Do you ‘feel’ a greater affinity for plants than for non-living objects, or are plants on a par with other objects in the non-human world?
Our contemporary understanding of the history of the universe, and of life in general, would suggest that we might feel some biological connection with the plant world.
We no longer believe that each species of organism was uniquely placed on Earth by God. Only in the last 150 years have we recognized that everything in the universe emerged from a point source at the Big Bang 13.7 billion years ago, and that the entire community of life arose from a common ancestor about 3.5 billion years ago. This means that all the matter in the universe is connected to a single origin, with its living component united through common heredity.
So how are we related to plants, in an evolutionary sense?
Multicellular animals evolved a little more than 0.5 billion years ago with the last common ancestor of plants and animals, estimated from molecular clock data, dating back about 1.6 billion years. Though we may never know for sure, it is likely that our common ancestor was a single-celled organism, and modern data suggests something akin to a protozoan.
We might look starkly different from plants but, having the same ultimate origin, we share genes that control metabolic pathways that are common to all living creatures.
What emerges from this characterization is a continuum of matter whose living component exists in degrees of organic complexity, but all with a common ancestor and a history of radiation and diversification by environmental adaptation.
But what does science tell us about the distinctions we make, on the one hand, between the living and non-living and, on the other, between plants and humans.
What, and how great, are our biological similarities and differences?
The article on life outlines the difficulties scientists confront when trying to provide a succinct definition of life. What are the key biological criteria that distinguish something that is inanimate (say, a rock) and something that is animate (say, a plant)?
The article suggested that, in spite of a host of conditions and criteria that might be chosen, our best guide is provided by what I have called the biological axiom – the biological necessity for all life to survive, reproduce, and flourish.
Life is clearly an activity in a way that a rock, or a dead body, is not. Life is more about process and change than it is about substance. More specifically, living organisms have some autonomy; some independence from their environments. A rock is passive and inert in relation to its surroundings while organisms manifest a capacity for independent action and reaction in accordance with the biological axiom. They can influence or initiate events going on both within themselves and in interaction with their surroundings through a complex system of integrated information processing and communication that is vastly different from the processes that go on in a rock. In short, they manifest agency.
But most organisms have no consciousness or ‘will’, so how can they manifest the purposeful activity we usually associate with agency?
The ‘behaviour’ of un-conscious organisms operates mindlessly by increasing the probabilities of some outcomes over others, notably those that favour their own existence and perpetuation. They promote outcomes that we would regard, in human terms, as ‘beneficial’.
This filtration or ‘favouring’ of some outcomes over others, and the way organisms exhibit ‘preferences’ for one situation over another are what distinguishes the animate from the inanimate.
This propensity for agential behaviour, founded ultimately on the biological axiom (which expresses value through ‘beneficial’ activity) is what makes organisms goal-directed or purposeful.
We humans, with our large brains, regard ourselves as supreme agents. Armed with self-aware hindsight (memory) and foresight (anticipation), and motivated by our beliefs and desires (ultimately founded on the biological axiom), we devise conscious and rational intentions appropriate to the present. This is our paradigm of agential behaviour.
What is often ignored is that un-conscious organisms express (albeit mindlessly and in crude form) many of the features we associate with human agency – including: reasoning, foresight, memory and hindsight, learning, valuation, purpose, intention, and sensation expressed through functional (purposive) design and behaviour. All organisms have the potential for ‘self-correction’ both in the immediate present and over many generations. Their agency means that they are flexible and can adapt, both short- and long-term.
The counterintuitive notion of mindless agency needs closer investigation.
Our health as humans (and, by extension, all organisms) is regarded as self-evident: it is not a matter of philosophical or scientific speculation or contention – it is a biological truth . . . an axiom . . . it is the point of departure for everything in biology. As Richard Dawkins expresses it: ‘We are survival machines‘. Though axiomatic, it may still be insisted that there is no logical necessity in the transition from statements of fact to statements of value. Because I feel ill, there is no logical necessity for me to visit a doctor. But with survival a ‘biological necessity’ there is little choice. There may be no logical necessity for values to flow from biological facts but organisms, of their very nature, have no choice: for an organism to exist without value is to deny life. For values to flow from biological facts is a biological necessity. And when our very existence is at stake, biological necessity trumps logical necessity.
We do not ask ‘Why do organisms try to survive and reproduce?’ because we understand that to deny survival and reproduction is to cease to exist – and that does not make biological sense. Organisms that do not, or cannot, survive and reproduce die out – and in ceasing to exist they become biologically irrelevant. Denying the biological axiom thus becomes incoherent.
