In an old essay on Ebon Musings, "Finding Beauty in the Mundane", I wrote in a contemplative mood:

Have you ever considered the trees? Though their kind of life is far grander, slower and more patient than ours, they are each individuals, as different as human beings are. They add beauty to the world, give peace in their dappled shade, freshen the air and enrich the earth, and turn even the most hard-edged urban environment into a blossoming garden. We humans grew up beneath the trees, and we love them still...

Several years later, I still find this to be true. Whether I'm depressed or whether I'm already feeling good, it's almost always the case that visiting a botanical garden or a nature preserve, or even just going for a walk on a tree-lined street, noticeably improves my mood. The sight of sunlight slanting down through green leaves never fails to give me a sense of calm and peace. I tend to think the cause is that looking up at a tree reawakens one's sense of perspective: it's hard to see your own troubles as so serious in the presence of an organism that measures time only in years and decades.

But trees have more than just aesthetic benefits. Human beings feel an instinctive attraction to nature and wilderness, what E.O. Wilson called biophilia, and we flourish in its presence. For example, in one famous study, surgical patients who could see trees outside their window recovered faster and required fewer painkillers than patients whose window looked out on a brick wall. Other studies have found that greener urban areas have lower crime rates and that being in green environments lessens the symptoms of ADHD and improves schoolchildren's academic performance. (And that's not even to mention the many environmental and economic benefits of trees, either.)

The most likely explanation for this is that millions of years of evolution have instilled in us a built-in preference for certain kinds of environments, namely those most similar to our species' ancestral habitat. Wilson argues that this is the savanna, an open grassland broken up by patches of forest. This is the habitat we evolved in, the one we're best adapted to, and when we're placed in such an environment, we tend to fare better both mentally and physically. Urban environments, by contrast, present very different stressors that the human species never evolved to deal with.

I wonder if this feeling of displacement from nature is something that plays a role in religious conversions. When people live only in cities, surrounded by concrete and fluorescent lights, separated from nature, they do feel a sense of isolation and loss, and most of them don't know why. Religious proselytizers, of course, claim they can offer something to fill that void, and to people who don't know the true cause of these feelings, it's probably an effective sales pitch.

But when you know the true source of these feelings, the imitation can't compare to the reality. As I found for myself, the feeling of awe induced by direct contact with nature at its most spectacular is an ecstasy that easily compares to anything offered by any church. That's a piece of knowledge we ought to spread more widely. If more people understood the true, natural roots of human spirituality, the artificial attractions of religion might not prove so resilient.

It's said that nothing is harder to kill than an idea. Trying to stamp out a deeply felt belief by force, especially a religious belief, not only makes its followers cling to it more tenaciously, it gives them an aura of martyrdom that makes the belief look even more attractive to outsiders. And when the belief in question is a religious belief whose scriptures claim that persecution of the faithful is a sign of their righteousness, these tendencies become all the stronger.

This is more than just an academic debate, unfortunately, because we're currently seeing it play out in the spread of militant Islam. In some form or another, Islam is practiced by almost a third of the population of this planet, and this means there's a vast pool of people who are susceptible to the siren song of radical preachers calling for violent jihad. Fundamentalism is spreading among them like a weed, and the memes that give fundamentalist Islam its resilience and persistence are interwoven with memes that encourage acts of bloodshed and terrorism: suicide bombings, chopping off heads and hands, stoning and hanging as routine punishments, the execution of apostates, the brutal oppression of women and religious minorities.

Nor can it be said any longer that militant, fundamentalist Islam is just an insignificant minority within a peaceful faith community. Polls of Muslim countries routinely find that majorities or sizable pluralities approve of tactics like suicide bombing, even against civilians (see p.39). And diplomatic organizations representing dozens of Islamic governments are still pressing for legal restrictions on free speech around the world. In most Muslim-majority nations, the rights of women and minorities, both de facto and de jure, are practically nonexistent.

We badly need to provoke a new Enlightenment in the Islamic world, but how? As any atheist knows, religious memes are self-protecting; they come packaged with concepts such as faith, obedience to religious authorities, the command to trust only one book, and the promise of hellfire for those who disobey or doubt, all of which make it difficult for people inside the religion to take a critical look at their own beliefs. Once they've taken root, they're very difficult to eradicate.

To answer this question, I think it's worth asking another one. Why is it that violent Islam has had so much success at spreading itself? How has it made so many converts?

I don't believe that it's because militant Islam is intrinsically more appealing than moderate Islam, or because it offers a stronger sense of purpose or identity. Nor is it because, as racists sometimes claim, Muslim people are less intelligent or more prone to violence than Westerners. I think the real explanation is very different and, once you realize it, much more obvious. Ayaan Hirsi Ali explains it in her book Nomad, describing her experiences with rootless Somali youth in Nairobi:

"Some of these young men later repented and joined the Muslim Brotherhood. They would go to Saudi Arabia on Islamic scholarships and come back as preachers of what we would now call radical Islam. Their own story was compelling, for they had been saved from evil, Westernized behavior when Allah showed them the straight path." [p.57]

The spread of radical Islam can be traced directly to the disastrous coincidence that the more severe forms of Islam, like Wahhabism, were born in and came to dominate the same countries that have some of the world's richest oil reserves. The leaders of these countries, all of which are theocracies, treated this discovery as proof that God favors their beliefs. And they've used - they're still using - their vast oil wealth to fund an evangelistic movement spreading the poison of militant Islam throughout the world.

