In 1950 the Italian physicist Enrico Fermi was discussing the possibility of intelligent alien life with his colleagues. If alien civilizations exist, he said, some should surely have had enough time to expand throughout the cosmos. So where are they?<\/p>\n\n\n\n
Many answers to Fermi\u2019s \u201cparadox\u201d have been proposed: Maybe alien civilizations burn out or destroy themselves before they can become interstellar wanderers. But perhaps the simplest answer is that such civilizations don\u2019t appear in the first place: Intelligent life is extremely unlikely, and we pose the question only because we are the supremely rare exception.<\/p>\n\n\n\n
A new proposal by an interdisciplinary team of researchers challenges that bleak conclusion. They have proposed nothing less than a new law of nature, according to which the complexity of entities in the universe increases over time with an inexorability comparable to the second law of thermodynamics \u2014 the law that dictates an inevitable rise in entropy, a measure of disorder. If they\u2019re right, complex and intelligent life should be widespread.<\/p>\n\n\n\n
In this new view, biological evolution appears not as a unique process that gave rise to a qualitatively distinct form of matter \u2014 living organisms. Instead, evolution is a special (and perhaps inevitable) case of a more general principle that governs the universe. According to this principle, entities are selected because they are richer in a kind of information that enables them to perform some kind of function.<\/p>\n\n\n\n
This hypothesis(opens a new tab), formulated by the mineralogist Robert Hazen and the astrobiologist Michael Wong of the Carnegie Institution in Washington, D.C., along with a team of others, has provoked intense debate. Some researchers have welcomed the idea as part of a grand narrative about fundamental laws of nature. They argue that the basic laws of physics are not \u201ccomplete\u201d in the sense of supplying all we need to comprehend natural phenomena; rather, evolution \u2014 biological or otherwise \u2014 introduces functions and novelties that could not even in principle be predicted from physics alone. \u201cI\u2019m so glad they\u2019ve done what they\u2019ve done,\u201d said Stuart Kauffman, an emeritus complexity theorist at the University of Pennsylvania. \u201cThey\u2019ve made these questions legitimate.\u201d<\/p>\n\n\n\n
Others argue that extending evolutionary ideas about function to non-living systems is an overreach. The quantitative value that measures information in this new approach is not only relative \u2014 it changes depending on context \u2014 it\u2019s impossible to calculate. For this and other reasons, critics have charged that the new theory cannot be tested, and therefore is of little use.<\/p>\n\n\n\n
The work taps into an expanding debate about how biological evolution fits within the normal framework of science. The theory of Darwinian evolution by natural selection helps us to understand how living things have changed in the past. But unlike most scientific theories, it can\u2019t predict much about what is to come. Might embedding it within a meta-law of increasing complexity let us glimpse what the future holds?<\/p>\n\n\n\n
Making Meaning<\/p>\n\n\n\n
The story begins in 2003, when the biologist Jack Szostak published a short article(opens a new tab) in Nature proposing the concept of functional information. Szostak \u2014 who six years later would get a Nobel Prize for unrelated work \u2014 wanted to quantify the amount of information or complexity that biological molecules like proteins or DNA strands embody. Classical information theory, developed by the telecommunications researcher Claude Shannon in the 1940s and later elaborated by the Russian mathematician Andrey Kolmogorov, offers one answer. Per Kolmogorov, the complexity of a string of symbols (such as binary 1s and 0s) depends on how concisely one can specify that sequence uniquely.<\/p>\n\n\n\n
For example, consider DNA, which is a chain of four different building blocks called nucleotides. \u0391 strand composed only of one nucleotide, repeating again and again, has much less complexity \u2014 and, by extension, encodes less information \u2014 than one composed of all four nucleotides in which the sequence seems random (as is more typical in the genome).<\/p>\n\n\n\n
But Szostak pointed out that Kolmogorov\u2019s measure of complexity neglects an issue crucial to biology: how biological molecules function.<\/p>\n\n\n\n
In biology, sometimes many different molecules can do the same job. Consider RNA molecules, some of which have biochemical functions that can easily be defined and measured. (Like DNA, RNA is made up of sequences of nucleotides.) In particular, short strands of RNA called aptamers securely bind to other molecules.<\/p>\n\n\n\n
Let\u2019s say you want to find an RNA aptamer that binds to a particular target molecule. Can lots of aptamers do it, or just one? If only a single aptamer can do the job, then it\u2019s unique, just as a long, seemingly random sequence of letters is unique. Szostak said that this aptamer would have a lot of what he called \u201cfunctional information.\u201d<\/p>\n\n\n\n
