Two studies push back the origin of the African Homo erectus by 10 million years
Anthropologists have long believed that our ape ancestors evolved an upright trunk to pick fruit in the forest, but new research shows that living in open woodlands and a diet of leaves pushed the apes to stay upright instead stature. The discovery pushes back the origins of Homo erectus and grassy woodlands from 7 to 10 million years ago to 21 million years ago.
Fruit usually grows on the outer branches of trees, and to reach the fruit, great apes must distribute their weight on these branches and then reach out to grab their prize. This would be much easier if the ape was upright. If its back is level, its hands and feet are usually below its body, making it difficult for it to move within picking range. This is how modern apes get fruit, and, presumably, why apes evolved an upright posture.
But the new study revolves around a 21-million-year-old fossil ape Moro Ape, suggests that this may not be the case. Instead, the researchers think that early great apes ate leaves and lived in seasonal woodlands, where tree canopies had broken down and open grassy areas. The researchers suggest that this landscape, rather than fruit in closed canopy forests, drove the apes’ erect stature.
The results are contained in two papers just published in the journal science.
The excavations in northwestern Kenya are part of a project to document climate some 21 million years ago. (courtesy of Kevin Uno)
a study Focus on a 21-million-year-old site in eastern Uganda.There, a team led by researchers at the University of Michigan and scientists at Columbia University Lamont-Doherty Earth Observatory and others have examined fossils found in a single formation, including Moro Ape, the oldest clearly documented ape. Also within this layer are fossils of other mammals, ancient soils called paleosols, and tiny particles of silica from plants called phytoliths.Researchers use this evidence to reconstruct the environment Moro Ape.
They found that plants living in the land experienced alternating seasons of rain and drought. It also means that for at least part of the year, the great apes had to rely on something other than fruit to survive.Taken together, these findings suggest Moro Ape Lives in open woodlands dotted with broken canopy forests of trees and shrubs.
“These open environments have been used to explain human origins, and it’s thought that between 10 and 7 million years ago, you started getting these more open, seasonal environments,” said lead author Laura MacLatchy of the University of Michigan. ’” It’s thought that our ancestors strode around on two legs because the trees were farther apart. “Now that we’ve shown that this environment existed at least 10 million years before the evolution of bipeds, we also need to really rethink the origins of humans,” MacLatchy said.
The first clues that these ancient apes ate leaves were in the ape’s molars, which have numerous peaks and valleys. Molars like these are used to tear fibrous leaves, while those used to eat fruit are generally more rounded.
The researchers also examined tooth enamel from apes, as well as enamel from other mammals found in the same layer. They found isotope ratios — the abundances of two isotopes of the same element — in tooth enamel suggesting that apes and other mammals have been eating so-called C3 plant, is more common today in open woodland or grassy woodland environments. C3 The plants are mainly woody shrubs and trees adapted to arid conditions, and the so-called C4 Plants are drought-adapted grasses.
Previously, researchers thought that regions of equatorial Africa around 20 million years ago were covered with thick forests, and that open seasonal woodlands and grasslands evolved only later.but second paper, Led by scientists at Baylor University, a panel of environmental proxies was used to reconstruct the vegetation structure at nine great ape fossil sites in Africa, including sites in eastern Uganda. These proxies show C4 In the early days, grass was everywhere. This suggests that these landscapes are open rather than forested.
“Isotopic data collected from ancient plant waxes and phytoliths Moro Ape The site provides strong evidence for C4 Grass on a local scale,” says Kevin One, a paleoclimatologist at Lamont-Doherty and co-author of both papers. “Other regional plant wax records from marine cores show little C4 Grasslands in eastern Africa at this time. So these new data are exciting because we now have a new piece of the puzzle to solve: why do we see different signals locally and regionally? “
To reconstruct the ancient environment at each site, the researchers performed carbon isotope analyzes of ancient soil organic matter, plant wax biomarkers, and phytoliths found at each site. Carbon isotope analysis revealed that the grasslands were home to a wide variety of plants, from those containing closed tree canopies to wooded grasslands.
Uno’s group at Lamont analyzed waxy biomarkers—substances left over from the waxy substance that protects leaves. These show a wide variety of shrubs and trees as well as grasses.Phytoliths—microscopic biological silicon bodies that give plants their structure and protect them from being eaten—provide further evidence for abundant C4 Grass, pushing back the oldest C evidence4 Grass-dominated habitats in Africa and globally have been present for more than 10 million years.
“These findings change what we know about early great apes and where, when and why they originated, traveling through trees and the ground in many different ways,” said Robin Bernstein, director of the National Institute’s Biological Anthropology Program. The Science Foundation that sponsored the research.
Adapted from a University of Michigan press release.
