Original: This unusual situation where females may have greater fitness when they help rear siblings rather than producing offspring is often invoked to explain the multiple independent evolutions of eusociality (occurring some 11 separate times) within the haplodiploid group Hymenoptera — ants, bees and wasps.
Simplified: This unusual situation where females may have greater fitness when they help rear siblings rather than producing offspring is often used to explain that eusociality evolved several times, independently in the haplodiploid group Hymenoptera — ants, bees and wasps.