Deep Evolutionary Origins of the Human Smile in Ancient Ancestors

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Virtual Model of the Ischnacanthid Acanthodian Jaw

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Side and oral views of a virtual design of the ischnacanthid acanthodian jaw revealing the tooth-rows and restoration of the tooth replacement. Credit: Martin Rücklin, Naturalis Biodiversity Center

The origins of a quite smile have actually long been looked for in the terrifying jaws of living sharks which have actually been thought about living fossils showing the ancestral condition for vertebrate tooth advancement and reasoning of its advancement. However, this view neglects genuine fossils which more precisely show the nature of ancient forefathers.

New research study led by the University of Bristol and the Naturalis Biodiversity Center released in Nature Ecology and Evolution exposes that the dentitions of living shark loved ones are totally unrepresentative of the last shared forefather of jawed vertebrates.

The research study exposes that while teeth developed when, complicated dentitions have actually been gotten and lost often times in evolutionary history and tooth replacement in living sharks is not the very best design in the look for healing options to human oral pathologies.

Lead author Martin Rücklin from Naturalis Biodiversity Center in The Netherlands stated: “We used high energy x-rays at the TOMCAT beamline of the Swiss Light Source at the Paul Scherrer Institut in Switzerland, to study tooth and jaw structure and development among shark ancestors. These ischnacanthid acanthodians possessed marginal dentitions composed of multiple, successional tooth rows, that are quite unlike the tooth whorls that occur in front of the jaw in acanthodians and across the jaws of crown-chondrichthyans.”

Ischnacanthid Acanthodian Jaw

Virtual area through the ischnacanthid acanthodian jaw revealing development lines and the addition of teeth utilized to rebuild the tooth replacement. Credit: Martin Rücklin, Naturalis Biodiversity Center

Co-author Professor Philip Donoghue from the University of Bristol’s School of Earth Sciences stated: “Dentitions of vertebrates are characterized by an organized arrangement to enable occlusion and efficient feeding over the lifetime of an animal. This organization and pattering of teeth is thought to originate in a universal development mechanism, the dental lamina, seen in sharks. The condition we see in the successional tooth rows cannot be explained by this mechanism.”

Co-author Benedict King from Naturalis Biodiversity Center stated: “Using state of the art probabilistic ancestral state estimation methods, we build on this discovery to show that teeth existed in the crown-ancestor of gnathostomes, whereas complex dentitions, tooth whorls, a dental lamina, and coordinated replacement, have all evolved independently and been lost several times in the early evolution of jawed vertebrates.”

Reference: “Acanthodian dental development and the origin of gnathostome dentitions” by Martin Rücklin, Benedict King, John A. Cunningham, Zerina Johanson, Federica Marone and Philip C. J. Donoghue, 6 May 2021, Nature Ecology & Evolution.
DOI: 10.1038/s41559-021-01458-4

This work was supported by the Dutch Research Council NWO (Vidi grant), the Natural Environment Research Council, the Paul Scherrer Institut, EU Horizon2020 and the Naturalis Biodiversity Center.