Your brain harbors a virus from millennia past. That ancient viral code may sit at the very foundation of human awareness.
Two studies appearing in the journal Cell in January reveal that eons ago, a virus fused its genetic material with the DNA of four-limbed creatures. This fragment of code remains active in modern human brains, performing a distinctly viral function: bundling genetic material and ferrying it from one nerve cell to its neighbors inside tiny capsules that closely resemble viruses. According to the research team, these small information parcels could be essential to how neurons interact and rewire themselves over time — functions believed to be fundamental to advanced cognition.
Although it might seem shocking that portions of our DNA trace back to viruses, this is far more typical than many realize. A 2016 Cell review reported that roughly 40 to 80 percent of the human genome originated from ancient viral insertions.
The reason lies in the nature of viruses themselves, which differ from bacteria that simply attempt to colonize a host. A virus functions as a genetic parasite, inserting its own code into host cells and commandeering them to serve its agenda — generally, producing additional copies of itself. While this typically offers no benefit or causes harm to the host, occasionally the introduced viral genes prove harmless — or valuable enough to persist. The 2016 analysis indicated that viral genes contribute significantly to immunity and to early embryonic development.
The recent research, however, pushes further. The researchers concluded that an ancient virus remains highly active within human and animal brain cells, playing such a vital role that complex thought as we know it probably could not have emerged without it.
Research Links Human Consciousness to a Primeval Virus
The Arc Gene
The investigators discovered that the viral gene called Arc activates shortly after a synapse fires, transcribing its directions into mobile genetic segments called RNA. (A synapse is the connection point between two neurons.)
RNA acts as DNA's envoy within the cell, ferrying genetic directions beyond the nucleus. Forming a single-stranded transcript of DNA's double helix, it delivers instructions wherever they're needed. (Notably, viruses typically encode their genetic information in RNA rather than DNA.)
Guided by the Arc RNA's directives, the neuron constructs capsids — virus-like shells — around the genetic material. These protective shells enable safe transit between cells. The studies showed that the package enters adjacent neurons, delivering its genetic cargo to them.
What this information accomplishes upon reaching a new cell remains unknown, yet the researchers observed that synapses deteriorate when the process is disrupted. The team also noted that irregularities in the Arc gene frequently appear in individuals with autism and other neurological variations.
In an accompanying commentary, two specialists uninvolved in the 2018 studies — and notably the same researchers behind the 2016 review — argued that this mechanism provides the strongest account to date of how neurons share the information required to rewire the brain across a lifetime.
"These mechanisms support brain activities spanning from basic classical and operant conditioning to human cognition and our sense of 'self,'"
— they observed. (Classical and operant conditioning refer to elementary learning processes in animals and humans based on rewards and punishments.)
Curiously, Arc appears to have transferred from virus to animal on multiple occasions. The studies revealed that Arc genes in humans and other four-limbed species share close ancestry, whereas those in fruit flies and worms seem to have originated independently.
In the commentary, the outside experts emphasized that the next research phase should unite neuroscientists with specialists in ancient viruses to determine precisely how Arc became embedded in the genome and what specific information it currently transmits between our cells.
First appeared on Live Science.
