Daylight Atheism > Human Evolution

Another Branch on the Human Family Tree

I haven't written about any new transitional fossils in a while, so it's a great pleasure for me to mention this one: a hominid skeleton nicknamed "Ardi", a specimen of Ardipithecus ramidus. This species was known from other fossil fragments, but Ardi is one of the oldest and most complete hominids found so far, and may give us the most insight yet into what the common ancestor of humans and chimpanzees looked like.

Ardi lived about 4.4 million years ago (by comparison, Lucy and her fellow australopithecines are about 3.4 million years old), in the Middle Awash region of modern-day Ethiopia. Today it's an arid badlands, but in that era, it was a lushly forested woodland, cool and wet but geologically active, with frequent volcanic episodes (a great boon to biologists, since volcanic rock and ash strata are easily dated with radiometric methods and give us good estimates of when a certain fossil lived). Primitive elephants, giraffes, horses, antelope, rhinos and monkeys are well-known from this area, as are other hominid specimens.

The fossil itself is believed to be a female. The bones were so poorly fossilized, according to the Science paper by Tim White and colleagues, that they would crumble if touched. The researchers painstakingly chipped them free of the rock they were encased in with dental picks, bamboo, and porcupine quills (!). From the fossil's discovery to its publication took nearly 15 years of preparation and study - but from all accounts, it was worth the wait.

In life, Ardi would have stood just under four feet tall and weighed about 110 pounds. The skull was small, about 325 cc, about the same size as a chimp's. Ardi's teeth suggest she was an omnivore, and from comparing other A. ramidus teeth and bones found in the region, White and his colleagues found little difference in tooth size or body size between male and female individuals. This suggests that their mating style was relatively peaceful, with little competition for mates (as compared to chimpanzees, who have massive canine teeth which are used to intimidate potential rivals) and possibly more stable pair-bonding and group cohesion.

Ardi's hands, feet and pelvis tell us a lot about how she got around. Hominids like Lucy show a mosaic of bipedal and arboreal adaptations - as Laelaps puts it, they "had their hands in the trees and their feet on the ground" - and Ardi shows a more primitive version of the same pattern, much as we'd expect from an ancestor of that age.

She stood and walked upright, though not as well as Lucy or as us, and her feet were becoming more rigid like ours, except that she also had an opposable big toe useful for grasping. Her arms were long enough to reach to her knees when standing upright, but her hands were not adapted for knuckle-walking. Nor did they have the specializations for climbing and hanging from trees that we see in modern apes. She still lived in the trees, but would have moved through them more slowly and carefully than chimps or orangutans, and was capable of descending to the ground and walking. This refutes the once-popular belief that bipedalism first developed when human ancestors left the forest for the savanna and adapted to stand upright so as to see over the grass - as shown by species like Ardi, bipedalism evolved before we left the trees.

Another popular but erroneous idea that Ardi refutes is that the common ancestor of humans and chimps looked basically like a chimp, and that humans have changed significantly while modern chimps are little different from our common ancestor. This is probably tied to the misconception of the "great chain of being" that sees humans as the highest or most advanced form of life on Earth. Ardi, who probably lived relatively near the time when our two lineages split, instead shows that both humans and chimpanzees have evolved and specialized since the time of our common ancestor, becoming adapted to two very different ways of life.

Other posts in this series:

Rebutting The Case for a Creator

Noble Africa

To those who are following the continuing genocide in Darfur, every day brings grim headlines:

Fighting has prompted thousands of people in the southern part of Sudan's Darfur region to seek security and shelter at a refugee camp in the northern part of the war-torn area, according to the United Nations.

...An estimated 300,000 people in the western Sudanese region have been killed through combat, disease or malnutrition, according to the United Nations. An additional 2.7 million people have been forced to flee their homes because of fighting among rebels, government forces and the violent Janjaweed militias.

Though its plight has attracted the most attention, Darfur is far from the only troubled region of Africa. There's the failed state of Somalia, now a haven for terrorism and piracy, and the outbreaks of famine and cholera brought on by the near-total collapse of Zimbabwe in the face of dictator Robert Mugabe's refusal to surrender power, to name just the two most prominent examples from recent headlines. How did we let this happen?

