New Research Forces a Rethink of Ape Evolution

A pair of studies show that the expansion of grasslands in Africa, thought to be key for hominin evolution, occurred millions of years earlier than believed – around the same time as the earliest apes

Human evolution is thought to have begun in a period of changing climate, when expanding savannas and receding forests forced our fruit-eating ancestors out of the trees and into grasslands to look for new sources of food. Previous research has placed this ecological transition at around 10 million years ago, but a pair of new interdisciplinary studies is changing our understanding of this process.

Two papers recently published in the journal Science indicate that as early of 21 million years ago, much of eastern Africa was covered open woodlands and savannah, and that in that environment, the earliest apes had upright backs and teeth made for shredding leaves.

Co-authors, from Left: David Fox (University of Minnesota, USA), Bill Lukens (James Madison, University, USA), Kirsten Jenkins (Takoma University Collage, USA), John Kingston (University of Michigan, USA), Al Deino (Berkeley Geochronology Centre, USA), Rahab Kinyanjui (Max Planck Institute of Geoanthropology, National Museums of Kenya).

© Bill Lukens

Co-authors, from Left: David Fox (University of Minnesota, USA), Bill Lukens (James Madison, University, USA), Kirsten Jenkins (Takoma University Collage, USA), John Kingston (University of Michigan, USA), Al Deino (Berkeley Geochronology Centre, USA), Rahab Kinyanjui (Max Planck Institute of Geoanthropology, National Museums of Kenya).

© Bill Lukens

“This evidence dramatically contradicts the traditional view of ape origins – that apes evolved upright torsos to reach fruit in forest canopies,” the authors say in a recent essay on The Conversation. “Instead, Morotopithecus, the earliest known ape with upright locomotion, consumed leaves and inhabited an open woodland with grassy areas.”

Dr. Rahab Kinyanjui, research group leader at the Max Planck Institute of Geoanthropology, was part of the international team whose results were recently published. Through examination of preserved plant remains (phytoliths) in the early Miocene sediments, Dr. Kinyanjui and her colleagues were able to provide evidence of the presence and abundance of C4 grasses that push back the spread of grasslands in Africa by 10 million years.

“These findings are important because they clearly demonstrate that engaging experts from different backgrounds and incorporating different lines of scientific evidence draws a clear picture of the past ecosystems,” explains Dr. Kinyanjui. “Together these insights give a better understanding of how past ecosystems influenced evolution of species, in our case the early apes.”

The new data contradicts the previous assumption that early Miocene ecosystems were entirely forested and instead shows that grasslands were a major component of the ecosystems in which apes first evolved. The authors hope that their findings will lead to the review of the faunal fossil community preserved and collected from this time period.