Jeff McMahan on eliminating carnivorism in the natural world

This is one of the most important and thought-provoking articles I've read in the New York Times in quite some time: The Meat Eaters by Rutgers philosopher Jeff McMahan.

In the article, McMahan asks the question, "Would the controlled extinction of carnivorous species be a good thing?" His conclusion is yes:

The conflict, therefore, must be between preventing suffering and respecting the alleged sacredness — or, as I would phrase it, the impersonal value — of carnivorous species. Again, the claim that suffering is bad for those who experience it and thus ought in general to be prevented when possible cannot be seriously doubted. Yet the idea that individual animal species have value in themselves is less obvious. What, after all, are species? According to Darwin, they “are merely artificial combinations made for convenience.” They are collections of individuals distinguished by biologists that shade into one another over time and sometimes blur together even among contemporaneous individuals, as in the case of ring species. There are no universally agreed criteria for their individuation. In practice, the most commonly invoked criterion is the capacity for interbreeding, yet this is well known to be imperfect and to entail intransitivities of classification when applied to ring species. Nor has it ever been satisfactorily explained why a special sort of value should inhere in a collection of individuals simply by virtue of their ability to produce fertile offspring. If it is good, as I think it is, that animal life should continue, then it is instrumentally good that some animals can breed with one another. But I can see no reason to suppose that donkeys, as a group, have a special impersonal value that mules lack.

Even if animal species did have impersonal value, it would not follow that they were irreplaceable. Since animals first appeared on earth, an indefinite number of species have become extinct while an indefinite number of new species have arisen. If the appearance of new species cannot make up for the extinction of others, and if the earth could not simultaneously sustain all the species that have ever existed, it seems that it would have been better if the earliest species had never become extinct, with the consequence that the later ones would never have existed. But few of us, with our high regard for our own species, are likely to embrace that implication.

Here, then, is where matters stand thus far. It would be good to prevent the vast suffering and countless violent deaths caused by predation. There is therefore one reason to think that it would be instrumentally good if predatory animal species were to become extinct and be replaced by new herbivorous species, provided that this could occur without ecological upheaval involving more harm than would be prevented by the end of predation. The claim that existing animal species are sacred or irreplaceable is subverted by the moral irrelevance of the criteria for individuating animal species. I am therefore inclined to embrace the heretical conclusion that we have reason to desire the extinction of all carnivorous species, and I await the usual fate of heretics when this article is opened to comment.

It's worth noting that McMahan, like a number of abolitionist transhumanists, have advocated something like this for quite some time now—a group of thinkers that includes myself, David Pearce, Pablo Stafforini, Michael Anissimov and others. David Pearce's contribution to the discussion is the most significant, and it would have been nice to have seen McMahan make mention of it.

As for me, I've argued for something even more extreme and sweeping than selective extinction or the reprogramming of predators; I've made the case that we are morally obligated to uplift the entire animal kingdom so that they may join posthumanity in postbiological existence.

With McMahan's contribution hitting the mainstream, however, I am excited beyond words. The meme is out there; now let's see where we take it.

Hitchens gets it wrong about Buddhism

"Don't believe me, don't believe anybody, don't accept anything based on tradition. Don't believe anything based on the fact that your community believes this or your country believes this or the people that you are around believe this." - Buddha

I’ve never really paid much attention to Christopher Hitchens, renowned and reviled critic of all things religious. But when my brother recently brought his anti-Buddhist sentiments to my attention I had to take a closer look.

As it turns out, he does indeed have some very uncomplimentary things to say about Buddhism.

Hitchens essentially believes that the West has been duped by what he regards as just another religion filled with all the usual trappings. He regards Buddhism as a “faith” that “despises the mind and the free individual." He says it preaches submission and resignation, and that practitioners come to regard life as a “poor and transient thing.”

In his book, God is not Great, Hitchens writes,

"Those who become bored by conventional "Bible" religions, and seek "enlightenment" by way of the dissolution of their own critical faculties into nirvana in any form, had better take a warning. They may think they are leaving the realm of despised materialism, but they are still being asked to put their reason to sleep, and to discard their minds along with their sandals."

Wow. Pretty harsh stuff. Hitchens doesn’t mince words and slams into Buddhism like he would any other religion.