Africa was the human race's first home. It is our birthplace, our cradle. The continent should be a sacred place to all of us, a living temple of memory reminding us of our origins. Instead, it's poverty-stricken, politically fractured, still laboring under corrupt autocracies and mired in backwardness and superstition. The picture is not all bleak - there are success stories, and notable bright spots - but even so, Africa as a whole lags behind the rest of the world, and still struggles with the legacy of imperialism and the unbridged chasms of its own political divides.

And yet, there was a time when all humans were Africans. Though we've spread all over the world in successive waves of migration, our genes have not forgotten the past. Whether you're European or Asian, from the Arctic or from Polynesia, your heritage can be traced back to families that lived in Africa millions of years ago. If you care to categorize on the basis of something as superficial as skin color, then you can know to a certainty that the blood of black men and women flows in your veins.

It was Charles Darwin who ventured the bold guess that the human race evolved in Africa, and the evidence has vindicated him. It's in Africa that we find the bones of our earliest known ancestors and our close cousins in the human family tree: species like Lucy's, Australopithecus afarensis, small hominids who had the heavy brows and brain size of chimpanzees but stood and walked upright like us. It's in Africa, in Laetoli, that we find the oldest trace evidence of human bipedalism: two trails of footprints frozen in stone, four million years old, where three people - perhaps a family of man, woman and child - walked together across a field of new-fallen volcanic ash. It's in Africa, in Tanzania's Olduvai Gorge, that we find the earliest stone tools. And more controversially, it's in Africa, at sites like Kenya's Koobi Fora, that we find possibly the earliest evidence for the domestication of fire.

In short, it's in Africa that we learned to be human. It was under the shade of Africa's trees that we first descended to the ground, and on African savannas that we stood upright and walked for the first time. The songs of our childhood were first sung beneath an African dawn; the stories that echo in your bones were first told around African campfires.

Of course, we did not stay in our birthplace forever. As the population grew and wanderlust took the human spirit, we flowed out in successive waves of settlement and conquest. We spread north into the fertile crescent of the Middle East, where we first domesticated animals and plants and built the world's oldest cities, and into Ice Age Europe, where we eradicated our brothers - the stocky, heavy-browed Neanderthals, who had lived and thrived in the frozen landscape for tens of thousands of years until we arrived. We walked across the Bering Strait into the Americas and fanned out across the Pacific by raft and canoe. We spread over the face of the earth, building mighty civilizations and forging empires in battle and conquest. And, in due time, the conquerors returned - to their own birthplace, had they but known it - and put it under their heel as well.

It took centuries for Africa to throw off that yoke, and the injuries that it suffered still are not fully healed. Its people still grapple with endemic disease, with political corruption and with their own tribalisms, all of which are exacerbated by poverty and international neglect. But still and all, Africa is a noble continent, not in the condescending caricature of the "noble savage", but nobility in the true sense of the word: those whose blood is purest, whose lineage traces back longest. It is still the home of the most deeply rooted branches of the human family tree: as Richard Dawkins writes in The Ancestor's Tale, the disappearance of everyone outside Africa would decrease human genetic diversity only slightly, while the disappearance of everyone in that continent would mean the loss of most of our species' gene pool. Compared to Africa, all the rest of humanity is a prodigal son, descended from a relatively small number of restless wanderers who left a great and ancient family to seek their fortunes in the world.

In the slow ascent of human progress, we have many milestones left to reach. There are ancient trouble spots throughout the world, and we can count ourselves more advanced as we overcome each of them. But the turmoil of Africa is our species' greatest shame. I can imagine an Earth where Africa takes its rightful place among the pantheon of peoples; an Africa where the archaeological sites of humanity's origin are sites of pilgrimage, sacred places preserved for all to see and walk in the footsteps of our ancestors. I can imagine an Africa that's peaceful and prosperous, where gleaming cities exist alongside the simple beauty and grandeur of the savannahs and rainforests that were our childhood home. We may, perhaps, have no right to call ourselves truly advanced until that world is a reality.

