On the Multiplicity of Species

We can explain the origin of species: where they came from and how (other species by mutation and natural selection). We can explain the diversity of species: how and why they differ from each other (adaptation to different environments). We can explain the complexity of species (progressive evolution with increasing design demands). But can we explain the multiplicity of species—the sheer number of them? There are about two million species currently existing on planet Earth and millions now extinct: why so many? Why not half a million or ten thousand or thirty-two? How many chemical elements are there? 266, according to my table—not millions. How many kinds of elementary particles are there? Half a dozen maybe. How many types of celestial bodies are there? Not more than a hundred. How many types of rocks are there, or types of mountains, or types of watery expanse? Not a great number. Nature doesn’t normally produce natural kinds in the high figures we find with animal (and plant) species. It seems excessive, anomalous, in need of explanation. If we came across a planet with, say, 200 species, we wouldn’t be astonished; we would find it perfectly natural. But our planet swarms with millions of animal and plant types, as if it can’t get enough—why? Surely, there was a time when it had many fewer (how many kinds of bacteria were there on early Earth?), so why did we end up with so many species?

We might compare the case to the existence of human artifacts: works of art, types of furniture, means of transportation, etc. There are a great many of these too, in excess of naturally produced (non-living) objects. The explanation is plain to see: they come from the human creative mind, particularly the faculty of imagination. There are hugely many things we can imagine, envisage, conceive of—and hence construct. Our intelligence generates multiplicity on a grand scale. So, is this why there are so many different species? That was the traditional way of thinking: a creative intelligence, equipped with mental multiplicity, is responsible for the multiplicity of species—God or some equivalent. This intelligence chose to create these many species and it had the power to do it. Why, is a question of theology—did God just wish to give his prize creation, Man, something spectacular to look at? But, ruling out this kind of answer, how did nature manage to produce such multitudinous diversity? We would expect to find a sea-dwelling species or two, and a few land-dwellers, and even several air-dwellers—but why untold millions? The Earth just doesn’t have the level of multiplicity capable of giving rise to the number of species we observe—it doesn’t have that many different environments. Mutational multiplicity won’t explain it—even if there were that many types of mutation, not all of them survive to create a new species. Nor is natural selection itself so numerically profligate—there are only so many ways of surviving and dying. Nor can we suppose that planet Earth possesses some sort of multiplicity genie or energy or soul—as if it just aches to produce as many species as possible. If I were pressed to estimate how many species there ought to be, given the physical conditions on Earth, I would say, oh, maybe 235, give or take. If I were an explorer from outer space four billion years ago, surveying the state of planet Earth, I would estimate that the planet would likely produce something on the order of a few hundred species, or even a number in the low twenties. For why should such a drab little place with not much going for it be able to give rise to such a multiplicity of life-forms? What if I told you that in a hundred years our planet would double its species plurality, or quadruple it, or more, so producing a billion species? Wouldn’t you find that rather implausible and in need of explanation. Yet that is what Earth did, in effect: it produced a heck of a lot of different plant and animal species, far more than would have been predictable. We take this for granted, because we see the multiplicity around us every day, but even still we are astounded when told the true numerical magnitude of species existing on Earth today. It seems hard to believe, almost miraculous, verging on the inexplicable. The number may as well be infinite!