Without logical grounds for value we must simply agree with Aristotle that, as living organisms, there can be only one conclusion – that ‘It is better to exist than not exist‘ – that ‘it is better to live than not live’. Aristotle’s biographer, evolutionary biologist Armand Leroi, retorts to the question ‘Why do organisms need to survive and reproduce?‘ with ‘Because natural selection made them so‘. A more adventurous outlook for humans is given by Steven Pinker at the head of this article.
Humanist scientists at the time of the Scientific Revolution were constrained by an overwhelming deference to the teachings of Aristotle, and a religious worldview that included a literal interpretation of the Bible. The world was God’s Creation: a manifestation of God’s supernatural agency.
To progress science these dual historical intellectual shackles had to be challenged. The wonder of nature, so saturated in God’s purposes, was replaced by the wonder of humanity, the creative imagination of human consciousness and subjectivity. If the purpose so pervasive in nature was not put there by God, it was concluded, it must have been put there by us. We project our own sense of purpose, our conscious intentions, onto purposeless nature. Nature itself has no purpose: it cannot deliberate. The language of purpose in nature, it was concluded, is therefore the language of metaphor.
It provides an answer to the question ‘What are organisms for?’ and much follows.
The purpose of living organisms is not something that we invent, something that our minds impose on the world. Organisms, including humans, are not purposeless. The purpose of organisms derives from their origin and place in the scheme of things, from their inner nature interacting with their outer environment. For humans this is manifest as mindful purpose (conscious intention): in non-human organisms it is the mindless purpose of goal-directed activity. In all organisms it is united under the ultimate purpose of survival and reproduction.
The resistance to purpose-talk in biology belittles the wonder of organic design. Natural selection is an ignorant and unconscious mechanical process, the operation of an iterative algorithm on matter. Superficially this seems mundane and unremarkable. However, structures like the human eye, ear, and brain demonstrate that we would do well to respect nature’s pre-conscious strategies since their outcomes have proved infinitely more sophisticated than anything we can do. We do the wonder of natural processes a great disservice by speaking of apparent reasons, apparent purpose, apparent values, and apparent design. This is what philosopher Dennett would call a ‘strange inversion of reason’. Is human consciousness an effect or a cause? Is the world a creation of conscious minds or are conscious minds a creation of the world? Is consciousness qualitatively different from other processes or is it a product of the same deterministic causal influences as the rest of the natural world?
The superficially innocent act of accepting the biological axiom as a normative statement has far-reaching consequences.
If we know what organisms are ‘for’, ‘why they exist‘, we can then identify their ‘goods‘ as ‘values’ that exist independently of human minds.
Living organisms would still strive to survive and reproduce (albeit unconsciously) in the absence of humans. And the ways (means) of achieving this goal are (unconsciously) valued (selectively filtered, or ‘chosen’) based on achieving these ends.
This selective filtering (increasing the probability of some outcomes over others) is the property of all organisms and it underpins all normativity, finding its most complex expression in the choices directed by human values. Organisms exist (fact), and they exist to survive, reproduce, and flourish (fact, value, purpose).
But isn’t this a metaphorical reading of human values into a value-neutral nature? Isn’t it imputing human values to creatures that cannot express value? How can we possibly claim that an oak tree has values!
The normativity inherent in the biological axiom is so pervasive in nature that trying to remove value and value-talk from biology is as difficult as trying to remove purpose-talk.
We are not being intellectually slovenly when we treat organisms as ‘agents’, and since they can be affected beneficially or adversely by events, they also have ‘interests’, albeit unconscious ones. Whether we give them ‘rights’ in return is another matter.
We have now established the foundations of agency in biological systems:
Living organisms manifest a drive to survive, reproduce, and flourish as a biologically necessary condition of their existence – referred to here as the biological axiom.
The biological axiom is a statement of both fact and value since expresses, as succinctly as possible, the grounding for all biological activity.
When we say ‘The eye is for seeing’ we are acknowledging that the existence of the eye is a consequence of a selection process. Where there is selection, there is selection ‘for’. And, in nature, where there is an aim, a ‘for’, and a beneficiary (under the conditions of the biological axiom), then there is both purpose and agency that is independent of human cognition.
Biological agency is expressed in terms of structural, functional, and behavioural flexibility – the ability to adapt, both short- and long-term.
