Atapuerca hominins may have reached maturity earlier than modern humans

Atapuerca hominins may have reached maturity earlier than modern humans

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A team of scientists from National Research Center on Human Evolution (CENIEH) has addressed for the first time the counting of the two types of growth lines that are observed in the enamel of the teeth of the hominids of Atapuerca, the Lower Pleistocene and Middle Pleistocene of Europe.

The research, published in the journal Scientific Reports, has focused on the species recognized in the deposits of the Sierra de Atapuerca.

The results indicate that enamel growth in these hominins could be up to 25% faster than in Homo sapiens.

The teeth grow like onions, tree trunks, stalactites, hair ..., that is, in layers and with regular intervals of formation, and it is precisely this way of growing that allows us to identify the different growth lines of the enamel”, Explains the paleoanthropologist Mario Modesto-Mata, from the CENIEH Dental Anthropology Group and main author of the work.

Researchers analyzed in detail the enamel formation of the Atapuerca hominids, both from the sites of the Sima del Elefante (1.2 million years), as well as the Gran Dolina-TD6 (Homo antecessor: 850,000 years) and the Sima de los Huesos, (430,000 years), as well as a relatively broad teeth of Homo sapiens.

How is tooth enamel formed?

exist two types of growth lines in enamel that remain unaltered throughout life: short stretch marks and long stretch marks.

Short stretch marks, technically called transverse striae, they are formed every day (circadian growth) through the deposition of specific proteins by ameloblasts, which are the cells responsible for forming enamel.

When proteins crystallize, a distance of a few microns can be observed between every two transverse streaks.

Approximately, every seven or eight days the work of the ameloblasts stops for a short time.

That brief stop leads to the formation of long stretch marks, striae visible with low magnification microscopes described by Anders Retzius as early as the 19th century.

Between each two striae of Retzius about seven or eight transverse striae are counted, which allows to know with great precision the time of formation of the enamel of the teeth.

That number, which is called periodicity, is constant in all the teeth of the same individual, and it appears to be different in each hominid species.

The data observed in this research suggest that periodicity was lower in ancestral species, as the hominids that lived in the Sierra de Atapuerca.

That is, the enamel of the teeth of humans recovered in the sites of the Sima del Elefante, Gran Dolina and Sima de los Huesos formed faster than in current human populations.

The study of enamel in the hominids of Atapuerca

The estimates made in this work indicate that the crowns of the teeth of species such as Homo antecessor formed up to 25% faster than those of recent humans”Says Modesto-Mata.

One of the main problems that the authors have faced has been the fact of working with teeth worn by the effect of chewing food.

A part of the growth streaks disappear at the same time that the enamel wears out due to use.

To solve this problem, we developed a statistical technique based on polynomial regressions that allows us to estimate the percentage of lost enamel, and thus be able to compensate for the missing growth lines”, Says the researcher.

The data obtained in this research, added to other ongoing studies on relative dental development and root growth, could provide the first solid evidence to demonstrate an advance in skeletal maturity of the species obtained in the reservoirs.cough of the Sierra de Atapuerca.

"If so, these humans reached adulthood several years before us”, Concludes Modesto-Mata.


Mario Modesto-Mata et al. "Short and long period growth markers of enamel formation distinguish European Pleistocene hominins" Scientific Reports March 13, 2020.
Source: CENIEH

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