Evolution has two ingredients, constant variation and constant selection.

Two important observations:

Variation in biology exhibits itself in myriad forms, but they all can be traced back to the second law of thermodynamics, which says that entropy (on average) always increases over time. (It is not a coincidence that Darwin formulated the theory of natural selection in 1850s, around the same time Clausius formulated the second law.)
If you decrease selection pressures, the fitness landscape expands. You see less people dying around you, but you also see more variety at any given time. As we learn to cure and cope with (physical and mental) disorders using advances in (hard and soft) sciences / extend our societal safety nets further / improve our parenting and teaching techniques, more and more people stay alive and functional to go on to mate and reproduce. Progress creates more elbow room for evolution so that it can try out even wilder combinations than before.
Conversely, if you increase selection pressures, the fitness landscape contracts, but in return the shortened life cycles enable evolution to shuffle through the contracted landscape of possibilities at a higher speed.
Hence, selection pressure acts like a lever between spatial variation and temporal variation. Decreasing it increases spatial variation and decreases temporal variation, increasing it decreases spatial variation and increases temporal variation.

These observations imply respectively the following:

Evolution never stops since the second law of thermodynamics is always valid.
Remember, Einstein discovered that space and time by themselves are not invariant, only spacetime as a whole is. Similarly, evolution may slow down or speed up in space or time dimensions, but is always a constant at spacetime level. In other words, the natural setting for evolution is spacetime.

It is not surprising that thermodynamics has so far stood out as the odd ball that can not be unified with the rest of physics. Principle of entropy seems to be only half the picture. It needs to be combined with the principle of selection to give rise to a spacetime invariant theory at the level of biological variations. In other words, evolution (i.e. principles of entropy and selection combined together) is more fundamental than thermodynamics from the point of view of physics.

Side Note: The trouble is that the principle of selection is a generative, computational notion and does not lend itself to a structural, mathematical definition. However the same can also be said for the principle of entropy, which looks quite awkward in its current mathematical forms. (Recall from the older post Biology as Computation that biology is primarily driven by computational notions.)

All of our theories in physics, except for thermodynamics, are time symmetric. (i.e. They can not distinguish the past from the future.) Second law of thermodynamics, on the other hand, states that entropy (on average) always increases over time and therefore can (obviously) detect the direction of time. This strange asymmetry actually disappears in the theory of evolution, where something emerges to counterbalance the increasing entropy, namely increasing control.

Side Note: Entropy is said to increase globally but control can only be exercised locally. In other words, control decreases entropy locally by dumping it elsewhere, just like a leaf blower. Of course, you may be wondering how, as finite localized beings, we can formulate any global laws at all. I share the same sentiment because, empirically speaking, we can not distinguish a sufficiently large local counterbalance from a global one. Whenever I talk about the entropy of the whole universe, please take it with a grain of salt. (Formally speaking, thermodynamics is not even defined for open systems. In other words, it can not be globally applied to universes with no peripheries.) We will dig deeper into the global vs local dichotomy in Section 3. (Strictly speaking, thermodynamics can not be applied locally neither since every system is bound to be somewhat open due to our inability to completely control its environment.)

1. Increasing Control

All living beings exploit untapped energy sources to exhibit control and influence the future course of their own evolution.

Any state that is not lowest-energy can be considered semi-stable at best. Eventually, by the second law of thermodynamics, every such state evolves towards the lowest-energy configuration and emits energy as a by-product. By “untapped energy sources” I mean such extractable pockets of energy.

So, put more succinctly, all living beings harness entropy to reduce entropy.

The accumulative effect of their efforts over long periods of time has so far been quite dramatic indeed: What basically started out as simple RNA-based structures floating uncontrollably in oceans eventually turned into human beings proposing geo-engineering solutions to the global climate problems they themselves have created.

Let us now look at two interesting internal examples.

1.1. Cognitive Example

Our brains continuously make predictions and proactively interpolate from sensory data flow. In fact, when the higher (more abstract) layers of our neural networks lose the ability to project information downwards and become solely information-receivers, we slip into a comatose state.

