The fact that humans who are not related by blood help each other repeatedly over time is demonstrably true—think of the ongoing mutual support that sustains your longest-running friendships.

The new paper draws on 20 years of research that Rubenstein and his colleagues have conducted on African starlings living in the harsh climate of east African savannas.

More information: Nature (2025). DOI: 10.1038/s41586-025-08958-4