An overview of evolution and the mind

[Brief summary of this post]

The human mind arose from three somewhat miraculous breakthroughs:

1) Natural selection, a process dating back about 2 billion years that changes through adaptations in response to new environmental challenges

2) Animal minds, which opened up a new branch of reality: imagination. Feedback led to computation and representation, which enabled animals to flourish.

3) Directed abstract thinking, the special skill that lets people abstract away from the here and now to the anywhere and anywhen with great facility, giving us unlimited access to the world of imagination.

Of the four billion years we have spent evolving, about 600 million years (about 15%) has been as animals with minds, and at most 4 million years (about 0.1%) as human-like primates. That brief 4 million year burst may have changed 1% to 5% of our genes, which numerically is just fine tuning already well-established bodies and minds. Animals diverged into over a million animal species, but the appearance of directed abstract thinking in humans changed the playing field. Humans could survive not just in one narrow ecological niche, but in many niches, potentially flourishing anywhere on earth and ultimately squeezing out nearly all animal competition our size or bigger. Other mental capacities coevolved with and help support directed abstract thinking, like 3-D color vision, face recognition, generalized use of hands, language, and sophisticated cognitive skills like reasoning with logic, causation, time, and space. Directed abstract thinking is a risky evolutionary strategy because it can be used for nonadaptive purposes, such as the contemplating of navels, or even spiraling into analysis paralysis. To keep us on the straight and narrow, we have been equipped with enhanced senses and emotions that command our attention more than those found in other animals, for things like love, hate, friendship, food, sex, etc. The more pronounced development of sexual organs and behaviors in humans relative to other primates is well known 12, but the reasons are still speculative. I am suggesting one reason is to motivate us to pursue evolutionary goals (notably survival and reproduction) despite the distractions of “daydreaming”. Books, movies, TV, the internet, and soon virtual reality threaten our survival by fooling our survival instincts with simulacra of interactions with reality.

The mind is integrally connected to the mechanisms of life, so we have to look back to how life evolved to see why minds arose. While we don’t know the details of how life emerged, the latest theories fill some missing links better than before. Deep sea hydrothermal vents 3 may have provided the necessary precursors and stable conditions for early life to develop around 4 billion years ago, including at least these four:

(a) carbon fixation direct from hydrogen reacting with carbon dioxide,
(b) an electrochemical gradient to power biochemical reactions that led to ATP (adenine triphosphate) as the store of energy for biochemical reactions,
(c) formation of the “RNA world” within iron-sulfur bubbles, where RNA replicates itself and catalyzes reactions,
(d) the chance enclosure of these bubbles within lipid bubbles, and the preferential selection of proteins that would increase the integrity of their parent bubble, which eventually led to the first cells

From this point, life became less dependent on the vents and gradually moved away. These steps came next:

(e) expansion of biochemical processes, including use of DNA, the ability of cells to divide and the formation of cell organelles by capture of smaller cells by larger,
(f) a proliferation of cells that led eventually to LUCA, the “Last Universal Common Ancestor” cell about 3.5 billion years ago,
(g) multicellular life, which independently arose dozens of times, but most notably in fungi, algae, plants and animals about 1 billion years ago, and
(h) the appearance of sexual reproduction, which has also arisen independently many times, as a means of leveraging genetic diversity in heterogeneous environments.4 and resisting parasites 5. Whatever the reason, we have it.

The net result was the sex-based process of natural selection that Darwin identified. Lifeforms now had a biochemical capacity to encode feedback from the environment into genes that could express proteins that would result in improving the chances of survival.

