​How ultraviolet radiation led to the biggest extinction of life ● It’s a bit confusing ● The origin of smallpox is much older than we thought

How ultraviolet radiation led to the greatest extinction of life

When we talk about the most destructive event in the history of life, the extinction of 80-90% of life forms 252 million years ago, it is a known fact that the entire process was generated by a mega-eruption of a supervolcano located in the territory of Siberia.

What has not yet been fully established are the steps or stages that led to the near-total extinction of life. However, a study recently published in the journal Science Advances draws attention to a phenomenon that at the time played a much more important role than previously thought: the destruction of the ozone layer and the effects of ultraviolet radiation on Earth’s organisms. .

Studies conducted on pollen from that period, that is, from the end of the Permian, were able to show, according to the researchers, one of the most important stages in that catastrophic episode. In particular, with the thinning or partial destruction of the ozone layer, all organisms were exposed to ultraviolet radiation. In this case, we will refer exclusively to plants.

Plants have the ability to change their chemical structure to protect themselves from UV radiation, but this reduces their ability to photosynthesize, and over time they become sterile. And they not only become sterile, but also lose their nutritional value. And this explains why the recent extinction was the only known one that affected insects. There was practically a domino effect, that is, the disappearance of plants and insects, which are the basis of the food chain, led to the mentioned disaster.

The situation is a bit confusing

We all know that the body of our distant ancestors was completely covered with hair. Hence the endless debates about how we, the most evolved, lost the genes responsible for such hairiness. Father Darwin, for example, supported this assumption and said that it could be sexual selection. As it turned out, the hairless were more attractive than the rest, hence the transfer of the mutation.

Looks like we haven’t lost anything. At least this is what a team of American geneticists claims in a study published in the journal eLife. They say hair loss is clear evidence of convergent evolution, particularly the appearance of traits in species with a very distant common ancestor. For example, the dolphin, which is still a mammal, but which, like man, no longer has hair, although its evolutionary steps were quite different from those of primates.

The fact is that the genes responsible for the growth of hair all over the body have not disappeared, at least in humans. Extensive genetic analysis by the researchers mentioned above has shown that, thank goodness, we still have these genes. They simply disappeared. As it turns out, Grandpa Darwin was right again, but more work is needed to prove it 100%.

The origin of smallpox is much older than we imagine

Smallpox, one of the most devastating diseases ever to be faced by mankind, killing more than 300 million people in the 20th century alone, was until recently considered a relatively new disease. The earliest evidence of its existence dates back to 1050 AD from Lithuania.

Apparently it was thought to be something older, as mummies in Egypt or China showed marks similar to those left by smallpox. On the other hand, there are other diseases that can leave similar symptoms. In the end, nothing was clear, and the only clear evidence remained Lithuania.

To solve this case, several specialists in Italy analyzed the genetic evolution of the smallpox virus (VARV). They found that the common ancestor of the smallpox virus and others like it appeared about 3,800 years ago. So it is possible that the mentioned mummies really had smallpox.

The idea is that this common ancestor could also have evolved from some even older viruses that infected humans as early as 7,700 years ago, perhaps even 8,000 years ago. It’s a good thing that humans stopped their evolution and smallpox was officially eradicated in 1980.

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