Debate sometimes still arises as to whether the Sobaipuri and other O'odham groups are related to the prehistoric Hohokam who occupied a portion of the same geographic area and were present until about the 15th century.
A key piece of the puzzle has recently been found when it was discovered that there was Sobaipuri (O'odham) present in the late prehistoric period (Seymour 2007a, 2011a, 2011b, 2014).
The position is no longer defensible that no one was present after 1400 CE [clarification needed] and that there was a substantial population decline in the prehistoric period (Seymour 2007c,d, 2011a, 2011b).
The issue of a continuum is implausible because archaeological and oral histories demonstrate [examples needed] that the local residents intermixed with and became O'odham.
This original native Sobaipuri settlement of San Cayetano del Tumacácori has been located archaeologically on the east side of the river (as shown on Kino's historic maps), providing evidence of a densely packed, well-planned, long-occupied village (Seymour 2007a, 2011a).
The first archaeological work was initiated by Charles C. Di Peso (1953, 1956) of the Amerind Foundation who established a program designed to understand the transition from prehistory to history.
She has mapped portions of their extensive irrigation systems and noted how their agriculture-based villages drifted along the river margins as groups grew and splintered through time (Seymour 1990, 1993, 1997, 2003, 2011a, 2011b, 2013).
In the early 1980s, archaeologist Bruce Masse (1981) excavated Sobaipuri sites on the lower (northern) San Pedro River, revising many of Di Peso's original perspectives and summarizing the state of knowledge about this group to that date.
Archaeologist Bruce Huckell (1994) documented three archaeological sites in the shadow of the Santa Rita Mountains north of Sonoita, Arizona.