Evolution Topics by Dr. Francisco AyalaApril 27, 2010
These topics were written by Dr. Francisco Ayala, Professor of Biological Sciences and Philosophy at the University of California, Irvine. He is a member of the President’s Committee of Advisors on Science and Technology, and has been President and Chairman of the Board of the American Association for the Advancement of Science.
Dr. Ayala is a highly respected evolutionary biologist who has received the 2010 Templeton Prize, an award issued each year by the John Templeton Foundation to a person “who has made an exceptional contribution to affirming life’s spiritual dimension, whether through insight, discovery, or practical works.” He is perhaps best known scientifically for his research into the evolutionary history of the parasite scientists have associated with malaria, with an eye toward developing a cure for the disease. He also pioneered the use of an organism’s genetic material as molecular clocks that help track and time its origins.
But for the past 30 years, he has been at the forefront of battles to keep creationism and its more-sophisticated offshoot, intelligent design, out of public-school biology classes, noting that they actually represent religion masked as natural science. At the same time, he has vigorously argued that religion is a vital pillar in American life, thereby confusing those who confuse religion with being anti-science.
The US scientific enterprise is the envy of the world, he says, and the country is the most religious of any nation in the western world. “It is nothing short of tragic to see these two pillars of society are often seen as in contradiction with each other,” he said during the award’s presentation Thursday at the National Academy of Sciences in Washington. “Properly understood, there can be no contradiction because they deal with different subjects,” he said.
Although he has been reluctant over the years to describe his own religious leanings, Mr. Ayala argues that religion and science are “different windows” for looking at the world. Only when each tries to make “assertions beyond their legitimate boundaries” do the two appear to clash.
“Science gives us an insight on reality which is very important; our technology is based on our science,” he says. “But at the end of the day, questions important to people, questions of meaning, purpose, moral values, and the like” are not answered through science.
Beyond championing the roles science and religion can play in their respective domains, he also has argued that “scientific knowledge, the theory of evolution in particular, is consistent with a religious belief in God, whereas the tenets of creationism and the so-called intelligent design are not.”
While intelligent-design advocates point to the complexity of many biological processes as too intricate to have emerged from a random evolutionary process, Ayala points to many of biology’s flawed designs as evidence of a lack of intelligence behind them. “Any engineer who would have designed the human jaw bone would be fired the next day,” he says. Instead, he terms biology’s flawed products as “a consequence of the clumsy ways of nature and the evolutionary process.”
Ayala, a professor at the University of California at Irvine, began his dual journeys into science and religion during his formative years in Spain, where he graduated from college with a bachelors degree in physics. After graduation, he studied theology there, and five years later became an ordained priest. But during his theological studies, two geneticists took him under their wing, and in 1961, Ayala moved to New York to take up graduate studies in evolutionary biology and genetics at Columbia University. And he left the priesthood. Over the course of his career, he has won awards for his scientific work and has served on several high-level science advisory panels in the US. In 2001, President George W. Bush awarded Ayala the National Medal of Science.
In a prepared statement, John Templeton Jr., the president and chairman of the John Templeton Foundation said, “Ayala’s clear voice in matters of science and faith echoes the Foundation’s belief that evolution of the mind and truly open-minded inquiry can lead to real spiritual progress in the world.” Ayala has donated the $1.42 million prize to charity.
I advance three propositions. The first is that Darwin’s most significant intellectual contribution is that he brought the origin and diversity of organisms into the realm of science. The Copernican Revolution consisted in a commitment to the postulate that the universe is governed by natural laws that account for natural phenomena. Darwin completed the Copernican Revolution by extending that commitment to the living world.
The second proposition is that natural selection is a creative process that can account for the appearance of genuine novelty. How natural selection creates is shown with a simple example and clarified with two analogies, artistic creation and the “typing monkeys,” with which it shares important similarities and differences. The creative power of natural selection arises from a distinctive interaction between chance and necessity, or between random and deterministic processes.
The third proposition is that teleological explanations are necessary in order to give a full account of the attributes of living organisms, whereas they are neither necessary nor appropriate in the explanation of natural inanimate phenomena. I give a definition of teleology and clarify the matter by distinguishing between internal and external teleology, and between bounded and unbounded teleology. The human eye, so obviously constituted for seeing but resulting from a natural process, is an example of internal (or natural) teleology. A knife has external (or artificial) teleology, because it has been purposefully designed by an external agent. The development of an egg into a chicken is an example of bounded (or necessary) teleology, whereas the evolutionary origin of the mammals is a case of unbounded (or contingent) teleology, because there was nothing in the make up of the first living cells that necessitated the eventual appearance of mammals.