There is an answer to our conundrum that one sometimes hears bruited, though it is seldom spelled out. It has to do with niches.[1] If you look in the dictionary under “niche”, you find “a shallow recess, especially one in a wall to display an ornament”, or “a comfortable or suitable position in life” (OED). The intuitive idea is that of a specific type of place or context in which something can be located—a sort of home. In biology a niche consists of a part of the overall environment in which an animal (or plant) finds its home—its comfort zone, its place of residence. It can be quite complex, involving food sources, conspecifics, predators, mating opportunities, territory, etc. The thought then is that there are as many niches as there are species: each species has its distinctive niche—its corresponding slice of the world. For every species, there is a niche that “fits” it—there is a one-one correspondence. Thus, the multiplicity of niches matches the multiplicity of species—the former explains the latter. A niche antecedently exists and a species comes to occupy it—that’s why there are as many species as there are. Niches have the right cardinality to explain species cardinality. But there are problems with this explanation. Can’t two or more species occupy the same niche? Butterflies, beetles, big cats—don’t the various species of these have the same “home”, occupy the same ecological niche? If so, species multiplicity exceeds niche multiplicity. Secondly, why should every potential niche be filled by an actual species? At one time most niches would have no occupants, since the right species had yet to evolve, so actual niches don’t entail actual species to fill them. Recesses don’t always have ornaments embedded in them. Maybe diverse niches explain species diversity, but they don’t explain species multiplicity. A watery niche explains the existence of a water-living species, and similarly for a terrestrial or aerial niche; but why so many such species? The structure of the environment doesn’t by itself generate such a multiplicity; we need some factor internal to life-forms themselves—some inner impetus towards endless multiplication. Is it all just a strange contingency with no systematic explanation, no underlying law? But the trend towards multiplicity is too strong to shrug off in this way. There seems to be a biological law of increasing species multiplicity during the course of evolutionary history, but the reason for this is obscure—or so it seems to me. It appears to be spontaneous, not predictable from the objective character of the environment—intrinsic to life itself. It is as if life revels in multiplying its forms—as if it favors creativity of life forms. But what sense does this make? It sounds mystical and New Age, yet another manifestation of the old elan vital.  And actually, even theologically, the situation is puzzling—why would God decide to make so many species? What is the point of thousands of species of beetle or butterfly? Consider a forest: full of trees of different species, but all living in the same stretch of geography—why not just one or two species? And it isn’t as if all these species are built to last—most species eventually go extinct. The multiplicity is constantly being whittled away, so why produce it in the first place? Nature seems populous beyond reason, pointlessly prolific. Just because it has the potential to house so many species (all those available niches), why must it do so? Darwin told us how one species evolves from another, but he didn’t tell us why so incredibly many species evolve this way. Species replace each other, but why do so many coexist? Even economic markets contain fewer products and they are the result of unlimited human creativity. Nature seems too creative—and yet it isn’t really creative at all (it has no imagination). We can see how a great many dog breeds came to exist by intentional artificial selection, but we can’t see how so many animal species came to exist by blind natural selection. Intentional breeding for variety doesn’t create as many distinct species as nature left to its own devices (think of butterflies). What law of nature explains this? What trait of God explains it, for that matter? Creationism doesn’t help with the problem (not that it has anything going for it anyway). Call this the mystery of multiplicity.[2]

[1] I could as well say habitat here—the totality of an organism’s impinging relevant environmental conditions—but I think “niche” better captures the idea we want.

[2] Darwin draws our attention to a similar problem about the multiplicity of human races: it is puzzling why these races exist in their actual plurality, given that there is little connection between human environments and human physiology (see The Descent of Man, chapter VII, “On the Races of Man”). There is really no reason to expect a variety of races given the places humans live and the life-styles they adopt. It is as if nature simply felt like having several races (and varieties within races) without any compelling reason to do so. I should also note that it is not even clear why there are two sexes in nature instead of one. This is taken by biologists to require explanation, and the explanations offered are controversial. Note, too, that bodily organs don’t have the enormous variety that species do—there isn’t a million types of internal organs, just a handful. Cell types are also few in number. Yet species of organisms climb into the big numbers—we don’t even know how many species exist on Earth exactly. There is nothing unnatural about a ten-species planet and yet on Earth nature has catapulted many millions of species into existence. We have a many-species problem.

Transitional Trump

Trump has finally made the transition (he’s a “trans”): from falsehood to nonsense. He has long been unconstrained by truth and tells whopping lies all the time. We are accustomed to that. But now he has gone a stage further: he has descended into nonsense (very Lewis Carroll). He is no longer constrained by logic and simple coherence (Gaza, Canada, the FBI, the CIA, etc. etc.). His followers lap it up, but it is amusing to see fellow politicians trying to make sense of it all. He gets that self-satisfied blank look on his face and starts spouting total rubbish—strings of words with no logical connection, odd divagations, meaningless phrases, massive non sequiturs, strange locutions, mangled words, weird fantasies. He seems to dwell on the borders of sanity. I wonder what the next stage will be: will it be pure gibberish? What will his supporters and enablers do then? Will they start to talk gibberish themselves, or try to offer meaningful paraphrases of his verbal tangles? How far can he go on the road to incoherence before they call a halt?