That's all fine and well, except that Buddhism isn’t just any other religion.

What Buddhism is

Yes, Buddhism has the characteristics of religion, but it offers much more than that.

It’s an epistemological philosophy and an intrapersonal approach to perception, self-awareness and self-regulation. It’s an aesthetic. It’s a non-anthropocentric ethical viewpoint that places an emphasis on meaningful, compassionate and genuine relationships. It's a type of Humanism. It encourages meditation and a mindful approach to living. It’s a worldview and methodology that promotes skepticism, rationality, empiricism and even non-conformity. It is the practical acknowledgment of the unavoidable perceptual subjectivity that is part of the human condition. It is the recognition that the mind matters and that conscious awareness can and should be optimized.

Buddhists believe that by paying close attention to moment-to-moment conscious experience it is possible to move beyond the sense of “self” in favour of a new state of personal well-being. And if this can be incorporated within the framework of formal scientific investigation, then all the better.

And all this without the usual baggage and expectations of most religions, namely belief in God, the soul, judgment and the afterlife. It does not promote any fixed dogma, nor does the practice result in feelings of guilt or shame. There are no 'sins' to be committed in Buddhism, nor are there highly polarized notions of right and wrong; practitioners simply do the best they can to mete out as little suffering to the world as possible.

But like all Big Ideas, Buddhism can be prone to abuse and misunderstanding -- and as Hitchens has correctly noted, even tribalistic tendencies.

Institutionalized Buddhism

Indeed, a big part of Hitchens’s grief with Buddhism is its questionable history and how it has become highly ritualized and filled with other-worldly beliefs. As he has said, “Buddhism can be as hysterical and sanguinary as any other system that relies on faith and tribe.” Hitchens has railed against the Dalai Lama and the Tibetan Buddhists. He condemns the Burmese dictatorship as a Buddhist one (which seems a suspicious claim to make these days seeing as thousands of monks have recently stood up against this regime). Hitchens dips deep into history and blames Buddhism for a number of misguided practices and atrocities.

While I agree that Buddhism has been used in this way and that blood has been shed in its name, I can’t agree that Buddhism is the cause of these things. What Hitchens is describing is the failure of human nature, the perils of insular groupthink, and politics itself. It is the same phenomenon that has led to the bastardization of the teachings of Jesus and the rise of such monolithic institutions as the Catholic Church (along with its sordid history of conquest and persecution). Consequently, Hitchens’s ire should be directed at the phenomenon of tribalism and not religion itself.

Buddhist faith?

Hitchens also makes the claim that Buddhists rely on faith. Undoubtedly, beliefs in reincarnation, karma and transcendence run deep within various Buddhist strains. This is currently a point of great contention among Buddhist scholars, some of whom, like the secular Buddhist Stephen Batchelor, contend that these precepts are unnecessary and that when it comes to metaphysics Buddhists should actually be agnostic. More traditional Buddhists, on the other hand, argue that belief in rebirth is absolutely necessary to the practice.

Interestingly, the Dalai Lama himself – a believer in reincarnation – maintains that science should take precedence over these sorts of notions. He once said, “My confidence in venturing into science lies in my basic belief that as in science so in Buddhism, understanding the nature of reality is pursued by means of critical investigation: if scientific analysis were conclusively to demonstrate certain claims in Buddhism to be false, then we must accept the findings of science and abandon those claims.”

Easier said than done, of course. Deeply embedded and ritualized religions have an incredibly hard time adapting to change -- including Buddhism.

As for the accusation that all Buddhists rely on faith, that's clearly a generalization. Most Buddhists, I would say, likely take nothing on mere faith alone.

Alternative perception

Hitchens also critiques the aims of Buddhist practice itself. He makes a number of suspicious claims -- that Buddhists despise the mind and the free individual, that Buddhism teaches submission and resignation, and that practitioners regard life as a fleeting thing full of suffering. He contends that Buddhists require a surrendering of the mind.

This is mostly nonsense. These claims have been countered elsewhere, so I won’t replicate them here, but there are a pair of issues I wish to address.

First, Hitchens appears to be confused. He seems to be conflating transcendental meditation (or something like it) with the more traditional practice of Vipasanna meditation and its focus on mindful awareness. There is nothing escapist or transcendent about this practice; rather, it's very much about focusing on the here-and-now and correcting the processes of a conditioned mind.