If many different aptamers can perform the same task, the functional information is much smaller. So we can calculate the functional information of a molecule by asking how many other molecules of the same size can do the same task just as well.<\/p>\n\n\n\n
Szostak went on to show that in a case like this, functional information can be measured experimentally. He made a bunch of RNA aptamers and used chemical methods to identify and isolate the ones that would bind to a chosen target molecule. He then mutated the winners a little to seek even better binders and repeated the process. The better an aptamer gets at binding, the less likely it is that another RNA molecule chosen at random will do just as well: The functional information of the winners in each round should rise. Szostak found that the functional information of the best-performing aptamers got ever closer to the maximum value predicted theoretically.<\/p>\n\n\n\n
Selected for Function<\/p>\n\n\n\n
Hazen came across Szostak\u2019s idea while thinking about the origin of life \u2014 an issue that drew him in as a mineralogist, because chemical reactions taking place on minerals have long been suspected to have played a key role in getting life started. \u201cI concluded that talking about life versus nonlife is a false dichotomy,\u201d Hazen said. \u201cI felt there had to be some kind of continuum \u2014 there has to be something that\u2019s driving this process from simpler to more complex systems.\u201d Functional information, he thought, promised a way to get at the \u201cincreasing complexity of all kinds of evolving systems.\u201d<\/p>\n\n\n\n
In 2007 Hazen collaborated with Szostak to write a computer simulation(opens a new tab) involving algorithms that evolve via mutations. Their function, in this case, was not to bind to a target molecule, but to carry out computations. Again they found that the functional information increased spontaneously over time as the system evolved.<\/p>\n\n\n\n
There the idea languished for years. Hazen could not see how to take it any further until Wong accepted a fellowship at the Carnegie Institution in 2021. Wong had a background in planetary atmospheres, but he and Hazen discovered they were thinking about the same questions. \u201cFrom the very first moment that we sat down and talked about ideas, it was unbelievable,\u201d Hazen said.<\/p>\n\n\n\n
\u201cI had got disillusioned with the state of the art of looking for life on other worlds,\u201d Wong said. \u201cI thought it was too narrowly constrained to life as we know it here on Earth, but life elsewhere may take a completely different evolutionary trajectory. So how do we abstract far enough away from life on Earth that we\u2019d be able to notice life elsewhere even if it had different chemical specifics, but not so far that we\u2019d be including all kinds of self-organizing structures like hurricanes?\u201d<\/p>\n\n\n\n
The pair soon realized that they needed expertise from a whole other set of disciplines. \u201cWe needed people who came at this problem from very different points of view, so that we all had checks and balances on each other\u2019s prejudices,\u201d Hazen said. \u201cThis is not a mineralogical problem; it\u2019s not a physics problem, or a philosophical problem. It\u2019s all of those things.\u201d<\/p>\n\n\n\n
They suspected that functional information was the key to understanding how complex systems like living organisms arise through evolutionary processes happening over time. \u201cWe all assumed the second law of thermodynamics supplies the arrow of time,\u201d Hazen said. \u201cBut it seems like there\u2019s a much more idiosyncratic pathway that the universe takes. We think it\u2019s because of selection for function \u2014 a very orderly process that leads to ordered states. That\u2019s not part of the second law, although it\u2019s not inconsistent with it either.\u201d<\/p>\n\n\n\n
Looked at this way, the concept of functional information allowed the team to think about the development of complex systems that don\u2019t seem related to life at all.<\/p>\n\n\n\n
At first glance, it doesn\u2019t seem a promising idea. In biology, function makes sense. But what does \u201cfunction\u201d mean for a rock?<\/p>\n\n\n\n
All it really implies, Hazen said, is that some selective process favors one entity over lots of other potential combinations. A huge number of different minerals can form from silicon, oxygen, aluminum, calcium and so on. But only a few are found in any given environment. The most stable minerals turn out to be the most common. But sometimes less stable minerals persist because there isn\u2019t enough energy available to convert them to more stable phases.<\/p>\n\n\n\n
This might seem trivial, like saying that some objects exist while other ones don\u2019t, even if they could in theory. But Hazen and Wong have shown(opens a new tab) that, even for minerals, functional information has increased over the course of Earth\u2019s history. Minerals evolve toward greater complexity (though not in the Darwinian sense). Hazen and colleagues speculate that complex forms of carbon such as graphene might form in the hydrocarbon-rich environment of Saturn\u2019s moon Titan \u2014 another example of an increase in functional information that doesn\u2019t involve life.<\/p>\n\n\n\n