The Story of Atheism

In my previous post, I wrote some thoughts on the power of storytelling and how atheists can use it to our benefit. In this post, I intend to apply those principles to tell a story: the story of atheism.

Because gods are fundamentally human creations, this is also a story of humanity. It opens in the time when the human race was newborn, when we had first come of age as conscious beings who could look around and conceptualize the world. I don't know the exact nature of the beings in whose minds these ideas first appeared - they may not have been modern Homo sapiens, but they were undoubtedly our ancestors and deserve to be described as such.

The end product is somewhat similar to my atheist psalm, "The Gods", somewhat similar to treatises on the origins of religion like Dennett's Breaking the Spell. In the name of narrative convenience and brevity, some details have been omitted from this story. Nevertheless, I think it captures an adequate, if simplified, account of events in our past that actually happened. Editorial suggestions are, as always, welcome.

In the beginning, Humanity was lonely and afraid. We had tremendous potential, but we were still simple creatures, knowing only the rudiments of survival, and at the mercy of a world that was chaotic and full of danger. Like children lost in the wilderness, we knew that we existed, but not where we had come from, nor what happened to us when we died.

To ease our loneliness and fear, in our imaginations we filled the world with other people: people who lived in fire and water, in earth and trees, in sun and moon. From what we knew then, this was reasonable: after all, the only other things we knew of that reacted to us with as much complexity and inscrutability as these natural phenomena were our fellow human beings. And if the natural events that governed our lives were personified, then perhaps those people could be supplicated in times of trouble, perhaps they could be persuaded to have mercy on us. But because these other people were invisible, we called them spirits; and because we could not control the seasons or the weather, we reasoned that these spirits must be more powerful than us.

When agriculture was discovered, our population expanded and we became sedentary. But this meant we were even more dependent on nature's favor, and staying in the good graces of the spirits became even more important. Thus, in our eyes, they became more powerful still, and were elevated from spirits to gods - invisible beings who had power over our lives, and who had to be appeased above all else. This was the birth of religion, as our duties to the gods became formalized, crystallizing from folk superstitions about what had seemed to bring prosperity in the past.

These ideas stayed with us, and as our knowledge and our civilization expanded, they too began to grow in scope. As tribes merged into nations, the gods ran together, like drops of water merging. When war was kindled, the rulers sought to fill their people with courage by assuring them that the gods were on their side and would see that they prevailed over the enemy - or, at worst, that their spirits would end up in a pleasant afterlife. And as human power continued to grow and nations were forged into empires, the gods of the victors grew ever more powerful, the success of their worshippers tangible proof of their expanding dominion over the earth.

At first, the gods and the earthly ruler were one, and the voice of the king was assumed to be the voice of the divine. Through assertions of power both earthly and in the afterlife, their sway was initially absolute. But as the gods grew in power and influence, it became more advantageous to claim the right to speak for them. This was especially true when disaster struck a society, when the rulers had made bad decisions and their link to the gods could be doubted. Small wonder, then, that prophets began to appear who preached that the existing authorities were corrupt, that the gods wanted something different of us, and that they had had an insight into this new path. And small wonder, too, that the more persuasive of these prophets attracted followings of their own.

What this led to was a decoupling of religion from the state apparatus and a flowering of religious creativity as new sects of every kind arose, expressing all the creativity of which the human mind is capable. Wherever there was a human need unmet by the existing society, new religions sprang up promising to fill it. Of course, the state-run religions still existed and often lashed out harshly at their competitors. In other places, new religions grew in power until they became the established authority, or were coopted by an existing state whose rulers found their tenets to be useful. And old religions that had become bureaucratic and impersonal were often outcompeted by younger, more vibrant faiths and dwindled away, their gods' voices fading to nothingness as their followers died out and their temples crumbled.

