The inter-island Kula exchange network within the Massim region of eastern New Guinea is unique in its complexity, with the historically recorded configuration between the northern islands archaeologically visible between 1350 and 1500 AD (600â€“450 calBP). The southern islands were incorporated sometime later, and Tubetube Island formed a major hub in this southern extension of the Kula. To assess the timing and extent of Tubetube Islander involvement, excavated obsidian was used as a proxy to assess social connections with other island communities within the ambit of Kula. Forty-nine pieces from two sites, Lagisuna and Tupwana, spanning the relevant period were chemically characterised using pXRF and determined to have been sourced almost exclusively from western and eastern Fergusson sources, respectively. We argue social connections between communities were village specific. Lagisuna had connections with the West Fergusson source region outside of the ethnographically known Kula network from 1500 to 1650 AD (450â€“300 calBP). Tupwana had maintained historically recorded kinship connections with important Kula communities on Duau and Dobu in the East Fergusson source region over several generations by at least 1800 AD (150 calBP), and probably intermittently from 1500 to 1650 AD. Our results support an increasingly nuanced model for the past development of Kula exchange.