Biological Species & Natural Kinds

If I have one big idea it is that one can understand Platonic and Aristotelian ontology and metaphysics better (or perhaps at all) by comparing them with modern evolutionary biology and vice versa.  I think I began to understand Aristotle much better, after decades of reading the Physics and the Metaphysics, when I realized that many contemporary debates in the philosophy of biology were recapitulating problems already present in Aristotle. 

Two days ago, I grabbed a book off my self on the way to the toilet.  Some of my biological processes seem to require reading material.  Darwinism and Philosophy [ed. Vittorio Hösle and Christian Illies (2005)] included an essay by Michael T. Ghiselin.  The latter is most famous for his answer to one of the great questions of modern biology: what is a species?  Is it a natural kind, like oxygen in the periodic table of elements?  Is it a group of (potentially) interbreeding organisms like elk?  Is it merely a customary grouping, like red pieces of laundry?  Each of these answers has its proponents. 

Ghiselin’s answer is that a species in an individual.  If that makes no obvious sense, you are in good company.  It made no sense to me until, sitting on porcelain and doing God’s work, I realized that Aristotle had joined the conversation.  By the time I finished the paperwork and returned to my desk, I was convinced that I understood Ghiselin’s argument and I was convinced that he was right. 

An individual is something that is located in space and time and, for that reason, has a history.  The Garmin fitness tracker on my left wrist is an individual; this one is mine, not somebody else’s.  The same is true of my wrist and me.  I had a beginning in time and my being traces a continuous path from that time and place to now.  The same is true of Homo neanderthalensis.  That species had a beginning, spread out across portions of the globe, and came to an end. 

Natural kinds are not located in time and space the same way.  Gold is gold wherever it occurs, whether it was dug up in California or discovered on Mars or produced in a supercollider.  As opposed to individual lumps of gold, gold has no history; it has only essential properties. 

Aristotle covered this same ground.  There are things that have properties-horses for example-and there are the properties that such things have-shape, weight, and species forms.  The things that have properties would seem to be the things that are real.  A horse can change color (age happens, even to Seabiscuit) and yet remain a horse; its color exists on in the horse and the color ceases to exist when the color has changed. 

This suggests one answer to the question: what is most genuinely real?  For the purposes of biology, at least, it is the individual organism.  From the horse one can abstract downward to its properties (color and size), its matter (meat and bone), and its parts (limbs and organs).  Likewise, one can abstract upwards to its species form, which links it to the other horses.  All of these are abstractions because they exist only in analysis; they depend for their reality on this here animal. 

Aristotle might have rested with this had he not inherited the central problem of Greek philosophy.  What is most real should be what is most knowable.  It is not clear that I can know anything about individual organisms.  Is she short or tall, young or old, alive or not.  On the other hand, I can know that horses are mammalian quadrupeds in a rather more secure way. 

Ghiselin’s view that species are individuals seems to address this problem.  If species are not eternal, they are not knowable in the same sense that triangles are knowable.  They are at least more knowable that a particular horse.  His account points, however, toward a solution to the problem. 

Ghiselin does not deny that the species as natural kind account points to something real.  The species horse is an emphatically real thing: there are lots of horses.  The natural kinds horse, mammal, etc., are real in so far as horses really are horses and mammals.  He just insists that natural kinds of this sort are properties of individual species. 

A good indication that we are on the right track is that our account to solve problems that once seemed too difficult.  I was raised, intellectually speaking, in a hotbed of natural rights theorists.  Under the guidance of Harry V. Jaffa, we took the Declaration of Independence very seriously.  In that I have not wavered. 

The Declaration speaks of the Laws of Nature and of Nature’s God.  Inferred from such laws is the self-evident truth that all men are created equal in so far as they enjoy certain unalienable rights.  Here I understand “men” to mean human beings.  My colleagues who reject evolutionary biology do so on the grounds that undermines confidence in the existence of a stable human nature that can bear such properties as unalienable rights. 

In the evolutionary scheme, species seem to differ not in kind but only in degree.  For example, lions and tigers can mate and produce ligers, hybrids that are not capable of having offspring.  This means that the two species share a large percentage of their DNA but not enough to produce a lineage.  So lions and tigers differ, genetically, only in degree.  Species as individuals emerged from common ancestors and so differ only in their unique history and genomic families.  From that point of view, the critics appear to be correct. 

