Atapuerca Hominids Grew Much Quicker Than Modern Humans

Scientists have proven that tooth enamel developed much quicker in ‘other’ hominids groups.

Fossilized bones and teeth tell scientists when organisms lived, and morphological differences provide evidence for the evolution of life on Earth over a million years ago. Now, researchers at the Dental Anthropology Group of the Centro Nacional de Investigación sobre la Evolución Humana ( CENIEH) have published a paper in the journal  Scientific Reports , which for the first time counts the two types of growth lines observed in the tooth enamel of Lower and Middle Pleistocene hominids in Europe’s Sierra de Atapuerca.

The new research was assisted by researchers from the New York University and University College London , but was led by the paleoanthropologist Mario Modesto-Mata. The results show the tooth enamel growth rates in these early hominids might have been up to “25% faster than in  Homo sapiens .”

The Oldest Homo Fossils Ever Found

The archaeological site of Atapuerca is located in the Atapuerca Mountains in the province of Burgos in northern Spain and archaeologists have discovered rich fossil deposits and hoards of stone tools belonging to the earliest known hominin residents in Western Europe.

Fossil of hominid teeth found in the Sima de los Hueso cave system in the Atapuerca Mountains. (UtaUtaNapishtim /  CC BY-SA 4.0 )

A 2016 Ancient Origins article presented the findings of Dr. Matthias Meyer based on fossil samples from Atapuerca who discovered “the separation of the line leading to Homo sapiens from the 'archaic' humans occurred between 550,000 and 800,000 years ago.”

And this suggested time period for the separation of modern humans and Neanderthals was based on the fossilized remains of the  Homo antecessor specimen found in the Sierra de Atapuerca dated at between 800,000 and a million years ago, which is “the best candidate to fill the key position of our last ancestor.”

Depiction of Homo antecessor / Homo sapiens from Sima de los Huesos, Atapuerca. (CENIEH)

Collecting Ancient Enamel Samples

According to an article in the journal Nature, a jaw fragment discovered in 1970s and a skull fragment in 1995 both belong to Homo heidelbergensis and date to between 600,000 and 400,000 years ago. And in 1994 and 1995, a further 80 bone fragments were dated to between 850,000 and 780,000 years old.

Adding to the scientists extensive collection of Homo sapiens teeth, the tooth enamel of Atapuerca hominids was collected from several sites including: Sima del Elefante, a 1.2 million year old ancient aven formed in cretaceous sandstone by an underground river and from Gran Dolina-TD6, a cavity infilled by at least 25 meters of Pleistocene sediments: and the chasm - Sima de los Huesos , dating to 430,000 years ago.

Atapuerca excavation site where the hominid teeth were discovered. (Mario modesto /  Public Domain  )

Analyzing the Enamel of Timeworn Teeth

In an article about these new findings published on CENIEH, Dr. Modesto-Mata says teeth grow in layers with regular intervals of formation like “onions, tree trunks, stalactites and hair,” and this enables the identification of growth lines in tooth enamel.

Tooth enamel has two types of growth lines known as short and long striations, which are unchanged throughout an individual's life. Short striations, known as cross-striations, form every day with deposits of proteins by the ameloblasts cells, which form enamel and once these proteins crystallize, the micron’s distance between successive cross-striations is measured.

Between what scientists know as “striae of Retzius,” about 7 or 8 cross-striations can be counted, which yields a number called the “periodicity,” which is different in each species of hominid and allows for precision dating of the enamel.

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The Ancients Had Stronger Teeth, Quicker

This investigation suggests the “periodicity” was lower in ancestral species living in the Sierra de Atapuerca, meaning, the human tooth enamel recovered from the Sima del Elefante, Gran Dolina and Sima de los Huesos sites formed “quicker than in modern humans.” The scientist estimations presented in their new study indicate that the crowns in  Homo antecessor  teeth formed “up to 25% more quickly than in recent humans,” the researchers wrote.

The new data gathered from this new research into tooth enamel development and root growth, is hoped to demonstrate the first solid evidence of “earlier skeletal maturity” for the species obtained from the sites of the Sierra de Atapuerca, and if the scientists are right, these humans had reached maturity several years earlier than we do, the paper concludes.

Top image: Individual XVIII teeth from la Sima de los Huesos, Atapuerca. Source: M. Modesto-Mata / CENIEH

By Ashley Cowie