In 2020, researchers described a fossil jaw from eastern Greenland, about 215 million years old, that has the oldest known molar-like teeth with two roots and two rows of cusps. It belonged to Kalaallitkigun jenkinsi, a mouse-sized close relative of the first mammals.
The study, published in the Proceedings of the National Academy of Sciences, also used engineering models to show that teeth with two roots withstand the forces of biting better than teeth with one root. That may help explain why broad chewing teeth and divided roots evolved together, a design human molars still carry.
For the full explanation, including what the researchers found, the study's limits and what it means for your own molars, read What a Tiny Jaw From Greenland Shows About the Origin of Molars.
Sources
Sulej T, Krzesiński G, Tałanda M, et al. The earliest-known mammaliaform fossil from Greenland sheds light on origin of mammals. Proc Natl Acad Sci U S A. 2020;117(43):26861-26867. doi:10.1073/pnas.2012437117. Retrieved via PubMed.
About the author. CJ Henley, DMD, is a general dentist in Jacksonville whose practice focuses on cosmetic and restorative dentistry, dental implants and dental care around head and neck cancer. Meet Dr. Henley.
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Updated October 2026.