Already you will have noticed my use of scare quotes when I use words usually reserved for humans and their mental activities when they are applied to non-conscious organisms. For simplicity, I will refer to these anthropomorphisms as human-talk.
Is human-talk a problem – can and should it be avoided? An example will help illustrate this problem.
We accept that consciousness can exist by degree: that dogs, fish, and even worms have consciousness, albeit consciousness that is different from human consciousness. We could use specialist terms to distinguish between worm-consciousness, fish-consciousness, and dog-consciousnesses but, instead, we accept that the word ‘consciousness’ can have a semantic breadth that includes animals other than humans while, at the same time, using human consciousness as a reference point (partly because we don’t know what any other kind of consciousness would be like, even though we assume it must be quite different from ours). In other words, we recognize a real (in the world) connection between these different kinds of consciousness: they are variations of the same entity.
Before Darwin, this connection would have been considered tenuous and therefore strongly resisted. Each organism, it was assumed, had been uniquely created and so any resemblances were coincidental and physically unconnected. Today we see the connection, not as some vague resemblance, but as part of an evolutionary physical continuity.
If we assume that worm consciousness is the same as human consciousness, then we are not only being anthropomorphic; we are also, we must assume, in error. But being anthropomorphic (using metaphorical ‘as if’ language) does not mean there is no consciousness in other organisms. All it means is that their consciousness is different from ours.
At the top of the list of biological differences between ourselves and plants is a mental distinction that we intuitively regard as crucial.
We humans have nervous systems and brains associated with mobility and conscious awareness. Brains give us the biologically unique capacity for reason, abstract thought, hindsight and foresight, learning, memory, and language. Plants have none of this. They are brainless, and therefore mindless, and unconscious. This is a vast gulf of difference.
Or is it?
In the following discussion I hope to show how, in the absence of brains and nervous systems, plants still perform many functions that we treat as uniquely brain-related . . . and to an extraordinary degree of sophistication.
Brains do not make as much difference as you might, at first, imagine.
Evolution of consciousness
Consciousness did not arrive on Earth with the breath of God.
Out of the uniform plasma that was first formed by the Big Bang evolved increasingly numerous and complex structures, along with their properties and relations.
The reasoning human brain with its capacity to represent the world in conscious thought, was ‘created’ by natural selection . . . an ignorant process devoid of conscious intention. Human intelligence itself arose out of an unintelligent mechanism . . . the 3.5-billion-year descent with modification of replicating matter that had acquired the capacity for heritable variation and, in interaction with the environment, differential reproduction. Consciousness gradually emerged out of the countless adaptive modifications and increasing material complexity generated by natural selection.
Our human pride, our anthropocentrism, does not acknowledge, as Aristotle did, that the purpose of human intention is just an extension of the real (not apparent) natural purpose that is inherent in all nature. Aristotle located purpose within nature. Darwin fine-tuned Aristotle’s conclusions by showing how natural selection provided purposive direction via functional adaptation. Then 20th century genetics demonstrated how like begets like, how in life there can be continuity of structure, function, and purpose.
Functions & ideas
Humans were created by nature: they are a consequence of natural reasons, natural function, natural value, natural purpose, and natural design. Nature has real (not added by the human mind) non-conscious reasons, purpose, and design. We resist this idea because we have a top-down human-conscious perspective on the workings of the world and its metaphysics. So, we assume that it is humans who reason, have purposes, and create designs. We forget that just as evolution of matter diversified into a tree of structural variety and graded complexity so its possibilities evolved in a similar way. Reasons, purposes, and design in nature was not created by humans, it ‘Bubbled up from the bottom, not trickled down from the top‘ (Dan Dennett).
Non-conscious reasons and purpose can be regarded as evolutionary precursors to the conscious intention of the mind, and to reason itself, all part of the continuity of goal-directedness inherent in the living world – from the simplest pre-conscious organisms to sentient animals, and rational humans. Teleology did not suddenly arrive on earth with the human intellect. Simply stating what structures and processes ‘do’ does not capture the goal-directed or teleological nature of natural-selection-produced functional adaptations. Aristotle was aware of all this but science is only now coming to grips with this subtle but far-reaching aspect of the world. Antipathy to Aristotle’s natural teleology (the presence within nature itself of ‘ends’ or ‘goals’) was an over-reaction against supernatural and superstitious accounts of nature that were being resisted during the Scientific Revolution. Subsequent philosophical attempts to expurgate teleology from biological language by converting ‘what it is for’ language into the language of ‘what it does’ or ‘how it works’ does not capture the ‘what it is for’ of pre-conscious adaptive selection.