I conclude that Darwin’s theory of evolution and explanation of design does not include or exclude considerations of divine action in the world any more than astronomy, geology, physics, or chemistry do.
The Darwinian Revolution
The publication in 1859 of The Origin of Species by Charles Darwin ushered in a new era in the intellectual history of humanity. Darwin is deservedly given credit for the theory of biological evolution: he accumulated evidence demonstrating that organisms evolve and discovered the process, natural selection, by which they evolve. But the import of Darwin’s achievement is that it completed the Copernican revolution initiated three centuries earlier, and thereby radically changed our conception of the universe and the place of humanity in it.
The discoveries of Copernicus, Kepler, Galileo, and Newton in the sixteenth and seventeenth centuries had gradually ushered in the notion that the workings of the universe could be explained by human reason. It was shown that the earth is not the center of the universe, but a small planet rotating around an average star; that the universe is immense in space and in time; and that the motions of the planets around the sun can be explained by the same simple laws that account for the motion of physical objects on our planet. These and other discoveries greatly expanded human knowledge, but the intellectual revolution these scientists brought about was more fundamental: a commitment to the postulate that the universe obeys immanent laws that account for natural phenomena. The workings of the universe were brought into the realm of science: explanation through natural laws. Physical phenomena could be accounted for whenever the causes were adequately known.
Darwin completed the Copernican revolution by drawing out for biology the notion of nature as a lawful system of matter in motion. The adaptations and diversity of organisms, the origin of novel and highly organized forms, even the origin of humanity itself could now be explained by an orderly process of change governed by natural laws.
The origin of organisms and their marvelous adaptations were, however, either left unexplained or attributed to the design of an omniscient Creator. God had created the birds and bees, the fish and corals, the trees in the forest, and best of all, man. God had given us eyes so that we might see, and He had provided fish with gills to breathe in water. Philosophers and theologians argued that the functional design of organisms manifests the existence of an all-wise Creator. Wherever there is design, there is a designer; the existence of a watch evinces the existence of a watchmaker.
The English theologian William Paley in his Natural Theology (1802) elaborated the argument-from-design as forceful demonstration of the existence of the Creator. The functional design of the human eye, argued Paley, provided conclusive evidence of an all-wise Creator. It would be absurd to suppose, he wrote, that the human eye by mere chance “should have consisted, first, of a series of transparent lenses … secondly of a black cloth or canvas spread out behind these lenses so as to receive the image formed by pencils of light transmitted through them, and placed at the precise geometrical distance at which, and at which alone, a distinct image could be formed … thirdly of a large nerve communicating between this membrane and the brain.” The Bridgewater Treatises, published between 1833 and 1840, were written by eminent scientists and philosophers to set forth “the Power, Wisdom, and Goodness of God as manifested in the Creation.” The structure and mechanisms of man’s hand were, for example, cited as incontrovertible evidence that the hand had been designed by the same omniscient Power that had created the world.
The advances of physical science had thus driven humanity’s conception of the universe to a split-personality state of affairs, which persisted well into the mid-nineteenth century. Scientific explanations, derived from natural laws, dominated the world of nonliving matter, on the earth as well as in the heavens. Supernatural explanations, depending on the unfathomable deeds of the Creator, accounted for the origin and configuration of living creatures — the most diversified, complex, and interesting realities of the world. It was Darwin’s genius to resolve this conceptual schizophrenia.
Darwin‘s Discovery: Design without Designer
The strength of the argument-from-design to demonstrate the role of the Creator is easily set forth. Wherever there is function or design we look for its author. A knife is made for cutting and a clock is made to tell time; their functional designs have been contrived by a knifemaker and a watchmaker. The exquisite design of Leonardo da Vinci’s Mona Lisa proclaims that it was created by a gifted artist following a preconceived purpose. Similarly, the structures, organs, and behaviors of living beings are directly organized to serve certain functions. The functional design of organisms and their features would therefore seem to argue for the existence of a designer. It was Darwin’s greatest accomplishment to show that the directive organization of living beings can be explained as the result of a natural process, natural selection, without any need to resort to a Creator or other external agent. The origin and adaptation of organisms in their profusion and wondrous variations were thus brought into the realm of science.
Darwin accepted that organisms are “designed” for certain purposes, i.e., they are functionally organized. Organisms are adapted to certain ways of life and their parts are adapted to perform certain functions. Fish are adapted to live in water, kidneys are designed to regulate the composition of blood, the human hand is made for grasping. But Darwin went on to provide a natural explanation of the design. He thereby brought the seemingly purposeful aspects of living beings into the realm of science.
