Ecomorphology in Kenya's Koobi Fora Formation: Reconstructing Early Pleistocene hominin paleoenvironments with 3D geometric morphometric analyses of bovid metapodials

This research presents a new method of ecological morphology (ecomorphology) analysis using three-dimensional geometric morphometrics to quantify shape variation in extant bovid metapodials with known habitat preferences. Extant data were used to create a model for classifying bones into distinct habitat categories and to test functional hypotheses related to locomotor behavior in different habitats. The model was then applied to fossils from the Koobi Fora Formation, Kenya, to assess the environmental context during important events in hominin evolution. The use of three-dimensional geometric morphometrics demonstrates significant improvement over traditional methods using caliper measurements. Discriminant function analysis successfully classified 94% of metacarpals and 93% of metatarsals into their correct habitat categories for modern specimens. The protocol was reduced to a subset of landmarks focused on the distal epiphyses. This model produced greater overlap, but classification success rates remained high, with 82% and 83% correct classification for modern metacarpals and metatarsals, respectively. We applied the reduced model to metapodials from Upper Burgi (1.98-1.87 Ma), KBS (1.87-1.56 Ma), and Okote (1.56-1.38 Ma) members in the Koobi Fora Formation. This location is important to understanding human evolution, fossil diversity, and paleoecology. Moreover, previous studies on faunal abundance, paleosol carbonates, and carbon isotopes provide a robust framework to compare the findings of this study. Our analyses classified the majority of fossil specimens as open-habitat dwellers, with a few specimens grouped as closed-adapted, the highest number of these falling within the Okote Member sample. This suggests that open and likely xeric environments dominated the East Turkana region during the Early Pleistocene. These findings are consistent with many previous reconstructions, though with a more open signal for the Okote Member than expected based on bovid abundance research.