SMU News – Evidence of an early savannah grass growing millions of years earlier than previously known may fundamentally change the understanding of life in the prehistoric world. A pair of studies funded by the National Science Foundation and published in the journal Science document the earliest evidence for locally abundant open-habitat grasses in eastern Africa and how those environments likely influenced early ape evolution.
“For more than a century, evolution of the human family has been associated with the spread of grasslands and in more recent thinking, woody grasslands in tropical Africa,” said Bonnie Jacobs, renowned paleobotanist and emeritus professor at SMU (Southern Methodist University, Dallas).
“This research provides solid evidence of the earliest common occurrence of C4 grasses, called savanna grasses, dating back to 21 million years,” Jacobs said, explaining that the discovery pushes back the oldest evidence of C4 grass-dominated habitats in Africa – and globally – by more than 10 million years. The significantly older timeline explored in the study that Jacobs pursued with lead author Daniel Peppe, associate professor of geosciences at Baylor University, calls for revised palaeoecological interpretations of the development of plants and mammals.
The appearance of these grassy woodlands earlier than previously theorized bolsters the findings of a companion study, also appearing in Science, that raises new questions about what sparked early apes to evolve an upright torso.
The related study, led by paleoanthropologist Laura M. MacLatchy, a professor at the University of Michigan, centered around a 21-million-year-old fossil ape called Morotopithecus, revealing evidence suggesting that early apes lived in a seasonal woodland with a broken canopy and open, grassy areas. As a result, her research team thinks this landscape drove apes’ upright stature, rather than terrain supporting fruit in closed canopy forests.
“The expectation was: We have this ape with an upright back. It must be living in forests and it must be eating fruit,” said MacLatchy. “But as more and more bits of information became available, the first surprising thing we found was that the ape was eating leaves. The second surprise was that it was living in woodlands with these grassy areas.”
The two papers grew out of a U.S. National Science Foundation-funded collaboration of international paleontologists, collectively known as the Research on Eastern African Catarrhine and Hominoid Evolution project or REACHE, whose members focus on different aspects of monkey and ape evolution.
Jacobs, a REACHE member, was invited to join Peppe’s research team early on because she has spent much of her career conducting research on fossils of ancient plant and animal life in eastern Africa and what it could tell us about past climate change.
SMU paleontologist Alisa Winkler – an expert on rodent and rabbit fossils who is also a REACHE member – helped MacLatchy with her study, having joined the research team 10 years ago.
Winkler has worked on fossil rodents from Moroto, Uganda, where fossils of Morotopithecus were found, as well as other sites in Uganda that have similarly-aged fossils. Her analysis of these rodents’ remains helped support the conclusions MacLatchy’s research team made based on other indicators regarding the geological age and paleoenvironment of Morotopithecus. Read the full article.