Darwin’s revolutionary achievement is that he extended the Copernican revolution to the world of living things. The origin and adaptive nature of organisms could now be explained, like the phenomena of the inanimate world, as the result of natural laws manifested in natural processes. Darwin’s theory encountered opposition in some religious circles, not so much because he proposed the evolutionary origin of living things (which had been proposed before, and accepted even by Christian theologians), but because the causal mechanism, natural selection, excluded God as the explanation for the obvious design of organisms.
The Roman Catholic Church’s opposition to Galileo in the seventeenth century had been similarly motivated not only by the apparent contradiction between the heliocentric theory and a literal interpretation of the Bible, but also by the unseemly attempt to comprehend the workings of the Universe, the “mind of God.” The configuration of the Universe was no longer perceived as the result of God’s Design, but simply the outcome of immanent, blind, processes. There were, however, many theologians, philosophers, and scientists who saw no contradiction then nor see it now between the evolution of species and Christian faith. Some see evolution as the “method of divine intelligence,” in the words of the nineteenth century theologian A.H. Strong. Others, like the American contemporary of Darwin, Henry Ward Beecher (1818-1887), made evolution the cornerstone of their theology. These two traditions have persisted to the present. Pope John Paul II has recently (October 1996) stated that “the theory of evolution is more than a hypothesis. It is … accepted by researchers, following a series of discoveries in various fields of knowledge.” The views of “process” theologians, who perceive evolutionary dynamics as a pervasive element of a Christian view of the world, are well represented in this volume.
Natural Selection as a Directive Process
The central argument of the theory of natural selection is summarized by Darwin in The Origin of Species as follows:
As more individuals are produced than can possibly survive, there must in every case be a struggle for existence, either one individual with another of the same species, or with the individuals of distinct species, or with the physical conditions of life. … Can it, then, be thought improbable, seeing that variations useful to man have undoubtedly occurred, that other variations useful in some way to each being in the great and complex battle of life, should sometimes occur in the course of thousands of generations? If such do occur, can we doubt (remembering that more individuals are born than can possibly survive) that individuals having any advantage, however slight, over others, would have the best chance of surviving and of procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed. This preservation of favorable variation and the rejection of injurious variations, I call Natural Selection.
Darwin’s argument addresses the problem of explaining the adaptive character of organisms. Darwin argues that adaptive variations (“variations useful in some way to each being”) occasionally appear, and that these are likely to increase the reproductive chances of their carriers. Over the generations favorable variations will be preserved, injurious ones will be eliminated. In one place, Darwin adds: “I can see no limit to this power [natural selection] in slowly and beautifully adapting each form to the most complex relations of life.” Natural selection was proposed by Darwin primarily to account for the adaptive organization, or “design,” of living beings; it is a process that promotes or maintains adaptation. Evolutionary change through time and evolutionary diversification (multiplication of species) are not directly promoted by natural selection (hence, the so-called “evolutionary stasis,” the numerous examples of organisms with morphology that has changed little, if at all, for millions of years, as pointed out by the proponents of the theory of punctuated equilibrium). But change and diversification often ensue as by-products of natural selection fostering adaptation.
Darwin formulated natural selection primarily as differential survival. The modern understanding of the principle of natural selection is formulated in genetic and statistical terms as differential reproduction. Natural selection implies that some genes and genetic combinations are transmitted to the following generations on the average more frequently than their alternates. Such genetic units will become more common in every subsequent generation and their alternates less common. Natural selection is a statistical bias in the relative rate of reproduction of alternative genetic units.
Natural selection has been compared to a sieve which retains the rarely arising useful genes and lets go the more frequently arising harmful mutants. Natural selection acts in that way, but it is much more than a purely negative process, for it is able to generate novelty by increasing the probability of otherwise extremely improbable genetic combinations. Natural selection is thus creative in a way. It does not “create” the entities upon which it operates, but it produces adaptive genetic combinations which would not have existed otherwise.