It\u2019s the same with chemical elements. The first moments after the Big Bang were filled with undifferentiated energy. As things cooled, quarks formed and then condensed into protons and neutrons. These gathered into the nuclei of hydrogen, helium and lithium atoms. Only once stars formed and nuclear fusion happened within them did more complex elements like carbon and oxygen form. And only when some stars had exhausted their fusion fuel did their collapse and explosion in supernovas create heavier elements such as heavy metals. Steadily, the elements increased in nuclear complexity.<\/p>\n\n\n\n
Wong said their work implies three main conclusions.<\/p>\n\n\n\n
First, biology is just one example of evolution. \u201cThere is a more universal description that drives the evolution of complex systems.\u201d<\/p>\n\n\n\n
Second, he said, there might be \u201can arrow in time that describes this increasing complexity,\u201d similar to the way the second law of thermodynamics, which describes the increase in entropy, is thought to create a preferred direction of time.<\/p>\n\n\n\n
Finally, Wong said, \u201cinformation itself might be a vital parameter of the cosmos, similar to mass, charge and energy.\u201d<\/p>\n\n\n\n
In the work Hazen and Szostak conducted on evolution using artificial-life algorithms, the increase in functional information was not always gradual. Sometimes it would happen in sudden jumps. That echoes what is seen in biological evolution. Biologists have long recognized transitions where the complexity of organisms increases abruptly. One such transition was the appearance of organisms with cellular nuclei (around 1.8 billion to 2.7 billion years ago). Then there was the transition to multicellular organisms (around 2 billion to 1.6 billion years ago), the abrupt diversification of body forms in the Cambrian explosion (540 million years ago), and the appearance of central nervous systems (around 600 million to 520 million years ago). The arrival of humans was arguably another major and rapid evolutionary transition.<\/p>\n\n\n\n
Evolutionary biologists have tended to view each of these transitions as a contingent event. But within the functional-information framework, it seems possible that such jumps in evolutionary processes (whether biological or not) are inevitable.<\/p>\n\n\n\n
In these jumps, Wong pictures the evolving objects as accessing an entirely new landscape of possibilities and ways to become organized, as if penetrating to the \u201cnext floor up.\u201d Crucially, what matters \u2014 the criteria for selection, on which continued evolution depends \u2014 also changes, plotting a wholly novel course. On the next floor up, possibilities await that could not have been guessed before you reached it.<\/p>\n\n\n\n
For example, during the origin of life it might initially have mattered that proto-biological molecules would persist for a long time \u2014 that they\u2019d be stable. But once such molecules became organized into groups that could catalyze one another\u2019s formation \u2014 what Kauffman has called autocatalytic cycles \u2014 the molecules themselves could be short-lived, so long as the cycles persisted. Now it was dynamical, not thermodynamic, stability that mattered. Ricard Sol\u00e9 of the Santa Fe Institute thinks such jumps might be equivalent to phase transitions in physics, such as the freezing of water or the magnetization of iron: They are collective processes with universal features, and they mean that everything changes, everywhere, all at once. In other words, in this view there\u2019s a kind of physics of evolution \u2014 and it\u2019s a kind of physics we know about already.<\/p>\n\n\n\n
The Biosphere Creates Its Own Possibilities<\/p>\n\n\n\n
The tricky thing about functional information is that, unlike a measure such as size or mass, it is contextual: It depends on what we want the object to do, and what environment it is in. For instance, the functional information for an RNA aptamer binding to a particular molecule will generally be quite different from the information for binding to a different molecule.<\/p>\n\n\n\n
Yet finding new uses for existing components is precisely what evolution does. Feathers did not evolve for flight, for example. This repurposing reflects how biological evolution is jerry-rigged, making use of what\u2019s available.<\/p>\n\n\n\n
Kauffman argues that biological evolution is thus constantly creating not just new types of organisms but new possibilities for organisms, ones that not only did not exist at an earlier stage of evolution but could not possibly have existed. From the soup of single-celled organisms that constituted life on Earth 3 billion years ago, no elephant could have suddenly emerged \u2014 this required a whole host of preceding, contingent but specific innovations.<\/p>\n\n\n\n