An Essay Concerning Worm Understanding

Your average worm has quite a bit of worm know-how. It knows how to dig a burrow of the right width, depth, and angle; it knows how to plug up the mouth of the burrow with leaves of various shapes and sizes; it knows how to produce castings of the right vermiform architecture; it knows how to position itself in the burrow when it is dry or cold outside. It has a kind of intelligence (worm consciousness is moot).[1] Worms have been around forever, so they must be doing something right; epistemologically, they are not absolute beginners in the art of survival. But they are deficient in the sensory department: they are blind and deaf, have only a crude sense of smell and taste, and are generally oblivious of the impinging world. They can, however, feel things and sense vibrations, so they are not entirely without sensory input: they are the recipients of tactile sense-data. Still, they are afflicted with poverty-of-the-stimulus: not much goes in and it is not very rich or instructive—it doesn’t encode what they manifestly know. The only conclusion we can draw is that their know-how is a result of innate endowment; it is instinctual and inborn. Worm knowledge (“understanding”) is in the worm’s genes. It isn’t just a copy of what their senses deliver. The worm’s slate is by no means blank. Nativism is true of the worm’s world-view. Empiricism is not a plausible theory of how worms come to know things. Evidently, all of its general knowledge is innate, with tactile sense-data confined to indicating the present state of the environment, these interacting with the general innate programs or proto-cognitions. A “rationalist” philosophy of worm intelligence would thus seem recommended: it comes from within not from outside. Even Locke would agree that much worm knowledge is not derived from the senses; it is derived from the genes and hence hereditary. It is ancestrally derived, no doubt going back many millions of years. Every worm generation automatically contains the knowledge that is helpful to worm survival and reproduction. Worms don’t learnwhat they know. Their burrow know-how is passed down the generations and does not need to be acquired anew by the individual. If we started our study of animal knowledge with worms, we would be disposed to a general nativism-rationalism. The poverty of the stimulus is only too apparent (Chomsky would have a field day with worm burrowing competence, which is quite complex and generative, even “grammatical”).

What proportion of total worm knowledge is innate? We would need to assign numbers to items of knowledge in order to answer this question (how many items of knowledge does a typical worm have?). We would also do well to assign a numerical value to the importance of the knowledge in question. These are not easy tasks, but I think a rough answer can be provided: most of the important stuff is innate. It isn’t that the vast majority of worm knowledge is based on sensory learning with only a small amount deriving from the genes. Just to have a heuristic figure, let’s say nine-tenths of it is innate, and this the good stuff. Innate knowledge is the rule not the exception. If a worm lost its stock of innate knowledge, it would be finished as a viable worm; it wouldn’t know what to do with itself. Partial lack would also be pretty catastrophic. True, its tactile sense is also important (the worm couldn’t survive for long with tactile blindness), but the innate component is clearly indispensable. Now, many species on Earth evolved from primeval worms, including humans, and animals tend to conserve the features of the animals from which they evolve—species evolve from small variations in their ancestor’s phenotype and genotype. Thus, later species often have a high proportion of genes in common with even their remotest ancestors (we are said to have 70% of our genes in common with the acorn worm). The basic structure of a derived species never strays too far from the structure of its ancestor species, despite superficial differences. So, I now want to suggest a biological law: later species have the same ratio of innate to acquired knowledge as their ancestors had. This law is empirical and testable (in principle), but on a priori grounds it is reasonable to expect it to hold. According to this law, then, human knowledge (we have been getting to that) is nine-tenths innate and one-tenth acquired (I am speaking approximately). A tenth of what we know we learned through our senses, but the overwhelming preponderance of our knowledge is inborn. Nearly everything we know we already knew in the womb. Of course, we know a good deal by means of the senses, particularly with regard to history and geography; but the really important stuff—the skeleton, the cognitive background—is innate. Possibly all concepts are innate in one way or another, as well as much propositional knowledge (and know-how): the foundations of knowledge, the building-blocks, are genetically specified. It isn’t that most knowledge is “empirical” with only a small amount “rational”; the opposite is the case. This is not the impression you get from classical discussions (Plato, Descartes, Leibniz): the idea tends to be that nearly all human knowledge is admittedly acquired through the senses, with only a small residue arising from the intellect alone. But the lowly worm teaches us otherwise: nature favors the innate over the acquired. If we trace our ancestry back through the generations to worms, we will find a steady adherence to the law adumbrated above; there is no sudden leap to an animal that reversed the polarities, as it were. Evolution never switched from the ratio set up at the time of those ancestral worms (they too, of course, come from a long line of earlier organisms successively modified). There was no saltation to an unprecedented empiricist mind; minds continued to be mainly innately formed. In the case of humans, we notice the acquired knowledge more, but from a deeper perspective innate knowledge is basic and ubiquitous. We are mainly native knowers. Our senses have not taken over the task of installing knowledge from our innate endowment; it isn’t that we have become blank slates, unlike the animals that gave rise to us. That would be evolutionarily bizarre, contrary to fundamental biological principles. Other bilateral creatures (fish, lizards, monkeys) did not suddenly convert to empiricism, so why should we? No, we are all modeled on that ancient prototype and progenitor—the humble burrowing worm. We all suffer from stimulus-poverty to one degree or another, which needs to be backed up with innate systems of know-how; empiricism is unlikely to be true of us alone. Nativism is the law of the land, the basic life plan. Nature favors the rationalist philosophy. The human brain is an evolved organ conforming to earlier brains; it is therefore primarily a device for storing innately given information, skills, and habits. And isn’t this what we should expect from a Darwinian point of view—isn’t it better for the genes to build vital knowledge in rather than leaving the individual organism to do all the epistemic work itself? Why take any chances? Worms need to hit the ground (literally) running (not literally), so they had better come equipped with the know-how they are going to need; you don’t want to be learning how to construct a burrow by trial-and-error or by watching another worm do it. A Darwinian perspective thus complements the arguments of the rationalist philosophers, strengthening their position: human (and animal) knowledge is largely inborn; it is the rule not the exception. The various forms of nativism that have been defended in recent years (conceptual, linguistic, moral, folk-physical, etc.) are thus instances of a general biological law, which we might call the Law of Genetic Epistemic Preponderance (the GEP Law), or the Worm Law in honor of that suggestive species).[2]

