Most human beings are capable of intuitively apprehending which actions and behaviors promote the well-being of others and which do not. In other words, human beings are, by and large, moral creatures. We are not fundamentally different from any other animal species in this regard. In his 1871 book The Descent of Man, Charles Darwin did not spare morality from the application of his theory of natural selection to human evolution:
The following proposition seems to me in a high degree probable – namely, that any animal whatever, endowed with well-marked social instincts, would inevitably acquire a moral sense or conscience, as soon as its intellectual powers had become as well developed, or nearly as well developed, as in man. 
These words can be considered to be the first incursion of reductionist biological thought into questions of morality and ethical behavior. The modern overlapping disciplines of sociobiology and evolutionary psychology, which grew out of this initial attack, is threatening to the traditional view held by most theists that morality and ethics are uniquely human characteristics endowed by God to his “pinnacle of creation.” 
Broadly speaking, theistic apologists have responded to the explanations of morality offered by evolutionary psychology and sociobiology in two ways. One is to recycle old arguments employed by medieval-era theologians into new formulations. For instance, one moral argument for theism widely favored by today’s theologians and Christian philosophers states that the sense of obligation to be moral is itself evidence of God’s existence. This is the tack taken by Christian theologian and apologist William Lane Craig, who writes,
If God does not exist, then it is plausible to think that there are no objective moral values, that we have no moral duties, and that there is no moral accountability for how we live and act. . . . If, on the other hand, we hold, as it seems rational to do, that objective moral values and duties do exist, then we have good grounds for believing in the existence of God. . . . We cannot, then, truly be good without God; but if we can in some measure be good, then it follows that God exists. 
Unfortunately for Craig, his argument lacks any explanatory power because he is simply begging the question. Even if “objective moral values and duties” do exist, how does it then follow that a personal God exists? The argument essentially boils down to the claim that if one understands anything about what is good and what is bad and is able to apply that knowledge more or less consistently, then that person must be employing an objective standard of some kind. Craig gives that standard a name, calling it “God.” But he nowhere demonstrates how the alleged existence of his God follows logically from the fact that people employ standards of right and wrong.
At no point does Craig’s argument address, let alone solve, a dilemma that has confronted the concept of a “god-given morality” for over two millennia. I refer to the famous Euthyphro dilemma, found in Plato’s Euthyphro dialogue, in which Socrates asks his interlocutor “Is the pious being loved by the gods because it is pious, or is it pious because it is being loved by the gods?”  To pose the dilemma another way, does God will us to engage in morally good acts because such acts are truly good, or are morally good acts so because they are willed by God? The first option implies that God, being merely a Moral Expert, is subject to standards independent of himself. “So if God is a moral expert, there must be some set of moral facts about which he is an expert,” writes John Danaher. “And these facts cannot depend on him for their truth or falsehood. Therefore, God’s existence is not necessary for moral realism to be true.”
If, on the other hand, God is a Moral Engineer, which is to say that the decrees and commands of God are moral merely because it is God who wills them, then we are not dealing with moral perfection but rather a morality by fiat that proceeds arbitrarily. “For moral perfection to be a property that is worthy of respect it must be something more than the mere exercise of divine fiat.” 
The other moral argument theists use to defend the existence of their God is one made in the “natural theology” tradition of William Paley. Modern apologists, particularly those with a scientific background, have sought to derive their transcendentalist account of morality from observable behavioral traits, such as altruism, that they claim are unaccounted for by naturalistic evolution alone. In effect, these apologists have simply applied the failed intelligent design hypothesis to the realm of human morality and ethics.
This is the approach taken by the well-known and widely-respected geneticist and Christian evangelical Francis Collins, current director of the National Institutes of Health and former head of the successful and groundbreaking Human Genome Project. In his bestselling 2006 book The Language of God, Collins makes a plea for the existence of a personal god that is surprisingly naïve, given his impressive scientific credentials. His argument is that his belief in a personal god is confirmed by his own innate sense of morality and his intuition of what is good and what is bad. Collins presents a textbook example of an argument from ignorance, stating that he does not see how that inner moral sense could have arisen without a supernatural being implanting it in his psyche. Collins’s appeal is of course not original. The famous – and highly overrated – early twentieth-century Christian apologist C.S. Lewis presented the same case in his popular 1952 book Mere Christianity. Collins quotes extensively from the section of Lewis’s book titled “Right and Wrong as a Clue to the Meaning of the Universe,” and is particularly impressed by the following passage:
If there was a controlling power outside the universe, it could not show itself to us as one of the facts inside the universe – no more than the architect of a house could actually be a wall or staircase or fireplace in that house. The only way in which we could expect it to show itself would be inside ourselves as an influence or a command trying to get us to behave in a certain way. And that is just what we do find inside ourselves. Surely this ought to arouse our suspicions? 