Our predictive mental models slowly decay due to entropy (That is why blind people gradually lose their abilities to dream.) and are also at constant risk of becoming irrelevant. To address these problems, our brains continuously reconstruct the models in the light of new triggers and revise them in the light of new evidence. If they did not exercise such self-control, we would be stuck in an echo chamber of slowly decaying mental creations of our own. (That is why schizophrenic people gradually lose touch with reality.)

Autism and schizophrenia can be interpreted as imbalances in this controlled hallucination mechanism and be thought of as inverses of each other, causing respectively too much control and too much hallucination:

Aspects of autism, for instance, might be characterized by an inability to ignore prediction errors relating to sensory signals at the lowest levels of the brain’s processing hierarchy. That could lead to a preoccupation with sensations, a need for repetition and predictability, sensitivity to certain illusions, and other effects. The reverse might be true in conditions that are associated with hallucinations, like schizophrenia: The brain may pay too much attention to its own predictions about what is going on and not enough to sensory information that contradicts those predictions.

Jordana Cepelewicz - To Make Sense of the Present, Brains May Predict the Future

1.2. Genomic Example

Since only 2 percent of our DNA actually codes for proteins, the remaining 98 percent was initially called “junk DNA” which later proved to be a wild misnomer. Today we know that this junk part performs myriad of interesting functions.

For instance, one thing it does for sure is to insulate the precious 2 percent from genetic drift by decreasing the probability of a mutation event to cause critical damage.

Side Note: It is amazing how evolution has managed to diminish the coding region down to 2 percent (without sacrificing any functionality) by getting more and more dexterous at exposing the right coding regions (for gene expression) at the right time. This has resulted in greater variability of gene expression rates across different cellular contexts.

Remember (from our previous remarks) that if you decrease selection pressure, spatial variation increases and temporal variation decreases. Nature achieves this feat via an important intermediary mechanism. To understand this mechanism, first observe the following:

Ability to decrease selection pressure requires greater control over the environment and decreased selection pressure entails longer life span.
Exerting greater control over the environment requires more complex beings.
More complexity and longer life span entail respectively greater fragility towards and longer exposure-time to random mutation events.
This increased susceptibility to randomness in turn necessitates more protective control over genomes.

Since an expansion in the fitness landscape is worthless unless you can roam around on it, greater control exerted at phenotypical level is useless without greater control exerted at genotypical level. In other words, as we channel the speed of evolution from the temporal to the spatial dimension, we need to drive more carefully to make it safely home. From this point of view, it is not surprising at all that the percentage of non-coding DNA of a species is generally correlated with its “complexity”.

I used quotation marks here since there is no generally-agreed-upon, well-defined notion of complexity in biology. But one thing we know for sure is that evolution generates more and more of it over time.

2. Increasing Complexity

Evolution is good at finding out efficient solutions but bad at simplification. As time passes by, both ecosystems and their participants become more complex.

Currently we (as human beings) are by far the greatest complexity generators in the universe. This sounds wildly anthropocentric of course, but when it comes to complexity, we are really the king of the universe.

2.1 Positive Feedback between Control and Complexity

Control and complexity are more or less two sides of the same coin. They always coexist because of the following strong positive feedback mechanism between them:

Greater control for you implies more selection pressure for everyone else. In other words, at the aggregate level, greater control increases selection pressure and thereby generates more complexity. (This observation is similar to saying that greater competition makes everyone stronger.)
How can you assert more control in an environment that has just become more complex? You need to increase your own complexity so that you can get a handle on things again. (This observation is similar to saying that human brain will never be intelligent enough to understand itself.)

2.2. Positive Feedback between Higher and Lower Complexity Levels

All ecological networks are stratified into several levels:

Internally speaking, each human being is an ecology onto himself, consisting of ten of trillions of cells, coexisting with equally many cells in human bacterial flora. This internal ecology is stratified into levels like tissues, organs and organ systems.
Externally speaking, each human being is part of a complex ecology that is stratified into many layers that cut across our relationships to each other and to the rest of the biosphere.

Greater complexity generated at higher levels like economics, sociology and psychology propagates all the way down to the cellular level. Conversely, greater complexity generated at a very low level affects all the levels sitting above it. This positive feedback loop accelerates total complexity generation.