This makes the otherwise mysterious success of Islamism much more understandable. There's nothing inexplicable about it - it's entirely to be expected that the wealthiest faction will have the most ability to spread its message. And this is all the more true when they're preaching to people in poor and developing nations, who stand to gain the most from affiliating themselves with the Islamist movement and the financial power that supports it. Most of these countries have governments that are weak, corrupt or autocratic, making an attractive alternative of charismatic Islamist preachers who claim to represent virtue and societal order. And in many poverty-stricken regions, Saudi-funded madrassas are literally the only source of education, which means these preachers face little resistance or competition in the battle for young minds. (This sheds some light on why the Afghani Taliban are so bent on destroying Western-built schools, especially girls' schools. It's not just because they want to keep women ignorant; it's because they fear the competition.)

And this theory points the way to breaking the power of radical Islam: We badly need to free ourselves from our dependency on fossil fuel. The fact that it lubricates every part of our economy means that America and the West are, in effect, paying a tax to the religious fanatics who desire our destruction. This isn't a new observation, of course, but I think this analysis clarifies the direct connection between our addiction to oil and the spread of jihadist ideologies that cultivate theocracy and terrorism.

If we could develop an alternative-energy economy not based on importing fossil fuels from the Mideast, the Islamist regimes would shrivel up and die, and the source of funding for al-Qaeda and its affiliates would dry up virtually overnight. As it is, we're bogged down in wars in Iraq and Afghanistan, spending billions of dollars and thousands of lives in a futile quest to establish Western-friendly regimes, while at the same time spending rivers of cash that flows to the factions resisting us. We're fighting the enemy with one hand while aiding them with the other. It would be laughably absurd, if the consequences weren't so deadly serious.

Atheists have a great number of famous names to our credit. We can justly claim renowned composers, scientists, musicians, civil rights leaders - and conservationists, as we'll see in today's post on the contributions of freethinkers.

Richard Leakey was born in Nairobi in 1944, son of the famous archaeologist Louis Leakey. The elder Leakey was a strong supporter of racial equality, and Richard's upbringing reflected that belief. He started school soon after the Mau Mau rebellion had been defeated, and when he spoke up in favor of the native Kenyans, his classmates taunted him as a "nigger lover", beat him, spat on him and forced him into a wire cage. Several online sources say that he also resolved never to be a Christian after he was caned for missing chapel services.

Partly due to incidents like this, Richard never finished high school. But despite this, he showed an impressive aptitude of his own for finding fossils of human ancestors - including Turkana Boy, one of the most complete hominid skeletons ever unearthed, which was discovered by a paleontological team under his direction. He also showed impressive skill at administration, becoming director of the National Museums of Kenya at just 25.

In 1989, in response to an international outcry over the slaughter of elephants and rhinos by poachers, President Daniel Arap Moi appointed Leakey head of the Kenya Wildlife Service and tasked him with protecting Kenya's endangered wildlife. Leakey accomplished this in characteristically bold fashion - by creating well-armed, specially-trained park ranger units that were authorized to shoot poachers on sight. Draconian though this seems, it was effective: almost a hundred poachers were killed during his first year at KWS, and poaching rates declined thereafter. Leakey also made international headlines when he burned 12 tons of confiscated illegal ivory, worth more than $3 million, in a massive bonfire.

In 1993, Leakey was flying a small private plane that crashed near the Great Rift Valley. This is widely believed, though never proved, to have been sabotage by someone seeking to assassinate him, probably in revenge for the anti-poaching campaign. He survived the crash, though he was badly injured and both his legs had to be amputated. Within a few months, however, he was up and walking again on prosthetics and back on the job.

Unfortunately, as a crusading reformist, Leakey may have been too zealous even for his own government. President Moi demanded that he reinstate 1,600 KWS employees who had been fired for corruption or inefficiency, and when Leakey refused, Moi gutted the agency, taking away most of its budget and power. Leakey resigned in protest, and in 1995, founded a new political party, Safina, devoted to the cause of reform. His campaign drew angry threats from British settlers who felt his zeal was putting them in jeopardy, and on one occasion, he was attacked by a mob loyal to Moi's party. As always, however, he refused to quit, and two years later, he won a seat in Kenya's Parliament. A year after that, with international lenders withholding funds because of pervasive corruption, Moi asked Leakey to rejoin his administration. As a January 2010 article in Sierra puts it:

So Richard Leakey, five times accused of treason — and of being a racist, colonialist, and atheist (the only accusation to which he pleads guilty) — was named head of Kenya's Public Service.

This time, Leakey had even more power than before: in his new job, he had authority second only to the president. But even this wasn't enough, and when his anti-corruption efforts ran into repeated political roadblocks, he quit for the second time. This time, he swore off politics for good.

At 65, Leakey still lives in Kenya, hale and hearty after two kidney transplants and still working to advance the cause of conservation in the country where he's spent nearly all his life. His most recent achievement is the launch of WildlifeDirect, a website that directly connects Western donors with conservationists and field biologists working with threatened and endangered species throughout the world. In 2008, WildlifeDirect helped to fund and train 700 park rangers in the Democratic Republic of the Congo.

Throughout his life, Leakey's zeal for combatting corruption has been exceeded only by his passion for bridging the gap between humans and nature, whether through unearthing our fossil past or preserving our threatened present for posterity. It's plain that his being an atheist didn't deprive him of an ethical compass. If anything, it contributed to the sense of profound interconnection with the natural world that's driven all the greatest advocates of conservation, past and present. Richard Leakey is one freethinker that atheists can be proud to have on our side.