There are at least two problems with Lewis’s argument. First, if there is a “controlling power outside the universe,” one that has the attribute of omnipotence, there is no reason why this entity should not be able to manifest itself within the observable natural universe. While the architect in Lewis’s illustration is obviously not a part of the house he designed, he could easily visit the house, walk around inside it, and interact with its residents in a tangible way. He could even show the residents the blueprints he wrote and explain in a detailed and precise way the engineering and constructing steps taken to build the house. Why couldn’t the all-powerful creator of the universe do the same for us?
Second, there is an archaic and problematic dualism inherent in Lewis’s argument. His unfounded assumption is that that which shows itself as “an influence or a command” moving us to act in certain ways is somehow a process fundamentally separate from natural processes. The evidence from modern genetics, neurobiology, and evolutionary psychology overwhelmingly contradicts this notion. Morality is inextricably bound up and intertwined with human behavior, and human behavior lies within the jurisdiction of scientific study. In other words, human morality is, contra Lewis, one of “the facts inside the universe.”
Collins’s commentary on the above Lewis quote comes in the form of the following personal testimony:
Encountering this argument at the age of twenty-six, I was stunned by its logic. Here, hiding in my own heart as familiar as anything in daily experience, but now emerging for the first time as a clarifying principle, this Moral Law shone its bright white light into the recesses of my childish atheism, and demanded a serious consideration of its origin. Was this God looking back at me?
And if that were so, what kind of God would this be? Would this be a deist God, who invented physics and mathematics and started the universe in motion about 14 billion years ago, then wandered off to deal with other, more important matters, as Einstein thought? No, this God, if I was perceiving Him at all, must be a theist God, who desires some kind of relationship with those special creatures called human beings, and has therefore instilled this special glimpse of Himself into each one of us. This might be the God of Abraham, but it was certainly not the God of Einstein. 
The facts of evolutionary history contradict Collins’s viewpoint. Morality developed in our distant ancestors long before monotheistic religion was invented to hijack and institutionalize it. If a personal God instilled a “special glimpse of Himself” into the psyches of our distant ancestors, surely that internal revelation would be accompanied by knowledge of the God who bequeathed it and what he wants from his creatures. Why did that revelation have to wait until the founders and codifiers of the Abrahamic faiths came along to disclose it?
Furthermore, we human beings are not “special creatures” in the sense that Collins makes us out to be. Beginning with Darwin in the nineteenth century, biologists and zoologists have shown through extensive documentation spanning the course of many decades that what we recognize as the moral sense is not unique to humans. Homo sapiens were not endowed from above with some special trait that sets us apart from the other animals. As documented extensively by primatologist Frans de Waal and others, several primate and mammalian species have been observed exhibiting social behaviors indicative of a rudimentary morality, including sympathy, a sense of social regularity that expresses itself in hierarchies of rank and order, sharing of resources and reciprocity, and conflict resolution by peaceful means.  These observations have led many authors from a wide variety of scientific disciplines to develop plausible and evidence-based hypotheses for how morality may have evolved by natural processes of biological evolution.  “Our moral sentiments,” writes psychologist and Skeptics Society founder Michael Shermer, “evolved out of premoral feelings of our hominid, primate, and mammalian ancestors, the remnants of which can be found in modern apes, monkeys, and other big-brained mammals.”  After surveying a representative sampling of the many hundreds of examples of proto-moral behavior in several species of mammals documented in the scientific literature, Shermer concludes,
The following characteristics appear to be shared by humans and other mammals, including and especially the apes, monkeys, dolphins, and whales: attachment and bonding, cooperation and mutual aid, sympathy and empathy, direct and indirect reciprocity, altruism and reciprocal altruism, conflict resolution and peacemaking, deception and deception detection, community concern and caring about what others think about you, and awareness of and response to the social rules of the group. 