All this was the pattern of human society for millennia. Belief in differing gods led to bloody wars between societies, but also sustained a shared cultural identity within a society, leading to a stable equilibrium. Every era had skeptics and doubters of the established faith, but few of them gained any great following, since they had no alternative religion to offer on which they could build a power base. But in one society in particular, there came an era of enlightenment, when great thinkers dared to ask questions of the world... and in at least one time, at least one place, there were enough skeptical minds put together to fan the embers that had been smoldering throughout human history into flame. The scientific age had dawned.

At its essence, the scientific era was underlain by a simple, revolutionary idea: statements about the world should not be accepted on the basis of faith, but proven by open and systematic testing. But simple as it sounds, the advances it brought us were immense. Fired by the thrill of discovery, the heralds of the scientific age sent their new paradigm sweeping out over the world like a universal acid, dissolving the superstitions and dogmas that had for so long impeded our thinking.

In the light of science, the natural phenomena that had once seemed so inscrutable, so humanlike, lost their mystery as the hidden rules underlying them were laid bare in all their grand, mechanical glory. We peered into the dark and discovered that the cosmos was not a place of thundering spirits or leering devils, but a vast machine, one whose guiding principles meshed with all the harmonious elegance and regularity of great gears. Even life itself, so long thought to be supernatural, was revealed to be another machine, albeit a particularly complex and subtle kind. The deities and demons that had once dwelled the interstices of our ignorance washed away like sand in water, as we learned about the origins of the world, of the human species, of the mind. At least in part measure, we have grasped the truth, and learned that it was far more intricate, more satisfying, and more wondrous than the imaginings of our youth. Science does not have every answer, nor does it offer guidance for every aspect of life, but when it comes to finding out how the world works, it has no equal.

The reverberations of this era of change are still with us. We live in a time, one ongoing since the Enlightenment, when the old certainties of faith are shifting underfoot. Every sect has dealt differently with these changes, but none have entirely avoided them. Some people are moving their gods into ever more rarefied realms to escape the relentless probing, crafting deities whose existence is indistinguishable from their nonexistence. Others, more militant, are reaffirming the old creeds with fiery zealotry, denouncing scientists for their godlessness, and boasting and cheering one another for their stubborn clinging to faiths that are childlike in their ignorant simplicity. Still others, probably the majority, have come to a reluctant accommodation with the scientific outlook, but banking their hope on finding tangible traces of the gods in the shrinking areas we haven't investigated - an unsustainable compromise, whether they know it or not.

And now, into this new world, come those who did not grow up in the shadow of gods, and who have taken the simple, revolutionary step of asking why we should believe any proposition for which there is no evidence. The crude fundamentalisms of humanity are all alike in their falsehood; the unfalsifiable beliefs are all alike in their irrelevance. In place of chasing these shadows and clutching at these mirages, this new generation of free thinkers has come to the realization that we should turn our attention to the things that are real, that are verifiable - the only important things. In place of trying to appease phantoms of our imagination, we should turn our attention to bringing goodness into this world and easing the burden of our fellow creatures.

The atheist view can seem cold and comfortless to novices, for it does not promise that all our hurts will be succored. Nor does it give us guardians hovering above to guide our steps. But where atheism requires us to abandon the consolations of childhood, it brings in their place the maturity of adulthood. Instead of clouded sight, it brings clear vision. Instead of gods and angels to watch out for us, it brings the realization that we must look out for each other. We live in a vast and uncaring cosmos, but we have each other to depend on, and the freedom to succeed or fail by our own efforts.

This is our story, and we are all characters in it, as well as the storytellers. But unlike any other character, we see the story we are in, and our choices will write the next chapter. In spite of everything, the darkness of our past may come sweeping back, and our future may be a fall back into the same precipice we have been painfully climbing out of. Or the slow, frustrating, yet upward trajectory of history may continue, into a bright future that surpasses our imagination as far as the truth surpasses the imaginings of the past.

The Scars of Evolution

Human beings, like all other species on this planet, have a history. We came into existence through a process of slow, grinding trial-and-error, occurring over geological time via the sieve of differential survival. And like all species, our bodies and our genes reflect and bear witness to that history. Far from being perfect, one-time creations, we still bear the scars of the evolutionary process that made us.

