Transcript Slide 1
Topic 18. Lecture 28. Importance of the Evolution of Life outside Life Sciences Evolution of life attracts more attention outside natural sciences that any other branch of biology. Let us consider implications of evolution to: 1) medicine, 2) psychology, 3) philosophy, 4) religion. Disclaimer: here, I will allow myself a liberty to express my own opinions on several subjects that are outside the area of my professional expertise. 1) Evolution and medicine Evolution of life is important for medicine due to a variety of reasons, including the possibility of rapid evolution of pathogens. Let us, however, concentrate on what evolution tells us about human biology, in particular, about human imperfection, which goes well beyond the hard limits imposed by the laws of physics. Evolutionary thinking allows us to recognize the following kinds of human imperfection: 1) Imperfection due to hard-to-improve suboptimality. 2) Imperfection due to easy-to-improve suboptimality. 3) Imperfection due to unconditionally deleterious alleles. 4) Imperfection due to conditionally deleterious alleles. 1) Imperfection due to hard-to-improve suboptimality These are cases of fundamental flaws in the design of human body, which apparently cannot be corrected by evolution. Let us consider 3 examples. 1a) Esophagus and trachea have a common opening. Because of this, humans are always at risk of chocking, in which case Heimlich maneuver must be performed at once. 1b) Human eyes are inverted, with blood vessels and fibers of the optic nerve approaching retina from the outer side. After 40, vitreous body often gets detached from the retina. Glial cells that surround the optic nerve that penetrates the retina often remain attached to the vitreous (Weiss ring), contributing to floaters that obscure vision. Posterior vitreous detachment Weiss ring 1c) Simultaneous evolution of bipedal locomotion and large brain tests the limits of what is consistent with the overall design of the mammalian body. Pelvis of a woman (top left), a man (top right) and a chimpanzee (bottom). Giving birth is difficult. 2) Imperfection due to easy-to-improve suboptimality We possess traits that were probably adaptive under environments of our ancestors, but are maladapted today. One might expect evolution to gradually change such traits. Human appendix is homologous to a welldeveloped portion of the digestive system in many other mammals. Although appendix probably has a function in immune response, its presence appears to be suboptimal. All humans has coccygeal vertebrae homologous to vertebrae in tails of mammals. Rarely, humans have vestigial tails, which may require surgical removal. Such tails are atavisms - a kind of homologous variation such that a rare variant within a species is more similar to other species (and presumably to ancestors) that the normal phenotype. Most of humans have non-functional wisdom teeth, sometimes impacted. These teeth probably lost their function due to changes in the overall anatomy of head and jaws. Currently, their presence is mildly deleterious. Ear muscles in modern humans are non-functional, although some individuals can deliberately move their ears. This is a benign vestige. 4) Imperfection due to unconditionally deleterious alleles A normal human being carries hundreds of alleles deleterious enough to be individually rare and to never become fixed in the population. A famous biologist James Watson carries at least ~1000 rare, mildly deleterious protein-altering alleles, and probably many more in his non-coding DNA. We still do not know what kinds of genetic variation underlies complex diseases. Definitely, rare alleles play a major role, but how common are common diseasecausing alleles? 5) Imperfection due to conditionally deleterious alleles After the last out-of-Africa dispersal, different human populations acquired some adaptations to their local environments, which are conditionally beneficial - and, thus, also conditionally deleterious. With some important exceptions, such as sickle-cell anemia, these adaptations are not very important in modern society. If you were a Masai living 100 years ago, marrying a white girl may be a bad idea, because your children would be prone to sunburns. Now, sunscreen can alleviate the problem. If you love milk, you may think twice before marrying a guy from Polynesia - because you may be unable to enjoy milk with your grown-up children. Alternatively, you can ignore this problem and marry who you like. 2) Evolution and psychology A lot of human mental features are not uniquely human. Animals are very capable of basic human emotions, such as joy and fear, and chimpanzees even possess rudimentary language abilities. However, other mental abilities are uniquely human. Is our ability to enjoy music and comprehend mathematics a product of natural selection? Could selection for better stone throwing produce Ramanujan, as an unintended by-product? Perhaps, the most mysterious facet of evolutionary psychology is the origin ethics. Remember 5 mechanism for the evolution of altruism: 1) Kin selection operates when the donor and the recipient of an altruistic act are genetic relatives. 