The Distinctions in The Tree of Life

(Depiction of The Forests of the Permian Period, all lost in “The Great Dying” of 250 mya.)

Our thesis has been the Wholeness of The Tree; its Gradualness of growth and change; its Continuity from bottom to top and side to side; its Contrasting set of Qualities and Values; Its Unity of Process. In this sense, Darwin and Dennett have argued that The Distinctions within The Tree are secondary, interdependent, and vague by comparison to this massive swath of overall Creative Unity. A true source of Awe, say I: A massive piece of Organic Art.

And Darwin said at the end of his “Origin” : “Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”

The Distinctions in The Tree of Life have Increased with Time

Dendrogram Eleven: An unusual one, from page 87 of Dennett’s Darwin’s Dangerous Idea [1995]; apparently specially formulated for this book. It clearly shows the explosion of diverse species with the discovery of the multicellular way of living at about 700 million years ago—that is 700 thousand of thousands of years in the past.)

In spite of its shocking Unity within a Massive Diversity, Lines of Distinction are evident. A Daylily is not an Elephant, as was initially suggested at the start of this series.

Darwin acknowledged this when suggesting we imagine all the “forms” that have ever existed returning to The Tree to create a most minutely grained array. When we look from one major branch to another, one side of the tree to another, “a natural arrangement” would be evident. Flowering Plants are not Mammals. And from bottom to top, the earliest creatures to the most evolved current forms, huge differences in size and complexity jump out at us. All the mitigating and intermediate living structures help to soften these largest differences, but these large differences do now exist in themselves as stark contrasts.

(The Species of Domestic Dog is a good example of the significance of Intermediate Forms. Its unity as a single gene pool and interbreeding population is only assured by its Variety of Varieties. The Tree of Life exists with this kind of extension of relations, only more so.)

Biologist Richard Dawkins suggests the following connection of relations within The Tree. At many points on a single branch and even between major branches of life, there can be a variety of Evolutionary Routes between any two distinct kinds of creatures. One route of development is assured, the one that actually exists through The Tree when two forms are traced back to their Nearest Common Ancestor and then their varied development understood from there. Dawkins then contends that other routes may be possible with different Evolutionary Pressures applied. Current forms are still evolving. The following example is a stretch, but it conveys the intended point, Maybe someday Pigs Will Fly!

Intermediate kinds of species are crucial to The Unity of The Tree of Life, but there are specific forces working against their survival. First, Competition will tend to hollow out The Tree. Darwin: “competition will generally be most severe between those forms which are most nearly related to each other in habits, constitution and structure…all the intermediate forms will tend to become extinct”(my emphasis).

(Hollowing out The Tree: Nine of our most prominent ancestors that are among the approximate 25 extinct species of Hominins–for which we have fossil evidence–that compose our evolution from our common ancestor with the chimpanzee over the past 7 million years: from Sahelanthropus tchadensis–oldest– upper left, to Homo floresiensis bottom left, to Homo neanderthalensis–most recent– bottom right. See the amazing six minute video by American Museum of Natural History: Seven Million Years of Human Evolution. Highly recommended!)

Second, Distinctions can be self-reinforcing. Once a living creature has begun to establish a “new way of making a living,” as it is often put, those initial developments set up (and foreclose) many secondary developments/adaptations. A very interesting discussion occurs in Dennett’s book concerning these “logical” developments in living bodily structure.

For example, it makes sense to have opposing thumbs and fingers, for grasping. A single finger at the end of an arm would not nearly be as useful. And the same for two arms as opposed to just one; or legs—two, four, six…make more sense in an engineering way than does just one leg, or three or five. And yet in fish, having one main central source of power or “push” in the rear—the tail—works quite well for locomotion in water. (These kinds of facts should also be taken into consideration for Wonders Three and Four from Part II of this series: Evolution by Natural Selection does discover Value and Efficiency, and in that way is (or is like) an intelligent process!) Once started down an evolutionary path, certain further adaptations become possible and more likely, while others less likely and less opportune.

(Bilateral Symmetry is smart! Mother Nature has well designed creatures.)

But as Dendrogram Eleven makes clear, several large Evolutionary Developments established a foundation from which a growing diversity and complexity of ways of life could occur. The revolution of the Nucleated Cell at about 1.4 billion years ago, and then the onset of Multicellular Creatures 700 million years ago. The first started the development of internal complexity, the “equipment” (says Dennett) to then diversify into many different relationships with the environment by which to survive and reproduce, as demonstrated in the multicellular stage. A diversity of Distinctions now started to become dramatic and self-reinforcing.

Third, Extinctions have hollowed out the array of forms in The Tree of Life. An elephant is very different from a day lily. Many different kinds of creatures have occurred in Life’s History, but in the Five Major Extinctions whole classes of significantly different creatures were lost. This set the creatures that survived (or were yet to evolve) into sharper contrast.

Crocodiles are an ancient life form—a “living Fossil”—that continues into today, as are horseshoe crabs; both are quite distinct in contrast to more modern creatures. It is estimated that for every one species alive today about 100 species have gone extinct. (Most specific extinction information from below from National Geographic 9/26/19)

(Dendrogram Twelve: an edited Tree of Exiting Life Forms. Notice in the middle of this tree ‘a bare spot.’ an open area below the three birds [Aves] and above the crocodilian and snake; that is where the synapsids and dinosaurs were before their extinction. Birds are now in sharper relief without the raptors that led to them. Thanks to FAIRHOPE GRAPHACS for the use of this tree.)

