Eusocial organisms such as ants are at the centre of a debate in sociobiology.

Credit: iStockphoto

SYDNEY: Eminent evolutionary biologist E.O. Wilson is trying to bring about the demise of the theory of kin selection, which has formed the foundation of the study of sociobiology since the 1960s.

"After four decades ruling the roost, it is time to recognise this theory's very limited prowess," E.O. Wilson writes this week in Nature.

The paper has sparked controversy among kin selection's supporters (read about it in Analysis: biologists slam kin selection heretics).

Wilson, along with Harvard colleagues and mathematicicans Martin Nowak and Corina Tarnita, sketches out an alternative pathway by which species may attain the complex social structures in which individuals cooperate to raise offspring.

Eusociality

Biologists use the term 'eusociality' to describe the hierarchial colony structure of ants, bees and wasps - and loosely, humans too.

Eusociality is a stable solution to group dynamics that occurs when the group of cooperate in caring for the young, the labour of reproduction is divided (that is, sterile workers help to raise young while fertile members are procreating) and at least two generations of life stages overlap in contributing to the colony.

But the question is: how do colonies form eusociality in the first place? It's got heavy evolutionary costs and is not very common in the animal kingdom.

My sister's keeper

For 40 years, kin selection has been the dominant paradigm for explaining the phenomena.

Kin selection theory (and the more general concept of inclusive fitness), asserts that altruistic behaviour will evolve by natural selection if the fitness advantage of cooperating compensates for the loss of fitness to the individual.

Kin selection is used to explain why some individuals will sacrifice their own reproductive potential in order to care for the offspring of relatives, such as sterile female workers and reproductive queens.

Kin selection not needed anymore

But according to the new study, "the theory of inclusive fitness rests on fragile assumptions, which rarely hold in nature… and is not needed to explain eusociality."

Instead, based on precise mathematical models they outline an allegedly simpler and superior approach involving three distinct steps by which species can bypass the evolutionary costs of eusociality.

Initially, species must form groups within a population, such as when parents and offspring remain together. Next, the species must accumulate traits arising through natural selection that favour the switch to eusociality, including most importantly the construction of a defensible nest.

Finally, in order to cross the eusociality threshold, individuals must develop genes that quell an individual's urge to disperse to start its own nest.

However, many of the most world's most prominent evolutionary biologists are set to defend kin selection.

Daniel Queller of Rice University, Texas told Cosmos Online "As far as I can judge, their theory is not really a new theory of eusociality. They have not explained how their theory differs from kin selection, or what predictions it makes".