Second, Hitchens complains that Buddhists favour subjectivity over objectivity. “[Y]ou're supposed to be the subjective judge of what you're experiencing, are you not?,” he asks. Hitchens, being the uber-materialist that he is, is concerned that Buddhists don’t believe that anything can be accepted at objective face-value, that Buddhists merely see existence as some sort of grandiose illusion.

Hitchens's special claim into the true nature of reality aside, he is a bit off course here and his concern is exaggerated. Buddhists do not deny the presence of the material world or the value of objectivity – far from. What they assert is that the Universe will always be perceived through the lens of an observer and that our comprehension of reality must always take this into account. The only way the world can be observed is subjectively; there can be no such thing as a truly objective observer. We can and should strive towards an objective frame, but the world will always be perceived by an observer, which is by definition a subject.

It’s okay to be spiritual, really it is

What irks me most about Hitchens’s critique of Buddhism is the sense I get that what he is really complaining about are personal quests for spirituality. In fact, some of his arguments are so pithy (like making fun of Buddhist koans and Steven Seagal) that I'm inclined to think he is slamming into Buddhism just for the sake of it -- because it's just another "religion" on his hate list.

But Hitchens hasn't done his homework and it shows. Moreover, his limited acceptance as to what kind of worldview and perceptual lens is acceptable is extremely limited and narrow-minded.

Ultimately, there’s nothing wrong with spirituality. Or, if you hate that word, a sense of existential awareness. In fact, I wish more people would consider the philosophic implications of existence and look deeper within themselves. There is far too much daydreaming going on today with people living way outside their heads.

On the issue of spirituality I’ll give Sam Harris the last word:

"There is clearly a sacred dimension to our existence, and coming to terms with it could well be the highest purpose of human life...[I]t must be possible to bring reason, spirituality, and ethics together in our thinking about the world. This would be the beginning of a rational approach to our deepest personal concerns. It would also be the end of faith."

Sources:
"An Interview with Christopher Hitchens," C. P. Farley.
"Christopher Hitchens reduces Buddhism to a phrase," True Ancestor.
"His material highness," Christopher Hitchens.
"Christopher Hitchens: Religion Poisons Everything," Jon Wiener
"Hitchens - Zen is not Great?," Flapping Mouths.
Wikipedia and Wikiquote.

The Fermi Paradox: Advanced civilizations do not…

This article is partly adapted from my TransVision 2007 presentation, “Whither ET? What the failing search for extraterrestrial intelligence tells us about humanity's future.”

As I stated in my previous article, “The Fermi Paradox: Back with a vengeance”:

The fact that our Galaxy appears unperturbed is hard to explain. We should be living in a Galaxy that is saturated with intelligence and highly organized. Thus, it may be assumed that intelligent life is rare, or, given our seemingly biophilic Universe, our assumptions about the general behaviour of intelligent civilizations are flawed.

A paradox is a paradox for a reason: it means there’s something wrong in our thinking.

So, let’s try to figure out what’s going on. Given the Great Silence, and knowing what we may be capable of in the future, we can start to make some fairly confident assumptions about the developmental characteristics of advanced civilizations.

But rather than describe the possible developmental trajectories of extraterrestrial intelligences (ETI's) (a topic I’ll cover in my next article), I’m going to dismiss some commonly held assumptions about the nature of advanced ETI’s – and by consequence some assumptions about our very own future.

Advanced civilizations do not…

…advertise their presence to the local community or engage in active efforts to contact

As SETI is discovering (but is in denial about), space is not brimming with easily detectable radio signals. SETI’s work during the past 40 years indicates that the quest to detect signals will not be easy.

This problem is not as simple as it sounds. A common apology is that we’ve only recently started our search and we have only scratched the surface. The trouble, however, is that it would be no problem for an ETI to communicate with us if they wanted to.

To do this all they would need to do is seed the Galaxy with Bracewell probes (a self-replicating communications beacon). This scenario was explored in Carl Sagan’s Contact in which a Bracewell probe was lying in wait about 26 light years from Earth in the Vega system. The probe was activated by our radio signals, causing it to direct powerful radio signals at Earth – signals that would not be overlooked.