Larger multicellular life diverged along two strategies: sessile and mobile. Plants chose the sessile route, which is best for direct conversion of solar energy into living matter. Animals chose mobility, which has the advantage of invincibility if one is at the top of the food chain, but the disadvantage of requiring complex control algorithms to do it. Animals further down the food chain are more vulnerable but require less sophisticated control. But how exactly did animals evolve the kind of control they need for a mobile existence? Sponges 6are the most primitive animals, having no neurons or indeed any organs or specialized cells. But they have animal-like immune systems and some capacity for movement in distress. Cnidarians (like jellyfish, anemones, and corals) feature diffuse nervous systems with nerve cells distributed throughout the body without a central brain, but often featuring a nerve net that coordinates movements of a radially symmetric body. What would help animals more, if it were possible, is an ability to move to food sources in a coordinated and efficient way. The radial body design seems limiting in this regard and may be why all higher animals are bilateral (though some, like sea stars and sea urchins, have bilateral larvae but radial adults). Among the bilateria, which arose about 550-600 million years ago, nearly all developed single centralized brains, presumably because it helps them coordinate their actions more efficiently, excepting a few invertebrates like the octopus, which has a brain for each arm, and a centralized brain to loosely administer. Independent eight-way control of arms comes in handy for an octopus; with practice, we can use our limbs independently in limited ways, but our attention can only focus on one at a time.

But how do nerves work, exactly? While we understand some aspects of neural function in detail, exactly how they accomplish what they do is still mostly unknown. Our knowledge of the mechanisms breaks down beyond a certain point, and we have to guess. But we can see the effects that nerves have: nerves control the body, and the brain is a centralized network of nerves that control the nerves that control the body. The existence of nerves and brains and indeed higher animals stands as proof that it is physically possible for a creature to move to food sources in a coordinated and efficient way, and indeed to enhance its chances of survival using centralized control. We can thus safely conclude, without any idea how they work, that the overall function of the brain is to provide centralized, coordinated control of the body.

For the most part, I will deal with the brain as a black box that controls the body and try to unravel its logical functions without too much regard as to its physical mechanisms. I will, however, try to be careful to take into account the constraints the brain’s structure entails. For example, we know brains must be fast and work continuously to be effective. To do this, they must employ a great deal of parallel processing to make decisions quickly. But let’s focus first on what they must do to control the body rather than how they do it.

To control a body so as to cause it to locate food sources, avoid dangers, and find mates requires that we start using verbs like “locate,” “avoid,” and “find”. We know minds can do these kinds of things while rocks and streams can’t, but how can we talk about them objectively, independent of the idea of minds? By observing their behavior. An animal’s body can move toward food as if it had a crystal ball predicting what it would find. It seems to have some way of knowing in advance where the food will be and animating its body so as to transport itself there. If rocks and streams can’t do it, how can animals?

The brain operates with a feedback loop of sensing, computing and acting. From an information standpoint, these steps correspond to data inputs, data processing, and data outputs. This is the crux of the computational theory of mind. When we speak of computation in this context, we are not referring to digital computation with 1’s and 0’s, but to any physical process that accomplishes information management. Information can be representational or nonrepresentational. Nonrepresentational information is just data that has value to the process that uses it. Raw sound or image data is nonrepresentational, as is much of the information supporting habitual behavior. Probably most of the information managed by the brain is nonrepresentational, but much of the information consciousness uses is representational. Representational information is grouped into concepts (e.g. objects) that describe essential and important characteristics of referents. Logical operations performed on the references are later applied back to the referents. For example, we recognize objects in raw image data by matching characteristics to our remembered representations of the objects.

At every moment the brain causes each part of the body to perform (or not perform) an action to produce the coordinated movement of the body toward a goal, such as locating a food source. Because there is only one body, and it can only be in one place at a time, the central brain must function as what I call a single-stream step selector, or SSSS, where a step is part of a chain of actions the animal takes to accomplish a goal. If the brain discerns new goals, it must prioritize them, though the body can sometimes pursue multiple goals in parallel. For example, we can walk, talk, eat, blink, and breathe at the same time. As I related in An overview of evolution and the mind, we prioritize goals in response to desires and subjective beliefs, which objectively and computationally are preference parameters that are well tuned to lead us to behaviors that coincide with the objectives of evolution (in the ancestral environment; they are not always so well tuned in modern times).

