Are We the Pinnacle of Evolution?

The term “evolution” conjures the picture of initially unicellular life marching triumphantly towards greater size and increasing complexity --and of humans as the undisputed pinnacle of evolutionary history. This smug view is compounded by the widespread notion that evolution and progress are synonyms. It is common in textbooks and popular accounts to depict evolutionary series as ladders --from hyracotherium, the “dawn horse”, to the modern horse; or from Australopithecus to exalted Homo sapiens.

       But, as Stephen Jay Gould has shown in his book Full House, ladders are misleading. Hyracotherium is indeed the ancestor of modern horses, and, yes, there is a continuous line from him to present-day Equus. But the line twists and turns in time, branching endlessly so that the “dawn horse” is also the grandfather of countless other species, some living, but most extinct. The same is true of the line of descent going from Australopithecus, of “Lucy” fame, to modern humans. The line is not a line --it’s a bush. Neanderthals, who can also claim Lucy as their grandmother, are not our direct ancestors.

       Evolutionary lineages in general are not linear. Today’s living species, which we might represent as the outer leaves of an evolutionary tree, are attached to twigs, which are attached to larger twigs, which shoot off from branches, which sprout from larger branches, which emerge from an ancient common trunk going way back into the past --some 3.6 billion years-- to the first living organisms, a kind of bacterium.

       The ladder representation conveys the false idea that evolution is going somewhere --that those first bacteria somehow knew they were to become us. But if ladders had any truth in them then the lower rungs ought to be extinct to open the way for the young, so to speak. Bacteria, however, thrive today. What’s more, by their diversity, by their presence in every nook and cranny of the earth, by their longevity, and by their sheer numbers, bacteria are and always have been the dominant organisms in this planet, as Gould argues in Full House. If we go back far enough, you and I have a common ancestor who was a reptile; go back even further and we will find we are related to a fish. Yet reptiles and fishes are alive and well today. Not the same species, to be sure, but modern ones which may be our cousins many times removed. Humans are not the end point of evolutionary history --all species living today are.

       Natural selection, the motor of evolution, does not have a plan. The only criterion for survival is adaptation to existing conditions. The dinosaurs didn’t die out because they were evolutionary failures or because they were less perfect animals than present-day animals. In fact, dinosaurs have been one of the most successful groups in the history of life. They dominated macroscopic life for over 200 million years. Mammals, in contrast, have only been conspicuous for some 60 million years. The dinosaurs died because their environment changed abruptly when a very large meteorite or comet collided with the earth, some 65 million years ago.

       Consider another example of the progress fallacy. Mammoths, the hairy ancestors of modern elephants, were well adapted to life in the latest Ice Age. Hairless elephants are well adapted to present-day conditions. But a hairless elephant, as Gould points out, is not a cosmically better elephant. When another ice age comes --and it will--, a hairy elephant will be more likely to survive.

       And this brings on my final point. Possible hairy elephants of the frigid future will NOT be mammoths. The mammoth is dead and gone. If elephants ever have hairy descendants, those descendants will be new adaptations to cold weather. They may conceivably look somewhat like mammoths --with all the hair and stuff--, but the resemblance will stem from the fact that both species are solutions to a similar problem --like bats and birds. Extinction, as diamonds, is forever.

A monk in his garden

Imagine a monastery in Moravia, and in the monastery a garden, and in the garden a monk. The monk is busy handling pea plants in pots, wrapping the flowers in paper bags after carefully dusting them with pollen from a different variety of the pea plant. He is no ordinary monk. He has studied mathematics and science. In a few years’ time he will be elected abbot of the monastery --which will force him to abandon his scientific work.

       He is Gregor Mendel, the father of the science of genetics, and his experiments with pea plants will provide the missing link to Charles Darwin’s theory of evolution by natural selection. But not before both Darwin and Mendel are dead and gone.

       Darwin will die in 1882, still plagued by the mystery of the mechanism of inheritance. The theory of evolution by natural selection requires that heredity work in such a way that mutations --or fortuitous variations in the hereditary makeup of an organism-- are passed on intact to offspring. This would guarantee the conservation of advantageous mutations (a longer neck in giraffes, a change in pigmentation in moths living in soot-covered trees in central England); whereas the alternative mechanism of blending inheritance --whereby offspring simply strike  an average between the characteristics of their parents-- would cut mutations in half with each generation, rapidly diluting their effect, advantageous or otherwise.