This post will discuss some of the lines of evidence which hint at humanity's past. I won't repeat that well-known example of an evolutionary vestige, the human appendix. Instead, I'm going to focus on a few other examples that aren't as widely discussed.

• Toes. It's only because we're used to having toes that we don't usually consider how strange they are. Why do our feet have these stubby, non-functional digits on the ends? They can't grip nearly as well as fingers, and we don't need them to balance or to walk. (Why not just have a fused front of the foot?) By contrast, anyone who observes other primate species can see that they have, not two hands and two feet, but four hands, all of which are good for grasping. As human beings gained the ability to stand and walk upright, our feet lost their grasping function, but the digits themselves, though now shrunken and largely useless, remain.

• Lanugo. This little-known developmental phenomenon is an important clue to our mammalian past. Lanugo is a coat of fine, downy hair that fetuses grow while in the womb, covering the entire body except for the soles of the feet and the palms of the hands. Typically, lanugo is shed by the seventh or eighth month of pregnancy, although premature infants may retain it for several weeks after birth. The question is why we grow it at all, and the theory of evolution can easily explain this as a vestigial characteristic retained from our furry ancestors.

• Goosebumps. Fitting neatly together with lanugo is the vestigial human trait called the pilomotor reflex. When a person is cold or frightened, tiny muscles at the base of each hair contract, causing body hair to stand on end. In animals with thicker fur, this is a useful reflex: erect hairs trap air to create a layer of insulation, and they also make the animal appear larger and more intimidating. In humans, however, it is pointless. Like lanugo, goosebumps are a giveaway clue indicating that relatively hairless human beings are descended from furry progenitors.

• Hiccups. Yes, hiccups are a sign of humanity's evolutionary past. In fact, unlike goosebumps or lanugo, which merely point to our shared history with hairier mammals, hiccups point all the way back to the time when humanity's ancestors were amphibians. According to this article by Neil Shubin (HT: The Panda's Thumb), the hiccup reflex is controlled by an area of the brain that we share with tadpoles. The hiccup consists of a sharp inhalation followed by a closing of the glottis (the valve at the top of the windpipe). In tadpoles, which have this same reflex, the inhalation draws water into the mouth, where the gills can process the oxygen it contains, but closes the glottis so the water does not enter the lungs. For tadpoles, it's a vital breathing reflex; in humans, it's a hiccup. And the same measures that often arrest hiccups in human beings (inhaling carbon dioxide, stretching the chest wall by taking a deep breath) also stop the gill-breathing reflex in tadpoles.

• The true human tail. One of the most shocking - for creationists, anyway - human atavisms is the true human tail. On rare occasions, human infants are born with short, non-prehensile, but undeniably real tails, up to several inches in length and containing nerves, blood vessels, muscle fibers, and sometimes even extra vertebrae. They can move through voluntary muscle contraction.

In fact, all human embryos grow tails while in the womb, and normally they are reabsorbed before birth. The true human tail is the result when this does not happen. Usually they are surgically removed, although they are benign. For an evolutionary scientist, the reason why we grow them is obvious: we are descended from an ancestor species which had them. For creationists, who claim that human beings were created complete and separate as we currently are, it must be difficult to explain why we have so many vestigial structures that link us to other species of mammals.

• The fused chromosome 2. It's long been known that human beings have 23 pairs of chromosomes, while the other great apes such as gorillas and chimpanzees have 24. It is all but impossible that the lineage that led to humans could have completely lost all this genetic material and still produced a viable organism. Where, then, did the extra chromosomes go?

Chromosomes are tipped with distinctive segments of DNA called telomeres and have another special segment called a centromere in the middle. Lo and behold, human chromosome 2 has a telomere on one end, then an inactivated centromere, then a segment of telomeres in the middle, then another centromere, then a final telomere - the structure we would expect to find if two chromosomes had fused into one. When we compare this chromosome to the two appropriate ape chromosomes, we find a compelling match, indicating that this chromosomal fusion occurred at some point after the human lineage split from our ape relatives.

