Early life forms on Earth were more likely to mutate and evolve much faster than today, according to a new study by scientists at the University of North Carolina, USA.
As a result of the analysis, scientists have found that spontaneous DNA mutations once occurred up to 4,000 times faster than today. The driving force behind the high speed of evolution was the significantly warmer climate on Earth.
The results of the study were published in the journal Proceedings of the National Academy of Sciences.
Analyzing chemical reactions, North Carolina researchers have found that the rate of chemical alteration of some DNA increases significantly with increasing ambient temperature. These chemical reactions are the driving force for the spontaneous mutation (and therefore evolution) of organisms.
Combining this discovery with recent evidence that life on Earth came at a time when our planet was significantly hotter than it is today, scientists have concluded that the rate of spontaneous mutations was then at least 4,000 times faster than today.
The question of whether life could evolve to its present level of complexity, given its limited time, has occupied the minds of scientists ever since Charles Darwin published his theory of evolution more than a century ago. So far, both Darwin’s supporters of evolutionary theory and skeptics have generally assumed that the speed of evolution has remained more or less constant over time.
The results of the new study answer the unanswered question of more than a century – significantly faster evolution means that species were able to evolve and multiply at a much faster rate, giving the Earth’s flora and fauna enough time to achieve the incredible diversity and complexity we currently see around us.
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The earth formed about 4.6 billion years ago from the dust and gas clouds that covered the early sun. It began its life as a wild, hot, melting rock world. After that, the Earth gradually began to cool. The top layer of the planet hardened, creating the Earth’s crust. As cooling continued, water vapor was released into the atmosphere, which began to fill Earth’s depressions about 4.3 million years ago, creating oceans.
“Recent evidence from rock samples in Australia shows that the first life forms on Earth appeared 4.1 billion years ago – almost instantaneously after the creation of liquid oceans,” said Richard Wolfenden of the University of North Carolina.
At that time, the Earth’s average temperature was close to the boiling point of water, 100 degrees Celsius. That’s 75 degrees more than today.
To understand the effect such high temperatures could have had on evolution, Wolfenden and his colleagues turned to research into the chemical reaction, cytosine deamination.
Experiments have shown that cytosine mutations at around 100 degrees Celsius accure more than 4,000 times faster.
“It was a surprise even to me. I thought the reaction rate might be faster than today, but I didn’t think the difference would be so huge, ”Wolfenden revealed.
But how did early life forms adapt to the conditions of the outside environment when their genetic material was so rapidly transformed by high air temperatures? Scientists do not yet have a clear answer to this question, but as an example of how life can survive successfully, they cite microorganisms that now live in hydrothermal springs deep in the oceans and can survive and reproduce at temperatures as high as 120 degrees.
“This discovery gives us an insight into the extent of the difficulties that primitive organisms had to overcome before they could evolve into complex systems with self-repair capabilities. It also demonstrates how the evolution that led to such a diverse world as we see today began, ”Wolfenden commented.