March 27, 2023
A study discovers a surprising link between teeth and pregnancy progression

A study discovers a surprising link between teeth and pregnancy progression

A series of humanoid skulls: juvenile Australopithecus, adult Australopithecus, adult chimpanzee, young chimpanzee, adult Homo erectus (center). Specimens photographed at the UO/Tesla Monson Museum of Natural and Cultural History. Credit: CENIEH

Humans have the highest rate of prenatal growth of any extant primate, but how this extraordinary rate arose has until now been a mystery. Leslea Hlusko, a scientist at the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), participated in a study led by Tesla Monson, a paleoanthropologist at Western Washington University (WWU) in the United States), which examines teeth, prenatal development rates and pregnancy progression. This research revealed a key piece of this puzzle in an unexpected place: the relative sizes of the fossil molars.

Teeth are indicators of what’s happening elsewhere in the body, and this study was published in the journal Proceedings of the National Academy of Sciences (PNAS)shows that they can be used as a map to help disentangle the effects of the interaction of genetics and development, and to improve our understanding of the history of life in the past.

Tesla Monson and her team, which also includes Andrew Weitz, of the Department of Environmental Sciences at WWU, scientists from the Berkeley Geochronology Center (USA) and CENIEH, studied fossils of the primate group that includes Paleo monkeys and apes World. as well as data gathered from fossilized molars and skull fragments from the terminal Miocene to the Plio-Pleistocene period, ranging from about six million to about 12,000 years ago.

The results show that hominids reached a prenatal growth rate that set them apart from all other apes a million and a half years ago, well before the evolution of the human species itself (between 300,000 and 200,000 years ago).

A study discovers a surprising link between teeth and pregnancy progression

The ultrasound of a human being at 26 weeks pregnant/Tesla Monson. Credit: CENIEH


Prenatal growth rate is closely related to intracranial volume and, paradoxically, to variation in molar ratios. “This shows that teeth can be an indicator of both prenatal growth rate and brain size, which is of particular importance to our ability to study the gestational development of our human ancestors because dental remains are the most abundant places in the fossil record,” says Hlusko.

This discovery of the relationship between molar ratios and prenatal growth rates has raised many new questions for evolutionary researchers, such as understanding the underlying genetic mechanisms. Another key question is whether this is also found in other mammals.

“While I don’t think our humanity can be limited to teeth, I do believe that some of it is recorded in our teeth. This work opens a window for studies of pregnancy and gestation. We can take dental material from human ancestors and other fossil primates to to find out what their pregnancies were like,” Monson concludes.

More information:
Tesla A. Monson et al, Teeth, prenatal growth rates, and the evolution of human pregnancy in later Homo, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2200689119

Reference: Study finds surprising relationship between teeth and pregnancy evolution (2022, November 8) Retrieved November 9, 2022 from html

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