A prehistoric pandemic that lasted 15 million years infected almost all living things: traces are still visible

Just a few years ago, we saw with our own eyes how destructive and dangerous a new virus, hitherto unknown to mankind, could become. But the coronavirus pandemic was far from the first such event.

According to IFL Science, scientists have discovered signs of a prehistoric pandemic that raged between 33 and 15 million years ago. At that time, a group of viruses infected many mammals that existed on our planet at that time. The pandemic (or rather, panzootics) also affected human ancestors and did not spared almost any species of higher animals. Moreover, we still find its signs in the DNA of modern mammals, including humans.

You may be surprised, but up to 8% of our genome consists of genetic sequences of retroviruses that once affected our ancestors long ago. The group of pathogens described by the scientists disappeared about 15 million years ago, but before that, it seems, they infected everyone they could.

According to their principle of action, any retrovirus, including modern ones, including HIV, in order to reproduce in a cell and spread, must insert a DNA copy of their RNA genome into the DNA of the host cell. Normally, this foreign genetic material is not passed on from generation to generation. But there is a possibility that ancient retroviruses learned to infect germ cells, such as eggs or sperm. This is how they passed on their genetic code to future generations of carriers.

And the mechanism of gene action is that retroviruses that penetrate germ cells eventually penetrate the genome of the population. Such retroviruses are called endogenous. Probably one of the most successful examples here is ERV-Fc, a retrovirus (or possibly a genus or family of retroviruses) that spread throughout the world between the Oligocene and early Miocene (between 30 and 15 million years ago).

A 2016 genome scan of 50 modern mammals revealed that ERV-Fc was present in the ancestors of at least 28 of them. In particular, scientists assume that the ancestors of tubeworms, mouse microcebus (a type of lemur), saimiri monkey, various marmosets, baboons, chimpanzees, humans, dogs and pandas suffered from it.

What is even more impressive is that this virus did not infect any ancestor of all these mammals just once, but passed from one species to another more than 20 times. Large-scale panzootics then covered all continents except remote Australia and Antarctica.

Today, the remnants of ERV-Fc do not seem to have any impact on human health. They just lie dormant in our genome. However, a deeper understanding of ERV-Fc and other endogenous human retroviruses could help improve our understanding of some modern diseases, such as HIV.

According to the study's lead author, William E. Diehl, mammalian genomes currently contain hundreds of thousands of traces of ancient viruses similar to ERV-Fc. "The challenge now will be to use ancient viral sequences to look back in time, which could prove useful in predicting the long-term effects of re-emerging viral infections. For example, we could estimate the impact of HIV on human health 30 million years from now. This method will allow us to better understand when and why new viruses appear and how prolonged contact with them affects the evolution of host organisms," explained Diehl.

Subscribe to OBOZ.UA channels in Telegram and Viber to keep up with the latest events.