Advantageous inequity aversion (i.e., the tendency to respond negatively to unfairness
that benefits oneself) usually develops in 6–8-year-olds. However, little is known about
the selection pressures that might have shaped this phenomenon. Using data collected from
120 4–8-year-old Finnish children, we tested two evolutionary explanations for the
development of advantageous inequity aversion: reciprocal altruism (i.e., benefiting from
sharing when the roles are likely reversed in the future) and inclusive fitness (i.e.,
benefiting from sharing with biological relatives that carry the same alleles). We first
successfully replicated a previous experiment, showing that 6–8-year-olds display
advantageous inequity aversion by preferring to throw away a resource rather than keep it
for themselves. Here, this behavior was also displayed in 5-year-olds. Using a novel
experiment, we then asked children to distribute five erasers between themselves, a
sibling, a peer, and a stranger. That is, an equal distribution was only possible if
throwing away one eraser. We found no support for advantageous inequity aversion being
shaped by either inclusive fitness or reciprocal altruism. Future studies could
investigate costly signaling and adherence to social norms to avoid negative consequences
as ultimate explanations for advantageous inequity aversion.