However, there is no theoretical limit to the number of uses an object has. This means that the appearance of new functions in evolution can\u2019t be predicted \u2014 and yet some new functions can dictate the very rules of how the system evolves subsequently. \u201cThe biosphere is creating its own possibilities,\u201d Kauffman said. \u201cNot only do we not know what will happen, we don\u2019t even know what can happen.\u201d Photosynthesis was such a profound development; so were eukaryotes, nervous systems and language. As the microbiologist Carl Woese and the physicist Nigel Goldenfeld put it in 2011, \u201cWe need an additional set of rules describing the evolution of the original rules. But this upper level of rules itself needs to evolve. Thus, we end up with an infinite hierarchy.\u201d<\/p>\n\n\n\n
The physicist Paul Davies of Arizona State University agrees that biological evolution \u201cgenerates its own extended possibility space which cannot be reliably predicted or captured via any deterministic process from prior states. So life evolves partly into the unknown.\u201d<\/p>\n\n\n\n
Mathematically, a \u201cphase space\u201d is a way of describing all possible configurations of a physical system, whether it\u2019s as comparatively simple as an idealized pendulum or as complicated as all the atoms comprising the Earth. Davies and his co-workers have recently suggested(opens a new tab) that evolution in an expanding accessible phase space might be formally equivalent to the \u201cincompleteness theorems\u201d devised by the mathematician Kurt G\u00f6del. G\u00f6del showed that any system of axioms in mathematics permits the formulation of statements that can\u2019t be shown to be true or false. We can only decide such statements by adding new axioms.<\/p>\n\n\n\n
Davies and colleagues say that, as with G\u00f6del\u2019s theorem, the key factor that makes biological evolution open-ended and prevents us from being able to express it in a self-contained and all-encompassing phase space is that it is self-referential: The appearance of new actors in the space feeds back on those already there to create new possibilities for action. This isn\u2019t the case for physical systems, which, even if they have, say, millions of stars in a galaxy, are not self-referential.<\/p>\n\n\n\n
\u201cAn increase in complexity provides the future potential to find new strategies unavailable to simpler organisms,\u201d said Marcus Heisler, a plant developmental biologist at the University of Sydney and co-author of the incompleteness paper. This connection between biological evolution and the issue of noncomputability, Davies said, \u201cgoes right to the heart of what makes life so magical.\u201d<\/p>\n\n\n\n
Is biology special, then, among evolutionary processes in having an open-endedness generated by self-reference? Hazen thinks that in fact once complex cognition is added to the mix \u2014 once the components of the system can reason, choose, and run experiments \u201cin their heads\u201d \u2014 the potential for macro-micro feedback and open-ended growth is even greater. \u201cTechnological applications take us way beyond Darwinism,\u201d he said. A watch gets made faster if the watchmaker is not blind.<\/p>\n\n\n\n
Back to the Bench<\/p>\n\n\n\n
If Hazen and colleagues are right that evolution involving any kind of selection inevitably increases functional information \u2014 in effect, complexity \u2014 does this mean that life itself, and perhaps consciousness and higher intelligence, is inevitable in the universe? That would run counter to what some biologists have thought. The eminent evolutionary biologist Ernst Mayr believed that the search for extraterrestrial intelligence was doomed because the appearance of humanlike intelligence is \u201cutterly improbable.\u201d After all, he said, if intelligence at a level that leads to cultures and civilizations were so adaptively useful in Darwinian evolution, how come it only arose once across the entire tree of life?<\/p>\n\n\n\n
Mayr\u2019s evolutionary point possibly vanishes in the jump to humanlike complexity and intelligence, whereupon the whole playing field is utterly transformed. Humans attained planetary dominance so rapidly (for better or worse) that the question of when it will happen again becomes moot.<\/p>\n\n\n\n
But what about the chances of such a jump happening in the first place? If the new \u201claw of increasing functional information\u201d is right, it looks as though life, once it exists, is bound to get more complex by leaps and bounds. It doesn\u2019t have to rely on some highly improbable chance event.<\/p>\n\n\n\n
What\u2019s more, such an increase in complexity seems to imply the appearance of new causal laws in nature that, while not incompatible with the fundamental laws of physics governing the smallest component parts, effectively take over from them in determining what happens next. Arguably we see this already in biology: Galileo\u2019s (apocryphal) experiment of dropping two masses from the Leaning Tower of Pisa no longer has predictive power when the masses are not cannonballs but living birds.<\/p>\n\n\n\n
Together with the chemist Lee Cronin(opens a new tab) of the University of Glasgow, Sara Walker of Arizona State University has devised an alternative set of ideas to describe how complexity arises, called assembly theory. In place of functional information, assembly theory relies on a number called the assembly index, which measures the minimum number of steps required to make an object from its constituent ingredients.<\/p>\n\n\n\n