2) Direct reciprocity requires repeated encounters between the same two individuals. 3) Indirect reciprocity is based on reputation; a helpful individual is more likely to receive help. 4) Network reciprocity means that clusters of cooperators outcompete defectors. 5) Group selection is the idea that competition is not only between individuals but also between groups. Is this enough to explain our ideas about good and evil? 3) Evolution and philosophy A lot has been said and written about implications of the evolution of life to the most basic, existential questions. Let us consider just one of them, perhaps the most fundamental one arguments for the existence of God . Such an argument appears if what we see requires God as an explanation. 1) Evolutionary argument of the existence of God? One can argue that we especially value altruism (charity), if: it is directed to strangers or even enemies (not our kin or members of our group) and it will not lead to any reward (including better reputation), at least in this world. How could this trait evolve by natural selection? In particular, Christian ethics is definitely counteradaptive. It looks like Jesus was familiar with modern analysis of the evolution of altruism, and demanded more from his followers, in his "Good Samaritan" parable. 29But he, desiring to justify himself, said to Jesus, "And who is my neighbor?" 30Jesus replied, "A man was going down from Jerusalem to Jericho, and he fell among robbers, who stripped him and beat him and departed, leaving him half dead. 31Now by chance a priest was going down that road, and when he saw him he passed by on the other side. 32So likewise a Levite, when he came to the place and saw him, passed by on the other side. 33But a Samaritan, as he journeyed, came to where he was, and when he saw him, he had compassion. 34He went to him and bound up his wounds, pouring on oil and wine. Then he set him on his own animal and brought him to an inn and took care of him. 35And the next day he took out two denarii and gave them to the innkeeper, saying, 'Take care of him, and whatever more you spend, I will repay you when I come back.' 36Which of these three, do you think, proved to be a neighbor to the man who fell among the robbers?" 37He said, "The one who showed him mercy." And Jesus said to him, "You go, and do likewise." Luke 10, 29-37 A "Good Samaritan" allele must have low fitness. Thus, Christian ethics cannot be of evolutionary origin. Thus, Christianity must be of supernatural origin. Thus, God exists. Are you convinced? Such counteradaptive (and, following this logic, supernatural) commands can be found in scriptures from many religions. If you give alms openly, it is well, and if you hide it and give it to the poor, it is better for you; and this will do away with some of your evil deeds; and Allah is aware of what you do. The Quaran, Sura 2 (The Cow), 271 All men tremble at punishment, all men fear death; remember that you are like unto them, and do not kill, nor cause slaughter. Dhammapada, Chapter X (Punishment), 129 46For if you love those who love you, what reward do you have? Even the tax collectors do the same, don’t they? 47And if you only greet your brothers, what more do you do? Even the Gentiles do the same, don’t they? 48So then, be perfect, as your heavenly Father is perfect. 1Be careful not to display your righteousness merely to be seen by people. Otherwise you have no reward with your Father in heaven. Matthew 5:46 - 6:1 I do not think that this evolutionary argument for the existence of God is better than other such arguments - but I still find it interesting. Evolutionary explanation of counteradaptive unrewarded altruism towards strangers - that it is just an unintended by-product of selection for altruism towards kin or of reputation-increasing kind does not look very convincing. 2) Evolution and argument from design Evolution certainly abolished the argument from design, as far as biology is concerned. We do not necessarily need Divine intervention to explain complex adaptations. One can say that before Darwin, belief in God was mandatory - and now it is optional. Well, may be this is the way it should be? William Paley, the author of the famous "watchmaker analogy". Finally, some obvious remarks: 1) Evolution, or any other natural process, could never establish what is good and what is evil - a point made by Immanuil Kant. 2) A human being does not originate from apes, or even from parents - we develop de novo from a zygote. 4) Evolution and religion Ongoing debates about reality of past evolution of life are due to opposition to this fact by some religious denominations. There is a pattern of parallel variation in its attitude towards evolution within Judaism and within Christianity. Judaism: Christianity: Orthodox young-Earth creationism Evangelicals Conservative partial acceptance of evolution Catholicism Reformed no problems with evolution Liberal Protestants I am less familiar with other religions, but they also show a lot of variation in their attitudes to evolution of life. Let us consider the well-articulated views of the Roman Catholic Church on this subject. They were first formally proclaimed by Pope Pius XII in 1950. ENCYCLICAL HUMANI GENERIS OF THE HOLY FATHER PIUS XII, 12 August 1950. 