A CONICET study has revealed how whales and dolphins evolved over 50 million years

A team of Argentine scientists from the National Scientific and Technical Research Council (CONICET) and the National University of La Plata (UNLP) has revealed how whales and dolphins evolved over the past 50 million years. Their study, published in the international journal Nature Communications, presents a new approach to understanding the evolutionary history of these marine mammals. The research analyzed the evolution of species alongside their ecological roles within marine ecosystems, using quantitative models and an extensive database containing information on both fossil and modern cetaceans. Factors such as body size, feeding habits, auditory capabilities, and environmental conditions were considered. The researchers identified three major stages in this evolutionary transformation. The first stage occurred during the Eocene and Oligocene periods, approximately 33 million years ago, when the ancestors of today’s cetaceans completed their transition from terrestrial environments to fully aquatic lifestyles. This marked a critical shift in their physiology and behavior, enabling them to thrive in oceanic habitats. The second phase took place between the late Oligocene and early Miocene, around 23 million years ago. During this time, baleen whales with specialized structures, such as the baleen plates used for filtering food, emerged from toothed ancestors. Simultaneously, the odontocetes, which include dolphins, sperm whales, and beaked whales, developed and diversified their echolocation systems, allowing them to navigate and hunt in complex underwater environments. The final stage unfolded during the Pliocene and Pleistocene epochs, roughly 2.58 million years ago. This period saw the extinction of numerous lineages, yet the core ecological functions previously performed by these extinct species persisted. These functions, such as those carried out by large filter feeders or top predators, remained intact, contributing to the current diversity of whales and dolphins. One of the most striking findings was the distinction between taxonomic diversity, the number of species, and ecological diversity, the variety of roles species play within an ecosystem. While there was a high number of species during the Miocene, they did not necessarily occupy a wide range of ecological niches. In contrast, the Plio-Pleistocene era witnessed the disappearance of many lineages without a corresponding loss of key ecological functions. This suggests that the stability of an ecosystem depends not just on the number of species present, but also on the persistence of essential functional traits. The study also highlighted the importance of certain evolutionary innovations. Once features such as baleen structures in whales or echolocation abilities in odontocetes emerged, they remained largely unchanged for millions of years, shaping subsequent evolutionary paths. According to Mariana Viglino, one of the researchers, these traits maintained specific specializations, leading to long-term adaptations. The work, authored by scientists affiliated with CONICET, UNLP, and other Argentine scientific institutions, aims to serve as a reference point for future studies on cetacean evolution. It underscores the complexity of evolutionary processes and the interplay between environmental changes and biological adaptation. As further research continues, the insights gained from this study could provide valuable context for understanding broader patterns of marine life evolution.