CARMO GALLO NETTO
M60-million-year-old herbivorous mammals, which developed in the period following the extinction of the dinosaurs (Paleocene), increased in size thanks to adaptation in tooth enamel. This is one of the conclusions of dentist Sérgio Peres Line, professor at the Faculty of Dentistry of Piracicaba (FOP) at Unicamp, in research with professor Lílian Paglarelli Bergqvist, from UFRJ. Both wrote an article in the prestigious American magazine Journal of Vertebrate Paleontology (December 2005).
Human tooth enamel serves as a fingerprint
Sérgio Line, who for the last ten years has been studying the development and structure of teeth, especially tooth enamel, is also the author of a method for human identification through enamel bands, which are unique to each individual, like fingerprints. . This process has already been patented by the Unicamp Innovation Agency (Inova) and described in May this year in the Proceedings of the Royal Society B, a British publication of the Royal Science Academy.
Passionate about evolution, the FOP professor explains that at the time of the dinosaurs, mammals did not have the same size as they do today. Once the dinosaurs were extinct, mammals began to colonize the planet. “The Paleocene is known as the period of great diversification of mammal species, which also increased in size and therefore had to feed more. The first stage in harnessing energy from food is chewing, the grinding of food, which is ensured by the teeth,” he notes.
Sérgio Line explains that an adaptation of the dentition then occurs, which becomes more demanding, so that it can withstand wear and tear. Herbivores, mainly, eat highly abrasive plants, because of the dust (silica) that is deposited on them. Furthermore, the mammal reaches reproductive age later, meaning it needs to live longer to ensure the procreation and survival of the species. Long life requires maintaining the functional capacity of teeth for a longer period of time. The professor adds that dental enamel is an extremely hard structure and the most mineralized in the body, formed mainly from the polymerization of calcium phosphate crystals, which are organized in the form of sticks arranged horizontally.
“We studied a collection of Paleocene teeth, as if it were a portrait of the period. We found that the larger species present a very rare adaptation of the tooth enamel: the composition in vertical bands, when horizontal bands are common, as occurs in the animals we find today, including herbivores. Vertical bands are more resistant to abrasion and delay tooth wear. We believe that this mechanism allowed the increase in the size of those mammals. Nowadays, this type of band is only found in rhinos”, explains the researcher.
In recent years, Sérgio Line started to collaborate with the Department of Paleontology at UFRJ, which maintained a research line on teeth in paleontology. “Professor Lílian Bergovist had already been studying a collection of herbivorous mammals in São José de Itaboraí, in Rio de Janeiro, for some years. This collection is particularly interesting because it is Brazilian, and because we are not a country rich in complete reptile and mammal fossils, as are found in Mongolia, Argentina, Chile and the United States. Brazil depends on the study of fragments, fragments of these fossils. In São José de Itaboraí there are fragments of thirteen species of mammals dating back to the Paleocene,” he informs.
Dental impression – Based on his studies, Sérgio Line also developed a method already described in the literature to determine the position of tooth enamel bands without destroying the tooth. This work led him to a method of human identification from these bands. He thus created the dental impression technique. For the researcher, his work is an example of how basic research can lead to interesting discoveries: “We initially had rare material and started studying it. The findings continued. The merit of this lies in knowing how to interpret the findings. In addition to contributing to the understanding of how evolution occurs, we were led to conclude that the structure of tooth enamel allows human identification”, he summarizes.