Have you ever wondered how humans evolved to have large brains and complex nervous systems? A new study published in the journal Cell suggests that ancient viruses that infected our ancestors millions of years ago played a crucial role in shaping our bodies and brains.
The Role of RetroMyelin
The study, led by Tanay Ghosh and Robin Franklin of Altos Labs-Cambridge Institute of Science, focused on the origins of myelin, an insulating layer of fatty tissue that forms around nerves and allows electrical impulses to travel faster. Myelin is essential for the functioning of the vertebrate nervous system, enabling rapid communication between different parts of the body and the brain.
The researchers discovered that a gene sequence acquired from retroviruses, which are viruses that invade their host’s DNA, is vital for myelin production. They named this sequence RetroMyelin, and found it in the genomes of modern mammals, amphibians and fish, but not in jawless vertebrates or invertebrates.
The Evolutionary Impact of RetroMyelin
The researchers concluded that RetroMyelin appeared in the tree of life around 360 million years ago, in the Devonian period, also known as the Age of Fishes. This was also the time when jaws first evolved in vertebrates, giving them an advantage over their jawless counterparts.
According to Franklin, RetroMyelin enabled nerve fibers to conduct electrical impulses faster without widening their diameter, allowing them to be packed closer together. It also provided structural support, meaning nerves could grow longer, leading to longer limbs.
“There’s always been an evolutionary pressure to make nerve fibers conduct electrical impulses quicker. If they do that quicker, then you can act quicker,” Franklin said. This was useful for both predators trying to catch things, and prey trying to flee.
The researchers also speculated that RetroMyelin may have contributed to the development of more complex brains in vertebrates, as faster nerve conduction would allow more information processing and integration.
Conclusion
The study reveals how ancient viruses that infected our ancestors millions of years ago influenced the evolution of our bodies and brains. It also shows how noncoding regions of the genome, which were once considered junk, can have important functions and evolutionary implications.
The study also raises new questions about the role of retroviruses in shaping other aspects of vertebrate biology, such as immunity and development.
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