Moving away from “the Muddle in the Middle” toward solving the Chibanian puzzle

Abstract

Sixty years ago, Sherwood Washburn 1 edited an influential volume entitled Classification and Human Evolution, which were the proceedings from the 1962 Wenner-Gren Symposium that was held in Burg Wartenstein (hereafter "BW'62") in Austria that focused on hominin systematics. One of the primary results from the BW'62 meeting was that the biological species concept (hereafter "BSC") became firmly entrenched in paleoanthropology as the structural framework for understanding hominin variation. The symposium results contributed toward the reduction in species names in human evolution, a trend that started in the late 1940s and became more prominent after 1950. 2 The effect of this paradigm shift resulted in an untenable assumption that a paleontologically defined hominin taxon represents a biological species (as defined by the BSC)-a problem that, to some extent, still exists in the field today. Unfortunately, this foundation has made it difficult to discuss the growing complexity in light of various evolutionary processes, particularly given how much the hominin fossil record has grown over the past 60 years. These questions and others were the focus of a recent Chibanian hominin systematics workshop (Meet the Chibanians: Late Middle and Early Late Pleistocene Hominin Systematics) that was held in Novi Sad, Serbia in May 2023 (hereafter "NS'23") that was funded by the Wenner-Gren Foundation and the Social Sciences and Humanities Research Council of Canada. NS'23 fell on the 60th anniversary of the BW'62 symposium that was formally published in 1963. 1 Importantly, NS'23 gathered 12 of the most active paleoanthropologists working on Chibanian hominin fossils, in addition to a paleogeneticist, a paleoproteomics specialist, and a paleoprimatologist to provide broader perspectives. The goals of the NS'23 meeting were to reassess the Chibanian hominin fossil record and move the field forward by identifying ongoing problems and suggesting steps to move toward solutions. Ultimately, we were interested in finding a way forward in hominin systematics that would allow us to move the field conceptually from the proverbial "Muddle in the Middle" toward a solvable "Chibanian puzzle."The Chibanian (ca. 774-129 ka) is increasingly recognized as an important geochronologic age (and chronostratigraphic stage) in which many major events affected our own evolutionary history.Among the topics that continue to receive substantial attention is what to make of the extent of morphological variation we observe among the Chibanian hominins discovered so far, and whether a single chronospecies can be used to effectively delimit a diverse range of specimens from Europe, Asia, and Africa. Between Homo

Candidate Denisovan fossils identified through gene regulatory phenotyping

“…Consequently, certain specimens have been classified as new provisional lineages (e.g., H. cepranensis [12, 13], H. bodoensis [14], and H. daliensis ), while others have been grouped together into broad and highly variable taxonomic groups such as H. heidelbergensis . The difficulty in defining and classifying fossils from this period is often referred to as “The Muddle in the Middle” [15].…”