Argentine study reveals 50-million-year evolution of whales and dolphins

A team of Argentine scientists from CONICET and the National University of La Plata (UNLP) has meticulously reconstructed the evolutionary journey of whales, dolphins, and other cetaceans over the past 50 million years. Their research details how these marine mammals transformed their relationship with the environment, marking a significant shift from terrestrial to fully aquatic existence.

The comprehensive study, published in the international journal Nature Communications, offers a novel approach to understanding cetacean evolution. By analyzing species' development alongside their ecological roles, the scientists employed quantitative models and a vast database encompassing fossil and modern cetacean information. Key variables such as body size, diet, auditory capabilities, and habitat were examined.

Researchers identified three pivotal stages in this evolutionary process. The first, spanning the Eocene and Oligocene epochs around 33 million years ago, marked the completion of the transition from land to a completely aquatic life. The second stage, from the late Oligocene to the early Miocene (approximately 23 million years ago), witnessed the emergence of baleen whales from toothed ancestors and the significant development and diversification of echolocation in toothed whales, including dolphins and porpoises.

Finally, the Pliocene-Pleistocene epochs (around 2.58 million years ago) saw the extinction of numerous lineages. However, this period did not eliminate the core ecological functions established by cetaceans; instead, it consolidated the diversity of whales and dolphins seen today. An intriguing finding was the distinction between taxonomic diversity (number of species) and ecological diversity, revealing that periods with high species numbers did not always correspond to a proportional variety of ecological niches.