“Less, But More”: How Losing Genes Can Make Life More Complex

 By: James Allen Jr. S. Yap | Paralogon 

In a surprising twist to our understanding of evolution, a recent study found out that losing genes can actually lead to more complexity. Researchers studying the tunicate Oikopleura dioica discovered that massive gene losses can cause bursts of gene duplication and diversification, an evolutionary pattern they call "less, but more."

Traditionally, scientists have long held to the "less is more" hypothesis, which postulates that adaptive benefits could result from gene loss alone. For instance, previous research has shown that gene losses in mammals, such as those linked to sensory adaptation or immunity, can lead to new physiological specializations and ecological advantages. The "less, but more" framework demonstrates that evolution is about how organisms balance both processes to increase adaptation rather than just gaining or losing genes. In O. dioica, the majority of Fibroblast Growth Factor (Fgf) gene subfamilies were eliminated, yet the few that remained were multiplied and developed new functions to compensate for what was lost. 

To uncover this pattern, researchers employed comparative genomic and phylogenetic analyses. Basic Local Alignment Search Tool (BLAST) searches were used to identify Fgf genes in various tunicate species, while Maximum-Likelihood phylogenetic trees and synteny comparisons were used to verify their evolutionary relationships. Such comparative and structural analyses are widely recognized as powerful tools for uncovering the molecular mechanisms that shape genome evolution and functional diversification. To determine whether Fgf genes had been lost or duplicated, they also examined conserved motifs and intron–exon organization in gene and protein structures. With the use of these combined techniques, they were able to precisely recreate the evolutionary history of the Fgf genes in tunicates.

Beyond mapping the genetic changes, the scientists used whole-mount in situ hybridization (WISH). This method revealed when and where each Fgf gene was expressed during O. dioica development, from unfertilized eggs to late-hatching larvae. Gene expression profiling is crucial in evolutionary studies because it connects genetic variation to developmental outcomes, helping explain how changes in gene number can lead to shifts in function or morphology. The researchers found that duplicated Fgf genes have assumed specialized roles in many tissues, including the nervous system, muscles, notochord, and epidermis, while maintaining important developmental processes that would otherwise have been lost. These results demonstrated that the species preserved and even diversified upon vital biological functions despite having a reduced number of genes.

Ultimately, this study emphasizes a fundamental evolutionary trade-off: losing genetic complexity can actually promote functional versatility and innovation. Genetic simplification in Oikopleura dioica resulted in a more specialized and adaptive organism. As the authors put it, evolution sometimes thrives not by adding more, but by doing "less, but more."