• The vitamin C pseudogene. Unlike most mammals, human beings can't synthesize their own vitamin C; we must ingest it as part of our diet, or else we get the disease of scurvy. Under the hypothesis of special creation, humans were created this way from the beginning, so we wouldn't expect evidence that we once had this ability but have since lost it. However, according to evolution, we are descended from other mammals, and since most mammals can make their own vitamin C, we'd expect that human ancestors did have this ability at some point as well. If this is so, our genes may preserve evidence of it.

Sure enough, human beings have a version of the vitamin C synthesis gene, but ours is "broken", disabled by mutations. Our primate relatives, who also lack this ability, also have broken versions of the gene. Just as evolutionary theory would predict, the same disabling mutations that exist in the human gene can be found in the genes of chimpanzees, orangutans, and macaques - compelling evidence that we are all descended from a primate common ancestor who incurred this mutation at some point in the past. (It's likely that this mutation wasn't selected against because all primate diets are rich in fruit, providing abundant vitamin C.)

Taken together, the scars of evolution provide abundant evidence of humanity's history. Like all species on this planet, we are not unique special creations. We are one end result of a long process of mutation sieved through selection, a countless series of adaptive compromises and tradeoffs. Our very bodies testify to the natural forces that have shaped us through the vast expanses of time.

Book Review: The God Part of the Brain

(Author's Note: The following review was solicited and is written in accordance with this site's policy for such reviews.)

Summary: Contains many interesting ideas, but the informed reader will find much to take issue with.

Atheist Matthew Alper's The God Part of the Brain seeks to explain the religiosity of humankind in terms of human evolution and the biology of conscious experience. Alper's hypothesis is that the increased intelligence that gave human beings an evolutionary advantage also gave us the ability to foresee our own inevitable deaths. To prevent people from becoming debilitated by this knowledge, evolution counteracted death anxiety by instilling in us a biological predisposition to believe in gods, a soul, and an afterlife. Now that we understand why we believe in these things, he argues, there is sufficient evidence to conclude that they are all just cognitive illusions and none of them are real.

Although this book contains many attention-getting ideas, I believe the skeptical, knowledgeable reader will find many good reasons to doubt its thesis. Alper has no formal scientific training that I know of, and is a layman when it comes to biology; and it shows. His conclusion that religious belief is genetically hardwired into the entire human species, so that belief in God is a human trait as natural and universal as language or walking upright, is far too sweeping. Not nearly enough in the way of evidence is presented to support it. Other than a brief, footnoted reference to a single twin study, his entire line of argument rests on the assertion that belief in gods, an afterlife, and a spiritual realm is found in every human culture, even if the specifics of that belief differ, and that the only explanation for this is that such belief is a genetically programmed instinct.

Since this is where Alper begins, this is where I will begin as well. It is not the case that every human culture since the dawn of time has believed in a dualistic, Platonic conception of reality. Here is how he puts it:

...every human culture has perceived reality as consisting of two distinct substances or realms: the physical and the spiritual.

...every culture has maintained a belief in some form of a spiritual reality. As this realm transcends the physical, things comprised of spirit are immune to the laws of physical nature, to the forces of change, death, and decay. Things therefore which exist as a part of the spiritual realm are subsequently perceived as being indestructible, eternal, and everlasting. (p.3)

While reading this passage, the counterexample that immediately came to my mind was Buddhism. Contrary to Alper's claims, Buddhism generally does not believe in a distinct substance called "spirit" that is immune to the laws of physical decay. On the contrary, the core Buddhist tenet of anatman (literally "no-soul") teaches that human minds, far from the imperishable ghost in the machine that Western religions envision them as, are made up only of mutable aggregates called skandhas that are mistakenly identified as an imperishable self. The belief that the self is immutable and permanent is one of the fundamental ideas that Buddhism teaches against, regarding it as a delusion that causes all the suffering that people experience. Buddhism generalizes this principle to the belief that all things are transient and impermanent. As explained on this site:

The one great law of the universe, then, is change. Phenomena come into being, mature and disappear. They are the result of conditions; when the conditions change, they also change or disappear. Even those things which appear as permanent are impermanent. Entire universes come into being, mature and disintegrate. Buddhism does not recognize a primal cause, nor does it recognize the existence of a permanent, unchangeable substance in anything. Rather, it sees all things as constantly changing, as conditionally created.

