The idea that mass extinctions allow many new species to evolve is a central concept for evolution, but new research using artificial intelligence to study fossils has shown that this is rarely true, and there must be another explanation, scientists write in a new study published in Scientific Eurekalert magazine.
Charles Darwin's landmark work On the Origin of Species ends with an excellent summary of his theory of evolution: “In this view that life, with its multiple abilities, was originally breathed into several forms or one, and that while this planet moves cyclically according to the invariable law of gravity, from such a simple beginning, endless forms, the most beautiful and most amazing, have developed and are developing. " In fact, scientists now know that most of the species that ever existed are now extinct.
In general, throughout the entire history of the Earth, the extinction of species was roughly balanced by the emergence of new ones, with several large temporary imbalances, which scientists call mass extinctions. Scientists have long believed that mass extinctions create productive periods of species evolution, or "radiation," a pattern called "creative destruction".
A new study by researchers at the Institute of Life Sciences on Earth (ELSI) at the Tokyo Institute of Technology studied the co-occurrence of fossil species using machine learning, and found that emissions and extinctions are rarely related, and thus massive extinctions are likely to rarely cause emissions of comparable magnitude.
Creative destruction is central to classical concepts of evolution. It seems clear that there are periods when many species suddenly disappear and many new species suddenly appear.
However, emissions comparable in scale to mass extinctions, which in this study are called mass emissions, received much less analysis than extinctions. This study compares the impact of both extinction and radiation over the period for which fossils are available, the so-called Phanerozoic eon. Phanerozoic (from the Greek for "explicit life") represents the very last ~ 550 million years of the total ~ 4.5 billion years of Earth's history and is important for paleontologists: before this period, most of the existing organisms were microbes that could not easily form fossils therefore, previous evolutionary history is difficult to trace.
New research suggests that creative destruction is not a good description of how species emerged or died out in the Phanerozoic, and suggests that many of the most prominent periods of evolutionary radiation occurred when life expanded into new evolutionary and ecological expanses, such as during the Cambrian explosion. the diversity of animals and the Carboniferous expansion of forest biomes. Whether this is true for the previous ~ 3 billion years, when microbes dominated, is unknown, since the paucity of recorded information on such an ancient diversity did not allow for a similar analysis.
Paleontologists have identified several of the most serious mass extinction events in the Phanerozoic fossil record. These include mainly the five major mass extinctions, such as the mass extinction at the end of the Permian, when it is estimated that more than 70% of species were extinct.
Biologists have suggested that we may now be entering a "sixth mass extinction" period, which they believe is mainly caused by human activities, including hunting and land-use changes caused by agricultural development
A well-known example of previous "Big Five" mass extinctions is the Cretaceous-Tertiary extinction (commonly abbreviated as "K-T", using the German spelling Cretaceous), which appears to have been caused by a meteorite hitting Earth ~ 65 million years ago. who destroyed the dinosaurs.
Observing fossils, scientists came to the conclusion that mass extinctions lead to the emergence of especially productive life forms… For example, it is generally accepted that the massive extinction of dinosaurs during K-T created a gap that allowed organisms such as mammals, to repopulate and "radiate", which made it possible for the evolution of all sorts of new species of mammals, ultimately laying the foundation for the emergence of man.
In other words, if the event of "creative destruction" had not occurred, perhaps we would not have discussed this issue.
The new study began with a casual conversation in the Agora, a large common room where ELSI scholars and visitors often dine and have new conversations. The two article authors, evolutionary biologist Jennifer Hoyal Cuthill (currently a Research Fellow at the University of Essex in the UK) and physicist / machine learning expert Nicholas Guttenberg (currently a Cross Labs Research Fellow working in collaboration with GoodAI in the Czech Republic), are at at the start of the work, were postdoctoral students at ELSI, discussing whether machine learning could be used to visualize and understand fossils. During a visit to ELSI, shortly before the COVID-19 pandemic began to restrict international travel, they frantically worked to expand their analysis to examine the correlation between extinction and radiation events. These discussions allowed them to relate their new data to the breadth of existing ideas about mass extinctions and radiation.
They quickly discovered that the evolutionary patterns identified by machine learning differed in key respects from traditional interpretations
The team used a new application of machine learning to study the temporal co-occurrence of species in the Phanerozoic fossil record by examining over a million records in a massive database of nearly two hundred thousand species.
Study lead author Dr. Hoyal Cathill said: “Some of the most challenging aspects of understanding life history are the sheer time scales and number of species. New machine learning applications can help us by allowing us to visualize this information in human readable form. so to speak, to hold in the palm of your hand half a billion years of evolution and receive new knowledge from what we see."
Using their objective methods, they found that the "big five" mass extinctions previously identified by paleontologists were attributed by machine learning to 5% significant disturbances in which extinction was ahead of radiation or vice versa, as well as seven additional mass extinctions, two combined mass extinctions - radiation and fifteen massive radiation. Surprisingly, in contrast to previous descriptions highlighting the importance of radiation after extinction, this work showed that the most comparable mass radiation and extinctions only occasionally coincided in time, refuting the idea of a causal relationship between them.
Co-author Dr. Nicholas Gutenberg said: "The ecosystem is dynamic, you don't have to break off an existing piece to create something new."
The team further discovered that radiation can actually cause major changes in existing ecosystems, an idea the authors call "destructive creation." They found that, on average, during the Phanerozoic eon, the species that made up the ecosystem at any given time almost all disappeared after 19 million years. But when mass extinctions or radiation occur, the rate of species change is much higher.
This allows a fresh look at how the current "Sixth Extinction" is happening. The Quaternary period, which began 2.5 million years ago, has witnessed repeated climatic shocks, including abrupt changes in glaciations, when high-latitude regions of the Earth were covered with ice. This means that the current "Sixth Extinction" is destroying biodiversity that has already been disturbed, and the authors estimate that it will take at least 8 million years for it to return to a long-term average of 19 million years
Dr. Hoyal Cathill comments that "every extinction that takes place before our eyes destroys a species that may have existed for millions of years before that moment, making it difficult for the normal process of "emergence of new species" to replace the lost".