Loss leads to gain

Hummingbirds display true hovering flight, an incredibly energy-intensive activity. Although much is known about the physiology of this movement, little has been known about the genetics underlying its evolution. Osipova et al. screened newly generated and previously sequenced bird genomes to search for key changes facilitating this high-energy locomotion. They found that a gluconeogenic muscle enzyme, FBP2, was lost as hovering flight evolved. Knockouts of this gene in avian cell lines led to an increase in glycolysis, mitochondria production, and mitochondrial respiration, all leading to higher energy efficiency. These results also illustrate how the loss of a gene can be adaptive