How did humanity emerge: scientists are closer to solving the origin of life

Just as none of us can remember the moment of our birth, scientists have a hard time pinpointing exactly how humanity came to be. But they are constantly searching for reasons and seem to have found a connection between the emergence of humans and the gravitational waves that permeate the universe.

Researchers from King's College London have published a preprint of the theory. According to the IFL Science portal, their article has yet to be reviewed and approved by the scientific community, but it is already generating considerable interest.

The authors of the paper reminded us that the life forms we know require only a few chemical elements: hydrogen, carbon, nitrogen, oxygen and phosphorus, as well as sulfur. Some simple species get by with just this set.

The first of these elements, hydrogen, appeared in the universe as a result of the Big Bang. The next three are the product of helium synthesis during the life of ordinary stars. Phosphorus was found in the remnant of the Cassiopeia A supernova, which supports the assumption that it is formed during the explosions of this type of star. Supernovae also produce sulfur and significantly increase the content of carbon and oxygen in space, which they generously distribute around them.

Mammals need 20 elements to build bones, including teeth, and organs. And to create two of them, say the authors of a paper presented in the Proceedings of the National Academy of Sciences (PNAS), you need more than just a supernova. They are the product of a process known as the r-process. It occurs in a keelboat - the merger of two neutron stars or a neutron star with a black hole.

Such an observation has been made before, but the authors of the new paper note that neutron star mergers are the product of gravitational waves. Given the scale of the universe, the probability of a collision between such rare objects as neutron stars is extremely small.

Neutron stars are the product of supernovae that are not large enough to form black holes. When two stars with masses of 10-25 solar masses form in a binary system, each of them can turn into a neutron star. Provided that none of the explosions is so strong as to throw one of the pair into space, the stars will continue to circle each other.

And this is where gravitational waves come into play. The powerful acceleration caused by the gravitational interaction of two extremely dense objects creates gravitational waves that take up energy. This process releases so much energy that we can detect its occurrence even at a distance of billions of light years. This energy doesn't come from nowhere, but comes from the shared orbit of neutron stars. As the orbit breaks up, the pair of stars gradually moves inward in an increasingly narrow spiral until they collide, forming a keeled star, and all the elements of the r-process with it.

If gravitational waves did not exist in space, kilonovae would be a much rarer phenomenon in space than they are now. The probability that they will occur during the lifetime of the Milky Way in a gravity-free Universe is small. And where there are no keeled, there are no r-process elements, suggest Professor John Ellis of King's College London and his co-authors. Since the elements of the r-process are iodine and bromine, which are essential for human existence, we can assume that without gravitational waves, the conditions for the emergence of humanity would not have been created in the universe.

This logical chain is already being called far from flawless. So it is quite right to assume that a smaller amount of bromine and iodine on Earth could have led evolution in a different direction. But this does not mean that this evolution would not have created something similar to us. For example, humans depend on iodine, which is involved in the regulation of metabolism in the thyroid gland. And also on bromine, which is needed for tissue development. However, given millions of years of evolution, it is possible that animals could have evolved to use other elements for similar functions.

Such a hypothetical scenario is probably impossible to prove or disprove convincingly unless scientists manage to find a large number of planets that formed so far from any star that they lack the elements of the r-process. But even if they do, it will take a very long time to examine them for the presence of advanced life.

On the other hand, these two elements may not be the only r-process derivatives needed by humans. The authors note that molybdenum is used by both animals and plants to carry oxygen atoms. And thorium and uranium are likely to be the cause of plate tectonic movement, one of the key properties of the Earth.

Moving further along a similar logical chain, one can question the connection between iodine and keelboats. It is now believed that these objects are the source of this element. But this is yet to be verified and confirmed. Moreover, it is known that some types of supernovae can also trigger r-processes. But it remains unclear how much iodine can be produced in this case.

Moreover, a small part of the iodine on Earth comes from the s-process, which does not require gravitational waves. According to the authors of the study, 4% of the element on our planet is derived from the s-process. And it is quite possible that this would be enough to support the evolution of mammals.

It is expected that in the near future it will be possible to verify at least some of the scientists' assumptions. If their estimate of the origin of iodine is confirmed, then iodine-129 is likely to be present in the material on the lunar surface. It will be possible to verify this during the next human landing on the Earth's satellite, which is scheduled for the next two years.

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