The Tree of Life is Full and It’s Distinctions are Narrow: Part III

(In this series—“Our Sacred World”—we have been exploring Distinctions, and especially distinctions within The Tree of Life. In this edition we will find that The Tree is very Full and the space for radically different Kinds of things is limited by the plethora of Individuals that already exist or have existed. Where do we, or Mother Nature, draw the lines for any “kind” of living thing among this array of “individual” living things? Is a Flower really that much different than an Mammal?” Are the lines disappearing?—–see the previous two posts in this section for parts one and two.)



(Varieties of Spaniels Darwin asks us to imagine the different species in the Tree of Life as finely arrayed in their Distinctions as these varieties of Spaniels. About 21 breeds of Spaniel are generally recognized.)

In his Origin of Species, Darwin imagines, “If every form which has ever lived on this earth were suddenly to reappear…all would blend together by steps as fine as those between the finest existing varieties,” (my emphasis).

(Beetles, the most finely arrayed Order that we know. Some 380,000 species have so far been recorded and they are “the most species-rich group of insects—and insects are the most species-rich group of animals.” Above is a drawing of some species of Bark Beetle and Skin Beetle. Darwin askes us to imagine the entire Tree of life this Necessarily Detailed! One of the most famous quips in the Evolution/God debate involves these critters. Asked what he can conclude about God, from his knowledge of biology, famous British biologist JBS Haldane said, “He has an inordinate fondness for beetles.” Quote thanks to The Economist magazine.)

The Tree of Life is full! Just as we saw that it was an unbroken chain of reproduction from bottom to top (First Wonder), so now we must understand it as full laterally around and along each branching point. Intermediate forms must have existed (and then perished).

(A return to Dendrogram 2 from the First Wonder. Theoretically a tree could be drawn that included a line for each living thing that ever existed! Now that would be Full, even in comparison to the above tree where each line should be thought of as many multiples of closely related Kinds of creatures. The origin of life is bottom middle and spreading left to right. The outer arching fringe is modern times. )

Dennett insists that “Gradualism” is at the core of Evolution. Darwin realized that the great complexity, diversity, and intricate organization of living things was not possible without a God-like Designer, unless it developed slowly and gradually through minute incremental additions and improvements. Something as complex as an elephant or daffodil could not naturally come into existence in one fell swoop, that would be Vastly Improbable.

Darwin realized that the world of living things and the fossil record suggested (was evidence of) its tree-like relationship of kinds (“forms,” as he so often called them) and its gradual historical development. Large improbable leaps were replaced in his thinking by very small developments! Any singular species or kind came into its own only by the narrowing of (the Selection from) a large array of similar forms. (This point will be returned to and developed.)

(Cichlid Fish, my do these little critters love to speciate! A favorite of aquarium hobbyists worldwide, in Lake Victoria alone there are over 500 species. Now imagine each species with more diversity—varieties—than the number of species themselves! Chart thanks to Seehausen, 2006.)

At any one time, every species contains a huge amount of diversity. At any point along the growth of The Tree, we can surmise “a luxuriant growth of short-lived alternatives,” says Dennett, that are too temporary and singular to be represented in our dendrograms that encompass billions of years and vast numbers of creatures and kinds of creatures. Any line in our dendrogram should be imagined fuzzy with variants that met with little reproductive success!

It is here that we come back to that original issue of individual and kind. Each individual must be (not its own species) but almost its own variety of a species, and Darwin emphasizes that every variety is “an incipient species” because it could be naturally selected to become the dominant “form” of its historically developing interbreeding and morphologically similar kind, i.e. a species. Varieties are “a less distinct and more fluctuating form,” he wrote, but “the term species…does not essentially differ from the term variety.” Nor is the term “variety” essentially different from the term individual, I think we should conclude.

(The species Domestic DogCanis familiaris–represents an extreme; there are huge anatomical differences among its varieties, yet still one species capable of interbreeding, in an extended kind of way.)

Both Darwin and Dennett strongly object to the traditional idea of “an essence,” especially for biological phenomena. In Darwin’s day, each species of living thing was thought to have its own essence to distinguish its absolute uniqueness. In this way, Essentialism is the opposite of Gradualism. An essence was considered timeless; it was a piece in the creator’s mind—God’s Eternal Plan. An essence was considered a kind of immaterial cause that was not a part of history, nor were living kinds considered to change in time.

Today, we still occasionally use that term (as above) by saying two things are “essentially” the same or different. Technically, in philosophy, an essence is the total uniqueness and singularity of a thing as its prime quality. These are “the cuts made at the joints in nature” that Plato wanted to make, as mentioned in the introduction to this series of posts. They are the lines that delineate nature’s true individuals and kinds.