The creative role of natural selection must not be understood in the sense of the “absolute” creation that traditional Christian theology predicates of the Divine act by which the universe was brought into being ex nihilo. Natural selection may rather be compared to a painter which creates a picture by mixing and distributing pigments in various ways over the canvas. The canvas and the pigments are not created by the artist but the painting is. It is conceivable that a random combination of the pigments might result in the orderly whole which is the final work of art. But the probability of Leonardo’s Mona Lisa resulting from a random combination of pigments, or St. Peter’s Basilica resulting from a random association of marble, bricks and other materials, is infinitely small. In the same way, the combination of genetic units which carries the hereditary information responsible for the formation of the vertebrate eye could have never been produced by a random process like mutation. Not even if we allow for the three billion years plus during which life has existed on earth. The complicated anatomy of the eye like the exact functioning of the kidney are the result of a nonrandom process — natural selection.
Natural Selection as a Creative Process
Critics have sometimes alleged as evidence against Darwin’s theory of evolution examples showing that random processes cannot yield meaningful, organized outcomes. It is thus pointed out that a series of monkeys randomly striking letters on a typewriter would never write The Origin of Species, even if we allow for millions of years and many generations of monkeys pounding at typewriters.
This criticism would be valid if evolution would depend only on random processes. But natural selection is a nonrandom process that promotes adaptation by selecting combinations that “make sense,” i.e., that are useful to the organisms. The analogy of the monkeys would be more appropriate if a process existed by which, first, meaningful words would be chosen every time they appeared on the typewriter; and then we would also have typewriters with previously selected words rather than just letters in the keys, and again there would be a process to select meaningful sentences every time they appeared in this second typewriter. If every time words such as “the,” “origin,” “species,” and so on, appeared in the first kind of typewriter, they each became a key in the second kind of typewriter, meaningful sentences would occasionally be produced in this second typewriter. If such sentences became incorporated into keys of a third type of typewriter, in which meaningful paragraphs were selected whenever they appeared, it is clear that pages and even chapters “making sense” would eventually be produced.
We need not carry the analogy too far, since the analogy is not fully satisfactory, but the point is clear. Evolution is not the outcome of purely random processes, but rather there is a “selecting” process, which picks up adaptive combinations because these reproduce more effectively and thus become established in populations. These adaptive combinations constitute, in turn, new levels of organization upon which the mutation (random) plus selection (nonrandom or directional) process again operates.
The manner in which natural selection can generate novelty in the form of accumulated hereditary information may be illustrated by the following example. Some strains of the colon bacterium, Escherichia coli, in order to be able to reproduce in a culture medium, require that a certain substance, the amino acid histidine, be provided in the medium. When a few such bacteria are added to a cubic centimeter of liquid culture medium, they multiply rapidly and produce between two and three billion bacteria in a few hours. Spontaneous mutations to streptomycin resistance occur in normal (i.e., sensitive) bacteria at rates of the order of one in one hundred million (1 x 10-8) cells. In our bacterial culture we expect between twenty and thirty bacteria to be resistant to streptomycin due to spontaneous mutation. If a proper concentration of the antibiotic is added to the culture, only the resistant cells survive. The twenty or thirty surviving bacteria will start reproducing, however, and allowing a few hours for the necessary number of cell divisions, several billion bacteria are produced, all resistant to streptomycin. Among cells requiring histidine as a growth factor, spontaneous mutants able to reproduce in the absence of histidine arise at rates of about four in one hundred million (4 x 10-8) bacteria. The streptomycin resistant cells may now be transferred to a culture with streptomycin but with no histidine. Most of them will not be able to reproduce, but about a hundred will start reproducing until the available medium is saturated.
Natural selection has produced in two steps bacterial cells resistant to streptomycin and not requiring histidine for growth. The probability of the two mutational events happening in the same bacterium is of about four in ten million billion (1 x 10-8 x 4 x 10-8 = 4 x 10-16) cells. An event of such low probability is unlikely to occur even in a large laboratory culture of bacterial cells. With natural selection, cells having both properties are the common result.
As illustrated by the bacterial example, natural selection produces combinations of genes that would otherwise be highly improbable because natural selection proceeds stepwise. The vertebrate eye did not appear suddenly in all its present perfection. Its formation requires the appropriate integration of many genetic units, and thus the eye could not have resulted from random processes alone. The ancestors of today’s vertebrates had for more than half a billion years some kind of organs sensitive to light. Perception of light, and later vision, were important for these organisms’ survival and reproductive success. Accordingly, natural selection favored genes and gene combinations increasing the functional efficiency of the eye. Such genetic units gradually accumulated, eventually leading to the highly complex and efficient vertebrate eye. Natural selection can account for the rise and spread of genetic constitutions, and therefore of types of organisms, that would never have existed under the uncontrolled action of random mutation. In this sense, natural selection is a creative process, although it does not create the raw materials — the genes — upon which it acts.