Humans are unique but not exceptional species of mammals.

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These people may think that they are part of an evolved society different from the other mammals that inhabit the earth. But their daily behavior and breeding habits are not much different from those of other mammals that hunt, forage, and raise and teach their young, the researchers suggest.

“It has long been argued that humans are an exceptional and egalitarian species compared to other mammals,” said Monique Borgerhoff Mulder, professor emeritus of anthropology at the University of California, Davis, and corresponding author of a new study. But, she said, this exceptionalism may have been exaggerated.

“Humans appear to resemble mammals that live in monogamous associations and, to some extent, those classified as cooperative breeders, where breeding individuals have to rely on the help of others to raise their young,” he said.

The UC Davis-led study, with the collaboration of more than 100 researchers from various institutions around the world, is the first to look at whether human males are more egalitarian than males among other mammals, focusing on the number of offspring they produce. .

The article, “Reproductive Inequality in Humans and Other Mammals,” was published this week (May 22) in the Proceedings of the National Academy of Sciences. Co-authors include researchers from UC Davis, the Santa Fe Institute, the National Institute for Mathematical and Biological Synthesis, and the Max Planck Institute for Evolutionary Anthropology, Germany.

The researchers collected data from 90 human populations comprising 80,223 individuals from many parts of the world, both historical and contemporary. They compared male and female records with lifetime data from 45 different non-human mammals in the wild.

The researchers found that humans are not exceptional, just other unique species of mammals. Furthermore, as first author Cody Ross, a former UC Davis graduate student in the Department of Anthropology now at the Max Planck Institute, points out, “we can quite successfully model reproductive inequality in humans and nonhumans using the same predictors.”

Egalitarianism in polygynous societies

Somewhat unexpectedly, by focusing specifically on women, the researchers found greater reproductive egalitarianism in societies that allow polygamous marriage than in those where monogamous marriage prevails. In polygynous systems, where men take multiple wives at the same time, women tend to have more equitable access to resources, such as land, food and shelter, and parenting assistance. This is because women, or their parents on their behalf, favor polygynous marriages with wealthy men who have more resources to share.

The researchers observed something else in their work.

“It turns out that monogamous mating (and marriage) can lead to significant inequalities among women,” Borgerhoff Mulder said. Monogamy, practiced in agricultural and market economies, can promote large differences in the number of children couples produce, the researchers found, as a result of large differences in wealth in those economies.

How humans can differ

The fact that men are relatively egalitarian compared to other animals reflects our parenting patterns. Human children are highly dependent on the care and resources provided by mothers and fathers, a factor that is unusual, but not entirely absent, in other mammals, the researchers said.

The critical importance of the complementary nature of this care, that each parent provides different and often non-substitutable resources and care throughout the long human childhood, is the reason why we do not show the enormous reproductive variability observed in some of the great apes. said researcher Paul Hooper of the University of New Mexico.

However, to support these inferences, anthropologists need more empirical data. “In summary, the importance of biparental care is based on our model, but needs further evidence,” said Borgerhoff Mulder.