Not so fast.  Individual species also present real differences in natural kind.  A particular lion may be so much a tiger, genetically speaking, and he may be bigger than more aggressive than another male lion when he squares off on the field of reproductive competition.  He is, however, no more a lion than any one of his competitors.  Socrates, Aristotle insists, is no more a man than any of his interlocutors. 

To bring this back to the Declaration, allow me to indulge in a little science fiction.  Suppose we encounter living organisms on another world.  Assume that these organisms emerged historically through the same evolutionary processes as life on earth.  We will find there no organisms that belong to the same species as those on our planet, at least in Ghiselin’s terms.  None of those species will have a common history with any of our species.  Yet the fact that we recognize them as living organisms means that they do share something vitally important.  The living organism is a natural kind.

Now suppose that we encounter Vulcans or something of that sort.  Green blood and distinct biological history notwithstanding, they are capable of symbolic communication and moral responsibility.  They can recognize mutual obligations between themselves and us newcomers.  They are capable of making contracts.  Are they “men” as the Declaration means that term?  Of course.

Human beings are certain kinds of beings.  Our species has its unique biological history, just as do individuals and populations of individuals within that larger individual that is our species.  While we are diverse in many respects, no son or daughter of humankind is more an organism, or a mammal, or a human being than any other.  I find the distinction between species as individuals and natural kinds to be worth thinking about.

A Horse is Of Course

I was interviewed today by David Tucker, Senior Fellow at the Ashbrook Center at Ashland University.  The interview will be posted soon and I expect that it will be available to anyone (I didn’t exactly ask!).  If so, I will post a link here. 

Our topic was Darwin and the Declaration.  While I was preparing for the interview, something occurred to me that might be worth further thought.  I am thinking it through here for the first time. 

One of the greatest innovations in Aristotle’s writing concerned a way of confronting apparent paradoxes.  A paradox occurs when something appears to be two things at the same time and the two things are apparently contradictory. 

To take a simple example, consider an oblong table not quite so wide than your hips and longer than the reach of both arms.  Standing at one end, it appears narrower than you.  Now walk around it and look at it from its middle.  From this point of view, it is wider than you.  That is the paradox: “narrower than you” and “wider than you” are contradictory propositions.  It can’t be both at the same time; and so, the table is impossible.  If this seems silly, more intelligent people than you or I have been driven to distraction by such things.  The obvious solution (once it occurs to you) is that the table is at least a two-dimensional object.  Its multi-dimensionality allows it to be both narrower and wider at the same time. 

Using this kind of strategy, Aristotle solved a wide range of problems in philosophy.  How is it possible that a baby can be both entirely material (the stuff of flesh) and also entirely formal (it’s a baby and not just a lump of stuff)?  Because organisms (and indeed all lumps) have these two dimensions‑material and form.  To complete the explanation, Aristotle added efficient cause (the baby is being pushed out of its initial state by its phusis, or nature) and it is growing toward maturity (the telos or end of its growth). 

Now consider a mature animal, say a horse.  How do we understand what this is?  On the one hand, it is one thing: this here animal.  “This here” is frequent Aristotelian terminology; it points you toward the thing to be examined.  On the other hand, it is many things: a head and a haunch, an outside with hide and eyeballs and an inside with organs.  We can keep searching down to cells, subcellular devices, complex and simple molecules, etc.  It is one thing and many at the same time. 

We can also go in the other direction.  The horse is one horse but there are other horses.  While it is one thing, standing alone in the pasture, it is part of one larger thing: the species Horse.  And Horse is one distinct thing and yet a part of a larger thing: Mammal, etc., etc. 

Here is what occurred to me today: horse and Horse are not quite the same thing.  To speak of a horse is to say that this here animal is horsy.  It has traits that we recognize and that allow us to place it in a larger category.  To speak of Horse is to speak about something just as real but rather larger: the collection of all the existing horses. 