The fact that the human brain was created by an ignorant mechanical process increases the wonder; it produced the intricately designed structural and functional complexity needed to produce reason, language, and abstract thought. As Aristotle noted: organisms like plants do not know, see, or feel with the same teleological intentionality as humans, but they possess a natural teleology. The denial of these reasons, purpose, and design is a human arrogance: it was natural teleology that created both humans and their minds.
Our scientific metaphysics tells us that reasons and purpose in nature are real. Our language will therefore be more effective when brought into line with our best science. It is OK to use quasi-conscious words like ‘design’, ‘purpose’, and ‘function’ because they reflect the quasi-conscious underlying phenomena.
Nature is part of what we might regard as a continuum passing from inanimate simplicity to intentional complexity with all living creatures products of the natural selection that generates functional adaptations. Plants are not conscious so the use of strong consciousness-talk to explain their physiology is metaphor, a distinction that is critical for scientific explanation. We use metaphor when we say that plants can ‘smell’ without a nose and ‘taste’ without a tongue, that they even have ‘awareness’ and ‘knowledge’ of the world as a rudimentary ‘consciousness’. This kind of language may assist our thinking but it also confuses difference.
Of course we can mistakenly attribute human motives to nature. But we must beware of throwing the baby out with the bath water. Nature demonstrates reasons, purposes, and design . . . even though it is unaware that it is doing so.
We know that, as humans, we have an anthropocentric and anthropomorphic cognitive bias. That is, we tend to explain the world in terms of our own human experience and understanding. So, for example, in our religions, both nature and Gods are personified, taking on human forms and characteristics. Even in science, humanity was for many years placed at the physical centre of the universe.
Among the vocabulary we associate with human experience are:
Thought words, like – ‘thought’, ‘concept’, ‘knowledge’, ‘calculation’, and ‘wisdom’
Sensation words, like – ‘feel’, ‘hear’, ‘desire’, ‘touch’, and ‘see’
Consciousness words, like – ‘memory’, ‘learning’, ‘intelligence’, ‘pleasure’, and ‘pain’ – which we tend to use for sentient animals with nervous systems though not, usually, for un-conscious life.
The appropriateness of consciousness-talk for describing the world is a contentious matter because there are no uncontroversial rules about word usage. If we say, for example, that ‘the heart wants to pump blood’ we are clearly being anthropomorphic. The heart cannot possibly ‘want’ things in the way that we ‘want’ things; so this is blatant as if metaphor. But when we say ‘the purpose of the heart is to pump blood’ though you might still regard this as metaphor, the conceptual association with human conscious minds is not obvious.
There are many examples like this. We might accept that an animal, like a unicellular paramecium, with light sensitivity can ‘see’, in a loose sense, but not in the same way that we do . . . it can only ever be as if the paramecium and plants ‘see’ because the plant has no nervous system or eyes.
Viewed through the prism of our consciousness, we humans seem very different from non-sentient organisms. But in a more general sense we also have much in common.
All life existing today has persisted by developing structural and functional adaptations to their historical surroundings. From this biological perspective consciousness is just another functional adaptation, albeit a very effective one. Consciousness-talk is a specialist vocabulary within a more wide-ranging language that encompasses the general interactions that occur between all organisms and their surroundings. Explanations of the inanimate tend to answer the question ‘How does it work?’ while un-conscious purpose in living matter prompts the question ‘What is it for?’ Conscious (sentient) questions take the form ‘How does it feel?’ and conscious reasons tend to answer question ‘What was the considered intention?’
This needs more explanation.
Although they cannot communicate the products of critical self-reflection like we humans. Though both monkeys and humans have reasons, purposes, functions, and values, it is only us humans that can represent these in spoken and written language (this distinction is described in more detail in purpose).
In practice we have simply adopted anthropomorphic words that are, by convention, of greater and lesser acceptability in scientific discourse. Just as we see in evolution an increasing differentiation of structures so, in language, we have a parallel differentiation in meaning.
From now on this article will use ‘human-talk’ for the reasons outlined above, but mainly because practical alternatives are scarce and human-talk can be regarded as a useful signal not for absence of properties, but for graded similarities.
The following is a glossary, not of metaphor, but some of the language of graded biological reality expressed in human-talk.
