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New research out of England has found that weaning in human babies is tied to prenatal tooth enamel growth rates.
The study, conducted at the University of Kent in Canterbury, calculated the prenatal rate that enamel increases in thickness and height on deciduous canines, incisors and molars. Researchers found that incisors develop quickly in the early stages of the second trimester, while molars and canines grow at a slower rate in the third trimester. This ensures that incisors will be able to erupt sooner after birth, at approximately six months of age.
This fact that this timing coincides with the transition from breast-feeding to weaning and the introduction of additional foods is no coincidence. In some primates (such as chimpanzees), weaning occurs much later than that, meaning that, compared to other primates, there is less time for human incisors to form, making it crucial that they develop faster. To compensate, the enamel in human teeth grows rapidly.
The research, which was conducted by Dr. Patrick Mahoney of the Kent Osteological Research and Analysis unit, plays into an anthropological debate on at what point in evolution early weaning in humans began.
The new information on tooth enamel growth can help solidify this timeline by increasing understanding of weaning in fossil ancestors. This has previously been hard to determine, as dental problems don’t present in every tooth the same way, and enamel cells deposit new tissue at different rates in different tooth types.
Up until this point, anthropologists have had to rely on the rare discovery of infant fossil skulls that were just presenting tooth eruption at the time of death – discoveries that have proven to be few and far between. The new research can help anthropologists by providing a prenatal enamel growth record that lasts long past tooth eruption and even death.
The study, “Dental fast track: Prenatal enamel growth, incisor eruption and weaning in human infants,” was published in the American Journal of Anthropology.