suggests that early Homo had evolved an extended growth phase before a general slow-down in life history, possibly related to biocultural reproduction rather than brain growth,” the authors write.
