Catalan researchers discover that worms challenge Darwin's theory of evolution.
A study reveals that these animals broke their genome into a thousand pieces to reconstruct it in a radically different way.
BarcelonaEvolution is a slow and gradual process through which species accumulate small changes over time, and only the individuals best adapted to a specific environment are able to survive and pass on their genetics to future generations. This is the theory developed by Charles Darwin in 1859. But the British naturalist could not explain why there are no fossil records of those intermediate forms that allow us to see the gradual evolution of species. This scarcity of samples led paleontologists Stephen Jay Gould and Niles Eldredge to propose that species do not change slowly, but rather remain stable for millions of years and suddenly make brief and radical evolutionary leaps. This is known as the theory of punctuated equilibrium, and now a study led by the Institute of Evolutionary Biology (IBE) has reached conclusions that support it and, therefore, challenge the Darwinian system.
Specifically, the Catalan researchers have discovered that sea worms broke their genome (their genetic material) into a thousand pieces to reconstruct it in a radically different way when they left the oceans to set foot on dry land 200 million years ago. This is an enormous reorganization of genes that "cannot be accounted for using the parsimonious mechanism proposed by Darwin," says Rosa Fernández, principal investigator of the Phylogenomics and Evolution of Animal Genomes group at the IBE and one of the authors of the study published this Wednesday in the scientific journal Nature Ecology and Evolution. To reach this conclusion, the researchers conducted a comparative study of the genomics of earthworms and their marine relatives, as well as other closely related species such as leeches.
The authors believe that the genetic mechanism they identified could transform our understanding of animal evolution. According to the study, these animals applied "genomic disorder" mechanisms to quickly adapt to life on land, reorganizing their genes to better respond to new challenges such as breathing and exposure to sunlight. However, the major changes in DNA required to adapt so quickly from the sea to land could have led to the extinction of the species. The researchers studied this mystery and discovered that the chromosomes of modern worms are much more flexible than those of vertebrates, which would explain why genes changed locations within the worms' genome and continued to function together.
Complementary theories
For Fernández, Darwin's and Gould's theories are compatible and complementary: "While neo-Darwinism perfectly explains the evolution of populations, it has not yet managed to explain some exceptional and crucial episodes in the history of life on Earth, such as the explosion of animal life first in the oceans, more than 5 million years ago, and the explosion of oceans on Earth, 200 million years ago in the case of earthworms." Furthermore, the results of the study open the door to a better understanding of genetic reorganization in humans, something important because it is a mechanism that has also been observed in the progression of cancer.
Specifically, there are various mechanisms of chromosome breakage and reorganization in cancer cells where changes similar to those detected in earthworms can be identified. The only difference is that while in earthworms these genomic breaks and reorganizations are tolerated, in humans they give rise to disease. Therefore, the authors believe that the conclusions could also be beneficial for human health.