We know that no such object exists in our solar system or within a radius of about 25 to 50 light years. Our radio activity should have most certainly activated any probe lying dormant in our local vicinity by know. It is also reasonable to assume that if ETI’s embarked on such a communications mission that every solar system would likely have its own Bracewell probe.

Which in turn raises a more troubling question: if ETI’s could construct and distribute probes in this way, why haven’t they gone the extra mile and spread other types of self-replicating devices such as uplift or colonization probes?

…engage in any kind of megascale engineering or stellar re-engineering that is immediately obvious to us within our light cone

All stellar phenomenon that we have observed to this point in time appears ‘natural’ and unmodified. We see no clusters of perfectly aligned stars, nor do we signs of Kardashev III civilizations utilizing the energy output of the entire Milky Way.

As for our light cone, the Milky Way is 100,000 light years in diameter; given the possibility that our Galaxy has been able to support intelligent life for about 4.5 billion years, a 100 million year time lag (at its worst) is not severe enough to cause observational problems (except for distant Galaxies).

…colonize the Galaxy

Our Galaxy remains uncolonized despite the theoretical potential for advanced ETI’s to do so – namely the time and the technology. All that would be required is a self-replicating Von Neumann probe that proliferates outward at an exponential rate. Technologies required to build such a spacecraft would include artificial intelligence, molecular assembling nanotechnology, and an advanced propulsion scheme like anti-matter rockets, beamed energy, or interstellar ram-jets.

The reason for non-colonization is not obvious (hence the Fermi Paradox). In addition to technological feasibility there is the issue of economic and sociological imperatives for colonization.

…sterilize the Galaxy

Finally, some good news. We know the Galaxy is not sterile because we exist here on Earth.

Like the colonization potential, the prospect for an advanced ETI to sterilize the Galaxy exists through the use of berserker probes (a term attributed to Fred Saberhagen). These probes could steer NEO’s at planets, unleash nanotechnological phages, or toast planets with directed beams of highly concentrated light.

And like the Bracewell scenario, if a beserker was lying dormant in our solar system it should have destroyed us by now. If sterilization is the goal, there is no good reason for it to wait – particularly as our own civilization hurtles towards a Singularity transition.

Reasons for unleashing fleets of berserkers can be conceived, including xenophobic sociological imperatives or a malign artificial superintelligence (pdf). And all it would take is one civilization to do it. But as Robert Freitas has stated, "The present observational record can only support the much more restricted conclusion that no rapacious galactic civilisations are currently loose in the Galaxy."

…uplift or interact with pre-Singularity intelligences and biospheres

As a civilization that has been left to fend for itself, we have to assume that we, like any other civilization out there, goes it alone. No one is coming to help us. The Great Silence will continue.

Moreover, our presence on Earth and our civilizational development can be explained by naturalistic phenomena. Our existence and ongoing progress has been devoid of extraterrestrial interventions. If we’re going to survive the Singularity, or any other existential risks for that matter, it will have to be of our own devices.

…re-engineer the cosmos

A number of prominent futurists, a list that includes Ray Kurzweil and Hans Moravec, have speculated that the destiny of advanced intelligence is to re-work the cosmos itself. This has been imagined as an ‘intelligence explosion’ as advanced life expands outward into the cosmos like a bubble. The entire Galaxy would be re-organized with much of its matter converted into computronium. Eventually, it is thought that the laws of the Universe will be re-tuned to meet the needs of advanced civilizations.

Unfortunately, we do not appear to inhabit a Universe that even remotely resembles this model. The cosmos appears natural and unperturbed.

This is reminiscent of the God problem and the presence of evil. We live in a Universe that is hostile, indifferent and pointless. If advanced ETI’s had the capacity to re-engineer the Universe such that it was safer, more meaningful and paradisical they would have done so by now. By virtue of the fact that we observe such a dangerous Universe we should probably conclude that such a project is not an option.

In the final part of this series I will make an effort to explain why advanced civilizations don’t do these things and what they might be doing instead.

Part I: Fermi Paradox: Back With a Vengeance

Part III: Fermi Paradox: Possible Solutions and Next Steps

The Fermi Paradox: Back with a vengeance

This article is partly adapted from my TransVision 2007 presentation, “Whither ET? What the failing search for extraterrestrial intelligence tells us about humanity's future.”