Two concrete examples:

The notion of an ideal marriage has evolved drastically over time, along with the increasing complexity of our lives. Family as a unit is evolving for survival.
Successful people at the frontiers of science, technology, business and art all tend to be quirky and abnormal. (Read the older blog post Success as Abnormality for more details.) Through such people, an expansion of the fitness landscape at the cognitive level propagates up to an expansion at the societal level.

2.3. Positive Correlation between Fragility and Complexity Level

Overall fragility increases as complexity levels are piled up on top of each other. In order to ensure stability, it is necessary for each level to be more robust than the level above it. (Think of the stability of pyramid structures.)

Invention of nucleus by biological evolution is an illustrating example. Prokaryotes (cells without nucleus) are much more open to information (DNA) sharing than the eukaryotes (cells with nucleus) which depend on them. This makes them simpler but also more robust.

It could take eukaryotic organisms a million years to adjust to a change on a worldwide scale that bacteria [prokaryotes] can accommodate in a few years. By constantly and rapidly adapting to environmental conditions, the organisms of the microcosm support the entire biota, their global exchange network ultimately affecting every living plant and animal.
Microcosmos - Lynn Margulis & Dorion Sagan (Page 30)

Whenever you see a long-lasting fragility, look for a source of robustness level below. Just as our mechanical machines and factories are maintained by us, we ourselves are maintained by even more robust networks. Each level should be grateful to the level below.

Side Note: AI singularity people are funny. They seem to be completely ignorant about the basics of ecology. Supreme AI will be the single most fragile form of life. It can not take over the world. It can merely suffer from an illusion of control, just like we do. You can not destroy or control what is below you in the ecosystem. Survival of each level depends on the freedom of the level below. Just like we depend on the stability provided by freely evolving and information exchanging prokaryotes, supreme AI will depend on the stability provided by us.

2.4. Positive Correlation between Fragility and Firmness of Identity

How limited and rigid life becomes, in a fundamental sense, as it extends down the eukaryotic path. For the macrocosmic size, energy, and complex bodies we enjoy, we trade genetic flexibility. With genetic exchange possible only during reproduction, we are locked into our species, our bodies, and our generation. As it is sometimes expressed in technical terms, we trade genes "vertically" - through the generations - whereas prokaryotes trade them "horizontally" - directly to their neighbors in the same generation. The result is that while genetically fluid bacteria are functionally immortal, in eukaryotes sex becomes linked with death.
Microcosmos - Lynn Margulis & Dorion Sagan (Page 93)

Biological entities that are more protective of their DNA (e.g. eukaryotes whose genes are packed into chromosomes residing inside nuclei) exhibit greater structural permanence. (We had reached a similar conclusion while discussing the junk DNA example in Section 1.2.) Eukaryotes are more precisely defined than prokaryotes, so to speak. Degree of flexibility correlates inversely with firmness of identity.

Firmer the identity gets, the more necessary death becomes. In other words, death is not a destroyer of identity, it is the reason why we can have identity in the first place. I suggest you to meditate on this fact for a while. (It literally changed my view on life.)

The reason why we are not at peace with the notion of death is that we are still not aware of how challenging it was for nature to invent the technologies necessary for maintaining identity through time.
Fear of death is based on the ego illusion, which Buddha rightly framed as the mother of all misrepresentations about nature. This is the story of a war between life and non-life, between biology and physics, not you against the rest of the universe or your genes against other genes.

3. Physics vs Biology

Physics and biology (with chemistry as the degenerate middle ground) can be thought of as duals of each other, as forces pulling the universe in two opposite directions.

Side Note: Simple design is best done over a short period of time, in a single stroke, with the spirit of a master. Complex design is best done over a long period of time, in small steps, with the spirit of an amateur. That is essentially why physics progresses in a discontinuous manner via single-author papers by non-cooperative genius minds, while biology progresses in a continuous manner via many-author papers by cooperative social minds.