Alper's understanding of Buddhism is seriously lacking. Several times, he mentions the Buddhist concept of nirvana, but speaks of it as if it were equivalent to the afterlife in the Western religions, a place where the immortal souls of the deceased go to dwell. Again, this is a gross mischaracterization of Buddhist teaching, which regards nirvana as a state of non-existence, insofar as it can be described in words at all. In fact, the word literally means "extinction".

Other examples could be adduced - the ancient Greek Atomists, some forms of Judaism - to show that not all cultures or religions believed in an immortal soul and a spiritual afterlife, as Alper incorrectly claims. The basic point is that the fundamental claim underlying all his assertions, the supposed universality of human belief in the spiritual, simply is not true.

In addition to this, I also find fault in Alper's scientific claims, specifically his claim that the only way to explain a universal or near-universal human belief is as a hardwired adaptation. Granted, in non-intelligent, non-sentient species that live their lives propelled entirely by instinct, it is a sound claim that any universally observed behavior must be dictated by genes. But human beings are obviously not such a species, and it is here that Alper's analogies between human religions and planarians turning toward light fall short. In addition to instinct, we have a wholly new level of mental and cultural complexity not shared by other species, and this undermines any simplistic claim that all our behaviors must be programmed by our genes.

Consider a parallel case. All human cultures have also worn clothes, in some form or another. Does this mean that clothes-wearing is also hardwired into us, programmed in our genes? Do the As, Ts, Cs and Gs of our DNA spell out instructions on how to cut and stitch a pair of pants, somewhere on our chromosomes? Are cultures that prefer robes, kilts or togas made up of mutants carrying an alternative allele of the clothes-wearing gene?

As any reputable biologist would agree, this is plainly absurd. There are very good cultural reasons why people wear clothes, including protection from the elements, societal notions of modesty, the desire to attract the opposite sex, and displays of social status. This commonality can be accounted for by basic, general similarities in the architecture of the human mind, and does not require elaborate scenarios postulating a specific selective advantage for early clothes-wearers. As compared to the null hypothesis, the claim that there exists a specific "clothes-wearing" gene is a positive assertion and as such takes on the burden of proof. Without empirical evidence to support such an idea, it becomes nothing more than a speculative "just-so" story, an example of armchair theorizing unsupported by the facts.

If religion is not a hardwired instinct, how else can its prevalence be explained? There are three alternatives:

1. The memetic explanation (adaptive): Religion is not hardwired in our genes, but has spread and become universal because it offered an advantage to human cultural groups that practiced it - societal cohesion and cooperation, willingness to sacrifice oneself in war, the establishment of law and order through divine-command morality, or whatever else - and groups that did not have this advantage were unable to compete with those that did, and eventually died out.

2. The spandrel explanation: Religion per se is not hardwired in our genes, but is an accidental byproduct of some other beneficial adaptation that evolution selected for in our species' past, such as the propensity to participate in dominance hierarchies, the desire to seek cause-and-effect relationships in the world, or the urge to anthropomorphize natural phenomena we do not understand. (See Daniel Dennett's Breaking the Spell for a run-down of these possibilities.)

3. The memetic explanation (parasitic): Religion is not hardwired in our genes, but has spread and become universal because it is advantageous to the religious memes themselves to do so. In this explanation religion is like a common cold virus, evolving in ways that improve its own propagation, even if this results in deleterious effects to the human beings who act as its hosts.

Note, also, that these explanations are not mutually exclusive. Like most complex natural phenomena, religion probably has multiple underlying causes, and the true explanation will almost certainly involve all of them to some degree. Personally, I lean towards a combination of 2 and 3, with a dash of 1. I do not, however, believe that religion is genetically hardwired into us, or that it would have entailed any adaptive advantage to humanity if it was.

