The first molars of adults contain their medical history from the fetal stage.
Researchers at McMaster University in Ontario, Canada, have discovered that a person's first permanent molars carry a lifelong record of medical information dating back to the womb, storing vital information that can connect maternal health to a child's health, even hundreds of years later. Dentin, the enamel material that makes up the bulk of a tooth, forms in microscopic layers that are likened to the rings of a tree. The proper formation of these layers depends on vitamin D. Dark lines develop during periods when the body is deprived of this essential nutrient, usually due to lack of sunlight.
The researchers, led by anthropologist Megan Brickley, had previously established that such microscopic defects remain in place and can be read later, just as a tree trunk can show years of good and poor growth. Because teeth do not decay as quickly as flesh and bone, they can retain such information for hundreds of years after death.
Combined with other data, Brickley says, the patterns in dentine can create banks of knowledge about past conditions, including the health impacts of living in low-light environments. It's a living fossil of your life, starting in the womb," he explains. It might be possible to remove anyone's molar and compare its health with the evidence in the tooth.
Early settlers in Canada, for example, who were often wrapped from head to toe, even in summer, commonly developed conditions such as rickets, or died prematurely from other conditions related to poor access to vitamin D. Now, the same team of researchers has established the value of such records, which begin during the original formation of teeth in the foetal stage, to reflect the health of the mother during pregnancy. All of the body's primary or 'baby' teeth, which begin to form in the womb, are lost in infancy.
The first permanent molars, which emerge around age 6, also begin to form in utero and remain in the mouth throughout adulthood, where they retain a record of vitamin D intake from the mother's pregnancy. That record provides a critical intergenerational link that can offer valuable clues connecting maternal health to a child's ultimate fate. We've been able to establish really clear evidence that there is part of the first permanent molar that records what happened in the mother's life," says Brickley. This is a tool that people can use. It can be used in current health research and bioarchaeological research.
The researchers examined modern and archaeological tooth samples, including teeth from two 19th-century Quebec skeletons, one from a three-year-old girl who had survived rickets as an infant and one from a young man. The girl's undescended molar showed that her mother had suffered a vitamin D deficiency during pregnancy, a possible clue to the girl's premature death. The young man's molar also showed that his mother had suffered from vitamin D deficiency, raising the possibility of a connection between his mother's health and her premature death.
At the time, Brickley explained, social practices and climatic conditions meant that pregnant women in particular would have had very little sun exposure, before it became clear how necessary sunlight or substitute sources of vitamin D are for good health.