Other posts in this series:

• The Contributions of Freethinkers

Sam Harris is famous for the argument that religion, even moderate religion, does harm by teaching that faith is a virtue that should not be questioned, which encourages militant and violent strains of fundamentalism. Today, I want to talk about another way, subtle but unmistakable, that religion causes harm to human beings.

Because of its tendency to treat all the statements of its founders and sacred texts as holy truth, religion has the effect of "freezing" the prejudices in vogue at the time of that religion's founding - encouraging followers to view them not as contingent or arbitrary cultural biases, but as the received will of God. And when a community of the faithful sincerely believes this, they'll perpetuate those prejudices for decades or centuries, long after the rest of the world has made enough progress to leave them behind. These preserved opinions are like fossils, surviving remnants of a more ancient era. But unlike fossils, they're still alive and malignant and able to do harm.

Consider the belief, still all too common, that rape victims are partially to blame for being raped if they drink or dress provocatively. This is a pernicious myth that's long been used, and is still being used, by rapists to excuse their actions and discourage rape victims from reporting the crime. It springs from the ancient prejudice that men can't be expected to exercise self-control in such situations, while women who are raped must have done something to tempt or incite the man into raping her. This is the sort of vile misogyny that our society should long since have discarded - but not only is it alive and well, it's still being propped up by patriarchal, male-dominated religions. Consider this story about a religious leaflet given to a woman in Virginia:

"You may have been given this leaflet because of the way you are dressed," it begins. "Have you thought about standing before the true and living God to be judged?"

..."Scripture tells us that when a man looks on a woman to lust for her he has already committed adultery in his heart. If you are dressed in a way that tempts a men to do this secret (or not so secret) sin, you are a participant in the sin," the leaflet states. "By the way, some rape victims would not have been raped if they had dressed properly. So can we really say they were innocent victims?"

This loathsome argument, though presumably from a Christian source, has much in common with the Muslim cleric who proclaimed that women who refuse to veil their faces are like "uncovered meat" that gets eaten by stray animals. Both of them justify their woman-hating, blame-the-victim attitude by passing it off as the word of God.

The same attitude is behind a new and worrying trend in American schools: religious-right legislators who've supported teaching creationism in science class are now broadening their sights to demand the teaching of "alternative views" about global warming, as well as other favorite right-wing targets. As the article notes, white evangelicals are among the least likely to accept the science behind climate change (and I've written before about similar views from both sides of the theological aisle).

It's no surprise that people who are hostile to the scientific worldview would oppose not just evolution, but other well-established scientific truths as well. A worldview founded on faith, fallacy and magical thinking is unlikely to accord scientific research the respect it deserves. (To cite another example, prominent creationists Philip Johnson and Jonathan Wells also belong to a pseudoscientific group which argues that HIV does not cause AIDS.) And since Christianity has, for the most part, become fused with the Republican Party in America, it was to be expected that there's hardly any daylight left between the political goals of those two groups. It started with Christians infiltrating and taking over the Republican Party platform, but it's fascinating to see how this connection now runs in the other direction as well - how the corporatist, social-Darwinian agenda of the GOP has become fossilized as the de facto position of evangelical Christianity.

The harm done by fossilized opinions is most obvious in Islam, where the status of women has scarcely advanced in fourteen hundred years. Laws still in force throughout the Muslim world allow men to take multiple wives, forbid women from getting an education or traveling outside the home without a male relative, devalue their testimony in court, and more. Just a few weeks ago, Muslim tribal elders in Bangladesh ordered the flogging of a rape victim - and Bangladesh is relatively advanced when it comes to women's rights, at least when compared to most other Islamic countries.

The next time you hear some mealy-mouthed accommodationist denouncing atheists for claiming "intellectual superiority" over believers, remind them of facts like these. If atheists' opinions are better, truer, more valuable than religious opinions, it's not because we're intrinsically smarter - it's because we are willing to change our minds when new evidence presents itself. Millions of religious believers' minds are mired centuries in the past, clinging to beliefs that we now know to be false and moral tenets that we now know to be atrocities. We have every right to feel superior to people who still hold such fossilized opinions.

Last month, in "Dreams of a Better World", I considered some of the immediate problems humanity could solve if we had the collective will to do so. I want to continue that theme in this post, but from a longer perspective.

Historically, humanity's knowledge has exceeded its wisdom. As soon as we invent a new technology, we begin adopting it on a wide scale, without asking whether we should or what the consequences might be. Many of our most pressing problems - multidrug-resistant diseases, global climate change, air and water pollution, the proliferation of nuclear weapons, the ongoing extinctions of species and destruction of habitat - trace back to this impulse.

Our powers of reason have brought us amazing advances in understanding and controlling the world; but those rational faculties have not, as of yet, mastered the baser instincts of greed, xenophobia, violence and tribalism that underlie them. Instead, our reason is too often enslaved to that darker side of our nature, becoming the servant of our destructive passions rather than their master. Hence, we see absurdities such as Islamist fanatics, who reject every other scientific advance of the last several hundred years, struggling to create nuclear weapons. The only scientific knowledge they accept is that which they can use to destroy. Doubtless, if evolutionary theory offered the key to creating deadlier biological weapons, all the universities in Islamic theocracies would have top-notch biology departments as well, next door to the theology departments still repeating the narrow dogmas of a medieval desert nomad.

