It’s not every day that the mainstream media admit that the origin of life is a mystery. But it happens.
In a recent article, “Origin-of-Life Theorists Fail to Explain Chemical Signatures in the Cell,” we noted the admission from Nature News: “How life began is one of nature’s enduring mysteries.” Now, a LiveScience article on MSNBC, titled “The mystery of how Earth’s primordial soup came to life,” asks: “What turned sterile molecules into living, changing organisms? That’s the ultimate mystery.”
But of course, the same media sources resist leaving the impression that we really don’t understand how life arose by natural chemical means. The article goes on to say:
Just as species are believed to have evolved over time, the individual molecules that form the basis of life also likely developed in response to natural selection, scientists say.
It sounds so easy, so simple. But how much have scientists actually explained? According to the article, they’ve explained how a couple of compounds in the primordial soup might have escaped destruction by UV radiation:
Molecules that could combine to gain attributes would survive longer and proliferate, while those that were more easily destroyed would fade away.
One example is the compound of glutamic acid and two glycine molecules.
Individually, each of these molecules was easily destroyed by ultraviolet radiation. But put together, they were extremely stable.
Yes, this compound might have been naturally selected to avoid destruction by UV radiation. But the problem is how to produce glycine in the first place. Origin-of-life theorists still haven’t shown there’s a viable mechanism capable of producing the organic molecules necessary for a primordial soup under the actual conditions on the early Earth.
Yet even once you’ve got a primordial soup of amino acids (or other organic molecules), you’ve got the problem of linking the primitive monomers into polymers. This can’t happen in an aqueous environment like a prebiotic soup because, as the U.S. National Academy of Sciences observes:
In water, the assembly of nucleosides from component sugars and nucleobases, the assembly of nucleotides from nucleosides and phosphate, and the assembly of oligonucleotides from nucleotides are all thermodynamically uphill in water. Two amino acids do not spontaneously join in water. Rather, the opposite reaction is thermodynamically favored at any plausible concentrations: polypeptide chains spontaneously hydrolyze in water, yielding their constituent amino acids.
But assuming that you can somehow get polypeptide chains out of the primordial soup, there’s no way to properly order the amino acids to produce something functional. This explanation from the article certainly doesn’t solve the problem:
“If you have to evolve a receptor composed of a precise ordering of 400 amino acids, it wouldn’t be possible to do it all at once,” [Michigan State University physiologist Robert Root-Bernstein] said. “You have to use stable modules.”
These modules are the compound molecules that have become stable by combining. If life assembled from combinations of these already-stable building blocks, rather than a random combination of raw molecules from scratch, the process would have been much more efficient.
“The difference between trying absolutely everything and trying a small number of stable modules is huge,” Root-Bernstein said. “It makes something that’s virtually impossible into something that’s very likely.”
The problem with this argument is that natural selection requires replication. But as far as we’re aware, life cannot replicate until many parts are present. Without natural selection, you’re stuck with what David Berlinski calls “sheer dumb luck.” Unless there’s some reason (and none is given in the article) to expect the spontaneous production of all the “stable modules” of the 400-amino-acid receptor, all you can rely on is sheer chance.
The odds of assembling a 400-amino acid receptor by chance are nil, but even if you had that receptor, it still is dramatically insufficient to yield a living, reproducing organism. No wonder biochemist Nick Lane observes that the “soup has no capacity for producing the energy vital for life.”
It’s time for a little reality check here: origin-of-life theorists need to explain how a myriad of complex proteins and features arose and self-assembled into a self-replicating life-form by unguided processes, but they are still scraping for mechanisms to explain how an inert primordial soup of organic molecules could have arisen in the first place.
I wish them the best of luck in their efforts, because they’ll need it. They are a long way from explaining how life arose. It looks like Nature was right after all: “How life began is one of nature’s enduring mysteries.”