Aristotle got hung up on this, and had a difficult time deciding whether horse or Horse was the real object of theoretical understanding.  Much the same thing happened in the philosophy of biology.  Some have thought that Horse is an individual, bounded in space and time and therefore just as much an individual as the horse I am riding on. 

We have here a paradox.  A species is something attributable to this here animal; yet, it is also a larger thing and, more interestingly, a thing that not only extends across space but also backwards in time.  Biological classifications are categories, conceptual boxes into which we place specimens; yet Horse is also a real object that occupies both local and temporal space, back to the ancestor of all horses. 

What is the real thing, the individual animal or the species extending backward and forward (hopefully) in time?  The task of philosophy is to explain how the answer can be yes.  

Darwin & the Declaration 2

In the Declaration of Independence, the Continental Congress appeals to the “Laws of Nature and of Nature’s God”.  Is a doctrine of natural law and natural rights compatible with a Darwinian account of the evolution of human beings? 

The most common argument to the contrary can be found, eloquently and intelligently presented, in S. Adam Seagrave’s “Darwin and the Declaration” [Politics and the Life Sciences, Spring 2011]. 

The proposition ‘‘all human beings equally possess certain basic rights,’’ or the distilled Declaration, necessarily assumes two important points: 1) that there is a group of beings called ‘‘human’’ whose members are specifically different from other organic beings; and 2) that each individual within this specific group of beings equally possesses things we call ‘‘basic’’ or ‘‘human rights.’’

By contrast: 

Taking Darwin’s arguments bearing on the specific differences defining human beings in the Descent and the Origin together, the steps of this argument may be represented as follows: 1) specific differences in general are vaguely and arbitrarily defined, since they actually differ only in amount or quantity from mere individual differences; 2) the entirety of organic nature presents an ‘‘insensible’’ or continuous series rather than a discrete one, since all differences between individual organic beings are in principle commensurable; and, 3) human beings are not exempt from this situation.

According to Seagrave, the doctrine in the Declaration requires an essentialist theory of species.  Every species is defined by a specific set of traits such that every member of the species has that set of traits and every individual who has that set of traits is a member of that species.  From the traits that define the human species, one can derive natural rights. 

In Darwin’s view, the species are distinguished only in matters of degree (some are bigger, some more intelligent, etc.)  So one species differs from another as the set of numbers from 13 to 50 differ from 45 to 76.  The distinctions between species are largely arbitrary, so there can be no essential natural rights belonging to such a messy smear of organisms. 

Darwin has been dead for 135 years, but let us assume that this is his view (I agree that it is) and that it represents the current state of Darwinian theory (it does not).  Is it true that there can be no specifically human rights if human beings differ from other animals only in degree?  No. 

Consider two rights: the right to vote and the right to drive.  Suppose that intelligence is a measurable factor and that we can place all mammalian brains on a scale from one to one hundred.  Suppose, moreover, that we determine that the capacity to make a choice and vote accordingly requires an intelligence of 67 or above.  Is it not obvious that all human beings would be above the line and all non-human organisms far below it?  The mental capacity required to participate in the franchise is like one of those height lines at the entrance to a Disneyland ride: you either get to ride or you don’t.  Taller people don’t get any advantage.  Animals don’t get on.  Likewise, being a stunt driver doesn’t get you more rights to drive than the average Joe.  Differences in degree could be the basis for specifically human rights even if that is all we have. 

The essentialist account of species has been rejected by modern biology because the latter wants a definition that covers all species great and small.  The if traits Y then species A just doesn’t work in a lot of cases of mammals, let alone plants and bacteria.  Wolves can mate with coyote; one species or two?  Horses and Donkeys can have sons but not grandsons.  Human beings qualify as species under all basic definitions: we breed only with each other and we represent the sole surviving branch on the hominin tree.  No one doubts that this is a real distinction. 

Just because the essentialist account of species doesn’t work with most species doesn’t mean that it never works.  Let us define a species by the following traits: it is a mammal and it is capable of powered flight.  That describes bats and only bats.  Let us define a species this way: one member can draw a stick figure on a white board with five lines and a circle.  A group of conspecifics can recognize that the figure indicates one of them.  That describes human beings and only human beings.  I suggest that what I just demonstrated is the power of logos.  All undamaged sons and daughters of sons and daughters have it. 