While we know the whole brain must function as an SSSS to achieve top-level coordination of the body, this doesn’t mean the SSSS has to be a special-purpose subprocess of the brain. For example, we can imagine building a robot with one overall program that tells it what to do next. But evolution didn’t do it that way. In animal minds, consciousness is a small subset of overall mental processing that creates a subjective perspective that is like an internal projection of the external physical landscape. It is a technique that works very well, regardless of whether other equally good ways of controlling the body might exist. As of now, we know that we can build robots without such a perspective, such as self-driving cars, but their responses are limited to situations they have learned to handle, which is nowhere near flexible enough to handle the life challenges all animals face. Learned behavior and reasoning are the only two top-level approaches to control that have a good degree of flexibility that I know of, but I can’t preclude the possibility of others. But we do know that animals use reasoning, which I believe mandates a simplified proposition-based logical perspective/projection of the world into a top-level portion of the mind that acts as an SSSS.

Brains use a lot of parallel processing. We know this is true for sensory processing because it provides useful sensory feedback in a fraction of a second, yet we know computationally that a non-parallel solution would be terribly slow. Real-time vision, for example, processes a large visual field almost instantly. Evolution will tend to exploit tools at its disposal if they provide a competitive advantage, so many kinds of operations in the brain use parallel processing. Associative memory, for instance, throws a pattern against every memory we have looking for matches. The computational cost of all those mismatches in just a few seconds is probably longer than our lifetimes, but that’s ok because our subconscious has nothing better to do and it doesn’t bother our conscious minds with the mismatches. Control of the body is another subconscious task using massively parallel processing. So sensing, memory, and motor control are highly parallel. But what about reasoning?

The SSSS is a subprocess of the brain that causes the body to do just one (coordinated) thing at a time, i.e. a serial set of steps. But while it produces actions serially, this does not prove that reasoning is strictly serial. Propositional logic itself is serial, but we could, in principle, think several trains of thought in parallel and then eventually act on just one of them. My guess, weighing the evidence from my own mind, is that the SSSS and our entire reasoning capacity is in fact strictly serial. Drawing on an analogy to computers, the SSSS has one CPU. It is, however, a multitasking process that uses context switching to shuffle its attention between many trains of thought. In other words, we pursue just one train of thought at a time but switch between many trains of thought about different topics floating around in our heads. Each train of thought has a set of associated memories describing what has been thought so far, what is currently under consideration, and goals. For the most part, we are aware of the trains we are running. For example, I have trains now for several aspects of what I am writing about, the temperature and lighting of my room, what the birds are doing at my bird feeder, how hungry I am, what I am planning to eat next, what is going on in the news, etc. These trains float at the edge of my awareness competing for attention, but my attention process keeps me on the highest prioritized task. But to prioritize them the attention process has to “steal cycles” from my primary task and cycle through them to see if they warrant more attention. It does that at a low level that doesn’t disturb my primary train of thought too much, but enough to keep me aware of them. When we walk, talk, and chew gum at the same time our learned behavior guides most of the walking and chewing, but we have to let these activities steal a few cycles from talking. We typically retain no memory of this low-level supervision the SSSS provides to non-primary tasks and may be so absorbed in our primary task we don’t seem to consciously realize we are lending some focus to the secondary tasks, but I believe we do interrupt our primary trains to attend to them. However, we are designed to prevent these interruptions from reducing our effectiveness at the primary task, for the obvious reason that quality attention to our primary task is vital to survival. The higher incidence of traffic accidents when people are using cell phones seems to confirm these interruptions. The person we are speaking to doesn’t expect us to be time-sharing them with another activity, which works out well so long as we can drive on autopilot (learned behavior). But when an unexpected driving situation requiring reasoning pops up we will naturally context switch to deal with it, but the other party doesn’t realize this and continues to expect our full attention. We may consequently fail to divert enough reasoning power to driving.