Adaptation – learning, intelligence
Agency – purpose
Autonomous activity – behaviour, agency, consciousness
Natural selection – self-correction, reason
Function – purpose
Information storage – memory
Recording variables – representing, forming a cognitive map, thinking
Here is a brainstorm of words we might associate with mental biological agency: intelligence, wisdom, behaviour, talking, communicating, knowing, remembering, learning, feeling (sentience/sensation) sensory system including tasting, seeing, hearing, feeling).
During cosmic evolution, physical structures and their relations increased in number and complexity: so too did their properties. This was a process of emergence as everything evolved from a point source.
It was argued above, that, although we can choose to use the word ‘consciousness’ in unique reference to human consciousness, in nature consciousness exists as a continuum. Associated with consciousness are properties that we also often regard as uniquely human – properties like intention and purpose, reason, knowing, remembering, intelligence, learning, and evaluation. Are these properties present in nature (in ‘reality’) in the same graduated way?
Although nature exists in graded complexity – a staged continuum – we like our ideas to be clear and distinct. It is simpler when properties are either present or absent, rather than present by degree. If we regard consciousness as a strictly human property, then it (and its associated properties – like reason, learning, memory, and purpose-intentionality) cannot be present in other organisms. So, what are we to call all these similarities or gradations when we do not feel inclined to extend their semantic breadth to include organisms other than humans?
Well, we could give them all separate names in an elaborate system of nomenclature. But that would be too complicated. Instead, we adopt a form of eliminativism. We put them in the too hard basket and describe them, confusingly, as ‘metaphor’. Rather than acknowledging their commonality in reality we equate the ‘as if’ they were human with ‘as if’ they exist at all. This is a strange inversion of reasoning – an anthropocentric mental leger-de-main that has caused untold biological damage as we conflate non-human with non-existence. By dismissing biological similarities in this way, we are not just diminishing their significance, we are denying their reality.
There are several reasons why we use human-talk:
. anthropocentric cognitive bias text
. genuine metaphor
. lack of appropriate vocabulary
. absence of convincing referents (e.g. not knowing the consciousness of a fish, or reasoning of an owl).
Without adequate vocabulary we inevitably revert to human-talk, which generates semantic and conceptual confusion, and scientific imprecision.
Human-talk will not go away, even in science, because (most of the time) it attempts to represent similarities that exist in nature, not just in human minds.
We need to look more closely at the way that we use this language.
Are plants conscious?
Clearly not in the way that we are conscious, but they are much more ‘conscious’ than our intuition might suggest.
We humans are aware and have an extraordinary ability to introspect but there is no philosophical agreement about the reality of the ‘self’ in self-aware: our inner theatre of selfhood could well be illusory. What is important is that we are aware of ‘something’, experiencing ‘something’. In responding to inner and outer environments it is clear that plants are also ‘aware’.
When reasons confer benefit on an organism by providing functions that can operate more or less efficiently we describe them as ‘purposes’. Functional adaptations are non-intentionally purposive. Like natural reasons, functional reasons (as purposes) are not metaphorical purposes (the reading of subjective human intention into nature) but functional reasons locked into the genetic and biological character of all organisms. If we assume that reasons, purpose, design, and value are, by definition products of the human mind, then there can be no acceptance of these ideas.
Principle 8 – Three loose categories of reason, purpose, and design are recognised by linguistic convention: simple reasons/purpose/design, pre-conscious reasons/purpose/design, and conscious reasons/purpose/design
This mentalistic classification into non-conscious, pre-conscious, and conscious categories has proved useful to science and common usage suggests that words like ‘purpose’, ‘adaptation’, ‘selection’, ‘function’, and ‘design’ are sometimes used in relation to pre-conscious functions and sometimes to conscious intentions, hence their ambiguity. These are, for lack of a better expression, quasi-consciousness words: they are terms used in the contexts of both the pre-conscious purpose and design resulting from natural selection and also the conscious reasons, purpose and design that are a result of human intention.
Principle 9 – The meaning of some words can entail more than one kind of reason/purpose/design (as manifest in the physical world) thus producing semantic demarcation disputes. ‘Purpose’ is one of these words
When we think of life as a system of information processing, then we see that it too has become more elaborate over time as organisms have become ever more comprehending and self-comprehending.
