How Termites Lost Genes to Gain Society

Termites operate some of the animal kingdom’s most remarkable “cities”, with colonies capable of growing to millions of members.

New research indicates that their route to such social living was not driven by accumulating genetic enhancements.

Rather, termites seem to have simplified their genomes, discarding genes that were no longer needed after cooperation and family-based living became dominant.

By following termites back to their cockroach-like forebears, scientists discovered that pivotal moves towards sophisticated social organisation were marked by gene loss rather than gene gain – particularly genes associated with reproduction and sperm competition.

These shifts suggest termite evolution involved more than creating new behaviours. Their biology was also remodelled to support life in a colony.

From cockroach relatives to wood-eaters

The process began with a change in lifestyle. Termites’ ancestors were not naturally social specialists; they resembled cockroaches and had similar ways of life.

At some stage, however, these insects began living inside and eating dead wood – a demanding, nutritionally poor food source that is difficult to exploit alone.

“Termites evolved from cockroach ancestors that started living inside and eating wood,” said study senior author Nathan Lo from the University of Sydney.

“Our study shows how their DNA changed first as they specialized on this poor-quality diet and then changed again as they became social insects.”

This transition was important because, although wood is plentiful, it offers little nutrition. To survive on it, an animal needs either powerful biological adaptations – or assistance.

Termites relied on assistance. The new findings suggest that, as collaboration became fundamental, their genetic toolkit altered in ways that made colony living simpler to sustain.

Termites lost genes but gained order

To follow these changes, the team compared high-quality genomes from cockroaches, “woodroaches” – close relatives that already live in smaller family groups – and several termite species with colonies of differing complexity.

One particularly clear and unexpected trend emerged: termite and woodroach genomes are smaller and less complex than those of cockroaches.

This runs counter to what many might predict. It is commonly assumed that larger, more sophisticated societies demand more sophisticated DNA. Here, however, the evidence suggests the opposite.

As termites came to rely more heavily on one another – pooling food, dividing labour and coordinating development – they seem to have lost numerous genes involved in metabolism, digestion and reproduction.

“The surprising result is that termites increased their social complexity by losing genetic complexity,” Lo said. “That goes against a common assumption that more complex animal societies require more complex genomes.”

This does not mean that termites genetically “degenerated”. Instead, the colony became the important unit.

When individuals depend on the group to survive – particularly to process food and nourish young – certain biological tasks can move from being “my job” to becoming “our job”. Across evolutionary time, termites may lose genes that have become less valuable in a shared social system.

Sperm without tails

The most striking losses concerned sperm. In many animals, cockroaches included, females may mate with several males, creating a contest within the reproductive tract.

Sperm that move more quickly and remain viable for longer have a better chance of success, so evolution favours traits such as a tail, or flagellum, that enables sperm to swim.

Termites differ: their sperm have no tails and cannot move. Such an extreme change strongly points to a major alteration in their mating system.

“This loss doesn’t cause monogamy,” Lo said. “Instead, it’s a strong indicator that monogamy has already evolved.”

Put another way, once termite ancestors adopted strict monogamy, the entire “sperm race” vanished.

With no competition between sperm from different males, there was no longer a strong evolutionary reason to retain the genetic machinery for producing fast-swimming sperm.

“Our results indicate that the ancestors of termites were strictly monogamous,” Lo said. “Once monogamy was locked in, there was no longer any evolutionary pressure to maintain genes involved in sperm motility.”

Family bonds in termite colonies

This finding contributes to a wider debate about the evolution of complex insect societies. One longstanding view holds that high relatedness within a group – close genetic connections – is necessary to keep extreme cooperation stable over time. Another argues that relatedness is beneficial, but not indispensable.

For termites, at least, this study supports the importance of relatedness. If their ancestors were indeed strictly monogamous, colony siblings would have been very closely related.

That would make it easier for natural selection to favour behaviours in which individuals give up their own chance to reproduce in order to help rear relatives. Simply put, helping siblings can still spread “your” genes because they share so many of them.

Food shapes termite roles

The researchers also examined the colony itself to understand how termites maintain their social system. Workers and royals do not emerge by chance.

Experiments described in the study show that nutrition during early life has a substantial influence on which role an individual eventually takes.

Larvae supplied with abundant food by older siblings increase their energy metabolism and become workers.

Although they do not reproduce, workers sustain the colony by building, foraging, defending it and feeding other members. Larvae given less food initially develop more slowly and retain the capacity to become future kings or queens.

“These food-sharing feedback loops allow colonies to fine-tune their workforce,” Lo explained. “They help explain how termites maintain stable, highly efficient societies over long periods.”

It is an effective internal regulatory system: heavily feed some young to create workers immediately, while keeping others as reserves that could later become reproductives. The colony can alter that balance according to its requirements.

Inbreeding, but with a purpose

A further complication arises when a king or queen dies. It might be expected that the remaining partner would mate with an outsider, yet termite societies often keep matters “in the family”.

One of the royal pair’s own offspring commonly takes the vacant position. This results in inbreeding within a colony, which may sound troubling until the colony’s priorities are considered: genetic relatedness and social stability.

That does not suggest termites avoid the dangers of inbreeding. However, the arrangement may continue because it preserves the close genetic ties that make intense cooperation evolutionarily viable.

Losing genes to gain society

Overall, the study provides an unexpectedly elegant account of how genetic shifts helped termites develop from cockroach-like ancestors into highly organised, enduring societies.

Their evolutionary route involved not only the emergence of new social behaviours, but also establishing monogamy, altering development through food sharing and allowing some genes to disappear once they were no longer useful.

“This work shows that understanding social evolution isn’t just about adding new traits. Sometimes, it’s about what evolution chooses to let go,” Lo concluded.