A large-scale genetic study of Mesolithic hunter-gatherer remains from the Atlantic coast of the Iberian Peninsula has discovered the earliest known human adaptation to marine-based neurotoxins. The study, appearing in Molecular Biology and Evolution, sequenced the genomes of 14 individuals found in ancient shell middens dating to 10,000 BCE. The analysis found a significant selection for a specific variant of the CYP2 gene family, which is responsible for detoxifying marine alkaloids produced by toxic algal blooms.
This genetic adaptation allowed the 'Iberian-Atlantic' foragers to safely consume large quantities of shellfish year-round, even during periods when red tides would have made the food source lethal to other populations. The researchers noted that this adaptation predates the Neolithic agricultural transition by several millennia, suggesting that the drive for dietary specialization was a primary force in the evolution of these coastal communities. The findings challenge the view that Mesolithic populations were merely opportunistic foragers, showing instead a deep biological specialization to their local environment.
The study also revealed that this specific genetic trait persisted in the local population for thousands of years, even after the arrival of early farmers from the East. Today, traces of this ancestral resilience can still be found in some modern populations in coastal Portugal and Spain. This research provides a new benchmark for understanding how human biology co-evolved with specific marine ecosystems and the unique chemical challenges they presented.