Why wouldn’t the mind evolve a capacity to reason with multiple tasks in parallel? I believe the benefits of serial processing with multitasking outweigh the potential benefits of parallel processing. First and foremost, serial processing allows for constant prioritization adjustments between processes. If processes could execute in parallel, this would greatly complicate deciding how to prioritize them. Having the mind dedicate all of its reasoning resources into a task that is known to be the most important at that moment is a better use of resources than going off in many directions and trying to decide later which was better to act on. Secondly, there isn’t enough demand for parallel processing at the top level to justify it. Associative memory and other subconscious processes require parallel processing to be fast enough, but since we do only need to do one thing at a time and our animal minds have been able to keep up with that demand using serial processing, parallel designs just haven’t emerged. While such a design has the potential to think much faster, achieving consensus between parallel trains is costly. This is the too-many-cooks-in-the-kitchen headache groups of people have when working together to solve problems. If the brain has a single CPU instead of many then parts of that CPU must be centrally located, and since consciousness goes back to the early days of bilateral life, some of those parts must be in the most ancient parts of the brain.

The brain controls the body using association-based and decision-based strategies. Association-based approaches use unsupervised learning through pattern recognition. It is unsupervised in the sense that variations in the data sets alone are used to identify patterns which are then correlated to desired effects. The mind then recognizes patterns and triggers appropriate actions. In this way, it can learn to favor strategies that work and avoid those that fail. While the mind heavily depends on association-based approaches for memory and learning, they do not explain consciousness or the unique intelligence of humans, which results from decision-based strategies.

Reasoning is powered by a combination of association-based and decision-based strategies, but the association-based parts are subsidiary as the role of decision-based strategies is to override learned behavior when appropriate. Decision-based strategies draw logical conclusions from premises either with certainty (deduction) or probability (induction). Reasoning itself, the application of logic given premises, is the easy part from the perspective of information management. The hard part is establishing the premises. The physical world has no premises; it only has matter and energy moving about in different configurations. Beneath the level of reasoning, the mind looks for patterns and distinguishes the observed environment into a collection of objects (or, more broadly, concepts). The distinguished objects themselves are not natural kinds because the physical world has no natural kinds, just matter and energy, but there are some compelling practical reasons for us to group them this way. Lifeforms, in particular, each have a single body, and some of them (animals) can move about. Since animals prey on lifeforms for food, and also need to recognize mates and confederates, an ability to recognize and reason about lifeforms is indispensable. Physically, lifeforms have debatable stability, as their composition constantly changes through metabolism, but that bears little on our need to categorize them. Similarly, other aspects of the environment prove useful to distinguish as objects and by generalization as kinds of objects. Animals chunk data at levels of granularity that prove useful for accomplishing objectives. Grouping information into concepts this way sets the stage for the SSSS to use them in propositions and do logical reasoning. Concepts become the actors in a chain of events and can be said to have “cause and effect” relationships with each other from the “perspective” of the SSSS. That is, cause and effect are abstractions defined by the way the data is grouped and behaves at the grouped level that the SSSS can then use as a basis for decisions. In this way, the world is “dumbed down” for the SSSS so it can make decisions (i.e. select actions) in real time with great quality and efficiency despite having just one processing stream.

We experience the SSSS as the focal point of reasoning, the center of conscious awareness, where our attention is overseeing or making decisions. Though it sounds a bit surprising that we are nothing more than processes running in our brains, unless magic or improbable laws of physics are involved, this is the only possible way to explain what we are and is also consistent with brain studies to date and computer science theory. The way our conscious mind “feels” to us, more than anything, is information. The world feels amazing to us because consciousness is designed so that important information grabs our attention through all the distractions. Our conscious experience of vision, hearing, body sense, other senses, and memory are all just ways of interpreting gobs of pure information to facilitate a continuous stream of decisions. The human conscious experience is a big step up from that of animals because directed abstract thinking enables us to potentially conceive of any relationship or system, and in particular powers our ability to imagine possible worlds, including self-awareness of ourselves as abstract players in such systems.

  1. Sexual selection by cryptic female choice and the evolution of primate sexuality,, Alan Dixson, 2002, Evolutionary Anthropology; 11 (S1): 195-199.
  2. Comparison of the sexuality of Humans,, Common Chimpanzees and Bonobos, 2009
  3. The Cradle of Life,, Nick Lane, 17 October 2009, The New Scientist
  4. Why Sex Evolved,, Jef Akst, October 13, 2010, The Scientist
  5. Evolution of sexual reproduction,
  6. Why sponges are animals,, Matthew Cobb

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