Genetic drift and gene flow in a prehistoric population of the Azapa valley and coast, Chile

Abstract

The present paper studies the evolutionary process operating on prehistoric groups from the Azapa valley and coast (northern Chile). The sample consists of 237 crania from the Archaic Late, Early Intermediate, Middle, Late Intermediate, and Late periods. Six metric variables were used, which were transformed to eliminate the special environmental component and to increase the proportion of genetic variance. Population structure was assessed using a method based on quantitative genetic theory, which predicts a lineal relationship between average within-group phenotypic variance and group distance to the population centroid. Results indicate that 17.5% of the total variance accounts for special environmental variance. An excess in extraregional genetic flow is observed in the population corresponding to the Early Intermediate period in the valley. A reduced differentiation is observed between Archaic and Early Intermediate coastal groups, as well as between the latter and the inhabitants of the valley in the same period. Genetic differences between both areas increased substantially since the Middle period. Evidence indicates that long-range gene flow was lower on the coast than in the valley, the lowest estimated Fst being 0.0199 for the total population (coast and valley), 0.0111 for the coastal population, and 0.0057 for the valley. Results are discussed in terms of regional archeological and ethnohistorical evidence, and a microevolutionary model is presented to account for the biological history of the population.

Coastal, valley, and oasis interaction: Impact on the evolution of ancient populations in the South Central Andes

“…These results confirm the previously proposed conclusions (Varela and Cocilovo, 2002;Varela et al, 2013) and are linked to the hypothesis of economic and social differences between the costal and valley groups (Rostworowsky 1981(Rostworowsky , 1986. Moreover, this evidence is consistent with the existence of two ceramic and textile traditions, one associated with the Pacific Coast and the other with highland and Cochabamba valley groups (Espoueys et al, 1995;Uribe, 1995Uribe, , 1999Uribe, , 2004Ag€ uero, 2000).…”

“…Furthermore, morphological difference has been demonstrated between the inhabitants of the coast and the inland valley of Azapa. The first represents a more genetically isolated group, whereas those from the valley show greater gene flow and an obvious similarity with the eastern valleys groups of Cochabamba, Bolivia (Varela and Cocilovo, 2002;Varela et al, 2013).…”

Resilience of small-scale societies’ livelihoods: a framework for studying the transition from food gathering to food production

“…An archeological example is represented by the Azapa Valley (northern Chile) where Varela and Cocilovo (2002) identified changes in population distribution dynamics over a period of about 6000 years. Their study highlighted that genetic changes in the population correlate well with population mobility, increase/ decrease of endogamy in the kinship structure, and changes in the economy, i.e., beginning of plant cultivation.…”

Functional‐cranial approach to the influence of economic strategy on skull morphology

“…For instance, Lewontin (1972), Relethford (2001Relethford ( , 2002, and Gonzá lez-José et al (2001) opted for focus on variation on different geographical levels, comparing within-and between-group variation on a continental scale vs. local populations. Conversely, Steadman (2001) and Varela and Cocilovo (2002) studied apportionment of variation based on a diachronic partition of samples. Our approach here considers an apportionment of variance based on the economic strategy.…”