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Anthropologists Publish on Tiniest Ever Fossil Ape Species Described

Fossil molars of simiolus minutus

Fossil molars of simiolus minutus

James rossie at social and behavioral sciences building
James Rossie on October 30, 2018, outside his office in the Social and Behavioral Sciences Building at Stony Brook University.

Stony Brook, NY, November 5, 2018 — Stony Brook University Anthropology Professor James Rossie and the late Andrew Hill, an anthropology professor at Yale University, were just starting their 2004 field season in the Tugen Hills, Kenya when Rossie plucked a tooth out of the sediment. Now, a study authored by the pair shows that this belongs to a new species of ape — the smallest ever yet described, weighing just under 3.5 kilograms — from 12.5 million year old sites in the Tugen Hills, giving important clues about the unexplained decline in diversity of apes during the Miocene epoch. The paper, entitled “A new species of Simiolus from the middle Miocene of the Tugen Hills, Kenya,” is scheduled to published in the December issue of The Journal of Human Evolution.

The late andrew hill anthropology professor
The late Andrew Hill

At the beginning of the Miocene epoch, there were only a few species of monkeys, while apes were represented by a broad radiation of species ranging from 4 to 50 kilograms; today, however, there are only a handful of ape species remaining. Precisely what caused the decrease in ape diversity and rise of monkey diversity is a mystery that paleontologists have been contemplating for decades, Rossie said, and many suspect that direct competition between the two groups was to blame.

“One thing this shows us is that some apes were leaning toward folivory at just the time when monkeys were evolving their uniquely effective adaptations for it,” Rossie said. “Under those circumstances, I’m not surprised that this is the last you see of these small apes. We’ve previously found the earliest colobine monkeys at these sites, and now we have an ape that looks like it would have been in direct competition with them for food.”

James rossie escavating at simiolu site
James Rossie excavating at one of the Simiolus sites in 2004.

Rossie said fossil molars from the tiny ape, now housed in the National Museum of Kenya, Nairobi, show evidence of leaf eating, which suggests that it was in direct competition with the earliest colobine monkeys for food resources. Rossie said the small ape is also the latest-surviving member yet described of the small apes that flourished in the early Miocene epoch.

The greatest obstacle to solving this puzzle is the relative scarcity of fossil sites in the middle of the transition, Rossie said – from about 14 to 6 Ma. The new species comes from sites in the Tugen Hills that are among a small number of African sites in this time range.

About Stony Brook University

The late Andrew Hill excavating alongside with Kamoya Kimeu at the Tugen Hills site in 2004.

Stony Brook University is going beyond the expectations of what today’s public universities can accomplish. Since its founding in 1957, this young university has grown to become a flagship as one of only four University Center campuses in the State University of New York (SUNY) system with more than 26,000 students and 2,600 faculty members, and 18 NCAA Division I athletic programs. Our faculty have earned numerous prestigious awards, including the Nobel Prize, Pulitzer Prize, Indianapolis Prize for animal conservation, Abel Prize and the inaugural Breakthrough Prize in Mathematics. The University offers students an elite education with an outstanding return on investment: U.S. News & World Report ranks Stony Brook among the top 50 public universities in the nation. Its membership in the Association of American Universities (AAU) places Stony Brook among the top 62 research institutions in North America. As part of the management team of Brookhaven National Laboratory, the University joins a prestigious group of universities that have a role in running federal R&D labs. Stony Brook University is a driving force in the region’s economy, generating nearly 60,000 jobs and an annual economic impact of more than $4.6 billion. Our state, country and world demand ambitious ideas, imaginative solutions and exceptional leadership to forge a better future for all. The students, alumni, researchers and faculty of Stony Brook University are prepared to meet this challenge.

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