Extra! Extra! "Researchers may have solved origin-of-life conundrum," a breathless headline announces in Science Magazine, ablaze with artwork of meteors striking the primitive, lifeless earth. Take me out to the ball game! It’s a triple-header today!
Writer Robert F. Service knows that the hometown team, the Darwin Dreamers, have been down on their luck ever since Charles Darwin’s pep talk about a "warm little pond."
The origin of life on Earth is a set of paradoxes. In order for life to have gotten started, there must have been a genetic molecule — something like DNA or RNA — capable of passing along blueprints for making proteins, the workhorse molecules of life. But modern cells can’t copy DNA and RNA without the help of proteins themselves. To make matters more vexing, none of these molecules can do their jobs without fatty lipids, which provide the membranes that cells need to hold their contents inside. And in yet another chicken-and-egg complication, protein-based enzymes (encoded by genetic molecules) are needed to synthesize lipids. [Emphasis added.]
(Aside: There’s no paradox at all if you add intelligence to your list of causes, but whatever.) Let’s let them go to bat. Here’s the pitch:
Now, researchers say they may have solved these paradoxes. Chemists report today that a pair of simple compounds, which would have been abundant on early Earth, can give rise to a network of simple reactions that produce the three major classes of biomolecules — nucleic acids, amino acids, and lipids — needed for the earliest form of life to get its start. Although the new work does not prove that this is how life started, it may eventually help explain one of the deepest mysteries in modern science.
(Aside: There’s no mystery at all if you add intelligence to your list of causes, but whatever.) Service calls a time out to warn the players about prior losses with origin-of-life research. There was the game between the RNA-Worlders and the Metabolism-Firsters that ended in a 0-0 draw. In 2009, John Sutherland pitched acetylene + formaldehyde to get RNA without enzymes. "Critics, though, pointed out that acetylene and formaldehyde are still somewhat complex molecules themselves," he notes. "That begged the question of where they came from."
Back to the game. What has Sutherland come up with this time? He found simpler molecules that can do the job: just combine hydrogen sulfide (H2S), hydrogen cyanide (HCN), and UV light. His team tried it and got "nucleic acid precursors" and more —
What is more, Sutherland says, the conditions that produce nucleic acid precursors also create the starting materials needed to make natural amino acids and lipids. That suggests a single set of reactions could have given rise to most of life’s building blocks simultaneously.
Is it a hit? Jack Szostak is cheering: "This is a very important paper," the veteran RNA-World hero shouts from the stands. "It proposes for the first time a scenario by which almost all of the essential building blocks for life could be assembled in one geological setting."
This is wonderful! You get free HCN from comets and their impacts. You get free H2S from volcanoes. You get free UV light from the sun. It’s a home run!
The umpire calls a conference. "Sutherland," he says, "I’m not sure the bat connected with the ball here." Sheepishly, Sutherland owns up:
That said, Sutherland cautions that the reactions that would have made each of the sets of building blocks are different enough from one another — requiring different metal catalysts, for example — that they likely would not have all occurred in the same location. Rather, he says, slight variations in chemistry and energy could have favored the creation of one set of building blocks over another, such as amino acids or lipids, in different places.
"You’re telling me that the amino acids might be in Africa, the nucleic acids might be in South America, and the enzymes at the North Pole? Nice try," the umpire says. "You gotta have a lot more players in the same place at the same time. Strike three."
"Oh, and another thing. All your players have to be southpaws or they can’t play. Them’s the rules."
The team members mumble as they head back to the dugout. It was such a great scenario. How could that grumpy umpire call us out?
Could life have kindled in that common pool? That detail is almost certainly forever lost to history. But the idea and the "plausible chemistry" behind it is worth careful thought, [David] Deamer says. Szostak agrees. "This general scenario raises many questions," he says, "and I am sure that it will be debated for some time to come."
"Hey, don’t worry about it," one of them pipes in, trying to be cheerful. "We’re not here to win. We’re just here to play the game."