\u201cLaws for living systems must be somewhat different than what we have in physics now,\u201d Walker said, \u201cbut that does not mean that there are no laws.\u201d But she doubts that the putative law of functional information can be rigorously tested in the lab. \u201cI am not sure how one could say [the theory] is right or wrong, since there is no way to test it objectively,\u201d she said. \u201cWhat would the experiment look for? How would it be controlled? I would love to see an example, but I remain skeptical until some metrology is done in this area.\u201d<\/p>\n\n\n\n
Hazen acknowledges that, for most physical objects, it is impossible to calculate functional information even in principle. Even for a single living cell, he admits, there\u2019s no way of quantifying it. But he argues that this is not a sticking point, because we can still understand it conceptually and get an approximate quantitative sense of it. Similarly, we can\u2019t calculate the exact dynamics of the asteroid belt because the gravitational problem is too complicated \u2014 but we can still describe it approximately enough to navigate spacecraft through it.<\/p>\n\n\n\n
Wong sees a potential application of their ideas in astrobiology. One of the curious aspects of living organisms on Earth is that they tend to make a far smaller subset of organic molecules than they could make given the basic ingredients. That\u2019s because natural selection has picked out some favored compounds. There\u2019s much more glucose in living cells, for example, than you\u2019d expect if molecules were simply being made either randomly or according to their thermodynamic stability. So one potential signature of lifelike entities on other worlds might be similar signs of selection outside what chemical thermodynamics or kinetics alone would generate. (Assembly theory similarly predicts complexity-based biosignatures.)<\/p>\n\n\n\n
There might be other ways of putting the ideas to the test. Wong said there is more work still to be done on mineral evolution, and they hope to look at nucleosynthesis and computational \u201cartificial life.\u201d Hazen also sees possible applications in oncology, soil science and language evolution. For example, the evolutionary biologist Fr\u00e9d\u00e9ric Thomas of the University of Montpellier in France and colleagues have argued(opens a new tab) that the selective principles governing the way cancer cells change over time in tumors are not like those of Darwinian evolution, in which the selection criterion is fitness, but more closely resemble the idea of selection for function from Hazen and colleagues.<\/p>\n\n\n\n
Hazen\u2019s team has been fielding queries from researchers ranging from economists to neuroscientists, who are keen to see if the approach can help. \u201cPeople are approaching us because they are desperate to find a model to explain their system,\u201d Hazen said.<\/p>\n\n\n\n
But whether or not functional information turns out to be the right tool for thinking about these questions, many researchers seem to be converging on similar questions about complexity, information, evolution (both biological and cosmic), function and purpose, and the directionality of time. It\u2019s hard not to suspect that something big is afoot. There are echoes of the early days of thermodynamics, which began with humble questions about how machines work and ended up speaking to the arrow of time, the peculiarities of living matter, and the fate of the universe.<\/p>\n","protected":false},"excerpt":{"rendered":"
In 1950 the Italian physicist Enrico Fermi was discussing the possibility of intelligent alien life with his colleagues. If alien civilizations exist, he said, some should surely have had enough time to expand throughout the cosmos. So where are they? Many answers to Fermi\u2019s \u201cparadox\u201d have been proposed: Maybe alien civilizations burn out or destroy […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-41","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/deusexmachina.solutions\/index.php\/wp-json\/wp\/v2\/posts\/41","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/deusexmachina.solutions\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/deusexmachina.solutions\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/deusexmachina.solutions\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/deusexmachina.solutions\/index.php\/wp-json\/wp\/v2\/comments?post=41"}],"version-history":[{"count":1,"href":"https:\/\/deusexmachina.solutions\/index.php\/wp-json\/wp\/v2\/posts\/41\/revisions"}],"predecessor-version":[{"id":42,"href":"https:\/\/deusexmachina.solutions\/index.php\/wp-json\/wp\/v2\/posts\/41\/revisions\/42"}],"wp:attachment":[{"href":"https:\/\/deusexmachina.solutions\/index.php\/wp-json\/wp\/v2\/media?parent=41"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/deusexmachina.solutions\/index.php\/wp-json\/wp\/v2\/categories?post=41"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/deusexmachina.solutions\/index.php\/wp-json\/wp\/v2\/tags?post=41"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}