Science—meaning, from its Latin root, the business of knowing—has little or nothing to do with absolute truth, consensus, authority, or belief. Science is about looking into what is really going on, and in most cases, like most things, it’s complicated. Science is an endless series of guesses and questions and refinements of knowledge which do not assume they will uncover a final and for-all-time answer.
Science is a process, written into the Scientific Method. First, you observe what’s going on around you, especially the occasions and outcomes that don’t seem to make obvious sense. These things make you wonder. Second, you think deeply about them and try to imagine what’s driving the observed outcome, why things work out that way, and what’s really going on here. From your thinking, you establish a guess or a principle, theory, or hypothesis about the part that you cannot directly observe: the part that explains the why or predicts the what. Third, you think of ways that your guess might be proven either right or wrong. Fourth, you devise and conduct one or more experiments under controlled conditions that would tend to prove or disprove your theory, guess, or principle. Your bet is: “If this happens during my experiment, then I’m likely to be right. If that happens, then I’m likely wrong.” Fifth, you communicate your theory, the tests you made, and the results in enough detail so that others can understand your idea, reproduce your test, and compare their own results.
The beauty of this process is that it’s entirely limited and incremental, as well as being purely democratic. You are testing your logic and reasoning in specific cases, and you are exposing yourself to questioning and either confirmation or refutation by independent minds. If your hypothesis covers only a specialized, limited case, or does not consider or allow for alternate theories, or if your test design ignores important variables, then your results will be revealed as possessing limited value and perhaps even no value. You can only lay claim to what you state and what you test, and even then your results are only valuable in terms of what others will accept as having been proved or disproved.
It’s really a difficult and demanding way to acquire knowledge—except for all the others, which are worse.1
The linchpin of the scientific method is disprovability. Your test has to show that your hypothesis and its predictions were either right or wrong. Your hypothesis has to allow for an outcome that disproves it. But this is not always obvious.
Take, for example, the proposition or hypothesis that everything we see and experience in the universe happens according to the design of an all-powerful, all-knowing, all-seeing intelligence that stands outside space and time. It may be a comforting belief. It may even be true. But how would you disprove it? Whatever conditional test you proposed, the results could always be explained as part of this intelligence’s deeper intention. It might, for example, be trying to sharpen your wits with a conundrum, or discourage your impertinence with an unexpected result, or simply torment you with doubt. You have no way of knowing or proving anything about this overriding intelligence and its hidden purposes.
Take, for another example—one that claims scientific provenance—the propositions of string theory in physics: that every particle we encounter is actually a tiny loop of stringlike material that’s vibrating in one of a number of microscopic dimensions not observable at the human or galactic scale. It’s an elegant idea, combining notions of both matter and energy. It’s supported by elegant mathematics. It may even be true. But how do you disprove it? How do you physically examine and measure dimensions that we cannot experience? How do you determine where the vibration leaves off and the inert string material begins? Whatever test you proposed, the results could always be explained as applying to a higher and coarser level of existence, under which lies a deeper, more fine-grained level at which string theory actually operates.
This looks superficially like the older conundrums in the physical sciences: that Newton’s laws seem to apply on a human or planetary scale, but don’t exactly work out at the level of galactic interactions or at the level of subatomic particles. At the galactic scale, you have the laws of Newton refined, enlarged, and overwritten by Einstein’s theories of special and general relativity. At the subatomic scale, you have Newton refined—and, in some cases, discarded and turned on its head—by the insights of quantum mechanics. The two approaches both work in their respective realms, generate hypotheses and predictions that can be proved or disproved, and answer a lot of important questions. But relativity and quantum mechanics are so far irreconcilable under any form of mathematics, because they take fundamentally different approaches and make mutually antagonistic assumptions.2
One might think then that something similar applies to the disjunction between the older stories of creation and earlier theories about the differences among plants and animals in biology and the insights of Charles Darwin. But Darwin’s theory of evolution is not an enlargement or refinement of earlier ideas but instead a total disconnect. And the people who disagree with and perhaps are offended by the implications of Darwin’s analysis want to attack it along several fronts.3
First, they want to explain that random chance is incapable of creating complex structures. I believe this is a misreading of both the theory and the events of biology. Random chance did not suddenly create a human eye with its ability to focus for varying distances, adjust to available light levels, and detect and discriminate colors among different wavelengths of light. Somebody didn’t roll the dice just once and a full-blown set of eyes came up. Instead, extant organisms and the fossil record show many examples of different stages in this development, from the light-sensitive chemicals in one-celled animals, to collections of light-sensing cells in many different organisms, up through various kinds and qualities of eyes.
