Evidence Found of Early Ape Habitat

Researchers found definite evidence of the habitat of the early ape Proconsul, an extinct genus that existed from 23 to 25 million years ago, on Rusinga Island, Kenya. The finding sheds light on the interaction between habitat preference and diversification of the early ape-human lineage.

The research, published in Nature Communications by Holly Dunsworth of the University of Rhode Island, discovered that the Proconsul inhabited "a widespread, dense, mulitstoried, closed canopy" forest, according to a press release.

Dunsworth, assistant professor of anthropology, said that her team studied 18 to 20 million year old fossils belonging to an individual Proconsul among contemporary geological deposits. The discovery points to the significance of forested environments in the ape's evolution, with tree stump casts, calcified roots and fossil leaves found in the same layer as the Proconsul.

"To have the vegetation of a habitat preserved right along with the fossil primates themselves isn't a regular occurrence in primate paleontology," she said. "It's especially rare to have so many exquisite plant fossils preserved at ancient ape sites."

Since scientists started studying fossils on Rusinga, this is the first time a substantial amount of fossil evidence has painted a picture of the Proconsul apes' habitat.

"It's probably the best evidence linking ape to habitat that we could ask for," Dunsworth said. "Combined with analyses of the roots, trunks and even beautifully preserved fossil leaves, it's possible to say that the forest was a closed canopy one, meaning the arboreal animals, like Proconsul, could easily move from tree-to-tree without coming to the ground. This environmental evidence jibes with our behavioral interpretations of Proconsul anatomy--as being adapted for a life of climbing in the trees--and with present-day monkey and ape ecology."

Evidence from the excavation site has helped the researchers understand the climate that existed millions of years ago.

"The precipitation was seasonal with a distinct wet and dry period. During the dry season, there was probably relatively little rainfall," said co-author Daniel Peppe of Baylor University, citing evidence from the forest soil. "Additionally, by studying fossil leaves at the site, we were able to estimate that there was about 55 to 100 inches of rainfall a year and the average annual temperature was between 73 and 94 degrees Fahrenheit."

More data will continue to come from the island, as Dunsworth says her research will continue.

"We don't know exactly what we're going to find, but without a doubt, if we keep searching, we're going to find knowledge about early ape evolution, which was, of course, a significant chapter in our own history," she said.