An international paleontology and paleoecology study, published in the journal Frontiers in Ecology and Evolution, falls in the wake of a long tradition of studies of the University of Florence and reconstructs the origins of living African Equus. The study examined and re-evaluated findings of fossil Equus and their close relatives recovered in Plio-Pleistocene strata of North and South America, India, Georgia, Italy and Africa, to further develop the life-long work of Augusto Azzaroli, one of the most important Italian paleontologists, and a professor at the University of Florence from 1960 to 1996.
An international team led by US researchers (Smithsonian Natural History Museum and Howard University in Washington DC), and made up of scholars from the Smithsonian Human Origins Program and the Department of Paleobiology (Richard Potts and Advait Mahesh Jukar), the National Georgian Museum in Tbilisi (Georgia, with Maia Buskianidze) and the Universities of Florence and Pisa published in Frontiers in Ecology and Evolution the results of their research (doi.org/10.3389/fevo.2019.00166).
The current African zebras - as Azzaroli had already concluded -had a common ancestor in North America, Equus simplicidens, which dates back to 4 million years ago. But the researchers - thanks to the analysis of the finds coming from some European, Asian and African sites - have succeeded in reconstructing the successive passages of the evolution of these mammals: the zebras have spread in Europe and in Asia starting from 2.6 million years ago (with the two species, Equus livenzovenzis and Equus stenonis), colonizing the main areas around the Mediterranean and the Caucasus and finally Africa.
“The history of research on zebras is closely linked to Florence,” explains Lorenzo Rook, professor of Paleontology and Paleoecology: “the exemplary type of Equus stenonis is preserved right here, in the Paleontology section of the Museum of Natural History of the University. This specimen is the representative of the species, found in the Upper Valdarno by Igino Cocchi, geologist and paleontologist, lecturer in 1860 at the Higher Institute of Advanced and Vocational Studies, the ancestor of the University of Florence. A century later, Azzaroli placed Equus stenonis within the evolution of the broad group of species belonging to the genus Equus and hypothesized its ancestor in North America; now the subsequent steps leading to Africa are completed. It is no coincidence that the study originated in Florence, thanks to the stay in our department as a Visiting Professor of Raymond L. Bernor, the first author of the work."
"A key point to understand the spread of zebras,” explains Omar Cirilli, PhD student in Earth Sciences (University of Florence and University of Pisa), “is certainly the site of Dmanisi, in Georgia, where - together with the first remains of Homo erectus discovered outside the African continent - two species have been found: one of large size, identifiable as Equus stenonis, and one of smaller dimensions still undetermined. Both show many similarities with living zebras (Equus grevyi). This data, supported by statistical and morphological analyses, highlights the paleontological importance of the Georgian site, placing it as a crossroads between the European, Asian and African worlds, also for the evolution of zebras as well as of humans.”
The research, however, does not stop there: the revision of the studies on fossils of the Equidae has allowed us to re-date the appearance on Earth - anticipating it over 2 million years ago - of the enigmatic Equus stehlini, a smaller species, similar to a donkey, found in Tuscany and described in the 1960s. Further studies are underway to clarify this new evolutionary story.
