According to assembly theory, before Darwinian evolution can proceed, something has to pick out for multiple copies of high-AI objects from the Assembly Possible. Chemistry alone, Cronin said, may be able to that—by narrowing down relatively complex molecules to a small subset. Ordinary chemical reactions already “select” certain products out of all of the possible permutations because they’ve faster response rates.
The specific conditions within the prebiotic environment, akin to temperature or catalytic mineral surfaces, could thus have begun winnowing the pool of life’s molecular precursors from amongst those within the Assembly Possible. According to assembly theory, these prebiotic preferences can be “remembered” in today’s biological molecules: They encode their very own history. Once Darwinian selection took over, it favored those objects that were higher in a position to replicate themselves. In the method, this encoding of history became stronger still. That’s precisely why scientists can use the molecular structures of proteins and DNA to make deductions in regards to the evolutionary relationships of organisms.
Thus, assembly theory “provides a framework to unify descriptions of selection across physics and biology,” Cronin, Walker, and colleagues wrote. “The ‘more assembled’ an object is, the more selection is required for it to return into existence.”
“We’re attempting to make a theory that explains how life arises from chemistry,” Cronin said, “and doing it in a rigorous, empirically verifiable way.”
One Measure to Rule Them All?
Krakauer feels that each assembly theory and constructor theory offer stimulating latest ways to take into consideration how complex objects come into being. “These theories are more like telescopes than chemistry labs,” he said. “They allow us to see things, not make things. That is just not in any respect a foul thing and might be very powerful.”
But he cautions that “like all of science, the proof can be within the pudding.”
Zenil, meanwhile, believes that, given an already considerable roster of complexity metrics akin to Kolmogorov complexity, assembly theory is merely reinventing the wheel. Marletto disagrees. “There are several measures of complexity around, each capturing a special notion of complexity,” she said. But most of those measures, she said, aren’t related to real-world processes. For example, Kolmogorov complexity assumes a form of device that may put together anything the laws of physics permit. It’s a measure appropriate to the Assembly Possible, Marletto said, but not necessarily to the Assembly Observed. In contrast, assembly theory is “a promising approach since it focuses on operationally defined, physical properties,” she said, “fairly than abstract notions of complexity.”
What’s missing from such previous complexity measures, Cronin said, is any sense of the history of the complex object—the measures don’t distinguish between an enzyme and a random polypeptide.
Cronin and Walker hope that assembly theory will ultimately address very broad questions in physics, akin to the character of time and the origin of the second law of thermodynamics. But those goals are still distant. “The assembly-theory program continues to be in its infancy,” Marletto said. She hopes to see the idea put through its paces within the laboratory. But it would occur out within the wild too—within the hunt for lifelike processes happening on alien worlds.
Original story reprinted with permission from Quanta Magazine, an editorially independent publication of the Simons Foundation whose mission is to reinforce public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.