Alper's hypothesis is an extreme version of genetic determinism: any cultural behavior that is widely or universally practiced must be dictated by genes that force us to instinctually behave in that way. No mainstream biologist or evolutionary psychologist that I know of holds to such a strong version of this idea, not even Richard Dawkins, who has been derided as an "ultra-Darwinian" by his critics.

There is another obvious counterexample to this claim: if Alper is correct, how could there be such people as atheists? He offers two possibilities to explain this. The first is that, like most genetic traits, religiosity exhibits a range of variation, and some people will be born with more or less capacity for it than others:

...there are those we might call spiritually/religiously deficient, those born with an unusually underdeveloped spiritual/religious function.... These are society's spiritually retarded, if you will, or, in keeping with the musical metaphor, those we might call spiritually tone deaf. (p.183)

This hypothesis does have one highly testable implication: there should be a genetic difference between theists and atheists. If it is true that religious belief is a preprogrammed genetic instinct to counteract the otherwise unbearable knowledge of mortality, it should follow that people who lack religious belief but are not crippled by dread must have a different gene that enables them to cope in another way. I strongly doubt any study will ever be performed that finds such a thing, but if one ever were, that would be compelling evidence in support of Alper's thesis.

But then again, there is another problem: what about people who convert from theism - often very intense, fundamentalist forms of theism, which Alper says lie on the opposite end of the bell curve of variation from atheists - who deconvert and become atheists? There are many such stories that could be produced. Are we to believe that these people's genes have changed during their individual lifetime? Obviously not.

Alper's suggestion is that these people's innate proclivities toward religion may have "atrophied", or that they have "chosen to suppress" them (p.183) - but if this is possible, it undercuts his entire hypothesis and throws its falsifiability into serious question. Alper's entire point is that the knowledge of one's future death is such a horrifying and debilitating awareness that people lacking a spiritual part of the brain literally could not survive and were driven to extinction (he says the knowledge was "jeopardizing our very existence" (p.183)). But now he implies that people can suppress this tendency without serious repercussions?

In a later chapter, this book also puts forth an inventive hypothesis, albeit one that strikes me as highly unlikely to be true. It suggests that America's high degree of religiosity as compared to most First World nations is due to a founder effect: most of the early immigrants were religious devotees fleeing persecution, who brought their genetic tendency toward dedicated religious practice to their new nation. If this were the case, how would we account for the fact that New England - site of settlement of the Puritans, one of the most fanatically religious of all America's immigrants, as Alper documents - is today relatively secular, as compared to the Bible-belt South, which was originally founded for economic profit? I suspect, again, the reasons for the United States' religiosity is cultural and not genetic: the Constitution's guarantees of a secular government have created a spirit of free-market competition among faiths, as opposed to the established European churches that became complacent and apathetic due to a lack of competition.

There is one more point I have to comment on. Despite being an atheist, despite proclaiming his confidence in science as the only truly effective method of understanding the world, there comes a point where Alper makes a truly bizarre philosophical claim that contradicts much of what he himself says:

As all of our perspectives are relative, no species, nor any individual within a species, can ever claim that its interpretation of reality constitutes any absolute truth... just as flies possess fly "truths," humans possess human "truths," neither being any more genuine or "real," just different. (p.226)

How can this not be read as a repudiation of everything he has spent the previous two hundred pages arguing? If different claims to truth are merely a matter of opinion and there is no way to determine which is more accurate, then his claims that evolution has given us a propensity to believe in God should also be viewed as mere opinion, no more valid than any alternative possibility.

This sloppy thinking is all too characteristic of the book, unfortunately. There are some interesting nuggets of information to be had, such as its citation of a deliciously ironic study that shows religious fundamentalists, not atheists, have often had stressed and difficult relationships with their fathers. But its major argument is little more than armchair philosophizing, lacking in substantial evidentiary confirmation, and contradicted in important ways by much of the evidence we do have.