Tuna (Bluefin)

# Evolutionary Timeline of Bluefin Tuna The bluefin tuna (Thunnus thynnus) belongs to the Scombridae family, with its evolutionary history rooted in ancient teleost fishes. Key evolutionary pressures included changing ocean temperatures, prey distribution, and the need for efficient predation in open waters. Major transitions involved the development of streamlined bodies, advanced swimming mechanics, and partial endothermy for maintaining activity in varying temperatures. ### Key Milestones: - **Eocene Epoch (56-33.9 million years ago)**: Emergence of early scombrid ancestors from perciform fishes, adapting to pelagic lifestyles amid warming oceans post-Cretaceous extinction. - **Oligocene-Miocene Transition (23-5.3 million years ago)**: Divergence of the Thunnus genus, with adaptations for high-speed swimming driven by cooling climates and expanding ocean basins. - **Pliocene Epoch (5.3-2.6 million years ago)**: Refinement of endothermic traits in bluefin tuna lineages, enabling migration across temperature gradients as ice ages began. - **Pleistocene to Present (2.6 million years ago - now)**: Modern bluefin tuna speciation, shaped by glacial cycles, ocean current shifts, and human-induced pressures like overfishing.