Collins disputes this: “Though other animals may at times appear to show glimmerings of a moral sense, they are certainly not widespread, and in many instances other species’ behavior seems to be in dramatic contrast to any sense of universal rightness.”  In his book The Moral Landscape, the neuroscientist Sam Harris responds to this statement with the following rebuttal:
One wonders if the author has ever read a newspaper. The behavior of humans offers no such “dramatic contrast” . . . How badly must human beings behave to put this “sense of universal rightness” in doubt? While no other species can match us for altruism, none can match us for sadistic cruelty either. And just how widespread must “glimmerings” of morality be among other animals before Collins—who, after all, knows a thing or two about genes—begins to wonder whether our moral sense has evolutionary precursors? 
These “glimmerings” of moral behavior are indeed abundant throughout the animal kingdom, especially among our fellow primates. Laboratory experiments have shown that rhesus monkeys will refrain from securing food for themselves if doing so causes their fellow monkeys to suffer from painful electric shocks.  Chimps appear to exhibit notions of fairness, albeit in a limited sense, in their behavioral reactions to the inequitable distribution of food rewards.  For example, in what is now a classic and much-cited experiment, primatologist Frans de Waal and psychologist Sarah Brosnan have documented capuchin monkeys throwing a tantrum when receiving cucumber slices upon completion of a task if they notice another monkey in the next cage being given a “higher value” food reward such as a grape for performance of the same task.  The primatologist Jane Goodall has described cases in which chimps have attempted to rescue other chimps from drowning in the moats that surround their enclosures.  There is even evidence of rudimentary empathy in mice and rats, the latter freeing caged and distressed rats of their own strain from their restrainers and even sharing chocolate contained in a second cage which they also open. 
Collins seems to be mistaking a “sense of universal rightness” for the evolution of culture, which may be unique to humans but is not the product of our biological nature, as Collins wants to argue. Through culture, we learn first how to express latent socially-adaptive instincts instilled by millions of years of evolution and then to institutionalize those instincts. Our enhanced morality, writes child psychologist Paul Bloom, “is the product of culture, not biology. Indeed, there might be little difference in the moral life of a human baby and a chimpanzee; we are creatures of Charles Darwin, not C.S. Lewis.” 
Many of the instincts that find their expression in the form of behaviors, belief systems, rules, and taboos are nearly universally shared by all humans. In an appendix to his book The Blank Slate, the experimental psychologist Steven Pinker provides a list of hundreds of such “human universals,” drawn from the work of anthropologist Donald Brown. These include right-and-wrong distinctions, empathy, the distinction between close and distant kin and the favoring of the former, reciprocity, food sharing, taboos placed on incest, and proscriptions on rape and murder.  This tells us that we do not need a supernatural being to tell us that murder is not conducive to the continued survival and well-being of the species. Obviously, if most people murdered other people on a regular basis, we would not be able to maintain a functional society. Nor do we need a god to tell us that being truthful is in most cases a virtue. Any society in which people lied as a matter of course and rarely spoke the truth would descend into unsustainable chaos.
It makes sense, then, that people nearly everywhere would consider truth-telling to be a virtue and murder to be a vice. As a species, we Homo sapiens have uniformly adopted certain moral precepts based not upon the dictates of a god or a supernaturally-inscribed innate morality, but rather upon our own need to live and thrive together in a productive society. This makes moral development a game of trial-and-error, which is why many of the changes in what is considered moral and immoral have changed rapidly throughout human history. For instance, in his book The Better Angels of Our Nature, Steven Pinker convincingly argues that since the Middle Ages, widespread changes in what is considered moral have been mainly responsible for a dramatic decrease in violence among the majority of societies and that the present day is very likely the most peaceful period in human history to date.  This should not be the case under the theistic account of morality. If a personal yet transcendent and all-wise God is the ultimate source of morality and values, we would expect to see the moral sentiments and beliefs of his “special creatures,” to whom he has supposedly bequeathed a hardwired moral compass, to be unchanging from our birth as a species to the present day. This is demonstrably not the case. The data of history indicate that if the theists’ God exists, his moral compass is just as malleable and subject to revision as is ours. More plausible is the argument that no god exists. Morality does not emanate from an objective external source; it is instead a natural byproduct of the impersonal survival-maximizing instincts that emerge in a bottom-up fashion from our genes.