But it's not just on those easy targets that I want to pin the blame. Too often, we in the allegedly enlightened West have been guilty of similar deeds, selectively using the fruits of science that offer us the most immediate benefit rather than asking what is moral or sustainable in the long run.

We invent ever-more efficient fishing technologies to scour the ocean of the increasingly few remaining fish, refusing to recognize the downward spiral our actions have created. We fuel our economy with dirty, polluting, high-carbon coal and oil because it's cheap - at least by the usual accounting - and to get it, we think nothing of drilling oil wells in delicate habitat, or bulldozing whole mountains and dumping the rubble into nearby streams and watersheds. We drain rivers dry to build ever more lavish cities and communities in the middle of the desert. We run industrial agriculture on vast quantities of fertilizers and antibiotics, and let someone else pay the cost for poisoned groundwater, dead zones in the oceans, and multidrug-resistant staph and tuberculosis.

To build a human society that can survive over the long term, we need to turn away from this. What we need, and what I hope, is that we'll begin asking ourselves not just whether we can do something, but whether we should - and if the answer is that we should not, that we will then collectively agree to forbear.

I don't mean to imply that there will be a single global authority dictating which technological avenues will or will not be pursued. That would be an abhorrent tyranny. I have in mind a different future: a world where people have as much as or more liberty than they do now, yet where the human race can come, freely and without coercion, to a universal consensus on which courses of action should be taken and which left alone.

This may strike you as an impossible dream. I admit that the evidence so far is against me: historically, if one person or group has been unwilling to cross a boundary, there's always another that will. But that's precisely the attitude that needs to change if humanity is to survive and prosper. As technology grows more and more powerful, smaller and smaller groups of people wield destructive potential that the entire human species didn't have even a hundred years ago. We need to make the transition to a world where this kind of power is used wisely by all who have access to it, and I believe we will.

How can the human race reach this level of unanimity? I answer that the things that hold us apart are mainly irrational impulses - racism, sexism, nationalism, religion - which encourage their followers to value one group, one land or one belief more than a rational accounting of its value would suggest. Thus, the answer is simple: Humanity will come together when we learn to overrule those superstitions and fully acknowledge - and live out - the supremacy of reason as a guiding principle. When that happens, we will be able to reach agreement on all the things that matter.

This isn't going to be a single event, nor will the world be transformed overnight. It may take centuries to complete. But I believe we're on the cusp of the transition, and we may even witness the beginning of it in our lifetimes. We'll begin to see consensus breaking out, unanimity gradually developing. By the time agreement finally arrives, it will doubtless seem so easy and natural, we'll wonder why it took us so long in the first place.

The literal meaning of the word "apotheosis" is "elevation to divine status" - and as I've previously said, I reject the idea that this should be our goal. The gods are petty, jealous, easily provoked creatures; they embody our worst traits, not our best, and we shouldn't be seeking to emulate them. But "apotheosis" has another, more fitting meaning: "the supreme or the best example", and that's a goal I can support without hesitation. We should all seek to become the best example of humanity, to unleash the potential for goodness inherent in every person. This state may seem to be impossibly far off, but if each of us does what we can to bring it into being, we may find it isn't as far as we think.

Guest Post by Rob Schneider

[Editor's Note: In my third anniversary post, I mentioned that I wanted to have more guest essays on Daylight Atheism, as well as more posts exploring issues where atheists don't all agree. This post accomplishes both those aims. Please welcome Rob Schneider (not that Rob Schneider) and his first appearance on Daylight Atheism.]

Veganism and vegetarianism have a bad reputation in our society. Those who identify as vegan or vegetarian tend to receive odd looks and questions like, "doesn't that burger look good?" We get labeled as "tree-huggers" and "extremists." It's remarkably similar to being out as an Atheist. I hope to answer some common questions and present a secular case for vegetarianism as a sound ethical choice.

I'll start by clarifying my terms. Vegan means refraining from the consumption of anything that contains animal products, especially things that come from animals with nervous systems. Yeast is ok, but a Vegan will avoid eating any food containing dairy, eggs or meats, and will carefully check ingredient labels to avoid additives from animal sources, such as gelatin (from hooves) or certain enzymes. Vegans also avoid any products containing animal hide, bones or other bits. Most vegans will use life-saving medicines made from animal components. The Vegan Society has a comprehensive list of animal products commonly found in food here.

Vegetarian covers a broad range of consumption choices. Strict vegetarians will use the same food guidelines as vegans, but use non-food products made from animal parts, such as leather shoes. Ovo-lacto vegetarians will consume eggs and dairy, but not meat. Some people will use the term vegetarian to mean that they avoid red meat, so they will eat fish and sometimes chicken. For this post, vegetarianism means the removal of all chicken, beef and pork from the diet.

I myself am a vegan, although I will be defending vegetarianism in this post. Without going into the animal welfare issues (which are well-documented elsewhere), my argument will focus on the environmental disruption and social justice issues caused by most large-scale farming practices.

Large-scale farming, also known as factory farming, is by far (pdf) the source of most animal products consumed in the West. Factory farming emphasizes size and concentration by confining a large number of animals into a small space. This causes numerous problems with waste management, greenhouse gas emissions and diseases.

