Theoretical origin of life: the latest review (Introduction)

by David Turell , Thursday, December 10, 2020, 20:38 (1226 days ago) @ David Turell

There are lots of worries about water, which can break up polypeptides and DNA:

https://www.nature.com/articles/d41586-020-03461-4?WT.ec_id=NATURE-20201210&utm_sou...

"Although many scientists have long speculated that those pioneering cells arose in the ocean, recent research suggests that the key molecules of life, and its core processes, can form only in places such as Jezero — a relatively shallow body of water fed by streams.

"That’s because several studies suggest that the basic chemicals of life require ultraviolet radiation from sunlight to form, and that the watery environment had to become highly concentrated or even dry out completely at times. In laboratory experiments, Sutherland and other scientists have produced DNA, proteins and other core components of cells by gently heating simple carbon-based chemicals, subjecting them to UV radiation and intermittently drying them out. Chemists have not yet been able to synthesize such a wide range of biological molecules in conditions that mimic seawater.

"The emerging evidence has caused many researchers to abandon the idea that life emerged in the oceans and instead focus on land environments, in places that were alternately wet and dry. The shift is hardly unanimous, but scientists who support the idea of a terrestrial beginning say it offers a solution to a long-recognized paradox: that although water is essential for life, it is also destructive to life’s core components.

"Surface lakes and puddles are highly promising, says David Catling, a planetary scientist at the University of Washington in Seattle. “There’s a lot of work that’s been done in the last 15 years which would support that direction.”

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"...life’s cornerstone molecules break down in water. This is because proteins, and nucleic acids such as DNA and RNA, are vulnerable at their joints. Proteins are made of chains of amino acids, and nucleic acids are chains of nucleotides. If the chains are placed in water, it attacks the links and eventually breaks them. In carbon chemistry, “water is an enemy to be excluded as rigorously as possible”, wrote the late biochemist Robert Shapiro in his totemic 1986 book Origins, which critiqued the primordial ocean hypothesis.

"This is the water paradox. Today, cells solve it by limiting the free movement of water in their interiors, says synthetic biologist Kate Adamala at the University of Minnesota in Minneapolis. For this reason, popular images of the cytoplasm — the substance inside the cell — are often wrong. “We are taught that cytoplasm is just a bag that holds everything, and everything is swimming around,” she adds. “That’s not true, everything is incredibly scaffolded in cells, and it’s scaffolded in a gel, not a water bag.” (my bold)

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"...studies have given momentum to the idea that life began on a well-lit surface with a limited amount of water. However, there is still debate over how much water was involved, and what part it played in starting life.

Like Deamer, Frenkel-Pinter argues that wet–dry cycles were crucial. Dry conditions, she says, provided an opportunity for chain molecules such as proteins and RNA to form.

"But simply making RNA and other molecules is not life. A self-sustaining, dynamic system has to form. Frenkel-Pinter suggests that water’s destructiveness could have helped to drive that. Just as prey animals evolved to run faster or secrete toxins to survive predators, the first biological molecules might have evolved to cope with water’s chemical attacks — and even to harness its reactivity for good.

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"...modern organisms use completely different chemical processes to make substances such as RNA. He argues that these processes must have arisen first, not the substances themselves. “Life, it picks very particular molecules. But you can’t pick them from the bench. You’ve got to make them from scratch and that’s what life does.'”

Comment: The Shapiro who is my hero is Robert. See my bold. His book, Origins is from 1986 and he could easily see the problems in trying to understand the origin of life, about which we are obviously no closer to a reasonable theory. His book is one of the first I read to divorce myself from Darwin. I've not presented the lengthy descriptions of all the current attempts to make an advance, just the obvious frustrations of the reviewing author. This problem is why I think it is a major proof of the need for a designer God.