Science examines the order of the world by looking for causes and reasons for the patterns of connection that we see in objects and events. Among the semantically slippery words we use to describe this orderliness and connection are: ‘cause’, ‘reason’, ‘law’, ‘function’, ‘purpose’, ‘preference’, ‘value’, ‘selection’, and ‘intention’. There is a semantic fluidity in many such words as we use them, sometimes in a domain-specific way, and sometimes more generally in the way we represent all or part of the physical continuum that passes from the inanimate to the living and, among the living, from the un-conscious . . . to the conscious . . . and rational- conscious.
One critical aspect of this concerns the degree to which our semantically fuzzy scientific language represents the world is coloured by our minds. This semantic nuancing is exemplified by the word ‘law’ which, in science, we use to express universal physical constants, while recognizing the origin of this mode of expression in human laws.
Science provides us with the best possible reasons and explanations for the way the world is.
The reason the Earth orbits the Sun lies within the universe itself, it is not a human invention: it is not created by the human mind, it is a natural reason.
Principle 1 – there are natural reasons why the world is as it is, reasons that are independent of human minds.
We humans are able to represent these reasons in our minds and communicate them to one-another using symbolic language. That is, we are reason representers. Although natural reasons pre-dated reason-representations we need our minds, our conscious powers of deliberation, to represent them.
When we apply the same thinking to living organisms it becomes problematic. There are reasons why spiders build webs – they do so to catch flies – even though they are not conscious of doing so. Humans, as reason-representers, can understand that this is a purposive activity, albeit a mindless one, but the purpose is not attached to the world, to the behaviour of the spider, it is attributed to the behaviour of the human mind. We mistakenly assume there is no purpose in nature: that it is only as if there is purpose in nature because we are superimposing the purpose that can only exist in human minds.
Principle 2 – humans, as reason-representers, are aware of natural reasons and can communicate these reasons to one-another
Plants as intellectual competitors
There are two major ways in which plants have pre-consciously ‘outwitted’ humans.
Firstly, and most dramatically, plants produce their own life-sustaining energy. That is, they manufacture food by using water from the earth, carbon dioxide from the atmosphere, and light from the Sun while they are simply ‘standing still’ … they are photosynthetic. This is an astounding achievement comparable to the evolution of the brain. Photosynthesis produces the energy currency on which the entire natural economy runs: it is the fuel that powers the global cycle of life. Motile organisms must move around to find their food: they must hunt, because they cannot make it themselves. Their energy can only come, ultimately, from plants which are the world’s primary producers. In other words, much of the historical evolutionary effort expended by animals in developing locomotory and nervous systems was only possible because plants had previously ‘solved’ the energy problem needed for life-support. We only have brains because we did not have the pre-conscious ‘intelligence’ to photosynthesize.
Secondly it is plants that were at the core of the Neolithic Agricultural Revolution. To all intents and purposes we have cereal plants to thank or blame for our domestication, our move from wild nature to cities and civilization – probably the most significant human social transition that was a by-product of our attention to vast areas of land where we carefully tended our food plants.
But for our plant-blindness and anthropocentrism it would be blatantly obvious to engineers, architects, artists, and indeed all of us, that plant structures demonstrates a preconscious ‘intelligence’ and ‘beauty’ and functional adaptation of extreme ‘wisdom’ that far exceeds anything our conscious brains can achieve.
Perhaps by using our reasoning consciousness to study and compare the reality of plants with our own human reality we can learn a few adaptive tricks. After all, our consciousness does allow us to make reality comparisons – which is something that a plant’s ‘awareness’ of the world cannot do … at least, not in the same vivid way.
With all this in mind lets now examine the plant functional analogues of the human senses.
Anticipation is a distinctive and critical feature of human conscious experience. It engages hindsight and foresight as tools for the management of behaviour in the present. It is also strongly associated with the concepts of knowing, learning, and remembering. All of these concepts, we assume, require a brain. Without a brain, the idea of plants ‘knowing’ anything at all seems absurd.
But let’s unpack a little of what we mean by a cluster of related concepts that include ‘knowing’, ‘learning’, ‘remembering’ (hindsight), ‘anticipation’.
Human memory is the subject of active research. Cognitive scientists distinguish between three kinds:
procedural memory – non-verbal or instinctive adjustment to external factors (riding a bicycle)
semantic memory – the acquisition of concepts (learning a language or mathematics)
episodic memory – the recollection of special events (21st birthday party or breaking a leg).
Only procedural memory does not require a brain.