Factory farming is often criticized for waste-management issues. Feedlot waste has been shown to have negative effects on the environment. The standard factory farm uses waste lagoons and spreader fields to hold the large amount of urine and feces generated by the animals. As you can imagine, the stench from a small lake of poop is vile, and has adverse effects on those who live nearby. Several studies (pdf) have shown that the fumes from feedlots cause health problems for those living nearby. Ammonia, Hydrogen Sulfide, Volatile Organic Compounds such as Methane and particulate matter are commonly found in the fumes coming from feedlots.

The feedlot lagoons and spreader fields often lack adequate runoff controls, so heavy rainfall or snow melt can cause direct leakage of the feces and urine into natural bodies of water and potable water sources for humans. This most commonly results in fish kills, but has also been shown to cause a long-term issue with mutated fish in streams.

According to The New York Times, "an estimated 30 percent of the earth's ice-free land is directly or indirectly involved in livestock production, according to the United Nation's Food and Agriculture Organization, which also estimates that livestock production generates nearly a fifth of the world's greenhouse gases — more than transportation." The amount of fossil fuel needed to grow meat is also considerable; "...if Americans were to reduce meat consumption by just 20 percent it would be as if we all switched from a standard sedan — a Camry, say — to the ultra-efficient Prius." According to Ulf Sonesson of the Swedish Institute for Food and Biotechnology, roughly half the diet-based greenhouse gasses come from meat production. Replacing 50% of the protein from meat with protein from soy in the western diet would dramatically reduce greenhouse gas emissions, "on the order of 70%."

In addition to the pollution issues, industrial animal farming is an incredibly inefficient food source. The grain fed to cattle in the USA alone would feed 800 million people. Livestock are also water-intensive sources of food. According to the Stockholm International Water Institute, a kilogram of grain-fed beef needs at least 15 cubic meters of water.

Thus far I have primarily talked about the environmental problems with using meat as a food source. There are numerous social problems with our modern meat industry as well. The modern US slaughterhouse industry has a history of food and worker safety violations, with the now-closed plant in Postville, IA, being just one example. Other abuses are regularly uncovered. Workers in US slaughterhouses are expected to work nearly twice as fast as workers anywhere else in the world. According to Eric Schlosser, author of Fast Food Nation, "...they [slaughterhouses] cut wages, they cut benefits, broke unions. And now it has one of the highest turnover rates of any industrial job." The modern US slaughterhouse has a turnover rate between 75% and 100% per year. The workers, mostly poor and many recent immigrants, are also working in what the Bureau of Labor Statistics says is the most dangerous job in America. Injuries are common due to the frantic pace of the work, the fact that power cutting tools are involved, and the amounts of blood and fat that end up on the floor while workers are moving around.

The modern industrial animal farm has many environmental and social costs that are not reflected on the in-store price tag. Our water and air are poisoned and our poor work in a dangerous job for little pay. While the modern steak is easier to buy than ever before, it is far more expensive than we as a society realize. We need to carefully re-think the true cost of our diet before we discover the bill is far more than we can afford.

On a wintry day late last year, I visited the Museum of Natural History in New York City. While touring the geology wing, I came across this boulder-sized chunk of a rock formation:

A banded iron formation from the geology exhibit of the Museum of Natural History. Photo credit to Erich Vieth.

It was out in the open with no ropes or glass around it, inviting visitors to touch it. I brushed a hand across its polished surface, which was as smooth and cool as a sheet of glass. Nothing about that touch hinted at the stone's age or history; yet it had traveled down immense vistas of time to come here, to our era, so that I could see and touch it on that day. And in the moment of that touch, I knew, I as a modern Homo sapien was briefly reunited with predecessors ancient beyond imagining, perhaps some that date back almost to the origin of life on Earth itself.

The curious, gorgeously colored strata of this stone are called banded iron formations. The dark bands are layers of metallic iron oxide compounds such as magnetite and hematite, while the reddish layers are silica-rich quartz minerals like chert, jasper and flint. Banded iron formations occur almost exclusively in very ancient rocks, and are common in strata dating to between 2.5 billion and 1.8 billion years ago. This is the period commonly called the Precambrian, although its more technical name is the Proterozoic Eon.

True multicellular life first appears in the fossil record at the very end of the Proterozoic, in the form of the bizarre and famous Ediacaran biota that would become the precursors of the Cambrian explosion. But for most of the Proterozoic, the most common fossils are stromatolites: puffy accretions of sedimentary rock laid down by vast colonies of bacteria.

The Earth in this eon was a different place. Most notably, from chemical and geological evidence, we know that its atmosphere had no oxygen. The only life was colonies of purple bacteria, making a living using the chain of chemical reactions called photosystem I, which converts light, carbon dioxide and hydrogen sulfide into sugar and releases sulfur as a byproduct. But the Proterozoic was when this began to change: this was the time when evolution invented photosystem II, the more advanced version of photosynthesis that uses water and carbon dioxide to make sugar, liberating oxygen as a byproduct. This is the very same set of reactions that sustains all green plants, and ultimately all animal life, today, two and a half billion years later.

At first, oxygen was an annoyance to Proterozoic life, but it soon became a menace. Unlike today, there were no oxygen-breathing animals to expire carbon dioxide and close the cycle, and so it quickly built up in the atmosphere as photosynthetic bacteria spread and thrived. To us, it's the breath of life, but to these bacteria, it was a deadly toxin.

