POST-PLEISTOCENE HORSES (EQUUS) FROM MÉXICO

For more than a century many paleontologists, biologists, paleoecologists, and archaeologists have contended that Equus species (American horse) became extinct on the North American continent by about 13,000 calibrated years BP – all part of the Late Pleistocene (Ice Age) extinction event. The paleontological project presented here that focuses on Equus from Rancho Carabanchel, San Luis Potosí, México became chronologically intriguing to us in having the horse consistently radiometrically dating into the Holocene, well beyond the presumed extinction event. Our approach to this observation was to conduct successive radiocarbon dates (n=19) tied as closely as possible to fossil remains and to stratigraphic units. The remains of the extant horse, Equus caballus, were recovered only in the upper-most Unit I while the extinct Equus cf. mexicanus, E. cf. conversidens, and E. cf. tau were recovered from the underlying Units II – VI of the late Holocene to approximately 45,000 calibrated years ago. We discuss how our data adds to the growing information which implies that horses may have persisted in this region of México well after the classical Late Pleistocene extinction event. Our conclusions may well illustrate that the extinction episode was actually a process lasting well into the Holocene and was not the event that many paleoecologists and archaeologist envision.