36. ... Teaching Authority of the Church does not forbid that, in conformity with the present state of human sciences and sacred theology, research and discussions, on the part of men experienced in both fields, take place with regard to the doctrine of evolution, in as far as it inquires into the origin of the human body as coming from pre-existent and living matter for the Catholic faith obliges us to hold that souls are immediately created by God. However, this must be done in such a way that the reasons for both opinions, that is, those favorable and those unfavorable to evolution, be weighed and judged with the necessary seriousness, moderation and measure, and provided that all are prepared to submit to the judgment of the Church. Some however, rashly transgress this liberty of discussion, when they act as if the origin of the human body from pre-existing and living matter were already completely certain and proved by the facts which have been discovered up to now and by reasoning on those facts, and as if there were nothing in the sources of divine revelation which demands the greatest moderation and caution in this question. 37. When, however, there is question of another conjectural opinion, namely polygenism, the children of the Church by no means enjoy such liberty. For the faithful cannot embrace that opinion which maintains that either after Adam there existed on this earth true men who did not take their origin through natural generation from him as from the first parent of all, or that Adam represents a certain number of first parents. Now it is in no way apparent how such an opinion can be reconciled with that which the sources of revealed truth and the documents of the Teaching Authority of the Church propose with regard to original sin, which proceeds from a sin actually committed by an individual Adam and which, through generation, is passed on to all and is in everyone as his own. In short, Humani Generis allows Catholics to accept evolution as a hypothesis, but forbids "polygenism". In 1996, John Paul II admitted that past evolution of life is "more than a hypothesis", but did not revisit an issue of human origin. Indeed, the lack of Adam-Eve bottleneck may create problems for those who accept the concept of original sin. However, many Christians (and other religious people) feel that evolution of life is outright inconsistent with their faith. Well, there are indeed some passages in the Bible which are literally inconsistent with Heliocentric solar system - so what? If Galileo is, after all, consistent with faith, why not Darwin? When people, in the name of God in which they believe, make ignorant and outright false claims, this is sad. Unless we are willing to entertain a possibility that God carefully planted all the evidence for past evolution of life in rocks and in our genomes, evolution has been established as a fact long time ago - there is nothing to debate here. The two chapters in Torah on which Jewish and Christian creationists base their claims (Genesis, Chapters 1 and 2) apparently do not demand a literal understanding. A bigger problem may be Noah's flood. There are a lot of creationist resources on the web: http://www.answersingenesis.org/ Some American debates about evolution sound strange to me. It is argued that creationism should not be taught in schools because it is religion. Well, if my religion says that 2x2 = 4, why not teach it in schools? Creationism should not be taught because it is false. Of course, the belief in God guiding past evolution of life in some imperceptible way is perfectly consistent with science. The same is true for any belief in divine Providence which does not violate the laws of nature. When a child dies - is this the will of God? I do not feel qualified to ponder such questions in public. Among the founders of modern evolutionary biology, you can find all kinds of beliefs. Ronald Fisher Anglican Sewall Wright Unitarian John Haldane Communist Theodosius Dobzhansky Orthodox John Maynard Smith Atheist Conclusions: Evolution must become the foundation for medicine, as it already became for biology. To what extent evolution explains us as humans is an interesting question personally, I think that not very much. Evolutionary biology is as consistent (or as inconsistent) with faith as any other field of natural sciences. It definitely abolishes the argument from design, but may also provide some reasons to believe in God. Creationism is false and sad and not interesting intellectually. Still, past evolution of life presents problems to some systems of religious beliefs. Quiz: Propose your own argument for the existence of God. If you cannot, at least do not forget to do your online evaluation of EEB 390.