Complex, evolving systems abound in our Universe, even beyond the realms of biology. From the growth of stars to prebiotic chemistry, diverse mixes of materials can often be shaped into far more complex forms.
Yet unlike other so many other physical phenomena, their changing nature is yet to be represented by a discrete law.
That's according to a US team of astrobiologists, philosophers, a mineralogist, a theoretical physicist, and a data scientist who describe the "missing law" of nature in an intriguing new peer-reviewed paper.
"Given the ubiquity of evolving systems in the natural world, it seems odd that one or more laws describing their behaviors have not been more quickly forthcoming," the authors write.
The team's own "law of increasing functional information" says evolution in all its forms inevitably leads to more patterning, diversity, and complexity in natural complex systems.
Evolution is certainly not unique to Earth's biosphere; it takes place in other extremely complex systems, such as our Solar System, stars, atoms, and minerals.
"The Universe generates novel combinations of atoms, molecules, cells, etc," says first author of the study, astrobiologist Michael Wong from Carnegie Institution for Science in Washington, DC.
"Those combinations that are stable and can go on to engender even more novelty will continue to evolve. This is what makes life the most striking example of evolution, but evolution is everywhere."
The paper describes how just hydrogen and helium – the two most abundant elements at the time of the Big Bang – coalesced to form the first stars. By the time a star reaches the end of its life it can generate more than 100 elements with around 2000 varieties of isotope.
On Earth, an enormous diversity of mineral 'species' were created from simple beginnings as the planet formed across 4.55 to 2.5 billion years ago. There are now more than 5,900 known mineral species on Earth, which became increasingly chemically complex as emerging forms of life released oxygen into the atmosphere.
Iron's reaction with oxygen-based minerals ushered in a new era in ancient life and laid the groundwork for our own evolution in tandem with other minerals.
The complexity of Earth's surface mineralogy grew further as life evolved from single-celled to multicellular organisms and ecosystems formed. The wide range of minerals that were formed changed the course of evolution and its options.
Biological and mineral systems continually interact to influence each other's diversity, and life as we know it is the result of this interaction.
"These evolving systems appear to be conceptually equivalent in that they display three notable attributes," the authors write.
"1) They form from numerous components that have the potential to adopt combinatorially vast numbers of different configurations; 2) processes exist that generate numerous different configurations; and 3) configurations are preferentially selected based on function."
So, is there something in the way information can be transferred that accounts for the shared characteristics of seemingly diverse evolving systems? Could there be a universal basis for selection? The team thinks both answers are yes.
"An important component of this proposed natural law is the idea of 'selection for function,'" says Wong.
According to Darwin, an organism's primary function in the context of biology is to ensure its own survival long enough to reproduce successfully. The team says this new proposal broadens our understanding by pointing out the existence of three distinct types of function in the natural world.
The most fundamental function we could call 'static persistence' – maintenance of stable atomic or molecular arrangements.
'Dynamic persistence' describes how systems that are dynamic and have access to constant sources of energy are also more likely to endure.
And lastly, 'novelty generation' refers to the propensity of evolving systems to generate novel configurations, which can result in surprising novel behaviors or characteristics.
Wong and team point out that physical laws of motion, gravity, electromagnetism, and thermodynamics govern the functions of macroscopic natural systems across space and time. So it makes sense that we should have a law of nature for evolution.
"An asymmetric trajectory based upon functionality may seem antithetical to scientific analysis," the team concludes.
"Nevertheless, we conjecture that selection based on static persistence, dynamic persistence, and novelty generation is a universal process that results in systems with increased functional information."
The study has been published in Proceedings of the National Academy of Sciences.