Another classification of memory includes:
sensory memory – which filters input from the senses
short-term memory – which can briefly hold up to seven or so objects, like numbers, in consciousness
long-term memory – which retains memories, sometimes for life
muscle-memory – the unconscious memorization of movements like playing a scale on the piano or tying a shoelace
immune memory – when our immune system remembers past infections
Only immune memory does not require a brain.
It also helps to think of memory as involving three key processes:
encoding – memory formation
storage – retention of information
retrieval – the recollection of information
This is the way we understand memory in computers.
Memory is usually related specifically to brains but, when ‘knowing, learning, and remembering’ are treated as ‘manipulating information’ then non-human organisms might be included. We can then usefully apply the last three categories (encoding, storing, and retrieval) to organisms in general.
Before we can have conscious memories, we need organisms and one feature of organisms that we tend to take for granted, and Aristotle did not, was the simple fact that ‘like begets like’. Humans do not give birth to fish.
We now know that the community of life almost certainly had a single beginning – that the entire complexity of life in all its complexity and diversity arose by descent with modification from a common ancestor. Only in the mid- 19th century, with Darwin’s theory of natural selection, did the mechanism for encoding this information become a central problem for biology when it was proposed that species changed, or evolved, over time.
Darwin outlined a mechanism whereby small variations in nature would be ‘selected’ (encoded into the characteristics of a particular organism) as a result of differential reproduction. That is, those variations that benefitted the organism would tend to persist under multiple replication. Beneficial variation was essentially a better ‘fit’ with the environment, improved functioning. Over thousands of generations information about the environment was being encoded in the genetic make of different organisms that gradually changed over time. The precise way thi sgenetic information remained unknownfor another century.
Information storage & retrieval
It was only in the 1950s that the astounding foundational structural simplicity of inheritance came to light when Watson and Crick identified the replicating double helix of DNA (present in the chromosomes found in the nucleus of every living cell) consisting of nucleotides in a particular sequence that pass from generation to generation, in egg and sperm, the coded information, as genes, that trigger the formation of those proteins that uniquely determine the physical structure and developmental processes that we associate with a particular species.
Information encoded in DNA is the plant’s blueprint for the future: here are the instructions that detail the way a new organism will unfold in a developmental process that proceeds from juvenile to mature adult as genes switch protein metabolism on and off to produce the structures by which we recognise one species rather than another.
A good example of plant memory occurs in the Venus’s Flytrap. When a fly first touches a hair an electrical potential passes from cell to cell which concentrates the ions in the cell, taking about 20 seconds to return to normal. If the hair is touched again the action potential is sufficient to trigger the trap to shut. This stops the trap shutting unnecessarily in a process that is vary similar to that which occurs in neurons.
Memory seems crucial to our human exisatence, total absence of memory is the subject of thriller movies and is hard to imagine. Pre-conscious plants have no memory at all and yet they have persisted, so how have they compensated? Like all pre-conscious organisms plants possess a rich arsenal of pre-conscious memory analogues. The important capacity from a biological standpoint is not whether we are ‘aware’ of the past but whether the organism has the capacity to incorporate past events into strategies relevant to the present. We call this process ‘learning’ but from a biological perspective From this perspective, whether we refer to these connections with the past as ‘recollection’, or ‘memory’ becomes incidental.
So how can organisms possibly possess these referencing to past events that we call ‘memory’?
Memory is one of the wonders of the biological world. Our genetic makeup, our genotype, carries information about our entire evolutionary history. Most obviously it passes this information from generation to generation as a blueprint that is unique to each kind of organism. A single generation requires a finely-tuned developmental sequence for structures and processes.
Just as humans have (conscious) reasons for their behaviour so a plant has (unconscious) reasons for developing structures that benefit its short and long-term existence. There are beneficial reasons (purposes) for functional design in nature even though these are not conscious reasons. We should not be ashamed of natural teleology even though consciousness-talk may not be appropriate to describe it.
The single key difference between plants and animals is that animals are motile: they can towards benefial influences in the environment and away from disadvantageous ones. Plants have had to confront weather, predators, and disease directly with no means of escape. We might assume that the wide diversity of sensory input needed to cope with mobility has ultimately given rise to nerve tissue. But plants, too, have evolved complex sensory and regulatory systems.
We believe we behave in certain ways due, on the one hand, to our unconscious impulses and intuitions and, on the other, our conscious deliberations. Consciousness, if we believe it has a physical basis that can be explained scientifically, is in this sense at one with all physical phenomena. Consciousness is thus an epiphenomenon of matter.