3.1. Entropy, Time and Scale

Note that entropy and time are two sides of the same coin:

Time is nothing but motion. Time without any motion is not something that mortals like us can fathom.
All motion happens basically due to the initial low-entropy state of the universe and the statistical thermodynamic evolution towards higher entropy states. (Universe somehow began in a very improbable state and now we are paying the “price” for it.) In other words, entropy is the force behind all motion. It is what makes time flow. The rest of physics just defines the degrees of freedom inside which entropy can work its magic (i.e. increase the disorder of the configuration space defined by the degrees of freedom), and specifies how time flow takes place via least action principles which allows one to infer the unique time evolution of a particle or a field from the knowledge of its beginning and ending states.

Side Note: It is not a coincidence that among all physics theories only thermodynamics could not be formulated in terms of a least action principle. Least action principles give you one dimensional (path) information that is inaccessible by experimentation. Basically, each experiment we do allows us to peak at the different time slices of the universe, and each least action principle we have allows us to view each pair of time slices as the beginning and ending states of a unique wholesome causal story. (We can not probe nature continuously.) Entropy on the other hand does not work on a causal basis. (If it did, then it could not be responsible for time flow.) It operates in a primordially acausal fashion.

When we flip the direction of time, thermodynamics starts working backwards and the energy landscape turns upside down. Time-flipped biological entities start harnessing order to create disorder, which is exactly what physics does.

The difference between physics and time-flipped biology is that former operates globally and harnesses the background order that originates from the initial low-entropy state of the universe and latter harnesses local patches of order created by itself. (This is why watching time-flipped physics videos is a lot more fun than watching time-flipped biology videos.)

Side Note: There are nano scale examples of biology harnessing order to create disorder. This is allowed by the statistical nature of the second law of thermodynamics which says that entropy increases only on average. Small divergences may occur over short intervals of time. Large divergences too may occur but they require much longer intervals of time.

The heart of the duality between physics and biology lies in this “global vs local” dichotomy which we will dig deeper in the next section.

It is worth reiterating here the fact that entropy breaks symmetries in the configuration space, not in geometric one. (It may even increase local order in geometric space by creating symmetric arrangements, as in spontaneous crystallisation, which disorders the momentum component of the configuration space via energy release.) Hence, strictly speaking, the “global vs local” dichotomy should not be interpreted purely in spatial terms. What time-flipped biology does is to harness local patches of configurational order (i.e. degrees of freedom associated with those locations), not spatial order.

Side Note: Entropy also triggers the breaking of some structural symmetries along the way. According to inflation theory, as the universe cooled and expanded from its initial hot and dense state, the primordial force split into the four forces (Gravitational, Electromagnetic, Weak Nuclear and Strong Nuclear) that we have today. (Again, as mentioned before, entropy is an odd ball among all physics theories and is not regarded as a force since it does not have an associated field etc.) This de-unification happened through a series of three spontaneous symmetry breakings, each of which took place at a different temperature threshold.

3.2. Entropy and Dynamical Scale Invariance

Imagine a very low-entropy universe that consists of an equal number of zeros and ones which are neatly separated into two groups. (This is a fantasy world with no forces. In other words, the only thing you can randomize is position. So the configuration space just consists of the real space since there are no other degrees of freedom.) Global uniformity of such a universe would be low, since there will be only fifty percent probability that any two randomly chosen local patches will look like each other. Local uniformity on the other hand would be high, since all local patches (except for those centered at the borderline separating the two groups) will either have a homogenous set of zeros or a homogenous set of ones.

Entropy can be seen as a local operator breaking local uniformities in the configuration space. Over time, the total configuration space starts to look the same no matter how much you zoom in or out. In other words, the universe becomes more and more dynamically scale invariant.

Note that entropy does not increase uniformity. It actually does the opposite and decreases uniformity across the board so that the discrepancy between local and global uniformity disappears. Close to heat death (maximum theoretical entropy), no two local patches in the configuration space will look like each other. (They will be random in different ways.)

Side Note: Due to the statistical nature of the second law of thermodynamics, universe will keep experiencing fluctuations to the very end. It can get arbitrarily close to heat death but will never actually reach it. Complete heat death means end of physics altogether.

Now a natural question to ask is whether there could have been other ways of achieving scale invariance? The answer is no and the blocker is an information problem. You can not have complete knowledge about the global picture without infinite energy at your disposal and without this knowledge you can not define a local operator that can achieve scale invariance. For instance, going back to our initial example, if your region of the universe happens to have no zeros, you would not even be able to define an operator that takes zeros into consideration. All you can really do is to just ask every local patch to scatter everything so that (hopefully) whatever is out there will end up proportionally in every single patch. Of course, this is exactly what entropy itself does. (It is this random, zero knowledge mechanism which gives thermodynamics its acausal nature.)

