Tooth Enamel Reveals Differences Between Neanderthal and Human Survival Tactics
A team of archaeologists and earth scientists from the United Kingdom and Portugal have just completed a comparative study of Neanderthals who lived in western Europe approximately 100,000 years ago and humans who occupied the same terrain tens of thousands of years later. The differences in how the two populations survived in the area was stark.
As detailed in an article just published in the journal PNAS, their research revealed some notable differences in the survival-related behavior patterns of the two populations, as might be expected. What was most remarkable is that their discoveries emerged exclusively from their study of tooth enamel samples, which were removed from teeth that belonged to ancient humans and Neanderthals and the animals they relied on as food sources.
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“This study shows just how much science has changed our understanding of archaeology in the past decade,” stated archaeologist and study research supervisor Alistair Pike, in a press release issued by the University of Southampton (Pike’s home institution).
“Previously, the lives and behaviors of past individuals was limited to what we could infer from marks on their bones or the artifacts they used. Now, using the chemistry of bones and teeth, we can begin to reconstruct individual life histories, even as far back as the Neanderthals.”
Neanderthal and Human Subsistence Strategies in Ancient Times
The teeth studied by the researchers were recovered during excavations inside the Almonda Cave system near Torres Novas in central Portugal. Neanderthals occupied this natural shelter first, starting at least 100,000 years before the present, while humans from the Magdalenian culture lived there much more recently, during a period ranging from 17,000 to 12,000 years ago. Each species left behind skeletal remains of various types, including a few well-preserved teeth.
Like other parts of the body, teeth and the enamel that cover them are constructed from the foods that living creatures consume. The chemical makeup of the tooth enamel will differ from species to species and person to person, which can reveal a lot of valuable information about the dietary choices of the people or animals whose teeth are studied.
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In this new study, the British and Portuguese researchers were able to measure differences in the chemical properties of the tooth enamel from ancient Homo sapiens and their Neanderthal cousins. Based on these differences, they determined that Neanderthals living on the Iberian Peninsula during the Middle Paleolithic period wandered far and wide across vast areas, chasing and hunting large animals that would have supplied them with ample quantities of food.
In contrast, early modern humans living in Portugal during the Upper Paleolithic hunted and consumed smaller animals for the most part, covering a swath of territory during their hunting forays that was only about half as large as that traversed by their Neanderthal forerunners.
Lower jaw of extinct species of Rhinoceros. (José Paulo Ruas/University of Southampton)
“The difference in the territory size between the Neanderthal and Magdalenian individuals is probably related to population density,” deduced study co-author João Zilhão, an archaeologist from the University of Lisbon. “With a relatively low population, Neanderthals were free to roam further to target large prey species, such as horses, without encountering rival groups. By the Magdalenian period, an increase in population density reduced available territory, and human groups had moved down the food chain to occupy smaller territories, hunting mostly rabbits and catching fish on a seasonal basis.”
Professor Zilhão’s presumption is logical, but not necessarily the only explanation. Representing two distinct species, Neanderthals and ancient humans may have had different preferences or caloric needs, and their choice of prey could have been based at least partially on these differences.
Mapping the Movements of Ancient Peoples with Chemistry
Strontium isotope ratios and the technology used to measure them were the key factors that led to these incredible discoveries.
Strontium is a chemical element found in rocks. As rock weathers over millions of years, the strontium inside gradually decays and changes its chemical makeup, which is reflected in its ever-evolving isotope ratios. Because geographical location impacts this decay rate, rocks from different places will have unique strontium isotopic signatures.
Weathering processes slowly turn crumbling rock into soil, but strontium isotope ratios are preserved despite this final transformation. The isotopic signature of the soil is then passed up the food chain to plants that grow in the soil and to the animals that eat those plants. If humans eat those plants or animals, they will absorb the strontium and it will be deposited in their tooth enamel, with the unique strontium signature still intact.
For scientists who examine such things, this pathway creates a clear link between humans, the foods they eat and the geographical location where those food sources can be found.
For the purposes of this study, the British and Portuguese scientists used a technique known as laser ablation to extract enamel samples from the teeth of two Neanderthals and one human whose remains were unearthed from beneath the floor of Almonda Cave. The former had lived approximately 95,000 years ago, while the latter had occupied the cave around 13,000 years ago.
“Tooth enamel forms incrementally, and so represents a time series that records the geological origin of the food an individual ate,” explained University of Oxford archaeologist and lead study author Bethan Linscott. “Using laser ablation, we can measure the variation of strontium isotopes over the two or three years it takes for the enamel to form,” Linscott continued.” By comparing the strontium isotopes in the teeth with sediments collected at different locations in the region, we were able to map the movements of the Neanderthals and the Magdalenian individual. The geology around the Almonda caves is highly variable, making it possible to spot movement of just a few kilometers.”
The researchers also studied the tooth enamel of several animals whose skeletal remains had been found inside the cave. These animals had been hunted for food by the Neanderthals and the humans, and it was possible to trace their migrations across the surrounding landscape based on their teeth’s strontium isotope signatures (which linked the animals to the plants they’d consumed during their movements). Additionally, the researchers measured the oxygen isotope signatures in their tooth enamel, knowing that these would vary depending on whether or not the animals had been active during the winter.
Relying on the data they obtained from this sophisticated form of analysis, the British and Portuguese scientists discovered that the ancient Neanderthals were hunting wild goats in the summer and horses, red deer and rhinoceros all year round. They pursued these animals over a territory that covered approximately 230 square miles (600 square kilometers).
The Magdalenian human, on the other hand, survived by consuming rabbits, freshwater fish, red deer and wild goats that lived within the boundaries of a 115-square-mile (300-square-kilometer) space surrounding the Almonda cave system.
This new study represents an extraordinary accomplishment, given that its results were obtained largely from inference and logical deduction. By studying just a few hominin and animal teeth preserved from prehistoric times, the British and Portuguese researchers were able to discover detailed information about the subsistence habits of Neanderthals and early modern humans, comparing and contrasting them to discern both the similarities and the differences.
Top image: A Neanderthal premolar tooth from the Almonda cave system, Portugal. Source: João Zilhão/University of Southampton
By Nathan Falde