Actually, random chance does not operate at the level of structure or purpose at all. Chance only plays a part in the theory at the level of occasional and undirected mutations to the genetic material that controls the nature and expression of proteins. These mutations are happening all the time in every organism, some with positive results, some with negative results, and some making no difference at all. The test of whether a mutation is used and preserved or eventually discarded is fitness for purpose. If the mutation helps the individual thrive and breed, it will likely stay and be transmitted to the next generation. If it hurts the individual, it will either die out immediately with the host organism or disadvantage the next and future generations. If the mutation has no obvious effect, it may either die out or persist, and if the latter, it may prove beneficial or hurtful later under changing circumstances. This test of fitness for purpose is not at all random but rather the most appropriate and important test for organisms inhabiting a dangerous and changeable world. It is the only test that matters.
Second, these people claim that no one has ever observed an “intermediate form,” halfway between one species or type of organism and another. They complain that the fossil record does not show such forms in support of, for example, a transition between apes and humans, or between lizards and dinosaurs, or between any two kinds of animals and plants. They focus a great deal of attention on the 19th-century notion of a “missing link.”4
Actually, such forms exist all over the place and throughout the fossil record. Fossils of the shrew-like mammal that survived the dinosaurs have been examined in detail and demonstrate many features that predate later mammals like rodents, dogs, and humans. Fossils of early snakes and lizards show how elements of their jaw hinge became the ear canal and the tiny bones—hammer, anvil, and stirrup—essential to mammalian hearing. And the process works backward, too, because we can trace in the flipper of a whale the bones from the front foreleg of its ancestral mammal, which walked on land, and associate with its vertebrae the vestigial bones of that ancestor’s pelvis. Life on this planet is a glissando of adaptive changes, from one shape and purpose to the next, one generation to the next.
Third, the people who dislike evolution claim that it’s just a theory and as such can never be proven. This claim has some merit, because evolution as currently understood depends on two separate processes: one, a random change to an organism’s genetic material; and two, the usefulness of that change in an environment subject to many different effects and conflicting factors. Neither the mutations nor the ecological conditions can be completely reproduced in the lab in order to arrive at the major dividing line in evolutionary theory: the creation of a new species. A species is generally defined as a population that can interbreed and produce viable and fertile offspring.5 Development of a new species generally takes a long time, the right conditions, and geographic separation from the ancestral gene pool.
Actually, we can see evidence of morphological and structural changes that take place fairly rapidly. For example, in studying finches in the Galapagos Islands, Peter and Rosemary Grant saw beak shape change from one generation to the next based on the availability of various seed types. For another example, we have been conducting a large-scale experiment with various types of antibiotics that has created new generations of bacteria that are resistant to their effects. For a third example, Craig Venter has organized at least two sea-going experiments that take genetic samples every couple of miles or so in the Baltic and Mediterranean seas and in the open ocean, looking for new bacterial and planktonic genes and charting their associated capabilities for use in synthetic biology. The genetic variations he discovered suggest that what we once thought of as distinct marine species are actually more like whole genuses and families. It would take time and effort to conduct an experiment designed to consciously create an entirely new species of bacteria or plankton—but probably easier there than with any species of finch, because of the faster generations and ease of isolation with microbes—but I have no doubt that eventually such an experiment could be done.
Given that evidence of evolution seems to be all around us, in terms of structural adaptation, genetic similarities, and traceable lineages, what would it take to disprove the theory of evolution? That is, aside from the claim that genetic mutation is simply the mechanism that an all-powerful, all-knowing intelligence has chosen for the way things work on this planet.
The first disproof—or evidence leading us to doubt the processes of evolution—would be to find a child that differed significantly in phenotype (appearance, structure, and development) as well as in genotype (genetic makeup) from its biological parents.6 Such a “cuckoo” would obviously raise questions of actual origins and the possibility of a hoax: did sperm A actually meet egg B to form a zygote as claimed? But if that chain of custody or provenance could be proved, then we would have a true biological oddity that would throw the principles of evolution into a quandary.
In this discussion, I’m not concerned with one or two single nucleotide polymorphisms (SNPs) that could result from mutations occurring sometime between the separation of the gamete from the parent and examination of the embryo. Those happen all the time.7 To be a convincing disproof of evolution, the certified child would have to be so changed from its parents that a preponderance of its genetic material had no connection, its appearance was vastly different, or its genetics and nature were not even of the same genus, species, or family. Such child would represent so great a deviation from what we currently expect of genetics, obstetrics, and medical theory that we would today consider it a miraculous birth.
A second disproof of evolution would be to find two species that appear to be closely related but that had totally different genomes. It’s not hard to find two unrelated species inhabiting similar ecological niches but that have different genomes. For example, bats and birds both fly by flapping their wings, and some species of each make their living by catching and digesting insects in flight. But one is a mammal, descended from that shrew-like creature that survived the dinosaurs, and the other is an Aves of lizard-like heritage and possibly descended from the dinosaurs themselves. Similarly, humans and octopi have very similar eye structures, but one is a vertebrate living on dry land and the other is not, and the two are separated by huge genetic distances.