Across town, another game is in progress. The Ames Flames are cheering. The Astrobiology Magazine paperboy shouts, "Extra! Extra! NASA Ames Reproduces the Building Blocks of Life in Laboratory." A photo shows them glowing in the light of intelligently designed lasers, flasks, and tubes.
NASA scientists studying the origin of life have reproduced uracil, cytosine, and thymine, three key components of our hereditary material, in the laboratory. They discovered that an ice sample containing pyrimidine exposed to ultraviolet radiation under space-like conditions produces these essential ingredients of life.
Looks good in theory; will it play out on the field? "Where will we get the pyrimidine?" a young player asks quizzically. "Oh, it’s probably in a comet or asteroid somewhere. That’s not our department."
The molecule pyrimidine is found in meteorites, although scientists still do not know its origin. It may be similar to the carbon-rich PAHs, in that it may be produced in the final outbursts of dying, giant red stars, or formed in dense clouds of interstellar gas and dust.
"See? The delivery guys always find some somewhere." "I’m confused," the novice replies. "Aren’t PAH molecules found in tailpipe soot? That hardly sounds like building blocks of life. And doesn’t UV light in space destroy pyrimidines?" "Shush, boy, this is a scenario, remember? We can always tweak the scenario to keep the fans on the edge of their seats."
In theory, the researchers thought that if molecules of pyrimidine could survive long enough to migrate into interstellar dust clouds, they might be able to shield themselves from destructive radiation. Once in the clouds, most molecules freeze onto dust grains (much like moisture in your breath condenses on a cold window during winter).
These clouds are dense enough to screen out much of the surrounding outside radiation of space, thereby providing some protection to the molecules inside the clouds.
"We tried that play in this test chamber," the veteran ball player reassures the boy. "We got a few pyrimidines to survive. So don’t worry. We don’t have to play a real game; just a plausible, imaginary one." Scott Sandford, an Ames Flames ace, explains:
"Nobody really understands how life got started on Earth. Our experiments suggest that once the Earth formed, many of the building blocks of life were likely present from the beginning. Since we are simulating universal astrophysical conditions, the same is likely wherever planets are formed," says Sandford.
"Just assume a can opener, in other words, and presto! You have lunch," another chimes in. "It’s easy."
Just in time, like in the movies: a superhero arrives! Coming all the way from Quanta Magazine is Jeremy England, a veritable Casey at the Bat. The crowd goes wild as the announcer blares over the speakers:
Why does life exist?
Popular hypotheses credit a primordial soup, a bolt of lightning and a colossal stroke of luck. But if a provocative new theory is correct, luck may have little to do with it. Instead, according to the physicist proposing the idea, the origin and subsequent evolution of life follow from the fundamental laws of nature and "should be as unsurprising as rocks rolling downhill."
It can’t be so easy. "You’re kidding; he uses the Second Law?" the manager asks. "Where was this guy when we needed him?" England taps the plate with his bat as the rumors fly. "Jeremy is just about the brightest young scientist I ever came across," Atillo Szabo says. "I was struck by the originality of his ideas." Mara Prentiss adds, "He’s trying something radically different… As an organizing lens, I think he has a fabulous idea. Right or wrong, it’s going to be very much worth the investigation."
Reporters scratch down their notes furiously. "New physics theory may kill off creationist argument," Market Business News prints alongside England’s picture. "God is on the ropes," Paul Rosenberg writes for the Richard Dawkins Foundation. "The brilliant new science that has creationists and the Christian right terrified."
Speech! Speech! The fans call out, wanting to hear a sample of his brilliance.
"You start with a random clump of atoms, and if you shine light on it for long enough, it should not be so surprising that you get a plant," England said.
Fans are shocked. They look disappointed. Slowly, individuals leave their seats and head back to their cars. They hardly hear the announcer any more.
The chemistry of the primordial soup, random mutations, geography, catastrophic events and countless other factors have contributed to the fine details of Earth’s diverse flora and fauna. But according to England’s theory, the underlying principle driving the whole process is dissipation-driven adaptation of matter….
"I didn’t come to watch another pantheist skit," one says to another. "Yeah, me neither," says the other. "Sounds like animism to me. As a hardball science fan, I don’t like what that guy is pitching."