[1] Charles Darwin’s The Formation of Vegetable Mould Through the Action of Worms is a good source of information on worms and their life-style (quiet, hidden, transforming).

[2] Darwin was impressed by the prodigious amounts of earth that are ingested by earthworms and ejected in the form of castings, thus altering Earth’s landscape. But he wasn’t so moved by the extent of their knowledge given their lack of sensory capacities; to me, they seem like epistemic prodigies, knowing so much but exposed to so little. Not the blank slate but the carved and ornamented slate. The worm is a rich repository of inborn information. Perhaps the senses evolved when organisms started to move around more; then they needed to see and hear. We are all worms in motion (no shame in that). Tubes on wheels, as it were. (The digestive apparatus is clearly vermiform.) Of course, we are very sophisticated worm-progeny, but our basic form is worm-shaped; we clearly didn’t descend from starfish or jelly fish or barnacles.

Education and Error

In education we seek to impart knowledge to the student. The logic of the process is additive: we add to the student’s stock of knowledge. But this has not always been the way education has been conceived: sometimes the aim is to subtract something—not knowledge, to be sure, but error. That was Socrates’ method: he had nothing positive to impart, but he did teach an important lesson—that his interlocutor did not know what he thought he knew. Socrates exposed error, false belief, unjustified assumption, fallacious reasoning. His aim was negative, but he had a salutary effect; he cleared the mind of error. For him, education was critical not constructive—not a matter of accumulating information. In this he belongs to a long line of destructively-inclined philosophers: the ancient skeptics, Plato (the cave), Descartes, Locke, Berkeley, Hume, Russell, Popper, and many others. They sought to undermine what we thought we knew, to refute, falsify, disprove. They did this because they recognized that human beings are singularly prone to error. We must therefore root out error before we can install truth. A crucial part of education is accordingly the removal of false belief. Perhaps this is all we can do, given the power of skepticism and the difficulty of obtaining knowledge. We can’t even define knowledge let alone acquire it! Maybe we should lower our sights and aim to instill skills and useful opinions. We can puncture pretensions to knowledge, but to impart actual knowledge is a tall order. So it has been supposed. If knowledge is wisdom, this seems realistic—how do you teach wisdom? (“Know thyself!” Okay, but how?) But you can at least teach the avoidance of stupidity—ignorance masquerading as knowledge. You can work to defeat sophistry, delusion, fallacious reasoning, outright falsehood. Education can be positively negative.

I say all this because today the urgent task is to defeat error: we are drowning in the stuff, up to our neck in it. We need to teach people how to avoid falsehood—children and adults both. Especially children, because they have no natural defenses against error—they believe what they are told. Thus, they need to learn logic, rational argument, scientific method, statistics, clarity of expression, epistemic modesty. Don’t teach them what to believe; teach them what not to believe. They need an education in criticism and sound thinking. Don’t stuff them with things they should know, the more the better; encourage them to question what they hear. This is banal advice, I know, but it has to be repeated—from Socrates to today. We are now suffering from an epidemic of misinformation, lies, empty slogans, ill-formulated policies, utter nonsense, bizarre conspiracy theories, and absolute crap. Education should equip students with the ability to criticize all this garbage, starting at the earliest days. Don’t teach them what they should believe but what they can believe—what can stand up to criticism. Bertrand Russell was described as a “passionate skeptic” and the label is not wide of the mark, but I would prefer “dispassionate analyst”. You don’t need to deny that human knowledge is possible, as the skeptic does, and you don’t need to get all hot under the collar about it; what you need is a calm habit of intellectual evaluation, careful, methodical. Boring, if necessary. The opposite of political. Socrates gives the impression that he doesn’t much care what the truth turns out to be; he cares only that it be arrived at in a rational manner. This is why Socrates is the founder of all that is good in what we call Western Civilization. The Socratic method is the best method of education. Popper was not wrong to focus on refutation not verification, rejection not acceptance. Everybody should take Error Avoidance 101.[1]

[1] Abby Philip is a contemporary model of what I am advocating: she calmy, pleasantly, firmly, corrects the errors of her guests on Newsnight (CNN, 10pm). Her style is serenely Socratic.