A fresh picture of apes, ancient Africa, and the origins of humans is painted by two research that were published in the journal Science on April 14. The earliest apes to emerge in Africa more than 20 million years ago were thought to have eaten mostly fruit and lived under the dense, closed canopy of a virtually continent-wide forest habitat. This was the popular theory at the time. The new findings suggest that early primates instead had a leafy diet in a more dry ecology of varied open woods with a lot of grasses.
The University of Washington’s paleobotanists and other researchers from across the world, including paleontologists, primate specialists, and plant scientists, have discovered evidence that dates the development of tropical ecosystems dominated by C4 grasses to more than 10 million years. In doing so, they establish a connection between the birth of C4 grasses, which are so termed because of the sort of photosynthesis they use to produce food from the sun’s energy, and the emergence of the ancestors of all living apes today. That includes humans, the most numerous primate in recorded history.
A semi-continuous forest was thought to have blanketed equatorial Africa during the early Miocene, between about 15 and 20 million years ago. According to that theory, the emergence of more open environments including C4 grasses didn’t occur until 8 to 10 million years ago. However, one research found some indications that C4 grasses existed in East Africa circa 15 million years ago. The goal of the study was to determine if it was an outlier or a sign of the genuine variety of ecosystems at that period.
Because there were so few plant fossils, the history of grassland ecosystems in Africa before 10 million years ago has remained a mystery, according to co-author Caroline Strömberg, the Estella B. Leopold Professor of Biology at the UW.
The National Science Foundation provided significant funding for the multinational partnership, which brought together a variety of lines of evidence in an effort to rebuild the species that dominated East Africa in the early Miocene. Researchers used investigations of fossilized soils, extinct animals, stable isotopes, and phytoliths, which are microscopic silica fragments from plants.
To reconstruct the kinds of plants that were present at various sites in East Africa during the early Miocene, Strömberg, a specialist in phytoliths, collaborated with co-authors Alice Novello, a former postdoctoral researcher at the University of Washington who is now employed at the Aix-Marseille University in France, and Rahab Kinyanjui of the National Museums of Kenya and the Max Planck Institute of Geoanthropology in Germany.
“Phytoliths are incredibly useful for illuminating the evolution of grassland ecosystems. The Burke Museum of Natural History and Culture at the University of Washington is home to Strömberg, who is also the curator of paleobotany. “They can tell us not just that there were grasses, but which grasses were there and how abundant they were on the landscape,” he added.
Their findings effectively refuted the idea that equatorial Africa was densely wooded during the early Miocene by combining their data with additional lines of evidence. Understanding the traits and adaptations of early apes is significantly impacted by the results.
“Multiple lines of evidence show that C4 grasses and open habitats were important parts of the early Miocene landscape and that early apes lived in a wide variety of habitats, ranging from closed canopy forests to open habitats like scrublands and wooded grasslands with C4 grasses,” said co-author and associate professor of geosciences at Baylor University Daniel Peppe. It fundamentally alters our perception of how ecosystems functioned as the contemporary African plant and animal community developed.
They said “What we found was thrilling and very different from what was the accepted story.” “We used to believe that, depending on the continent, tropical, C4-dominated grasslands had only recently emerged. Instead, both phytolith and isotopic data revealed that C4-dominant grassland ecosystems first evolved in eastern Africa during the early Miocene, over 10 million years earlier.
Phytoliths from a location in East Africa that was examined for this study. A C4 member of the grass family (Poaceae), which now includes maize, wheat, and rice, is most likely the source of the phytolith in the middle of the image on the right. The 10 micrometer scale bar is in the upper right corner.A. Novello
The team also reports data regarding Morotopithecus, a 21-million-year-old fossil ape, in addition to its findings about C4 grassland habitats. Anthropologists have long believed that the upright torso our ape ancestors developed allowed them to collect fruit in the woodlands. An ape’s upright position makes it simpler for its hands and feet to grasp onto various trees. Undoubtedly, Morotopithecus stood straight and tall. The team’s paleontologists carefully examined the molar’s structure and the chemical makeup of its tooth enamel to ascertain the diet of the animal.
“The anticipation was that we would see an upright-backed ape. According to co-author and University of Michigan professor of anthropology Laura MacLatchy, “It must be eating fruit and living in forests.” “But as more and more evidence came to light, the first unexpected discovery we made was that the monkey was consuming leaves. The fact that it lived in a forest was the second surprise.
Morotopithecus lived in a seasonal woodland with a fragmented canopy made up of trees and bushes, as well as open, grassy regions, according to the evidence gathered collectively. The team’s efforts to reconstruct the vegetation and environment also revealed that Morotopithecus had to eat leaves and other plant materials rather than fruit for at least a portion of the year.
Another theory about the origins of humans is that bipedalism developed in reaction to the rise of grassland settings in Africa between 10 and 7 million years ago. However, the abundance of C4 grass and forest ecosystems appeared far earlier than previously believed.
