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Inequality among animals can shed light on social evolution

Wealth inequality is typically considered for human populations. Now, a new study suggests that wealth inequality in animals can shed light on social evolution.

Adapting the study of wealth inequality in humans, the researchers show how wealth – material goods, individual attributes, or social connections – occurs broadly across animal species and can be distributed equally or unequally. This framework explores the idea that the unequal distribution of wealth has important consequences for all animal societies.

Inequality is one of the greatest challenges of a modern society that presents consequences to all. Scholars study inequality to understand where it comes from and how policies could help produce more equitable societies.

Eli Strauss from the Max Planck Institute of Animal Behavior in Germany (MPI-AB) and Daizaburo Shizuka, from University of Nebraska-Lincoln are both behavioral ecologists who study social evolution in non-human societies. 

“Reading these fascinating sociology and economics papers, it struck me that this work shares a common goal with my work in animal behavior, which is that we both want to understand how inequality arises and affects outcomes for individuals and groups,” said Strauss.

Researchers have previously explored differences among animals in their physical traits, territory, resources and the social power they wield. However, these dimensions were not previously grouped under the umbrella of inequality. For the first time, the study gathered research from different academic fields to bridge the divide between inequality research in human and animal societies. 

In humans, “inequality” exists when something of value is distributed unequally among individuals. Usually, that value is defined as their wealth. 

To understand the value of wealth among animals, the scientists turned to research that explores inequality in hunter-gatherer societies. “These societies show varying degrees of wealth inequality, but wealth isn’t limited to bills and coins,” said Strauss. 

Instead, anthropologists view wealth as individual characteristics like knowledge or hunting ability, and social connections. For instance, a woman could be wealthy by owning many cows, being skillful at growing crops, or having influence in her society.  

The human dimensions of wealth also operate in animals, through territory ownership and access to food. In dolphins and crows, for example, tool use techniques are valuable pieces of information that open up new foraging opportunities.

Social relationships are also a critical source of wealth in many species, who form alliances to help rise through societal ranks. Interestingly, wealth in animals can also be transferred to offspring. 

Animal wealth can be spread evenly among individuals or can be concentrated in the hands of just a wealthy few. Inequality research can help to further understand how animal societies work. 

“The structure of a society has a lot of different influences on all individuals that live within it. In many cases, the differences between individuals arise from the various ways in which unequal societies affect them,” said Shizuka.

“In turn, individuals try to exert control over or navigate these unequal systems in different ways. The biology of animal societies includes these types of dynamics, and we can’t understand the evolution of social animals without recognizing this feedback between the individual and the society.”

Strauss and Shizuka are hopeful that their findings will guide future research on wealth inequality across species, as this could lead to a better understanding of social evolution.

“We can look to other species to understand the general evolutionary processes that produce all animals, ourselves included, but the question of what makes an ethical human society is fundamentally a moral question where the social lives of animals can’t guide us,” said Strauss. “This is something we need to figure out on our own.”

The study is published in the journal Proceedings of the Royal Society B Biological Sciences.

By Katherine Bucko, Staff Writer

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