Science Corner: Ask Your Parents Where Life Comes From

Lent is halfway through, we’ve set our clocks ahead, and Peeps are on the store shelves. It must be nearly spring, and so soon young men’s fancies will lightly turn to thoughts of life. New life will be everywhere: blooming flowers, baby birds, buzzing cicadas. We know where this life comes from. But where did the first life come from? That remains a mystery, yet one which many young folks of all sorts seek to unravel. One group in Scotland has gone so far as to build their own “Chemputer” to help, and its first results are starting to come in.

The goal of the “Chemputer” is to automate chemical synthesis, making chemistry more reproducible between labs and less labor-intensive. Instead of having to measure and mix the chemicals yourself, you program the amounts and the steps into a computer and a robot will do the actual work. Not a C-3P0 or Data-style android, but a robot more like those on factory assembly lines. You could use a setup like that to synthesize a specific compound. Or you can use it to automate experiments involving various reaction mixtures with results to be observed. That is the setup used for a new paper investigating the origin of life by Silke Asche, et al.

In particular, the question at hand is where selection comes from. We know that selection can occur with populations of living organisms via differential reproduction; that’s how we got corn to be tasty, for example. But selection of some form likely needed to kick in even before there was life as we know it (i.e. cellular life). The alternative is a world where lots of chemicals are made, but all in roughly equal and very small quantities. In that scenario, you don’t get enough of anything in particular, like amino acids or lipids or RNA, that could be used to make something like a living organism that can reproduce itself from more of those same parts.

To put it another way, think about the process of typing. I could just mash away at the keyboard and I’d get strings of letters and punctuation. All the individual letters would still appear a lot, as would all the possible two-letter combinations. But as you look for longer and longer sequences, each sequence of that length appears less and less often. But because I have a selection process for choosing the letters, certain sequences appear much more often than you’d expect by chance, like ‘letter’ and ‘life,’ while others like ‘weo’ never appear at all. That imbalance–many repetitions of a few things that should be rare and no instances of many other things of equal likelihood under uniform randomness–has been put forward as a signature of selection and was what Asche et al. were looking for.

Specifically, they were looking for short sequences of amino acids that formed in the presences of various minerals. Using something called a “Mad Mining Rock Crusher” they pulverized different types of rocks into millimeter-scale pebbles. Those pebbles could then serve as reaction surfaces for amino acids to react and form short chains. If the minerals had no impact on which reactions occur, the compositions of those chains should look like keyboard mashing; every combination in roughly equal proportion based just on length. But if the minerals biased the process, certain chains should show up more often. (Where the robot comes in is handling the repetitive task of adding the amino acids and then removing some of what was made and putting in fresh amino acids at regular intervals to see what happened over time.)

What they found was indeed that some permutations of amino acids showed up preferentially in the presence of the minerals. Even more interestingly, the different minerals had noticeably different preferences, which lends credence to the idea that there is a selection process happening and not just random mixing. With random mixing, one would expect similar results from all minerals. And in fact some of the minerals did produce results more or less the same as no mineral, but some had more distinctive patterns.

Making short polypeptides is still a long way from making a living organism. And we don’t even know if these are interesting polypeptides, although even small ones like these can in principle have catalytic activity or other interesting chemical features. But if specific minerals can have a selective effect on amino acid chemistry, that could be a useful clue about how life began or at least could arise. And even if not, the “Chemputer” might still be a fruitful addition to our scientific toolbox. Origin of life research has already yielded nanopore sequencing technology as a side benefit; this could be another such spandrel from the field.

And where does that leave God, some might wonder. If we suppose God played the selective role, introducing minerals could be seen as replacing God. Or we might suppose God played a role further downstream, such that any notion of prebiotic chemistry contributing to life is an unwanted replacement. To me, picking anywhere and saying “That’s God’s job” implies a picture like an assembly line with God occupying a discrete position. Of course then God could be subject to replacement just like a robot replacing a human factory worker. Do we make God the shop foreman or the manager or the factory owner then, or maybe the architect of the factory? Again, that feels too constrained. Maybe modern fabrication just doesn’t offer a useful analogy. Maybe the best analogy is still the biblical one of the potter, an artisan who is hands-on through the entire process. His work may be mediated by tools and maybe their touch is what the clay physically experiences, but the potter is always involved. If that is not apparent to us, that is because we only see the pots and never the clay as it would be if there were no potter.