According to a recent study by the University of Leeds, when life on Earth began approximately 2.4 billion years ago, our planet was actually quite inhospitable to life.
Based on computer simulations, researchers discovered that at one point, the level of ultraviolet (UV) radiation on the Earth’s surface was 10 times higher than previously estimated.
Excessive UV radiation can cause dangerous harm.
The research team noted that the past 2.4 billion years represent a crucial chapter in the development of the biosphere. Significant concentrations of oxygen emerged in the atmosphere, reaching current levels around 400 million years ago. This substantial amount of oxygen has partially paved the way for the emergence of more complex multicellular organisms and animals.
According to the lead author of the study, Gregory Cooke, these findings suggest the evolutionary impact of UV radiation since many forms of life are known to be negatively affected by high levels of UV radiation.
Cooke stated: “We know that UV radiation can cause dangerous harm if exposure is too high. For example, it can lead to skin cancer in humans. However, some organisms have effective protective mechanisms and can even recover from exposure to UV radiation. While increased UV radiation levels would not prevent the emergence or evolution of life, it acts as a selective tool, favoring organisms capable of coping with higher levels of UV radiation.”
Scientists have speculated for decades that the ozone layer protects life from ultraviolet radiation when the concentration of oxygen in the atmosphere was only about 1% compared to the current 20%. However, the new study does not support this theory. Through computer modeling, experts found that the oxygen concentration at that time may have been much higher, around 5-10% of current levels in the atmosphere.
This means that there were periods when UV radiation levels on the Earth’s surface were even greater than previous hypotheses suggested. Scientists believe this has occurred at various points in Earth’s developmental history.
Cooke remarked: “If our model indicates scenarios regarding the concentration of oxygen in Earth’s atmosphere, then for over a billion years, Earth may have been subjected to much higher levels of UV radiation than previously imagined. This could have interesting consequences for evolution. The exact timing of when animals appeared or the conditions they faced in oceans or on land is unknown. However, depending on oxygen levels, animals and plants may have had to endure much harsher conditions than in today’s world. We hope that insights into the evolutionary impact will gradually be revealed in the future.”
The study was published recently in the journal Royal Society Open Science.
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