Researchers have utilised shark teeth from a 13th-century fishing site in southern Brazil to gain insight into how the local ecosystem has evolved over time.
The excavation of the Rio do Meio site, undertaken to salvage artefacts threatened by an apartment development, yielded a wealth of archaeological treasures, including pottery, tools, and animal remains.
Among these remains were the severed heads of sharks, left behind by Indigenous fishers who frequented the area 750 to 500 years ago. These shark teeth, now housed in the museum at the Federal University of Santa Catarina (UFSC), have become invaluable resources for scientific study.
Researchers embarked on a comparative analysis of these ancient shark teeth with modern specimens collected from the same region. Using stable isotope analysis, a method that offers insights into an animal's diet and environment, the researchers discerned differences between the ancient and modern teeth. These disparities likely reflect shifts in the marine ecosystem over the centuries and shed light on how sharks have adapted to these changes.
Contrary to the misconception that shark teeth are merely triangular and pointy, this research highlights the multifaceted nature of these biological structures. Researchers noted that both the shape and chemistry of shark teeth can offer valuable information to scientists.
By analysing the collagen within shark teeth, which contains elements like nitrogen and carbon obtained from the animal's diet, researchers can infer details about the sharks' feeding habits and their position within the food chain. Higher values of nitrogen isotopes indicate a predator that feeds higher on the food chain, implying a diet primarily composed of carnivorous or herbivorous prey rather than plants.
The study revealed that centuries ago, different shark species were consuming prey from similar levels of the food web, indicating a high degree of diet overlap. This phenomenon suggests a resilient food web, where predators have access to a variety of prey species. Such diversity ensures that predators like sharks have alternative food sources if one prey species becomes scarce.
Overall, this research underscores the importance of ancient shark teeth as windows into past ecosystems and highlights their relevance in understanding how marine environments have changed over time.
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