But these “joints” do not exist in the world of living things, Darwin and Dennett argue. In The Tree of Life, only The Tree itself is a singular unit approaching an essential quality; all that is in it exists only by relation to all else in it, and all that has been in it. In Dennett’s heralded book, he concludes his chapter titled “The Tree of Life” by saying, “Any acceptable explanation of the patterns we observe in the Tree of Life must be contrastive,” must only be understood in relation to the rest of the Tree and its history. To be “alive,” is to be a part of this larger whole.

(Humans in contrast to some other primates, and now add to these, in your imagination, numerous additional intermediate cases. Comparatively” is how all living things exist and must be understood.)
(Comparative Brain Sizes of Mammals. Making sense of the creatures in the Tree of Life is by comparison to each other. Numerous small distinctions must be made. Plants are not nearly so complex or integrated to have a brain or nervous system. Insects have very tiny brains that do not do much for them. Most of their behaviors are controlled by various ganglia [small neural junctions] spread throughout their body.)

There are other examples of the tight blend of various kinds of living things.

Separate species do sometimes interbreed. Wolves, coyotes and dogs not only have great morphological similarity (“form”) but can and do occasionally interbreed and bare fertile offspring. Domesticated dogs are of one species (Canus familiaris) though many of their varieties are incapable of actually mating, but due to the large and varying degree of intermediate sizes and shapes of dogs, genes from the most different varieties can co-exist and form a vast array of “mutts.”

And at the other extreme, in some cases, a difference in species and a lack of interbreeding can arise from changes that are insignificant at many other points. The Herring Gull of England apparently interbreed with the Herring Gulls of Iceland and Greenland as their range stretches westward to eventually circle the North Pole. In North America this interbreeding continues but some slight coloration variations are evident. As this species’ range crosses over to northern Asia interbreeding continues and coloration differences increase. This trend continues across Siberia and back through northern and eastern Europe until this range of birds returns to England as two different species with some color differences and a refusal to interbreed! Maybe these birds see or hear or smell something more subtle and important in their slight differences than is apparent to humans! These Gulls represent the other extreme from domestic dogs: two separate species but little anatomical (and geographic) distinction between them.

(Two Species of Gull: Herring Gull of England will breed with its kin to the west. (photos thanks to
(Lesser Black-Backed Gull of England will breed with its kin to the east, but not with Herring Gulls.)

At any one time, The Diversity of Kinds of living things is Vast and it can also be subtle. Each individual living thing is not its own kind, but almost its own variety of a kind. The Tree of Life is lush with Kinds within Kinds and Varieties within Varieties. In this sense, it exhibits an amazing Fullness.

(Dendrogram 7 [an upside down Tree]: Animals as Kinds within Kinds, and Kinds composed of Individuals. Notice the Ant, in the middle of this Tree, it is an Insect. Scientists have identified 900 thousand different species of insect and estimate there are twice that still unidentified. Total individual insects in the world is estimated to be 10 quintillion—a 10 with 18 zeros behind it. Now there is an amazingly full branch in a very full tree of life!)

Especially if we consider the Tree of Life historically, its Distinctions between species and individual living things within each species (their varieties) are very fine-grained. The Principle of Gradualism is essential to this Theory of Evolution by Natural Selection. The reality of Gradualism is supported by massive amounts of data along with the logic necessary for any Materialistic and Naturalistic theory of the character and origins of living things.

The following Wonder Six in THE TREE OF LIFE is an additional corollary of The Principle of Gradualism. AMAZING HOW SUBTLE ARE THE DISTINCTIONS IN THE WORLD OF LIVING THINGS!



(THE SPECTRUM OF VISIBLE LIGHT: Let’s talk about making Distinctions: where does the color Green start?)

A shocking contention. Our ordinary intuitions deeply mislead us when we think that there must have been “a first human,” “a first mammal” and even “the first living thing.” It is as if we believe, at some exact point, a fish gave birth to an amphibian, or a lizard gave birth to the first mammal, or life suddenly sprung from non-life. That did not happen and we must learn to give ourselves over to the spirit of Gradualism and the seamless character of The Tree of Life and we will see that the idea of a “first” is only a “supposedly important question,” says Dennett. The idea of “The First…” is misleading and means a radical change at some exact point, a break in continuity. But how else can we understand it?