Let’s try another.  One animal watches two others.  One of the observed helps the other and the other refuses to return the favor.  The observer is offended.  I can’t be certain, but I expect that this is something all human beings and only human beings are capable of.  We are capable of conscious, deliberate, moral responsibility.  It is in that capacity that the rights mentioned in the Declaration are grounded. 

Aristotle advised us that we can’t expect the same precision in moral reasoning that we can expect in mathematics.  That doesn’t mean we can’t make rational moral judgments.  Biology is messy, but not incoherent.  Human beings are more than animals.  We are, however, at least animals.  There is the direction political theory most face.  

Darwin & the Declaration

I am participating in a webinar next weekend on “Darwin & The Declaration.”  I will also be delivering a paper on the same topic in San Francisco at the annual meeting of the American Political Science Association.  Or at least I will if the panel proposal has been accepted.  I haven’t heard for sure yet.  I am even contemplating a book on the same topic.  Offered here are some preliminary thoughts. 

The Declaration of Independence is the founding document of a republic, styled the United States of America.  That document has the purpose of defending the separation of the colonies from the mother country; its importance lies, however, in the principles on which that defense rests.  Here is the central passage.

We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness. — That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed.

Charles Darwin, who was born on the same day as Abraham Lincoln and came into his own at the same time, is the author of The Origin of the Species.  Darwin asked two fundamental questions: why do living organisms display such an astounding variety of forms and how is that these forms are so manifestly adapted to the tasks of surviving and reproducing in their environments? 

He answered the first question with descent with modification.  Just as a pair of breeding beagles produces a litter with diverse offspring, so an existing species can produce a litter of diverse subspecies.  Some of these will become distinct species in their own right. 

The answer to the second question, his fundamental breakthrough, is natural selection.  Individuals and species that are well adapted to their respective environments continue to branch out on the tree of life.  Those that are ill-adapted are culled from the tree by a failure to leave descendants.  As the tree branches out into all the available ecological niches we get not only a bewildering collection of creatures but also a progressive assortment of levels of organization, from the simplest single celled creatures to centipedes and certified public accountants. 

It is not immediately obvious how the document and the theory relate to one another.  The one speaks of inalienable rights, governments, and consent.  The other of biological descent and the struggle for survival and fecundity.  There is a common assumption, however, that the two are mutually irreconcilable.  The Declaration is a political document based on moral principles.  Descent with modification and natural selection are, to be sure, amoral processes.  If, as may be, homo sapiens inherited the earth by eradicating a considerable number of hominin species, there doesn’t seem to be anything moral about that. 

To see what is at stake here, we need to return to the Declaration.  This is what precedes the passage quoted above.

When in the Course of human events it becomes necessary for one people to dissolve the political bands which have connected them with another and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.

That famous phrase, the Laws of Nature and of Nature’s God, is pregnant with meaning.  “Nature’s God” indicates an appeal to divine authority, but only such as can be read from the Creator’s work.  The “Laws of Nature” are a valid standard only if they are in fact laws of nature. 

Confronted with Darwin’s interpretation of the laws of nature, a defender of the Declaration has three choices.  First, she could reject evolutionary theory altogether.  That would mean rejecting modern biology, as evolutionary theory is its central theory.  It would probably mean rejecting geology as well (google “young earthers). 

Second, she could argue that moral and political laws are entirely distinct from the laws of biology, much as sociologists distinguish between sex (biological concept) and gender (socially constructed).  That would mean that there are two distinct laws of nature, one supported by science and the other…by what?  Without a theological basis, the Declaration’s laws of nature become mere cultural artefacts, like a preference for pastel colors in architecture; with a theological basis, in what sense are they natural? 

The only viable alternative is to show that the laws of nature as they are articulated by modern biology in fact support the principles articulated in the Declaration.  This is what I propose to do.  I will argue that the liberty spoken of the document is another iteration of the principle of autonomy, which is itself a fundamental principle of all life.  I will argue moreover that the moral equality spoken of in the document is an emergent feature of human evolution.  I hold that modern evolutionary theory powerful supports the doctrine of the Declaration of Independence.  Stay tuned.