Objectives We investigate intracemetery biological variation at the Fort Ancient SunWatch village (800–500 BP.) to test the hypothesis that the SunWatch population consisted of spatially structured biologically differentiated kin groups consisting of distinct local Late Woodland and non‐local Mississippian biological populations. Material and Methods The SunWatch sample contains 166 individuals: 63 adults and 103 subadults. We analyze intracemetery biological variation using two feature sets: the buccolingual diameters of the polar teeth in the permanent (n = 37) and deciduous (n = 26) dentitions. We apply matrix correlation models to biodistance and grave distance matrices in both data sets, evaluate burial outliers and individuals exhibiting a rare dental feature with interindividual biological distances, and evaluate potential cultural subgroups with Mahalanobis' distance. Results Matrix correlation analyses for both feature sets as well as interindividual and subgroup distances indicate the SunWatch village cemetery was kin structured, contained a single primary biological population, and also contained a small number of non‐local individuals most of whom were from closely related populations. We thus reject the hypothesis that the SunWatch population consisted of biologically distinct Late Woodland and Mississippian biological populations. Discussion Although SunWatch village exhibited cultural attributes characteristic of both local Late Woodland and non‐local Mississippian groups, biologically the village was composed of one primary population. The lack of evidence for marked biological differentiation in the SunWatch village area at about 800–500 BP. suggests diffusion and acculturation may account for Mississippian cultural characteristics in southwestern Ohio Fort Ancient villages. If gene flow or migrations from biologically distinct Mississippian populations into southwestern Ohio occurred, either or both likely occurred well before 800 BP. This would have allowed the process of admixture time to produce a relatively homogeneous, nondifferentiated population. The latter alternative is consistent with the appearance in southwestern Ohio of non‐local individuals at one site linked to surrounding Mississippian regions at about 950 BP. Am J Phys Anthropol 160:719–728, 2016. © 2016 Wiley Periodicals, Inc.