       Mendel will die in 1884 in total obscurity. The revolutionary nature of his experiments will only be recognized in 1904, when three European botanists will independently rediscover his work.

       Ironically, Darwin’s would-be savior was already working with his pea plants when the great scientist published The Origin of Species, in 1859. Mendel’s method of “hybridization” was straightforward. First he would open a pea flower before it was fully developed, removing the anthers (or male sexual organs) with tweezers to avoid self-pollinization. Then he would dust the flower’s stigma with pollen from the selected variety, immediately wrappping the flower in a paper bag to keep away other pollen. Finally, he would wait patiently for the plant to produce seeds and for the seeds to produce the next generation of plants. Mendel then recorded the results.

       The monk chose pea plants because they have traits (such as blossom color and plant height) that are easily distinguishable and that breed true. Thus, he crossed six-foot plants with one-foot plants, and plants with purple blossoms with plants with white blossoms. Would the result be three-foot plants with mauve-colored blossoms, as the popular theory of blending inheritance dictated?

       In contrast with other botanists who had performed hybridization experiments before him, Mendel had studied mathematics and was an able statistician. He found that when he crossed six-footers with the short variety the first-generation hybrids were all six-footers. No intermediate-sized plants were produced. However, when these first-generation hybrids were allowed to self-pollinize, the result was astonishing --the second generation included both tall plants and short plants, and in an approximately three-to-one ratio. A similar result was obtained for six other contrasting traits.

       Mendel’s conclusion was that, contrary to popular belief, the parent’s traits are not blended in the offspring. Inheritable characteristics are determined by units of inheritance that are segregated rather than blended in the offspring, with certain traits dominating over their “recessive” opposites (i.e. long stem versus short stem). Today we call these units “genes.” Mendelian genetics meshed perfectly well with natural selection. In the first decades of this century, genetics and evolution became integrated in what is known as the synthetic theory of evolution.

Literary Theme with Biological Variations

In his short story "Pierre Menard, Author of Don Quixote" the Argentinian writer Jorge Luis Borges recounts the story of a symbolist author in turn-of-the-(last)century France who endeavors to rewrite Miguel de Cervantes’ celebrated work. Pierre Menard, however, is no mere parasite intending to copy or paraphrase Cervantes. His intent is to write a verbally identical book based on his own experience. Menard, alas, dies after completing only two chapters. But how fascinating those two chapters can be! Read as the work of a twentieth-century writer, Menard’s Don Quixote is a completely different book.

This, of course, is only possible in Borges’ brilliant fantasy world. In real life, if you hold two books in your hand --for example, Cervantes’ Don Quijote de la Mancha and Menard’s Don Quijote de la Mancha--, and the books correspond word by word, or almost, you immediately smell a rat. The books must --to say the very least-- have a common ancestor. They can’t really be independent.

Odoriferous rodents of the same kind assail the discerning noses of biologists when they compare organisms from the present and from the past using the tools of old and new biological disciplines such as embryology, anatomy, genetics, and biochemistry. Charles Darwin’s original treatise was a steamroller of evidence for “descent with modification.” Today, evolutionists possess further detailed and consistent proof of the fact of biological evolution.

Consider the backbone in humans. Humans, as you probably know, walk upright most of the time. Our backbones are placed in the back (duh). But look at the famous roof at the Museo de Antropología, in Mexico City. Here it is: 

A hypothetical Cosmic Engineer designing humans from scratch would have endowed us with sturdier “backbones” passing through the center of the torso, not along the back. As things are, we are well adapted to an upright posture, but not perfectly adapted, because we have only recently evolved from ancestors that went about on all fours. Imperfections such as are manifest in anatomical studies argue for evolution and against design.

Anatomy, physiology, embryology and other tools that were already available in Darwin’s time can probe only so deep into the similarities of organisms, and go only so far back in time. It is the more recently developed field of molecular biology that provides the most detailed and convincing evidence that we are all, from human to bacterium, ultimately related by descent from common ancestors.

