Why did the chicken cross the Wallace Line? Archeological evidence suggests human-mediated dispersal of Gallus to Flores first occurred at least 2.25 ka cal. BP

Domesticated chickens (Gallus gallus domesticus) are a dominant part of the global human diet. Although the early domestication history of this species remains disputed, Mainland Southeast Asia (MSEA) is assumed to have been the initial domestication center. The eastward spread of chickens into Island Southeast Asia (ISEA) and the Pacific is typically attributed to human-mediated dispersals. Chicken remains are relatively common at Pacific Neolithic sites but are extremely rare in the archaeological records of MSEA and ISEA. Therefore, the exact routes and timing of the human-mediated spread of chickens from their native range in MSEA into the Pacific remain questions of interest. Here, we present the earliest evidence of Gallus on the Indonesian island of Flores at Liang Bua. This site has yielded an extensive stratigraphic sequence that spans from similar to 190,000 calendar years (ka) ago until the present and includes dense accumulations of faunal remains. Twelve bones from the cave's Holocene deposits have been identified as Gallus. The oldest remains, a right and left coracoid, were each directly dated to similar to 2,250 calibrated radiocarbon years before present (ka cal. BP), whereas the youngest Gallus elements are similar to 0.3 ka old. Although wild Green Junglefowl (Gallus varius) and Red Junglefowl (Gallus gallus) are found on Flores today, the absence of either of these species in deposits at Liang Bua older than similar to 2.5 ka as well as the size and shape of the oldest coracoids suggests that these remains likely represent domesticated G. gallus. This is the first evidence for domesticated chickens in the Neolithic of Flores and the first directly dated Gallus remains in Wallacea. The absence of chickens in the fossil record of ISEA suggests that Red Junglefowl (and perhaps Green Junglefowl also) reached Wallacea via human-mediated dispersal(s) at least similar to 2.25 ka cal. BP.