Chimpanzee and bonobo mothers carry their dead infants for hours or even months as an extension of maternal attachment, according to research published on the 16th (local time) in the international journal Biology Letters. Oxford University anthropology researcher Rhys Hammond and colleagues analyzed 83 cases across 15 African study sites, including Tanzania, Uganda, and the Democratic Republic of Congo, finding that infant corpse transport is closely linked to the cause of death, the infant’s age at death, and the mother’s inter-birth interval.
Four Primary Drivers of Primate Corpse Carriage
Historically, scientists assumed that primate mothers carried deceased offspring simply because of a cognitive failure to understand death. To test existing hypotheses, the Oxford research team examined 83 cases and identified four primary factors influencing the duration of corpse transport: cause of death, pre-existing social bonds, inter-birth intervals, and ambient temperatures.
Mothers carried infants who died from disease longer than those who died from trauma such as infanticide. Furthermore, older infants were carried for extended periods. Regions with longer average inter-birth intervals also exhibited longer corpse-carrying durations, while lower temperatures delayed decomposition and extended the time mothers held the bodies.
Did you know? Researchers noted that in many observed cases, chimpanzee mothers continued to carry infants whose bodies had already mummified. Mummification provides a clear and continuous signal of death, proving that mothers do not carry the bodies out of sheer ignorance that the infant has died.
Why Disease Deaths Trigger Longer Maternal Investment
The research team suggests that mothers carry disease-fated infants longer because they can maintain their maternal attachment behaviors without interference. When an infant is killed by a male through infanticide, a mother continuing to carry the body risks facing additional aggression from males.
Early abandonment of an infanticide victim functions as a behavioral adjustment to protect the mother from physical risk. Conversely, when an infant dies of disease, those social risks are absent, allowing the expression of maternal attachment to continue unimpeded.
Implications for the Evolution of Human Death Concepts
Science has yet to definitively prove whether non-human primates understand the irreversibility of death. However, this study demonstrates that existing maternal behavior systems alone can explain corpse-carrying without requiring human-like cognitive processing of mortality.
Corresponding author Thomas Püschel explained that understanding how chimpanzees and bonobos react to death helps illuminate the origins of human death concepts. The complex ability to understand death as a final state likely emerged independently in the human lineage after humans and chimpanzees split from a common ancestor.
Frequently Asked Questions
How long do chimpanzee and bonobo mothers carry dead infants?
Depending on various factors, mothers carry deceased infants anywhere from a few hours to several months.
Why do mothers stop carrying infants killed by infanticide sooner?
Carrying an infant killed by infanticide poses a risk of additional physical aggression from males, prompting mothers to abandon the bodies earlier for their own safety.
Do chimpanzees understand that their infants are dead?
While researchers observed mothers carrying mummified remains—a clear physical indicator of death—it remains unproven whether non-human primates fully grasp the irreversibility of death.
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