A new study shows that termites evolved complex social structures by losing genes rather than gaining them, with monogamy playing a key role. Researchers traced this evolution from cockroach ancestors to massive colonies. The findings challenge assumptions about social complexity in insects.
Termites form some of the largest insect societies on Earth, with colonies reaching millions of individuals. A study published on January 29 in Science explains how these eusocial insects arose from solitary cockroach-like ancestors.
The research, led by Professor Nathan Lo from the University of Sydney's School of Life and Environmental Sciences, involved an international team from China, Denmark, and Colombia. They analyzed genomes from cockroaches, woodroaches, and various termite species. Termite and woodroach genomes proved smaller and simpler than those of cockroaches, with losses in genes related to metabolism, digestion, and reproduction.
"The surprising result is that termites increased their social complexity by losing genetic complexity," Professor Lo said. This counters the idea that advanced societies demand more intricate genomes.
A pivotal change was the ancestors' shift to eating dead wood, sparking genetic adaptations for a poor-quality diet and eventual sociality. Monogamy emerged early, evidenced by the loss of genes for sperm tails—termite sperm cannot swim, unlike in promiscuous cockroaches.
"Our results indicate that the ancestors of termites were strictly monogamous," Professor Lo noted. "Once monogamy was locked in, there was no longer any evolutionary pressure to maintain genes involved in sperm motility."
Food sharing further structured colonies. Larvae fed abundantly by siblings develop into non-reproductive workers, while those receiving less become potential kings or queens.
"These food-sharing feedback loops allow colonies to fine-tune their workforce," Professor Lo explained. After a king or queen dies, an offspring often succeeds them, promoting inbreeding and high genetic relatedness.
"From an evolutionary perspective, that reinforces relatedness even further," he added. Funded by sources including the Australian Research Council, the study highlights how gene loss and behavioral shifts built termite mega-societies.