At the same time, another process was taking place. Weathering of the Earth's primordial rocks had been releasing iron, most of which washed down to the sea and ended up as iron ions dissolved in the oceans. Until then, that iron had had nothing to react with, but when it encountered oxygen, the two chemically combined into iron oxides like magnetite and hematite. These compounds are insoluble, and when they formed, they precipitated out and sank to the ocean bottom, gradually building up those dark silver layers.

With iron reactions steadily removing oxygen from the atmosphere, anaerobic bacteria thrived for a time. But eventually, there was no more free iron. Once that point was reached, oxygen started to build up in the atmosphere. Heedless, the bacteria kept churning it out - until a toxic tipping point was reached, and the Earth's atmosphere was changed to such an extent that it became poisonous to Earth's life. The consequence was mass death among the planet's abundant bacterial colonies - an oxygen holocaust that knocked life back down to nearly nothing. Only a few anaerobes survived, in isolated nooks and crannies where the deadly gas did not reach.

After this catastrophe, the planet would have seen several million years of relative quiet. In this life-poor era, layers of silica minerals were deposited on the ocean floor. But in the meanwhile, erosion continued to free up iron atoms, which slowly scrubbed the atmosphere and oceans of oxygen. Eventually, the world was cleansed, and life bounced back, spreading from its refuges to once again cover the planet. Of course, this exuberance contained the seeds of its own downfall - bacteria still spewed out the waste oxygen that they could not abide - and the cycle repeated, not just once but many times. Each time, a layer of iron oxides was deposited, followed by a layer of iron-poor silicates in the aftermath. And that leads me back to the Natural History Museum, on that cold winter day where I stood and brushed a hand across a banded iron formation.

Looking at this stone, you get some idea of the dizzying vistas of geological time, as well as the turmoil that life has endured to reach the present day. Each of those colorful red and silver layers represents what was, in its own era, a disaster beyond imagining, one that reset life to its starting point. Each of those layers, as well, is a silent testament to life's tenacity in the face of overwhelming odds. Of course, the cycles of growth and destruction did not last forever. Eventually, evolution found a way, as evolution nearly always does, and oxygen was tamed to become a power source in an entirely new metabolic cycle. The oxygen-breathers arose, the remaining anaerobes retreated to the deep crevices of rocks and the sea, and life found a new equilibrium, with the balance of the atmosphere permanently changed. All the oxygen we breathe today is biologically produced, a tangible proof of life's power to reshape its own world.

As well, these banded iron formations may be a metaphor for our own foolhardiness. In our time, we too are changing the composition of the planet's atmosphere, this time through the release of greenhouse gases. In the process, we are becoming the first species since the ancient photosynthetic bacteria to have such a global effect. The danger we face may not be as severe - but it is severe enough. Those bands of iron are not only a record: they are a warning of what happens when life reshapes its own environment without thought for the consequences.

Today's post on morality concerns environmental conservation and sustainability. Human civilization has historically behaved (and many still do behave) as if the Earth was there to be conquered and natural resources were limitless. Environmental devastation is not solely the product of industrialized society; ancient cultures did the same thing, even those with tools no more sophisticated than the hand ax. For instance, as Jared Diamond wrote in his book Collapse, the reason for the disappearance of the Easter Island civilization was that the natives completely deforested the island (in part to make the log rollers used to transport the moai, the massive stone heads they are famous for), resulting in severe soil erosion and the collapse of agriculture.

But, of course, environmental destruction is most serious in industrialized societies with the technology that gives them the power to do the most damage. The damages we are still inflicting on the planet are legion: the collapse of fisheries and the mass extinction of species, tropical deforestation and the destruction of vanishing habitats, pollution in the air and water, the exhaustion of fresh water and the spreading of desert, and last but not least, the emission of greenhouse gases that accelerate global climate change, with potentially catastrophic effects worldwide.

The secular moral system of universal utilitarianism offers a set of principles through which to judge these actions. UU's main tenet is that we should maximize opportunities for human happiness over time. This leads directly to the conclusion that any use of natural resources which can be sustained indefinitely should be preferred to a use which destroys, or exhausts, the thing being used - for destructive use offers at most a single opportunity to improve human welfare, while sustainable use offers unlimited opportunity. This sweeping conclusion applies to everything from the preservation of species, encouraging the protection of living things and habitats threatened with extinction, to energy, where we should prefer indefinitely renewable energy sources such as solar and wind and immediately begin to phase out those that are not renewable.

Although conservation has numerous benefits for people who are alive today, its greatest repercussions will be felt by those in the future. As I wrote in a past comment, we cannot rationally apply UU to the desires of merely potential people - for there are a limitless number of these, and trying to anticipate their wants would result in paralysis. But there is a special case: we should try to anticipate the desires not of individuals, but of the next generation as a whole, because barring some unprecedented disaster, we know that there will be a next generation. This means that the impacts of our decision will be multiplied "down the line", affecting all our future descendants, which makes it all the more vital that we use the earth sustainably, with an eye to the future, rather than sacrificing it for short-term gain.

For cases where wealthy nations destroy the environment for the sake of convenience or luxury, all this should be uncontroversial. But one of the complicating issues is that environmental degradation is usually linked to overpopulation, as increasing numbers of people have an ever heavier footprint on the natural world. UU entails the pragmatic principle, that we cannot reasonably make some rule a moral obligation if it would impose unrealistic burdens on the people asked to follow it. By this principle, we cannot ask people to preserve the environment - it would be immoral to ask them to preserve the environment - if that required them to sacrifice their lives or the lives of their loved ones, or to give up hope of attaining a standard of living that many wealthy nations enjoy.

