From natural theology to the extended synthesis: Historical milestones and conceptual expansions in evolutionary biology

This article explores the historical development of evolutionary biology-from Natural Theology to the Modern Synthesis (MS)-and the ongoing debate around the Extended Evolutionary Synthesis (EES). Over the past 2,500 years, evolutionary thinking has emerged from the interplay between empirical discoveries and dominant philosophical paradigms. Beginning with Aristotle and Saint Augustine, we trace how Darwin and Wallace introduced a scientific framework grounded in natural mechanisms. In the early 20th century, the MS unified Mendelian genetics and Darwinian selection, forming a gene-centered model of evolution focused on mutations and population dynamics. In recent decades, discoveries in epigenetics, phenotypic plasticity, symbiosis, niche construction, and cultural inheritance have challenged the explanatory scope of MS. The EES seeks to incorporate these processes not by discarding Darwinian principles, but by reinterpreting them through a systems biology lens. This mostly represents a conceptual shift in focus: from linear, gene-driven causality to multilevel, reciprocal, and environmentally embedded dynamics. While gaining traction, the EES has been criticized for its lack of formal models and predictive frameworks, remaining a contested proposal. Ultimately, evolutionary biology continues to evolve as a powerful scientific tradition, driven by humanity's enduring quest to understand the origins and evolution of life on Earth.