LOGAN -- The mystery was whether Proconsul, an extinct genus of primates, had the physical and mental ability to survive in two distinctly different African environments -- one a savanna with a few trees, the other a moist, tropical region with a canopy that would have provided the ancient apes more food and protection from predators.
And being that the prehominids in question lived 23 million to 25 million years ago, it was a bit of a cold case.
Utah State University's Jim Lutz, a wildland resources assistant professor, was part of the team that cracked that case, documented in the issue of Nature Communications released today.
"We now have definitive evidence Proconsul lived in more than one habitat, and one of those was a dense, closed-canopy, tropical forest," said Lutz, a forest ecologist.
"By examining the ancient trees' stump casts, calcified roots and fossil leaves, as well as soil at the site of the teeth discoveries, we were able to determine the existence of a forested environment."
Proconsul's skeletal anatomy indicates a flexible back somewhat similar to modern monkeys, but without a tail. The mammal's anatomy suggests ape-like grasping and climbing abilities. Proconsul displayed a mixture of Old World monkey and ape characteristics.
The study began after the 2011 discovery of four ancient teeth, the remains of ancient trees preserved in volcanic ash, and fossilized leaves on Rusinga Island in Africa's Lake Victoria.
Baylor University geologist Daniel Peppe, who co-authored the study with his doctoral student and lead author Lauren Michel, said previous work at the island's fossil sites yielded contradictory environmental preferences for Proconsul.
Lutz said it was known previously that Proconsul lived in open areas, perhaps ones like the savannas in Africa today.
"The issue was whether Proconsul also lived in a forested environment. If it did, it would have had to deal with two very different habitats at the same time, and that would have introduced evolutionary selective pressure," Lutz said.
"Members of the same species would have to be mentally and physically adapted to survive on the forests and the savannas."
To survive in drier areas with limited vegetation, Lutz said, some wildlife strategies might have included running and hiding from predators, or adopting nocturnal behavior.
A forested area likely would have provided more food and hiding places, and perhaps a canopy to keep climbing prehominids safe from predators below, he said.
But one issue for the scientists was that the area where the four ancient teeth were discovered is not a forest today.
"It's in what is Kenya now, and the climate is very dry, and people often harvest the trees," Lutz said. "There is human use of the land."
Lutz's part of the study was to work with charts of where the fossilized tree trunks were discovered.
By studying their proximity to each other, and comparing his findings to forests around the world, Lutz was able to prove that the fossilized stumps in Kenya were comparable in diameter and proximity to tree trunks in multiple canopied forests that exist today.
So Proconsul, in its day, appears to have been the master of diverse environments.
Lutz considers the study a triumph of interdisciplinary collaboration.
"A really important part of the story is about scientists working together," he said.
"Specialists worked together, experts in paleo environments and hominid evolution. I study forests. It is only by scientists in these very different fields working together that we could come up with enough evidence.
"I'm happy I could contribute a small piece of what was needed."
Contact reporter Nancy Van Valkenburg at 801-625-4275 or firstname.lastname@example.org. Follow her on Twitter at @SE_NancyVanV.