Defeating this problem requires tackling it from both ends. The world's wealthy nations absolutely should give up their use of unsustainable luxuries to show that they are making a sacrifice in this effort (although in the long run, most of those sacrifices will pay for themselves). Moves to reduce urban sprawl, increase the amount of protected habitat, and migrate away from fossil fuels are essential. In the meantime, we should initiate an aggressive effort to stem the tide of global population growth, through female empowerment, education on family planning and the distribution of contraception. Helping these societies to become industrialized will also help in the long run to reduce family sizes and level off population growth. All these measures will put a stop to the necessity of colonizing previously uninhabited land for survival.

In the long run, the interests of humanity are not opposed to the goal of protecting nature. Safeguarding species and habitat, fighting pollution and global warming, and investing in a sustainable infrastructure that treads more lightly on the planet will lead to stability, security and good lives for billions of human beings. Only in the near term, driven by unsustainable growth and short-sighted profit motives, does the conflict arise. And if we let the short term win out over the long term, the consequences will be disastrous. Rising seas and shifting weather patterns could turn cities into deserts, lead to staggering mass exoduses and catastrophic natural disasters, and trample the few remaining untouched parts of the planet underfoot. Global poverty will explode, as will famine, disease and drought; and we will enter into what E.O. Wilson called an "age of loneliness", when the beauty and the grandeur of biodiversity has been all but erased.

This is one track. Down the other lies a quieter, richer and more beautiful world: a place where we have learned from our mistakes, where we have drawn back and allowed nature to recover, and where human beings live within the world and not at its expense. Even beside its freely given beauty and grandeur, nature provides us with countless services we rely on, yet often take for granted: waste recycling and remediation, fresh air and clean water, productive soil and crop pollination, and many others as well. It still remains to be seen which of these two worlds we will bring into existence.

Other posts in this series:

• On the Morality Of...

I recently finished watching Planet Earth, the award-winning BBC nature documentary series narrated by David Attenborough. As its title implies, Planet Earth is an effort of considerable ambition: the filmmakers set out to produce a series that would provide a survey of our world's natural grandeur and biodiversity. To a remarkable extent, I think they succeeded. Of course the full richness of Earth's biosphere could not be exhaustively chronicled, but this series touches on many of the high points. It sweeps across every region of the planet, documenting our world's remaining wildernesses and some of the more important species that live in them, in the process filming things that have never been caught on camera before. In its scientific breadth and scope, in the beauty it depicts, and in the reasons it gives us both to fear, and more importantly, to hope, Planet Earth compares favorably to Carl Sagan's Cosmos.

The series consists of eleven episodes, each of which chronicles a different type of ecosystem flourishing on our planet. Over the course of the series, we're taken from icy tundra and boreal forest to tropical jungle, from the rich shallow seas to the blackness of the ocean abyss, from soaring mountains to desolate deserts to the eerie dark worlds of the cave systems beneath the planet's surface. Each episode is fifty minutes, plus a ten-minute ending segment called "Planet Earth Diaries" that shows how some of the more difficult-to-obtain shots were filmed - a nice touch that gives one appreciation for the truly heroic dedication of the photographers who traveled to some of the most remote, wild areas of the planet, braving all manner of harsh and grueling conditions, and worked in some cases for weeks on end just to catch a few moments of action on film. Three additional episodes, collectively titled Planet Earth: The Future, make the case for conservation using footage from the series and interviews with prominent advocates for the environment.

But the focus of the show, as I said, is on the breathtaking natural beauty of our planet and the wonderful, intricate tree of life that flourishes upon it. I couldn't do justice to all the high points in this one post, but here are a few that particularly stood out to me:

• a snow leopard, one of our planet's rarest and most elusive predators, hunting twisted-horned markhor antelope in the Himalayas of eastern Pakistan - the first close-up images of snow leopards in the wild ever filmed;
• the vast precipice of Venezuela's Angel Falls, the world's highest waterfall - a sheer drop of nearly a kilometer, so high that the falling water is blown into mist before it reaches the bottom;
• Nile crocodiles exploding out of the water to grab migrating wildebeest crossing their river - the terrifying tenacity of the bull crocodiles is shown when one of them, after grabbing a wildebeest's leg in its jaws, wrestles with its unlucky prey for over an hour before finally dragging the wildebeest into the water and drowning it;
• parachute divers leaping into the sunlit shaft of Mexico's Cave of Swallows, a dizzying sheer drop deeper than the Empire State Building is tall;
• a male polar bear, starving and exhausted after a long swim in the open water of the melting Arctic, desperately attacking a herd of bull walruses;
• a spectacular sequence in which an entire pride of African lions hunts and kills an elephant;
• the elaborate courtship displays of New Guinean birds of paradise;
• a band of chimpanzees waging war on a rival tribe, slipping silently into their adversaries' territory before erupting in a furious charge of intimidating shrieks and hoots; the savage hand-to-hand fighting ends with the losers being torn apart and, in some cases, devoured by the winners;
• banded sea kraits - aquatic snakes - swimming as smoothly as eels to hunt fish among the coral reefs of the Pacific;
• Borneo's Deer Cave, where a flock of three million bats has created a guano mound the size of a large building, covered with swarming, voracious cockroaches;
• in the Azores, a school of hundreds of dolphins herding scad mackerel, working in unison to encircle their prey and drive them closer to the surface, where diving cory shearwaters soar down to share in the hunt;
• the lush communities of strange life that thrive around hydrothermal vents on the ocean floor, powered by the superheated plumes of mineral-rich water erupting from fissures in the crust, like oases in the abyssal dark. When these vents stop erupting, a whole community can collapse from vibrant life into a dead, frozen forest of tube-worm skeletons - a devastation treated by the film with all the gravity of an empire's fall;
• a vast flock of migrating Baikal teal - hundreds of thousands of birds, all flying in unison - and the camera pulls back, and back, and still further back, until each individual bird is just a tiny speck, and still the whole flock cannot fit on the screen at once;
• and last but not least, time-lapse shots of the seasons changing, even time-lapse shots from space that show rivers flood, forests turn green, snow and glaciers advance - I don't know how these were taken or whether they were special effects.

