Old virus may have been responsible for human consciousness

Where does human consciousness come from? According to two articles published in Cell magazine in January, a virus linked its genetic code to the four-limb animal genome long ago and may have been responsible for major changes in our thinking process.

According to the researchers, this code snippet is still very much alive in the brains of humans today, where it accomplishes an essential task: packaging genetic information and sending it from nerve cells to its neighbors in small capsules that look very much like the virus itself.

More common than it looks

According to the researchers, these small packets of information may be essential for nerves to communicate and reorganize over time - tasks deemed necessary for higher-order thinking.

Although it seems surprising that some of the human genetic code came from a virus, this is actually more common than you think: according to an article published in 2016 in the same magazine, between 40% and 80% of the human genome. It comes from some kind of viral invasion.

How viruses work

Viruses are not just beings that try to make the body a home, but bacteria. In fact, the virus is a genetic parasite. It injects its genetic code into the host's body and hijacks it, making it work for its own purpose - typically, this means more virus production.

The process is usually completely useless or harmful to the host's body, but can sometimes be beneficial. The 2016 study found that viral genes play important roles in the immune system as well as in the early days of embryonic development.

According to the researchers, in addition to the fact that this ancient virus is still very active within human brain cells, it is so important that thought processes as we know them would probably never have arisen without it.

The role of Arc

Shortly after a synapse (the junction between two neurons) fires, the viral gene known as Arc comes alive, writing its instructions in the form of pieces of a mobile genetic code known as RNA.

Following the virus's instructions, the nerve cell builds "capsids" (envelopes similar to the virus itself) around it. These envelopes allow RNA to travel safely between cells, entering neighboring neurons and passing their packet of genetic information along with them.

It is still unclear what this information does when it arrives in a new cell, but the researchers found that without this process, synapses would disappear. What's more, problems with the Arc gene tend to arise in people with autism and other atypical neural conditions.

The next step in this research is to bring together neuroscience and ancient virus specialists to understand the mechanisms that explain how Arc came to the genome and what exactly information is passing between our cells today.