Rediscovering our relationship with the sea: Unlocking the evolutionary history of the mighty bluefin tuna using novel paleogenetic techniques and ancient tuna remains

The relationship between Mediterranean civilizations and Atlantic bluefin tuna (Thunnus thynnus) is the stuff of legends, having survived the rise and fall of several empires, endured dramatic climate shifts and witnessed the passing of millennia. While this relationship was documented by ancient philosophers and poets and is presently studied by scientists and the fishing industry, mysteries surrounding the species endure. Today traditional fishing techniques are fading into the past and industrial fisheries threaten the survival of the species. Herein, we have used novel molecular techniques to analyze DNA extracted from tuna bones excavated from late iron age and ancient roman settlements in coastal Iberia (4th-2nd century BC), tuna remains buried beneath the sands of Constantinople’s Byzantine-era harbour (4th-15th century AD), vertebrae closeted away in Europe’s oldest university (1911-1925) and flesh harvested from present day giant tunas. Several techniques were used to scan the entire genome for single nucleotide polymorphisms and the migration of non-coding genetic elements (NGS) as well as target changes occurring in genes subject to selective pressures (PCR and Sanger sequencing). By focusing on genes associated with metabolism, growth and immune response and changing allele frequencies indicative of population structuring, we are attempting to reconstruct the species’ adaptive response to fisheries pressure and a changing sea. Perhaps by understanding the evolutionary path taken by a species with which we have a shared past, we can discover a way to preserve a species and our relationship with the eternal sea, our past and future.