Reply to Storey et al.: More DNA and dating studies needed for ancient El Arenal-1 chickens

In their letter, Storey et al. (1) concede that there is no direct genetic support for Polynesian–South American contact. However, they claim that linguistic, archaeological, and ethnohistoric evidence supports Polynesia as the most likely source of the El Arenal-1 chickens. We disagree on two grounds. First, such indirect evidence is conjectural, documents no eastward expansion to South America, and says nothing about the prehistoric availability of particular mtDNA haplotypes. Second, our central point was that analyses of all available ancient (2) and modern chicken mtDNA data reveal that the El Arenal-1 chicken carries a worldwide genetic signature potentially available to any of the possible introduction routes via Europe, Asia, and Polynesia (3). In contrast, none of the unusual genetic signatures from Easter Island chickens have been reported from South America (3).

The argument rests entirely on the radiocarbon dates. Current isotopic data indicate a fully terrestrial dietary signature (1). However, contrary to Storey et al. (1), El Arenal-1 is indeed a midden where chicken bones were found associated with marine organisms (4), and there are no local isotopic standards available to confirm the relationship between diet and isotopic signatures. Any marine input for the two new dates (1) would be consistent with a post-Columbian chronology. A region-specific set of isotopic standards and radiocarbon and stable isotope determinations for a large number of specimens of several species at the site are required as a matter of priority including dating additional chicken bones in independent laboratories to ensure reliable radiocarbon measurements (5).