17-million-year-old teeth open window into early ape and human evolution
Fossilized primate teeth can provide insights into the role that seasonal climate and behavior may have played in the evolution of humans and primates, an international team of scientists has shown in a new study.
The study examined oxygen isotopes in teeth from a 17-million-year-old site in the Turkana Basin in northwestern Kenya.These include the teeth of a mysterious gorilla known as Ape. This research just released inside Proceedings of the National Academy of Sciences,
To put these fossils in context, the researchers also measured oxygen isotopes in the teeth of modern primates across equatorial Africa and analyzed the isotopic signatures they produced. The team, led by postdoctoral scientists Daniel Green at Columbia University’s School of Climate and Tanya Smith at Griffith University in Australia, found that modern oxygen isotopes (natural variations of oxygen with different masses) record conditions such as rainy seasons and droughts, environmental elevation and vegetation. , and changes in primate behavior.
The arid, fossil-rich landscape of Kalodir in the Turkana Basin region of Kenya, once the forest home of ancient apes ape 17 million years ago.Photo: Susannah Cotter
In modern teeth, researchers have found that teeth can even indicate human changes to natural landscapes, such as the damming of rivers, and record specific meteorological events. Measurements of modern monkey teeth documented prolonged droughts in one case in Ethiopia, and extreme rainfall events in another in Uganda. Working with primatologists, the researchers were able to determine that teeth were forming when these climatic events occurred.
In the context provided by modern primates, the authors then analyzed data from ape found at a site called Kalodirr and compared their results to rainfall patterns simulated by climate models from 17 million years ago.
The researchers showed that ancient apes experienced wet and dry seasons of varying intensities over time, which may have been influenced by natural variations in Earth’s orbit around the sun.These results also suggest that specialized jaw adaptations — thick enamel and strong masticatory muscles — can help ape Eat hard foods during drought or resource-scarce seasons.
“The effects of climate change on the earliest African great apes are poorly understood, as detailed records of seasonal changes in the early Miocene are sparser,” Green said. “Oxygen isotopic composition ape and closely related herbivores suggest that ape behavior and anatomy in this part of East Africa were influenced by seasonal environments long before the origin of humans. “
Lead author Daniel Green examined fossil material from Kenya’s Turkana Basin.
Another key finding of the team’s study is that studies of oxygen isotopes in human fossils (our ancestors) have so far underestimated chemical changes in their teeth. For this reason, it is difficult to estimate how their behavior on the African savannah varies with the seasons.
The study “has broad implications, as seasonal changes in resource availability are thought to have influenced the evolution of great apes, early humans and modern humans,” Smith said.
The research leverages innovations in high-resolution chemical measurement technology driven by Ian Williams of the Australian National University, who is a co-author of the paper. Teeth grow in microscopic time increments similar to tree rings, but in childhood, tooth increments are formed every day rather than every year. Thus, through the innovation provided by Williams’ work, researchers were able to restore seasonal changes in body and environmental chemistry that occurred millions of years ago.
For the past five years, Green, Smith and Williams have been working to refine these techniques and apply them to living and fossil humans. In 2018, their work provided the first detailed assessment of ancient seasonality from the teeth of Neanderthal children. The team is currently planning to collect fossilized hominin teeth from Africa from the Turkana Basin.
The paper was co-authored by Janaina Ávila, Griffith University; Susanne Cote, University of Calgary; Wendy Deckers, Durham University; Daeun Lee and Christopher Poulsen, University of Michigan, Ann Arbor. The research was funded by Harvard University, Columbia University and Griffith University.
Adapted from a Griffith University press release.
