Evolution may have moved at a furious pace on a much warmer Earth

Earth
A composite image of the Western hemisphere of the Earth. Credit: NASA

Early life forms on Earth are likely to have mutated and evolved at much higher rates than they do today, suggests a new analysis from researchers at the University of North Carolina.

In a study published this week in the Proceedings of the National Academy of Sciences, Richard Wolfenden, PhD, and his colleagues found that the rate of a certain chemical change in DNA - a key driver of organisms' spontaneous mutation rates and thus of evolution's pace—increases extremely rapidly with temperature. Combining that finding with recent evidence that life arose when our planet was much warmer than it is now, the scientists concluded that the rate of spontaneous mutation was at least 4,000 times higher than it is today.

"At the higher temperatures that seem to have prevailed during the early phase of life, evolution was shaking the dice frantically," said Wolfenden, Alumni Distinguished Professor of Biochemistry and Biophysics at the UNC School of Medicine.

A much faster pace of evolution means that species could have proliferated much more rapidly than they do now, affording the flora and fauna of Earth ample time to acquire their enormous diversity and complexity.

That issue—whether life could have evolved to its present level of complexity within the time available—has lingered ever since Darwin published his theory more than a century and a half ago. Throughout that debate, both skeptics and proponents of evolutionary theory have often assumed that evolution's pace has stayed more or less constant over the eons.

The planet formed about 4.6 billion years ago from the cloud of dust and gas surrounding the early sun, and began as a hellish world of molten rock. It cooled until a crust condensed, and eventually, around 4.3 billion years ago, liquid brine began to fill the lower elevations, forming oceans.

"Recent evidence from rock samples in Australia indicates that life forms arose on Earth as early as 4.1 billion years ago - almost in the blink of an eye after the appearance of liquid oceans," Wolfenden said.

At that time, the average temperature at the Earth's surface would have been near the boiling point of water - 100 degrees Celsius, about 75 degrees higher than today.

To get some idea of the effect of such a high temperatures on the rate of evolution, Wolfenden's team examined a chemical reaction known as cytosine deamination, which occurs from time to time in all cells and may be the single most frequent cause of spontaneous DNA mutations.

In the deamination reaction, cytosine—the DNA base molecule known as "C" in the genetic code—loses an ammonia-like "amine" group of atoms. Deamination leads to the mutation of the cytosine into the DNA base thymine ("T" in the genetic code).

Wolfenden's team experimentally determined the rates of spontaneous deamination at different temperatures for cytosine and several cytosine-related molecules. In collaboration with the UNC lab of Ronald Swanstrom, PhD, the Charles P. Postelle, Jr. Distinguished Professor of Biochemistry at UNC, the researchers also measured the rates of cytosine deaminations and spontaneous C-to-T mutations in single-stranded DNA from the HIV virus that causes AIDS. The results showed that the rates of cytosine deamination, for isolated molecules and for single-stranded DNA, rose very steeply as the temperature increased. The scientists then added the assumption that Earth's surface temperature has itself changed exponentially - following Newton's law of cooling - over the period in which life has existed.

"Cytosine-based mutations, when the temperature was near 100 degrees C, occurred at more than 4,000 times the modern rate,"Wolfenden said. "To me, that was surprising. I thought the ancient rate would be more rapid than the modern rate, but not that rapid."

How could early life forms have coped with a high-temperature environment where their genetic material was being altered so rapidly?

"That question is still out there," Wolfenden said. He noted, though, that there are microorganisms even now that normally live in hot springs or deep-sea thermal vents, and somehow survive and multiply at temperatures as high as 120 degrees C.

Originally, DNA was stabilized to some extent by the presence of a complementary strand of DNA, and as evolved, they developed increasingly sophisticated mechanisms for repairing DNA damage.

"These findings give us some idea of the burden faced by primordial organisms before they evolved sophisticated systems for repair," Wolfenden said. "And they offer another clue about how evolution kick-started the creation of the diverse world we see today."


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Heat helped hasten life's beginnings

More information: Cytosine deamination and the precipitous decline of spontaneous mutation during Earth's history, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1607580113
Citation: Evolution may have moved at a furious pace on a much warmer Earth (2016, July 6) retrieved 23 August 2019 from https://phys.org/news/2016-07-evolution-furious-pace-warmer-earth.html
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Jul 06, 2016
What were the natural background radiation levels, UV, and cosmic ray flux at the time?