THE FIVE MAJOR EXTINCTIONS that helped to Distinguish the Life Forms in our current Tree of Life.

  • The Ordovician Extinction, 445 mya. Most life was in the sea, and up to 85% of species were lost at this time. Caused by plate tectonic movement, the most well know class of animal lost were massive varieties of trilobite, one of the most common animals of the time.
(Ya gotta love those Trilobites! So far over 20,000 fossil species described. With us no more!)
  • Late Devonian Extinction, 370 mya. Caused by volcanic activity and meteor strikes and resulted in a 75% extinction rate of living things mostly in the sea. Most noted victims were Conodonts, and Goniatites (which were similar to modern octopus and squid.) Also lost were the dominant fish of these times, the Placoderms; not a single species of them survived this and the next extinction.
(Not Nice! Conodonts: eel-like creatures with maximum size so far found to be about 1.5 ft. or 40 cm. 11 fossil imprints exist and plenty of fossilized teeth.)
(What a shame, we lost all the Armored Fish! Placoderms–“plate skinned” fish–dominated the waters in the Devonian Period and ranged from 15 cm. to 9 m. in length. An apex predator, there are over 400 fossil species identified.)
  • “The Great Dying” of the Permian-Triassic Extinction, 250 mya. 96% of sea species and 75% of land species perished. Caused by massive volcanic activity in Siberia which released huge amounts of carbon into the air and onto the land. Lost in the carnage were most varieties of synapsid, who ruled the land before this extinction and before the dinosaur.

(A synapsid, Lystrosaurus or “shovel-lizard, is one of the ancestral relatives of mammals. Once referred to as a “mammal-like lizard,” now referred to as a “stem mammal.” Six recognized fossil species with sixes from .5m to 2.5m long.)
(Another cute one? Also lost, the Placerias, an anomodont. Grew to one U.S. ton—2,000 lbs., just smaller than British tonne.)
  • The Triassic-Jurassic Extinction, 200 mya. Again it was volcanos, but this time from the middle of Pangaea that broke apart the ancient supercontinent and formed the Atlantic Ocean. It is estimated that 80% of all species went extinct. This extinction finished off the Conodonts. Many forms of Crocodile-like creatures also were extinguished but those that survived then diversified and flourished into the Jurassic period were they eventually met their almost complete end. It is this extinction that starts the age of the dinosaur.
(The array of extinct Crocodilians. Some lived completely in the sea. Others rose on their hind legs and ran for short distances! As small as 2 ft. (40 cm.) or as large as 40 ft. (12 m.), some had long legs and somewhat resembled a dog. Once a vast order, now only a few of its families and species currently survive.)
  • The Age of Reptiles comes, and then goes with The Late Cretaceous Extinction, 65 mya. The cause of this extinction is still debated but it is generally connected to the impact of a 7.5 mile (12 km.) rock from space crashing into the Earth at 45,000 mph. off the coast of the Yucatan Peninsula of today’s Mexico. 76% of all species were extinguished including all dinosaurs except for one of its branches, birds! This is the last of the Great Extinctions, but of course many argue that we are currently in the midst of another extinction.
(Amazing to think that Dinosaurs came in an array, as they must, of course. Above are the Tyrannosauroids.)
(Sauropsods—All gone!— of which the Brontosaurus is our most commonly known example: four-legged, longnecked herbivorous dinosaurs.)
(Dendrogram Thirteen: partial Tree of Sauropod Dinosaurs. 300 described fossil species so far! From Wilson & Sareno, 1998)


How vast The Tree of Life! How full! How amazing the process of Evolution! This short review of major extinctions has made me aware of how many times The Great Tree has had to regrow itself or at least huge portions of itself. And yet, we can return to the opening statement:

“Our thesis (is) the Wholeness of The Tree; its Gradualness of growth and change (between extinctions); its Continuity from bottom to top and side to side; its Contrasting set of Qualities and Values; Its Unity of Process. In this sense, Darwin and Dennett have argued that The Distinctions within The Tree are secondary, highly interdependent, and vague by comparison to this massive swath of overall Creative Unity. A true source of Awe, say I: A massive piece of Organic Art.”

And Dennett says at the end of his Darwin’s Dangerous Idea : “The Tree of Life, an utterly unique and irreplaceable creation…(It) is neither perfect nor infinite in space or time, but it is actual, and if it is not Anselm’s ‘Being greater than which nothing can be conceived,’ it is surely a being that is greater than anything any of us will ever conceive of in detail worthy of its detail. Is something sacred? Yes, say I with Nietzsche. I could not pray to it, but I can stand in affirmation of its magnificence. This world is sacred.”

THANK YOU, I hope you learned as much as I did! For details, Please return to the previous 4 posts in this series, temporarily stored in The Connection, Varied Topics section.

One thought on “The Distinctions in The Tree of Life

  1. Very interesting Greg. I did not know much about this ( only the dinosaurs were wiped out ). Saw a recent article on sharks teeth discovered in the millions at the bottom of the Indian Ocean. Will send to you if I can find it.


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