If you were raised religious, you might have heard this biology "lesson" before: A student is handed a paper bag and a ball point pen. The teacher dismantles the pen into a pile of plastic and metal bits and an ink cartridge, then tosses it in the bag. The student is instructed to shake the bag for as long as possible and reassemble the pen.
After several frustrating, unsuccessful minutes, the student is told, "See? This is why the origin of life via evolution could never happen. You could shake that bag for a million years and it would never assemble into a functional pen. How could something as complex as a human being emerge from randomness?"
I was independently given this exact demonstration at least three times in my life: once at church, once at school and once by my own father. Of course, it's an oversimplification and not really demonstrative of the conditions that created life on Earth, but it's been a tactic for dismissing the theory of abiogenesis, or how non-living things like carbon atoms can seemingly self-assemble to create living cells.
On the surface, the idea of abiogenesis does seem illogical, and the timescales — millions and billions of years — are barely comprehendible to the human mind. It's hard to fathom this stuff, but it's more complicated than spontaneous generation. Life didn't just poof into existence like some kind of magic trick, but slowly formed through intricate chemical processes that spawned some of the building blocks of life, called amino acids.
Even Charles Darwin pondered the possibility of a "warm little pond," later described as a "primordial soup" by Russian biochemist Alexander Oparin, which could form the proteins necessary for making amino acids. These scientific theories were intriguing, but science is about more than just hypothesizing. Scientists need to be able to test these ideas.
After a few days, the water in the Miller-Urey experiment turned pink, then a dark red. When the solution was analyzed, it was discovered to contain many of the specific amino acids necessary for life.
The first time this was done was in 1952. Stanley Miller and Harold Urey, two chemists at the University of Chicago, designed a closed glass loop to mimic the water cycle on an ancient Earth. It included water, hydrogen, methane and ammonia, which they believed composed Earth's early atmosphere. In one section, water was boiled to emulate evaporation, which was then zapped with electrodes in another section to echo lighting. The liquid was then condensed and flushed through the system again and again.
After a few days, the water in the Miller-Urey experiment turned pink, then a dark red. When the solution was analyzed, it was discovered to contain many of the specific amino acids necessary for life, giving weight to the abiogenesis theory. This experiment has been reproduced numerous times with various tweaks, including conditions that may be created by meteorites containing organic molecules. But these experiments still leave many unanswered questions about how life may have formed billions of years ago.
Researchers at Purdue University's chemistry department have reported a recent breakthrough that lends even more evidence to abiogenesis. A study recently published in Proceedings of the National Academy of Sciences, describes experiments involving electrified nano-sprays that were blasted at a mass spectrometer, a device that can measure the shape of molecules.
The sprays were filled with two amino acids, glycine or L-alanine, and squirted out of an opening just a few millionths of a meter across. Sometimes they were streamed at each other, to demonstrate how such water droplets collide in air. Just milliseconds later, when the molecules pinged the mass spectrometer, they had formed chemical bonds called dipeptides. These bonds are necessary to form proteins, which make up living things.
The chemical reactions themselves aren't so complex either; and by studying the Earth's core, we also know that the necessary chemicals in question existed in abundance in the planet's early days.
"This is the first demonstration that primordial molecules, simple amino acids, spontaneously form peptides, the building blocks of life, in droplets of pure water. This is a dramatic discovery," Dr. Graham Cooks, an analytical chemistry professor at Purdue's College of Science, said in a statement. "This is essentially the chemistry behind the origin of life."
These experiments could simulate almost identical water droplet impacts in the ancient atmosphere through waves smacking rocky beaches, generating ocean spray. Millions of years of these processes could have generated that amino acids that bonded to form proteins, which constitute the plasma membranes of cells, chromosomes and much more.
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None of this is anything like shaking a baggie full of pen parts. It's more like jostling a sack full of magnetic Legos, which fit together easily and are attracted to each other through chemical bonds. And there aren't just a few parts, but billions and billions of Legos, all of them bouncing around for millions of years. The chemical reactions themselves aren't so complex either; and by studying the Earth's core, we also know that the necessary chemicals in question existed in abundance in the planet's early days. All the pieces were there, with the right kinds of planetary conditions to push them together, so it's not as implausible as some make it out to be.
However, for these amino acid bonds to form in the first place, there needs to be dehydration. Amino acids can't form if it's too wet, making the oceans "unfavorable" for the necessary chemistry, as Cooks and his colleagues put it.
This is the so-called "water paradox," which a paper published last year in The Journal of Physical Chemistry A put succinctly: "water is necessary for life, yet its presence poses a challenge to the formation and preservation of many critical biomolecules." The paper analyzed recent evidence that when water meets air, it could create the necessary conditions.
Cooks' experiment does a good job of confirming this is actually possible. And the implications here are huge. First, it justifies using water as a key ingredient to look for when searching for life outside our planet. Alien worlds teeming with liquid H2O are more likely to produce extraterrestrials. If it could happen here, it could happen elsewhere in the Universe.
Second, these chemical reactions could speed up the development of pharmaceutical drugs and novel disease treatments. As Cooks put it, "using droplet chemistry, we have built an apparatus, which is being used at Purdue now, to speed up the synthesis of novel chemicals and potential new drugs." In the future, the same chemical reactions necessary for forming life could help sustain it.
We still don't know exactly how life originated on Earth, and we'll never be 100 percent certain without a time machine. But experiments like these strengthen the argument that, under the right conditions, living organisms can arise from a chemical chowder. Life's origins will likely always be a mystery, but advancements in science continue to make the enigma a little less puzzling.
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