 Charles Darwin, The Descent of Man, and Selection in Relation to Sex (London: Murray, 1871), pp. 71-72.
 For a layman’s introduction to the development and findings of evolutionary psychology, see Robert Wright, The Moral Animal: Why We Are the Way We Are (New York: Vintage Books, 1994).
 William Lane Craig, “The Indispensability of Theological Meta-ethical Foundations for Morality,” Foundations 5 (1997): 9-12. Available online at http://www.leaderu.com/offices/billcraig/docs/meta-eth.html (accessed July 21, 2015).
 Plato, Euthyphro (10a). G.M.A. Grube’s translation in Plato: Five Dialogues, 2nd ed. (Indianapolis, IN: Hackett Publishing Company, 2002), p. 12.
 John Danaher, “God and Morality (Part 2): Owing Duties and the Euthyphro Dilemma,” Philosophical Disquisitions, January 2, 2010, http://philosophicaldisquisitions.blogspot.com/2010/01/god-and-morality-part-2-owing-duties.html (accessed July 23, 2015).
 C.S. Lewis, Mere Christianity (Westwood, NJ: Barbour, 1952 [New York: HarperCollins, 2001]), p. 24.
 Francis S. Collins, The Language of God: A Scientist Presents Evidence for Belief (New York: Free Press, 2006), p. 29.
 Frans de Waal, Good Natured: The Origins of Right and Wrong in Humans and Other Animals (Cambridge, MA: Harvard University Press, 1996).
 Leonard D. Katz, ed., Evolutionary Origins of Morality: Cross-Disciplinary Perspectives (Thorverton, UK; Bowling Green, OH: Imprint Academic, 2000). For highly accessible information and more references relating to the evolution of morality via naturalistic processes, I recommend Douglas Allchin’s website “The Evolution of Morality,” http://www1.umn.edu/ships/evolutionofmorality/ (accessed August 4, 2015).
 Michael Shermer, The Science of Good and Evil: Why People Cheat, Gossip, Care, Share, and Follow the Golden Rule (New York: Times Books, 2004), pp. 26-27.
 Ibid, p. 31.
 Collins, The Language of God, p. 23.
 Sam Harris, The Moral Landscape: How Science Can Determine Human Values (New York: Free Press, 2010), p. 170.
 J.H. Masserman, S. Wechkin, and W. Terris, “’Altruistic’ Behavior in Rhesus Monkeys,” American Journal of Psychiatry 121 (December 1964): 584-585.
 S.F. Brosnan, “How Primates (Including Us!) Respond to Inequity,” Advances in Health Economics and Health Services Research 20 (2008): 99-124.
 Frans de Waal, Stephen Macedo, and Josiah Ober, Primates and Philosophers: How Morality Evolved (Princeton, NJ: Princeton University Press, 2006), pp. 44-49; Frans de Waal, The Bonobo and the Atheist: In Search of Humanism among the Primates (New York and London: W.W. Norton & Company, 2013), p. 232.
 Jane Goodall, Through a Window: My Thirty Years with the Chimpanzees of Gombe (Boston: Houghton Mifflin, 1990), p. 213.
 D.J. Langford, et al, “Social Modulation of Pain as Evidence for Empathy in Mice,” Science 312, no. 5782 (June 2006): 1967-70; I.B.-A. Bartal, J. Decety, and P. Mason, “Empathy and Pro-social Behavior in Rats,” Science 334, no. 6061 (December 2011): 1427-30.
 Paul Bloom, “Did God Make These Babies Moral? Intelligent Design’s Oldest Attack on Evolution Is as Popular as Ever,” New Republic, January 13, 2014, http://www.newrepublic.com/article/116200/moral-design-latest-form-intelligent-design-its-wrong (accessed August 9, 2015).
 Steven Pinker, The Blank Slate: The Modern Denial of Human Nature (New York: Viking, 2002), pp. 435-39; Donald E. Brown, Human Universals (New York: McGraw-Hill, 1991).
 Steven Pinker, The Better Angels of Our Nature: Why Violence Has Declined (New York: Viking, 2011).