In a new publication in the Journal of the History of Biology, KLI postdoctoral fellow Marcelo Domingos de Santis challenges the conventional narrative of the systematics wars, arguing that Joseph Felsenstein’s influential “Hennig’s Dilemma” fundamentally misrepresents Emil Hans Willi Hennig’s original writings. Felsenstein’s critique asserted that Hennig’s phylogenetic method relied on biologically unrealistic assumptions, the absolute certainty of ancestral states, the prohibition of reversal, and the forbiddance of homoplasy, thereby depicting parsimony as flawed and clearing the path for maximum likelihood dominance. Through an examination of historical texts such as Hennig’s 1950 work, he contends that these attributed assumptions are absent from Hennig’s actual epistemic framework. Marcelo reframes this issue as “Felsenstein’s Dilemma”, a persistent uncertainty stemming from historical misinterpretation, and argues that the dilemma functioned as a powerful rhetorical device rather than a valid methodological refutation. He concludes that the subsequent marginalization of morphological data indicates the systematics wars are not truly over.

Publication:
de Santis, M. On “Hennig’s Dilemma” and the Post-Systematics Wars. J Hist Biol (2026).
https://doi.org/10.1007/s10739-026-09854-x