The organic compounds known as aminoacids can be numbered in the hundreds, yet all bacteria, plants, animals and fungi synthesize all their proteins based on just 20 aminoacids, the same 20 for all living beings. Further, for all its staggering diversity, all life on Earth depends on the same few chemical pathways (fermentation, photosynthesis, respiration) to produce energy and build cell components. The molecular and chemical uniformity of life can only be accounted for by evolution.
Molecular biology is unique as a tool for comparative analysis of species in that it allows scientists to precisely quantify the degree of similarity of different organisms. The protein cytochrome c of humans is identical to that of chimpanzees. It differs by one aminoacid from that of rhesus monkeys, by 12 from that of horses, and by 21 aminoacids from that of tuna fish. Comparing the DNA of two species, molecular biologists can now even determine approximately how far back in time the species’ most recent common ancestor lived in the same way that linguists can tell how recently two languages diverged from a parent language by analyzing their similarities.

This is only a paltry sample of facts that can only be explained by evolution. Darwin himself provides many more in The Origin of Species. Today all scientists agree that, as Theodosius Dobzhansky, a leading evolutionist, once said: “Nothing in biology makes sense except in the light of evolution.”

Darwin's Nose

The course of history rarely hinges on the impact of a single individual...let alone an individual’s nose. Yet Charles Darwin’s nose --which one captain Robert FitzRoy disliked at first sight-- was a hair’s breadth from disqualifying its owner for the post of “naturalist” aboard HMS Beagle, departing on a voyage around the world. The young Darwin had been recommended for the job by his mentor, professor John Steves Henslow, after several candidates had turned down FitzRoy’s overtures.

Charles’ father, Dr. Robert Darwin II, was a respected physician, the son of another doctor Darwin, Erasmus, who at the close of the 18th century had proposed one of the many theories of evolution then in vogue. The ponderous and imposing doctor Robert wanted his son to follow in his footsteps, but Charles gave up medicine after witnessing an operation performed without the aid of anesthetics. In the wake of this incident, doctor Darwin had decided that his son should become a clergyman. This decision seemed to suit the indolent Charles, and so he set off to Cambridge University.

Charles Darwin had some time earlier began collecting insects spurred by his cousin William Darwin Fox. The new hobby soon became an obsession. “I am dying by inches, from not having anybody to talk to about insects,” he wrote to his cousin.

Charles sought after new beetle varieties. He was more interested in collecting as many different kinds as he could get his hands on than in dissecting and classifying them. “I will give proof of my zeal,” he wrote in his autobiography.
One day, tearing off some old bark, I saw two rare beetles and seized one in each hand, then I saw a third and new kind, which I could not bear to lose, so that I popped the one which I held in my right hand into my mouth. Alas! It ejected some intensely acrid fluid which burnt my tongue so that I was forced to spit the beetle out, which was lost, as was the third one.

It was at Cambridge that Darwin, aged 22, met the botanist J. S. Henslow. Henslow, a revered teacher, developed a great fondness for his pupil. “What a fellow that Darwin is for asking questions,” he once remarked. Chalres, his mind still set on a career in the Church of England, had finally found a passion.

One day, returning home from a walking tour of North Wales with the geologist Adam Sedgwick, Charles found a letter from Henslow waiting for him. Her Majesty’s Ship Beagle, commanded by captain Robert FitzRoy, was soon to set sail for South America on a scientific voyage that would eventually take her around the world. “Capt. F. wants a man (I understand) more as a companion than a mere collector and would not take any one, however good a naturalist, who was not recommended to him likewise as a gentleman,” wrote Henslow.

FitzRoy was rather cold on his first meeting with Darwin. Charles was a bourgeois from a liberal family, whereas the captain was an aristocrat and a headstrong conservative. FitzRoy felt particularly hostile toward the young man’s nose. It was not the nose of a man who could withstand the hardships of life at sea. But in the end Charles’ enthusiasm and good nature won the seaman over and he was given the position.

And so Charles Darwin embarked in what was to be a five year trip around the world, during which his early belief that species were immutable was to be shaken and eventually shattered, to be replaced by the conviction that they had evolved through the ages. Twenty-odd years after Darwin’s return to England, the naturalist poured the results of his musings in a beautiful book that changed the world --The Origin of Species.