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Could chemical evolution produce DNA?

An inquirer asks about recent hype concerning claims that DNA building blocks could be produced by random, undirected chemistry. Ph.D. chemist Dr Jonathan Sarfati responds with both general advice about chemical evolution claims, and some specifics about this latest one.

Erin C. writes:

Dr Sarfati replies:

Dear Erin

Thank you for writing to CMI.

As a rule, we can’t normally grant requests to respond to articles or YouTube videos online, otherwise we would have no time for anything else!

But as it turns out, CMI scientists had already come across this paper and discussed it informally. Note that every ostensibly new chemical evolution paper is a tacit admission that other scenarios don’t work. We have an article advising how we should assess any new paper.¹ But let’s look at this latest one anyway.

“The essential feature of the new pathway, as Trapp explains, is that the sugar is not linked to the base in a single step. Instead, it is built up on the preformed base by a short sequence of reaction steps involving simple organic molecules such as acetaldehyde and glyceraldehyde.”^2,3

That is, they did not synthesise any of the four DNA bases, but presupposed them. Not surprising, since there is no good prebiotic route to cytosine especially, and the others are unstable. And how nice that they have used pure, uncontaminated reagents to make the sugars, instead of the diluted and grossly contaminated gunk that results from Miller–Urey-type experiments. We have long known about formose reaction (or Butlerov reaction, after eminent 19th-century Russian chemist Alexander Mikhaylovich Butlerov) to make sugars from simple aldehydes in alkaline conditions. But to get useful amounts, we must stop this reaction at just the right time, otherwise the Cannizzaro reaction and caramelization would destroy them.⁴

So after finding a chemical pathway for adding a (simple) sugar moiety to an existing nucleotide, what happens next? How do we take this product and polymerize it (to make some actual DNA)? How do they make sure that the added sugars are homochiral? After that, how does random chemistry add information (in thermodynamic terms, reduce configurational entropy)? How did they do all this before DNA breaks down, given its known instability? Note that RNA is even more unstable, which is really saying a lot, thanks to the extra hydroxy group on the ribose.

It would take far more than this paper even to make a small dent in our overview paper on chemical evolution,⁵ for example. In short, the claims are hyped to the hilt.