Jul 07, 2016
Wow!!!!! This article is replete with evolutionary so-so stories!
1.
The planet formed about 4.6 billion years ago from the cloud of dust and gas surrounding the early sun

Planets have NEVER been observed to form by accretion all by themselves. EVER. This is an unscientific statement and pure conjecture at this stage.
2.
recent evidence that life arose when our planet was much warmer than it is now

Life cannot arise from materials by pure random physical and chemical processes all by itself. That is simply impossible. There is no real evidence to support such a mythical notion. On the contrary, there is about 6000 years of fully observed, repeated and confirmed evidence that once something dies it stays DEAD and NEVER, EVER rises to life again all by itself.
3. Where did the heat come from after 1 billion years. Current theory suggests that the sun was much smaller and hence cooler than now. So didn't the earth cool off after formation in 1Ga?

Jul 07, 2016
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Jul 08, 2016
mindless

is what happens when you simply swallow the humanist story hook line and sinker. You stop thinking for yourself because you don't want to go against the stream of naturalism even if it is patently absurd. You have to deny that what you witness with your eyes and mind as pure design and call it an accident of nature - no matter how that notion goes against the grain of established principles of physics, biology and chemistry.

Jul 08, 2016
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Jul 08, 2016
The temperatures when DNA replaced RNA as genetic material wasn't all that high though. The root of heat stress proteins is at 70 degC.

Somewhat non-intuitively RNA, which is less chemical stable than DNA with a half life against hydrolysis of 4 years vs ~ 0.5 Myrs, can be more heat stable as shown by melting curves. [ https://en.wikipe...analysis ]

There were all sorts of factors that increased early evolution rates, and the effect has been seen in realy protein folds. So the idea of astrobiologists holding to a constant early evolution rate is overblown.

Kudos for referencing the 4.1 billion year old putative fossils, though.

@Shootist: Surface UV was higher (no oxygen, so little high altitude ozone). But go a meter down, and the cells wouldn't notice.

Jul 08, 2016
replete with evolutionary


It is about biology, yes, good of you to notice ...

Planets have NEVER been observed to form by accretion


... wich makes it odd when you jump to astronomy.

As it happens, we have images. [ http://www.sci-ne...448.html ]

Life cannot arise from materials by pure random physical and chemical processes all by itself.


Of course it can, we are the evidence. The early Earth was sterile. Now it is not. So emergence of life happened, all by itself, observably.

But see biology above, no one but you has claimed it is "pure random", a lot of natural selection was involved. That is why the article notes the higher evolution rate early on.

Jul 08, 2016
FredJose perfectly demonstrates the projected narrative of self-delusion. Every one of his statements stands in direct opposition to the overwhelming mass of evidence we've collected. Worse, he considers fantastic and physically impossible agency to be the superior explanation for our physical world- all just to convince himself that he will live forever.

Jul 09, 2016
Yes, The Way of The Crank is an odd one.

I am more miffed that they lump everything from physics and cosmology to biology as '[biological] evolution' - when it goes against their crank narrative - but not as the "astrobiology" it is. It is analogous to lumping geology into 'gravity' or architecture into 'hammering'.

Yes, of course I realize it is their dumb way of poisoning the well.

Jul 11, 2016
TBGL, agreed. How is it for some that a long absent (at best), omniscient alien, that created the universe be acceptable as an article of blind faith, but simple bacteria arising in a broth of warm water and organic chemistry is just too much to accept?

Jul 11, 2016
More important than this boring and tired old "debate," is the inference that a warm planetary phase followed by a cooler phase within certain limits to be defined may be critical to forming more complex life.

Jul 11, 2016
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Jul 11, 2016
FredJose 1 /5 (18) Jul 07, 2016

Planets have NEVER been observed to form by accretion all by themselves. EVER


OMG! I just realized that not one person has ANY observational evidence that sediments turn to rock! They must not exist. There are no sedimentary rocks!

I should watch that. One of these EU nutters will start on about how all rocks are volcanic in origin.

That would be VE nuts (volcanic earthers). EU ones just think electricity moved all the rocks around...

Jul 11, 2016
More important than this boring and tired old "debate," is the inference that a warm planetary phase followed by a cooler phase within certain limits to be defined may be critical to forming more complex life.


Like whiskey.
Heat it up to distill it -
let it sit in a cool barrel for a few years to make it really tasty...

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