Biology on the other hand creates low entropy islands by dumping entropy elsewhere and thereby works against the trend towards dynamical scale invariance. It is exactly in this sense that biology is anti-entropic. Entropy is not neutralized or cancelled, instead it is deflected through a series of brilliant jiu jitsu strokes so that it defeats its own goal.

Physics fights for dynamical scale invariance by breaking local uniformities in the configuration space and biology fights against dynamical scale invariance by creating local uniformities in the configuration space. This is the essence of the duality between physics and biology, but there is a slight caveat: Physics works on a global scale and hails down on all local uniformities in an indiscriminate manner, while biology begins in some local patches in a discriminate manner and slowly makes its way up to global scale, conquering physics from inside out, pushing entropy to the peripheries. (Biology needs to be discriminative since only certain locations are convenient to jumpstart life, and it needs to learn since - unlike physics - it does not have the privilege of starting global.)

Let us now scroll all the way to the end of time to see what this duality means for the fate of our universe.

3.3. Ultimate Fate of the Universe

There is no current scientific consensus about the ultimate fate of the universe. Some cosmologists believe in the inexhaustible expansion and the eventual heat death, some others believe in the unavoidable collapse and the subsequent bounce. Since nobody has any idea about how dark energy, dark matter and quantum gravity actually work, everything is basically up grabs.

Side Note: Dark energy is uniformly-distributed and non-interacting. It is posited to be the driving factor behind the acceleration of the uniform expansion of space. Dark matter on the other hand is non-uniformly-distributed and gravitationally-attractive. Together dark energy and dark matter make up around 95 percent of the total energy content of the universe. Hence the reason why some people call junk DNA, which make up 98 percent of human genome, as the dark sector of DNA. Funnily enough, in a similar fashion, more than 90 percent of the more evolved (white matter) part of the human brain is composed of non-neuron (glial) cells . (Neurons in the white matter, as opposed to those in the gray matter, are myelinated and therefore conduct electricity at a much higher speed.) It seems like the degree of complexity of an evolving system is directly correlated with the degree of dominance of the modulator (e.g. non-neuron cells, non-coding DNA) against the modulated (e.g. neurons cells, coding DNA). Could the prevalence of the dark sector be interpreted as an evidence that physics itself is undergoing evolution? (Note that, in all cases, the scientific discovery of the modulator occurred quite late and with a great deal of astonishment. Whenever we see a variation exhibiting substructure, we should immediately suspect that it is modulated by its complement.)

One thing that is conspicuously left out of these discussions is life itself. Everyone basically assumes that entropy will eventually win. After all even supermassive black holes will inevitably evaporate due to Hawking radiation. Who would give a chance to a phenomenon (like life) that is close to non-existent at the grand cosmological scales?

Well, I am actually super optimistic about the future of life. It is hard not to be so after one studies (in complete awe) how far evolution has progressed in just a few billion years. Life is learning at a phenomenal speed and will figure out (before it gets too late) how to do cosmic-scale engineering.

Since no one really knows anything about the dynamics of a cosmic bounce (and how it interacts with thermodynamics), let us finish this long blog post with some fun speculations:

The never ending war between physics and biology may be the reason why time still exists and the universe still keeps on managing to collapse on itself while also averting a heat death. Life could have learned how to engineer an early collapse before a heat death or how to prevent a heat death long enough for a collapse. Life could have even learned how to leave a local fine-tuned low-entropy quantum imprint so that it is guaranteed to reemerge after the big bounce.
What if life always reaches total control in the sense of Section 1 in each one of the cosmic cycles and becomes indistinguishable from its environment? Could the beginning state of this universe’s physics be the ending state of the previous universe’s biology? In other words, could our entire universe be an extremely advanced life form? Could this be the god described by Pantheists? Was Schopenhauer right in the sense that the most fundamental aspect of reality is its primordial will to live? Is the acausal nature of thermodynamics a form of pure volition?