Biologist Richard Dawkins makes the point in the following way. In our line of human descent, if we go back into our past in the range of “185 million generations of parents and grandparents and great grandparents…we come face to face with a fish.…[then] your fish ancestor had a fishy child, who had a fishy child, who had a child…who 185 million (gradually less fishy) generations later, turned out to be you.” In this way, Dawkins resists radical jumps, his point is No Firsts,” just infinitesimal developments all the way up (and all the way across) The Tree of Life.

Primates, a line of successive adaptations. “Primates have many features in common. In general, they have large brains, eyes that face forward, and thumbs that can bend to meet the other fingers.But can we supply further ‘missing links?’

A more formal way to think of this is that complex things, like “human,” “mammal,” and “life,” have no essence. As discussed earlier, they are not primarily one overwhelming characteristic (an essence) but a collection of traits highly associated. And when living things change, it is not because they are finally displaying what was really already there ‘deep down’ and “intrinsic” to them, i.e. their essence. Dennett phrases the point made above by Dawkins in the following way: new kinds of living things “must grow out of something less, something quasi-, something merely as if rather than intrinsic” (his emphasis). It is not that ‘in the heart’ of the ancestor that was common to both ourselves and the gorilla lurked the goal of being human. Living things are not related that way; they are far more contingent.

Darwin recognized this when imagining the reappearance of all former living creatures and the tighter blending that would create among species today. No clean and simple “definition” of the different kinds would be possible, only “a natural arrangement” would be evident. “It would be quite impossible to give definitions by which each group could be distinguished from other groups, as all would blend together,…nevertheless a natural arrangement would be possible,” said Darwin. No tight definitions possible; no essences found to sharply distinguish each kind of creature, he is contending. The Tree of Life flows and grows slowly from part to part, branch to branch, time to time.

(A simple array of hominids. Yes, we can further fill the gap between other primates and humans. It is often only a human convention to declare “firsts” and think of all living things in clearly distinguished groups with starts and finishes.)

Even the “Origin of Life” falls to this qualification. Look it up, what are the main characteristics of life? Are there four—sensation, growth, reproduction, self-regulation—are there five, are there eight? “Life” seems to be a collection from many different directions. Regardless, says Dennett, “a good Darwinian” will know how to deal with this familiar problem of “origins”; for each trait “a still simpler form” of it will be sought: a simpler form of genetic code, a simpler form of metabolism, a simpler form of flight…

And what will we find when move back in time—as if in a time machine, suggests Dennett—to this new situation of the simpler form? Will we find that simpler form distinct and outstanding due to its abilities and unusual skills in comparison to its contemporaries? Was our “fishy” ancestor—for example—better, more distinguished, than its other fishy contemporaries? Was ‘The First Living Thing’ more obviously ‘alive’ than many of its contemporaries? No! Only with large amounts of time and many further developments did one such creature turn out to be what we sometimes want to call “The First Living Thing.”

Today, Life distinguishes itself from Non-Life in many important ways, several suggested previously. But in the time span of its origin, Life displayed a “near-invisibility,” to use Dennett’s words. It did not obviously distinguish itself from many of its contemporaries and Only Time Would Tell. In the early stages, ‘Life’ was only one chemical reaction among many.

The idea “Life,” like the idea “Speciation,” has “a curious property,” says Dennett, “You can’t tell it is happening at the time it occurs.” Only many years later, many generations later, is it clear that something important had to have started in the past—many important current distinctions must now be based in some antiquity—and we may begin to search for it. It is a “retrospective coronation,” as we talked about the winner of our coin-flipping tournament in Wonder Two. This ‘origin of life,’ or ‘the first mammal,’ are understood only with hindsight.

So, many of Life’s events are not immediately obvious; they draw no clear line at the time of their supposed origin; their significance is only eventually displayed. In this way, There are No “Firsts!”

Dennett goes so far as to say, “There is not and could not be anything internal or intrinsic to the individual…from which it followed that they were—as they later turned out to be—the founder of a new species” (or even the first living thing), Dennett’s emplhasis. I feel the urge to say, “Not even some trait that was ‘small’ and beneath our notice that was there and the basis of the origination?” But Dennett’s answer is No, it is not our inability to see some break-point; it is Nature’s real and continuously unbroken form! There are no break-points; no exact joints at which to make the cuts.

That is awesome.