But what if you had two robins, or a robin and a dove, and the two birds were alike in everything else—their structures, activities, diets, morphology, and phenotype—yet their genomes were as far apart as bats and birds, or humans and octopi? Such a discovery would suggest that something else—maybe a divine and playful intelligence—was ordering the nature of life on Earth.
The third disproof would be to find another type of genetic organization at work. So far, every domain, kingdom, and phylum of organisms on this planet—bacteria, archaea, fungi, plants, animals, and you-name-its—found in the most isolated locations, from freshwater lakes under the Antarctic ice sheets to volcanic vents along the mid-ocean ranges, uses the same genetic system. The four bases of DNA—adenine, cytosine, guanine, thymine—are attached to ribose sugar rings, which are strung on a phosphate backbone and arranged in reading groups of three bases each to call for combinations from among just twenty different amino acids to make all the possible proteins used in earthly biology. Aside from minor differences—like replacing thymine with uracil, and dropping the OH group from the ribose ring’s two-prime carbon, in creating and processing RNA—everything we consider to be alive uses this same system. No organism uses just three bases, or up to five, in its genetic material, or assembles them into two-base or four-base reading groups, or makes use of any of the 500 other possible amino acids to make strange and different proteins. And no organism uses some other type of protein-coding system, perhaps based on silicon instead of carbon in its bases and sugar rings, or arsenic instead of phosphorus in its backbone.
If we found another genetic system in operation on this planet, it would suggest a separate and unique creation. It wouldn’t actually disprove “descent with variation,” which is the core of current evolutionary theory. But it would indicate that what is going on in biology is different from what we currently imagine. That would suggest some principle, mechanism, or hypothesis which our biological scientists have not yet considered and discarded.
But we haven’t discovered any such thing. And in the meantime, until we do, evolution as a hypothesis and a working model explains so much of what we see and orders our thinking so clearly—and without those nasty mathematical dislocations that separate relativity from quantum mechanics in the study of physics—that the theory of evolution has no peer. Even if it remains just a theory, it works awfully well.
1. A thought stolen from Winston Churchill: “Democracy is the worst form of government, except for all the others that have been tried.”
2. I’m not bothered by this and prefer to take a wait-and-see approach as to whether either one will prevail or some third kind of “mechanics” is waiting outside human knowledge and still to be discovered. For now, I’m content to think that, as the biomarkers and medical treatments appropriate for an elephant may be different from those for a flea, so the cosmic experience and the quantum level represent different cases.
3. Let me say here at the outset that I’m a convinced evolutionist, satisfied with the theory’s ability to explain what we see and its every encounter with developments in morphology, paleontology, and genetics.
4. The notion goes back to a creature that is not great ape and not human but has features of both and sits midway between them. The last hundred years has dredged up successive waves of skeletons of varying ages that show this progression. The confusion may lie with the misconception that we humans evolved from any of the present day or recent forms such as chimpanzees, gorillas, or Neanderthals. The truth is, all of these forms are our cousins, and together we all point back to some earlier ancestor.
5. In this context, horses and donkeys are separate species, because their offspring may survive to maturity but cannot breed a new generation. Horses and zebras are in the same situation. Rarely, however, a female mule has been known to reproduce if mated with a purebred stallion.
For a long time, H. sapiens and H. neanderthalensis were thought to be in this relationship, as separate species of the genus Homo. However, recent sequencing of the Neanderthal genome and comparison with our human genome suggest that in lineages tracing back to European populations, which came in contact with the Neanderthals between 50,000 to 30,000 years ago, some humans may possess up to 4% Neanderthal genes. This implies interbreeding with fertile offspring, and so the two groups are probably subspecies of an as-yet unnamed Homo species and not truly separate.
6. In this case, I’m not concerned with issues of adoptive parents or surrogacy, but the simple coming together of egg and sperm to form an embryo, regardless of legal conditions or laboratory circumstances.
7. And I’m not talking about chimeras, either. These are organisms resulting from one or more fused embryos, in which the individual ends up possessing cells and tissues with different genetic backgrounds. Such an individual might have both male and female organs or possess two different blood types. Chimeras are strange, but they do not violate any biological or evolutionary principles.
In ancient times, chimeras were strange creatures with misaligned body parts: head of a lion, body of a goat, tail of a lizard. Famous ancient chimeras included winged horses like Pegasus, griffins (head, wings, and talons of an eagle, haunches of a lion), or even the humanoid centaurs (half-man, half-horse) and fauns (half-man, half-goat). Needless to say, as viable anatomical structures, these creatures were and are wholly mythical.
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