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08/06/2025 10:00

How Sibling Cooperation Drives the Evolution of Family Life

Theresa Hübner Pressestelle
Universität Bayreuth

    Researchers at the University of Bayreuth have discovered that offspring of burying beetles benefit from having siblings—regardless of whether their parents are present to provide care. This challenges the long-standing paradigm that sibling rivalry over parental resources outweighs any benefits, making siblings a disadvantage for individual offspring. The findings are published in the journal The American Naturalist.

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    Why it matters

    Whether in insects or humans, social relationships play a vital role in the lives of many animal groups, with family life being particularly significant. Although family life has evolved independently many times across different animal groups, social interactions often show similarities: parents interact with each other and with their offspring, and the offspring interact among themselves. Research into the effects of social isolation—such as the absence of parents—has traditionally focused on primates or rodents. However, these animals typically cannot survive without parental care, limiting the insights such studies can offer into the effects of social isolation. Studies like the one carried out in Bayreuth, which examine social interactions in other species, help explore the evolution of family life and generate hypotheses about how family structures may have developed in other animals, including humans.
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    For a long time, interactions between parents and their offspring were considered the main evolutionary driver of family life in the animal kingdom. However, recent studies across various species suggest that other forms of interaction also play a crucial role in the development of social behaviour. “There are still significant gaps in our understanding of how sibling interactions work alongside parent-offspring interactions, and what happens when sibling contact is absent under different forms of parental care—especially how sibling interactions are influenced by the presence of parents,” says Paul Huber, doctoral researcher in the Evolutionary Animal Ecology research group at the University of Bayreuth and lead author of the study.

    “A deeper understanding of these aspects could be key not only to grasping the evolution of family life but also to expanding our knowledge of the development of highly social species, including humans,” adds Prof. Dr. Sandra Steiger, Chair of Evolutionary Animal Ecology at the University of Bayreuth.

    To address these knowledge gaps, the Bayreuth researchers studied the parental care behaviour of the burying beetle Nicrophorus vespilloides. In this species, both mother and father typically care for the larvae by preparing the carcass in which the offspring are raised and feeding them after they hatch. However, the larvae can survive even in the absence of one or both parents. The ability to benefit from parental care without being dependent on it makes Nicrophorus vespilloides an ideal model organism for studying the role of family member isolation in animals.

    In their experiment, the researchers raised larvae either alone or with siblings. The larvae were randomly assigned to different test groups: parental care by both parents on a prepared carcass; no parental care but a prepared carcass; no parental care and an unprepared carcass. In a second experiment, individual larvae or sibling groups were cared for either by both parents or by just one.

    “Our study shows that larvae benefit from the presence of siblings both when parents are present and when they are absent. This is surprising, as it was previously assumed that while siblings may cooperate in the absence of parents, they compete for attention and resources when parents are present,” says Huber. The researchers suspect that a shared begging behaviour among larvae may reduce the effort required per individual while increasing overall parental investment in the brood.

    The study was conducted as part of the project “The effect of social isolation on offspring performance: an evolutionary, ecological and molecular perspective” (STE 1874/12-1), funded by the German Research Foundation (DFG). Running from 2023 to 2026, the project aims to deepen our understanding of the effects of social isolation across multiple levels.


    Contact for scientific information:

    Prof. Dr. Sandra Steiger
    Evolutionary Animal Ecology
    University of Bayreuth
    Phone: +49 (0)921 / 55-2740
    E-Mail: sandra.steiger@uni-bayreuth.de


    Original publication:

    Paul Huber, Stefanie Bartl, Jan Schneider, Sandra Steiger. Better Together: Offspring Benefit from Siblings in Both the Absence and the Presence of Parents. The American Naturalist (2025)
    DOI: https://doi.org/10.1086/736816


    Images

    Parents of the black-horned burying beetle (Nicrophorus vespilloides) caring for their larvae on a carcass.
    Parents of the black-horned burying beetle (Nicrophorus vespilloides) caring for their larvae on a c ...
    Source: Heiko Bellmann
    Copyright: Heiko Bellmann


    Criteria of this press release:
    Journalists, Scientists and scholars
    Biology
    transregional, national
    Research results
    English


     

    Parents of the black-horned burying beetle (Nicrophorus vespilloides) caring for their larvae on a carcass.


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