Plants, like all living organisms today, are a product of evolution extending back 3.5 billion years. Contained in their genes are the ‘memories’ of past environments since it is the historical response of every organism to its ancient environments that has produced the physical bodies they possess today. This we can speak of as genotypic ‘memory’, the inherited memory of the past. But there is also phenotypic memory, the ‘remembered’ response to the environment in the present. This will be discussed under subsequent headings.
It seems that although we have a virtually infinite store of memories the proteins involved in memory maintenance are few.
We associate science with the establishment of universal laws and general principles about the natural world. Characterized like this we tend to think of the universal laws of physics. Biology is then the subset of complex (living) matter that exists within all-embracing physics.
It is the universal law-like statements of physics that are so impressive as they approximate the absolute certainties of mathematics, and the dictates of Gods.
Maths is built on axioms – statements that are taken as self-evident, foundational, and uncontroversial. A couple of examples from Euclid’s geometry would be that ‘Things that are equal to the same thing are also equal to one another’ and that ‘All right angles are equal to one-another’. To deny an axiom is to place the whole related enterprise or discipline in question. If we argue that Euclid’s axioms are mistaken then we are, in effect, undermining confidence in the entire enterprise of Euclidian geometry.
We respect the empirical generalizations of science (its principles and laws) for their predictive power. Physical constants, the laws of physics, have the properties of axioms because they resist contrary evidence and cannot be altered substantially without transforming our understanding of theoretical foundations. Physical laws are, as it were, the axioms or foundational principles of physics.
Can there be axioms in biology?
Well, if there are axioms in biology then, as a biology student, I was certainly never taught them. Since biology is restricted to the study of life, then its axioms would, presumably, set out life’s universal conditions.
Perhaps the nearest we get to such foundations today is a list of contentious characteristics said to define what it is to be a living being – characteristics like metabolism, nutrition, growth, and reproduction. Though text books often present such a list, getting agreement from the biological community as a whole as to what should appear on this list, (and its order of priority), is no simple matter, especially as definitions of life are further complicated by artificial intelligence and synthetic life forms. This question is therefore generally avoided or not addressed in a coherent way. The idea of biological axioms is therefore reckoned an unproductive avenue of research.
Aristotle was a specialist in first principles. He wrote the world’s first systematic treatise on logic, Organon, much of which still stands today as the foundation for deductive logic. As stated, the strength of axioms is that thay provide a starting point or foundation – they are a backstop to the tendency for scientific questions to pass into an infinite regress.
Aristotle noted that in order to continue existing, to perpetuate their kind, living beings must reproduce. He summarized this principle by saying that all living creatures ‘partake in the eternal and divine’ indicating that they can replicate their kind (species) indefinitely provided they can survive to reproduce. Today, using different words, we might refer, like Richard Dawkins, to the ‘immortality of our genes’. For Aristotle the intellectual search for the foundation of biology, what it means to be a living being, ended with ‘survival and reproduction’. Any cursory examination of general biology texts reveals this as a general (though often not explicit) assumption. It is a truism about life that cannot be expressed in simpler terms.
You might object to the idea of there being any biological axioms, let alone this particular one. Such an axiom does not have the universality of a physical law, nor does it seem to have the same degree of necessity as physical laws. You might think of other properties that are uniquely biological. However, other suggestions – like, say, growth and metabolism -do appear to be second-order.
Four kinds of matter
From antiquity humans have found it useful to distinguish four kinds of matter:
a) the set of all matter ordered by necessity (‘necessity’ = the laws of physics)
b) the subset of all matter that is living, which consists of semi-autonomous units that are the products of natural selection (genetic information accumulated under the influence of the sorting algorithm of natural selection).
c) the subset of living matter that is conscious (sentient) with the capacity to experience comfort and pain
d) the further subset of conscious living matter that has the capacity for foresight and hindsight, abstract reasoning, self-awareness, creation of complex technology, sociality, and language i.e. human beings.
This categorization is useful understanding apparent disjunctions in the continuity of the universe.
— First published on the internet
GLOBAL OCEANIC & TERRESTRIAL PHOTOTROPH ABUNDANCE – Sept 1997 to Aug. 2000.
As an estimate of autotroph biomass, it is only a rough indicator of primary production potential and not an actual estimate of it.
Provided by the SeaWiFS Project, Goddard Space Flight Center and ORBIMAGE.
Courtesy Wikimedia Commons – Accessed 9 September 2021