Source: Paleoceanography and Paleoclimatology
Great apes began to diverge from other primates around 25 million years ago, according to eastern African fossil records. Though it would take another 20 million or so years for upright-walking hominins to appear, understanding the habitats of early apes helps clarify how environments drove the evolution of our distant ancestors.
Munyaka et al. excavated and analyzed fossils from an approximately 20-million-year-old early Miocene site in western Kenya called Koru 16. The now-extinct Tinderet Volcano repeatedly blanketed the area in ash, preserving it for millions of years, and today, the site hosts fossils from an array of plants and animals.
Many prior studies focused on the area around Koru 16: The first primate fossils from the site were discovered in 1927, and famed anthropologist Louis Leakey led multiple digs there.
As part of the new research, scientists uncovered fossils of approximately 1,000 leaves and many vertebrates at two subsites between 2013 and 2023. The specimens included those of a new type of large-bodied ape and two other previously known ape species, bringing the total number of vertebrate species discovered at the site to 25.
By examining the shapes of fossilized leaves, the geochemistry of fossilized soils (paleosols), and the distribution and density of fossil tree stumps, the researchers determined that the Koru 16 site was likely located within a warm, wet forest, with rainfall amounts similar to those of modern-day tropical and seasonal African forests. However, the ancient ecosystem likely hosted more deciduous plants than do modern tropical forests. The vertebrate fossils the researchers analyzed were consistent with apes, pythons, and rodents that might have lived in such an environment.
The researchers suggest that this ancient forest environment—which was interspersed with open areas and frequently disturbed by fires, floods, or volcanic eruptions—played a role in shaping the course of evolution for early apes. (Paleoceanography and Paleoclimatology, https://doi.org/10.1029/2025PA005152, 2025)
—Madeline Reinsel, Science Writer