(Light of Iris by Georgia O’Keeffe 192

When our ancestors “won” in the game of life, it was much like the coin-flipping tournament from Wonder Two. But unlike the coin-flipping, the winner not only moved on to the next round so did its off-spring that then composed the species, the kind, as it faced its next round of challenges. Its off-spring and those off-spring’s off-spring created an array of varieties or variations even closer than the Spaniels pictured previously. It is from that array that the new winner was naturally selected, but at that time it stood out in no obvious way from its kindred contemporaries.*

And Luck did play a large role in its “conquest.” Lucky that the didn’t get stepped on in its infancy and die, or been eaten. Lucky that all its grandchildren didn’t all freeze to death in a subsequent harsh winter. Lucky that it just happened to possess the mutation in its genome that gave it a slight difference from its very similar co-specifics. Lucky that it had more luck than those others whose lines of descent were extinguished with time. As Dennett said of the coin-toss tournament, and this still applies, the winner was only revealed in hindsight, as the other competitors were pared away: “it is a retrospective coronation,” and “an historical accident.”

Our common sense understanding of Evolution is distorted in this way. We tend to think of the winners as advancing due to their own skill and superiority, smiting their competition in a very clear and deliberate way: head-on, mano a mano. That is not the way Natural Selection works. “The winners” end up chosen through a vast array of circumstances that stretch through a vast sequence of time, but survivors they are. This process is massively contingent, but The Tree of Life continues to grow based on, and shaped by, all these historical accidents!

(Fossil of a Cynodont, a mammal-like reptile about “the size of a loaf of bread and resembling a scaly rat.” 235 mya and found in South America. A mammal-ish reptile and a reptile-ish mammal. Photo and quote from National Geographic.)

Some fish slowly became more amphibian-like, and some amphibians became more reptile-like and then mammal-like and then more human-like. It is our desire for clarity that leads us to imagine sharp and once-and-for-all divergences in Evolution’s developments. It is our convention to think in terms of “firsts,” but it is not nature’s way. “So much the worse for our conventions,” says Dennett.

Dennett’s book is fulfilling its promise to challenge, and even threaten, Our Traditional Ways of Thinking. What are the implications of this extreme form of Gradualism? The Tree of Life is Full of Awe, we may come to believe; to some of us this may be threatening and even “awful” in its more modern sense.

(Awesome and Awful: Marc Chagall’s Moses and the Burning Bush (a work–like evolution itself–with prolonged history of production and revision). I have been unable to determine the meaning of the Hebrew script above the tree.. The two bursts of flame arising form Moses’ head suggest to me that This Tree is blowing his mind. I am working towards a similar response from Our Tree.)

*These are difficult concepts. I am still not sure I understand them or have them accurately stated. The issue may come down to a basic and vague issue of the unit of evolution. Is it the individual organism, the species of closely related organisms, or, as theorist Richard Dawkins has suggested, the genes that compose the individuals? If we are looking for something exact and continuous without change in the history of evolution, it may only be small bits of genetic code, not any of the fleeting phenotypic forms they acquire, i.e. organisms. I am still working on this question.



3 thoughts on “The Tree of Life is Full and It’s Distinctions are Narrow: Part III

  1. Greg, Thanks for sending the Tree of Life article. Very interesting and I think well stated. To me the problem is not how full the tree is and how gradual the changes/differences, but that we are in a great extinction exacerbated by human-caused climate change. The tree will look and behave much differently in 20 or 50 years than it had for hundreds of thousands of years! All due to our arrogance as a species on that tree.

    Dr. Mark K. Wourms
    Executive Director
    Bernheim Arboretum and Research Forest
    PO Box 130, KY 245
    Clermont, KY 40110
    (502) 955-8512


    1. Thanks for the comment! Ya, we are messing it up. Humans need to treat “The Tree” with great reverence! It and the forces that created it Could Be held very near and dear to us. Wait for the next and final post; Ill be interested in your reactions.
      Thanks Mark, and thanks for your beautiful place—I need to get down there again.


      1. Mark, a further thought.
        Do you agree with the No Firsts contention? It is a shocking consequence of the Extreme Gradualism argued for that you seem to accept but find of not much consequence. Both those points are Mother Nature being very Philosophically Provocative. She is providing evidence Against Our Stubborn Individualism and giving us an opportunity to understand Nature in a Reverential Way. It is a Nature Religion Connection, and the basis for the respect and self-control we need to overcome our various natural and human crises.
        It is also a way to overcome the gap left by some forms of Atheism—the emotional gap of “connectedness”—and further ammunition to combat the Religious Mythology of especially Fundamentalist Christianity and Islam.
        So, I think that the Fullness of The Tree and the Philosophical Holism it supports may be a key to a better world. At least it makes me feel better (Ah, isn’t that nice; GregWW feels better!) and provides me with some ‘spiritual’ motivation.


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