Evolutionary Anthropology Society
Oral Presentation Session
Fitness interdependence, here broadly referred to as the shared influence of individuals in
replicating their genes into the next generation, attempts to measure ‘stakes’ that
individuals have in one another (Roberts 2005). Stakes can often be defined as genetic
relatedness, thus kinship is important to any study of interdependence and cooperation.
Recent work in the evolutionary origins of cooperation and altruism suggest that these
phenomena go beyond Hamilton’s rule. Examples range from Jones’ (2016) assertion that
social norms are key players in cooperation and altruism to Cronk et. al (2018) and Aktipis et.
al’s (2018) fitness interdependence models. This paper acknowledges and builds off of
these various approaches. However, previous models only extend to cooperation and
altruism between relatively close kin, albeit still beyond Hamilton’s rule. I will present
data, from the Iban of Borneo demonstrating that cultural traditions influence cooperation not only goes far
beyond Hamilton’s rule, but even beyond the kinship extensions put forth elsewhere. The
previous models focus on cooperation and interdependence between living kin, while my
model emphasizes the interdependence between ancestors and descendants. This shift in
focus brings to light the influence that traditions have on human behavior, creating
interdependence between ancestors and their, sometimes very distant, descendants.
Gotong-royong, the Iban practice of mutual aid in rice planting, serves to exemplify the
process of traditions promoting cooperation between descendants. Furthermore, the rice