Evrim Yazgin
Cosmos science journalist
New research has shown that the earliest apes – ancestors of modern great apes and humans – evolved in tropical forests in the shadow of a violent volcano.
Apes first emerged about 25 million years ago (mya). Scientists are now beginning to understand how the environment shaped the earliest apes.
The hominin group of apes are those that include human species and our direct ancestors. This group split from the other apes within the broader hominid group about 7 mya and developed bipedalism.
A paper published in the journal Paleoceanography and Paleoclimatology describes fossils excavated in the Koru 16 palaeontological site in western Kenya. Koru 16 preserves an ancient ecosystem dating to about 20 mya, during the early part of the Miocene epoch which lasted 23 to 5.3 mya.
Over the course of this geological period, the climate dried, isolating the forests of eastern Africa and providing the environmental pressure for bipedalism in hominin ancestors.
But the early Miocene was wet and warm with much of Africa still covered in tropical and subtropical rainforest. It is this kind of habitat which saw the emergence of the first apes.
Primate fossils were first discovered at Koru 16 in 1927.
Palaeontologists uncovered 1,000 fossil leaves and many fossil vertebrates in new excavations between 2013 and 2023. Among the vertebrate fossils were those of 2 early ape species already known to science, and a third large-bodied ape which is a new species.
Among the 18 vertebrate species are fossils belonging to pythons and rodents. A mammal carnivore belonging to the extinct hyaenodont group and a relative of ungulates (the group which includes deer, antelope and pigs) was also found.
The shapes of the fossilised leaves, geochemical analysis of ancient soil and fossil tree stump distribution shows that the Koru 16 site preserves an ancient warm, wet forest with mean annual temperatures greater than 25°C. Average yearly rainfall would have been about 2,000mm – similar to Africa’s surviving rainforests.
The forest was interspersed with open areas. This ancient rainforest was no blissful paradise.
Geological evidence shows the region was frequently subjected to fires, floods and volcanic eruptions from the now extinct Tinderet Volcano. The volcano repeatedly blanketed the area with volcanic ash, preserving the animal and plant fossils for millions of years.