The one caveat I would offer is that Planet Earth is a nature documentary, which means most of the sequences are of animals doing what animals normally do in the wild. If you're the kind of person who finds that boring, you'll probably be bored by this as well. There are plenty of hair-raising moments, but the purpose of the show is not to keep viewers constantly on the edge of their seat. Personally, I found it a spectacular glimpse of some of the Earth's last remaining places of wild beauty. If that description appeals to you, then I can safely say that you'll love Planet Earth, and I would definitely recommend it.

Today is - at least to my northern hemisphere readers - the winter solstice, shortest day of the year. For three months now, we've seen the sun set and the night fall progressively earlier each day. But this date marks the terminus of that trend, and though the heart of winter still lies ahead, from now on the days will start to grow longer again.

The solstice has always been a date invested with great importance. In the bitter depths of winter, our ancestors surrounded themselves with all the plants they could find that stayed green and grew - conifers, mistletoe, holly - perhaps as a form of sympathetic magic intended to speed the return of spring, or perhaps simply to draw comfort from the presence of life around them when so much else was barren and dead. On this day, those defiant celebrations came to their high point. The ceremonial kindling of flame; the feasts and the good cheer; the companionship and gift-giving - all are meant to remind us that the dark and the cold do not have exclusive power over our lives, and that the spring will come again.

As we can imagine, our ancestors were utterly dependent on the cycle of the seasons, and it's no surprise that they imbued this date with vast symbolic significance. Mythologies and traditions clustered around this date, and the calendar soon became cluttered with the dying and rising gods of the harvest. At first these religions were living metaphors, reflecting humanity's rudimentary understanding of the annual pattern of plant death and rebirth. But as time went by, the symbol gradually took precedence until it superseded the reality, to the point that many people today are ignorant of the harvest metaphor and think that the mythology is all. Yet even today, when so many of us are divorced from the land, we still feel nature's rhythms. We too feel the sinking of the sun in our veins, and we too kindle lights in anticipation of the sun's annual return. Not for nothing is the humanist reinvention of these ancient agricultural holidays named HumanLight.

As I say, humanity was once at the mercy of the seasons. Indeed, to a much greater extent than most people realize, that is still very much the case. We depend on the natural world for a huge variety of vital services - fresh air and water, fertile soil, natural waste disposal and remediation, the fertilization of our crops, buffering against storm and drought, ore and timber and fuel, new pharmaceuticals and other products - services that would cost us trillions of dollars if we had to supply them ourselves. The critical drought facing Georgia reminds us that, despite the emancipation of science and technology, our well-being is still very much tied to the ebb and flow of nature.

However, the balance of power is no longer tilted completely to one end. As the natural world influences us, so too do we influence it - and often, not for the better. Rather than treating natural capital as something valuable in its own right, both economically and for less tangible reasons, humanity for most of its history has taken the view that the world is valueless until we harvest and exploit it. And now that humanity is a planetary civilization, that outlook necessarily has planetary repercussions.

The most serious of those repercussions that we are now confronting is the threat of climate change, caused by the extraction and burning of fossil fuels which every year sends billions of tons of carbon dioxide into the atmosphere. After many decades of unwise use, we are now facing the real prospect of permanently altering climate patterns worldwide, with drastic consequences both for thousands of other species and for tens of millions of members of the human species. We're gambling recklessly with our own future, and though it's not too late to turn things around and avert the worst possible effects, the time to act is short, and the changes we must still make are vast.

It may help to put our struggle in perspective if we realize that climate change is the defining issue of our time. In two hundred years, or five hundred years, or a thousand years, conflicts like the "war on terrorism" will be historical footnotes however they turn out. But people may be living for tens of thousands of years with the repercussions of what we do to our planet here and now, in this generation. For better or for worse, we will be remembered.

Thankfully, there are signs that the global community has at last woken up to the impact of climate change, and is taking steps - frustratingly slow, but still promising - steps to solve the problem. The recently concluded 2007 United Nations Climate Change Conference in Bali, Indonesia, successor to the Kyoto Protocol, seems to have been a qualified success, with many nations agreeing to take concrete steps toward reducing their emissions - despite opposition by the U.S. that weakened the language of the final agreement. (I'm ashamed that my country, out of all the nations in the world, was the roadblock to solving this serious global challenge. We still have far too many anti-science ideologues polluting our government.) This is a problem that can only be confronted and solved collectively, and much work remains to be done.

Nevertheless, on this solstice season, we have seen the way leading to the future, and there is still reason to hope. Like almost all the problems we face, this is one where we lack neither the ability nor the resources. All we need is the will of the global community of nations and of humankind itself.