The present research examines the consumption, treatment, and disposal of the human placenta in a sample of 179 societies. The findings reveal differences between placental mammals and humans as maternal placentophagy, the consumption of the placenta, is rare. Treatment and disposal of the placenta is variable but ubiquitous cross-culturally.

Using a sample of 60 societies from eHRAF, this study explores the cross-cultural commonalities and differences in human-pet dynamics. The authors focus on understanding the range of functions of pets and the positive or negative treatment of pets. In addition, they test whether human investment in pets is a significant challenge of evolutionary theory. First, the results support that there are distinct functions of pets, challenging the common view of contemporary function of pets as emotional surrogates. Secondly, the data collected show an ambivalent treatment of pets across cultures, including small-scale societies. Finally, the research does not support the idea that human investment in pets sacrifices their reproductive success.