The Fermi Paradox is alive and well.

As our sciences mature, and as the search for extraterrestrial intelligence continues to fail, the Great Silence becomes louder than ever. The seemingly empty cosmos is screaming out to us that something is askew.

Our isolation in the Universe has in no small way shaped and defined the human condition. It is such an indelible part of our reality that it is often taken for granted or rationalized to extremes.

To deal with the cognitive dissonance created by the Great Silence, we have resorted to good old fashioned human arrogance, anthropocentrism, and worse, an inter-galactic inferiority complex. We make excuses and rationalizations like, ‘we are the first,’ ‘we are all alone,’ or, ‘why would any advanced civilization want to bother with us backward humans?’

Under closer scrutiny, however, these excuses don’t hold. Our sciences are steadily maturing and we are discovering more and more that our isolation in the cosmos and the dearth of observable artificial phenomenon is in direct violation of our expectations, and by consequence, our own anticipated future as a space-faring species.

Indeed, one of the greatest philosophical and scientific challenges that currently confronts humanity is the unsolved question of the existence of extraterrestrial intelligences (ETI's).

We have yet to see any evidence for their existence. It does not appear that ETI’s have come through our solar system; we see no signs of their activities in space; we have yet to receive any kind of communication from them.

Adding to the Great Silence is the realization that they should have been here by now -- the problem known as the Fermi Paradox.

The Fermi Paradox
The Fermi Paradox is the contradictory and counter-intuitive observation that we have yet to see any evidence for the existence of ETI’s. The size and age of the Universe suggests that many technologically advanced ETI’s ought to exist. However, this hypothesis seems inconsistent with the lack of observational evidence to support it.

Largely ignored in 1950 when physicist Enrico Fermi famously asked, “Where is everybody,” and virtually dismissed at the seminal SETI conference in 1971, the conundrum was given new momentum by Michael Hart in 1975[1] (which is why it is sometimes referred to as the Fermi-Hart Paradox).

Today, 35 years after it was reinvigorated by Hart, it is a hotly contested and relevant topic -- a trend that will undoubtedly continue as our sciences, technologies and future visions develop.

Back with a vengeance
A number of inter-disciplinal breakthroughs and insights have contributed to the Fermi Paradox gaining credence as an unsolved scientific problem. Here are some reasons why[2]:

Improved quantification and conceptualization of our cosmological environment
The scale of our cosmological environment is coming into focus. Our Universe contains about 10^11 to 10^12 galaxies, giving rise to a total of 10^22 to 10^24 stars[3]. And this is what exists right now; there have been a billion trillion stars in our past Universe. [4]

The Milky Way itself, which is considered a giant as far as galaxies go, contains as many as 400 billion stars and has a diameter of 100,000 light years.[5]

Improved understanding of planet formation, composition and the presence of habitable zones
The Universe formed 13.7 billion years ago. The Milky Way Galaxy formed a mere 200 million years later, making our Galaxy nearly as old as the Universe itself. Work by Charles Lineweaver has shown that planets also began forming a very long time ago; he places estimates of Earth-like planets forming 9 billion years ago (Gyr).

According to Lineweaver, the median age of planets in the Galaxy is 6.4+/0.7 Gyr which is significantly more than the Earth’s age. An average terrestrial planet in the Galaxy is 1.6 Gyr older than the Earth. It is estimated that three quarters of earth-like planets in the Galactic habitable zone are older than the Earth.

We have a growing conception of where habitation could be sustained in the Galaxy. The requirements are a host star that formed between 4 to 8 Gyr ago, enough heavy elements to form terrestrial planets, sufficient time for biological evolution, an environment free of sterilization events (namely super novae), and an annular region between 7 and 9 kiloparsecs from the galactic center that widens with time. [6]

The discovery of extrasolar planets
Over 240 extrasolar planets have been discovered as of May 1, 2007[7]. Most of these are so-called “hot Jupiters,” but the possibility that their satellites could be habitable cannot be ruled out. Many of these systems have stable circumstellar habitable zones.

Somewhat shockingly, the first Earth-like planet was discovered earlier this year orbiting the red star Gilese 581; it is 20 light years away, 1.5 times the diameter of Earth, is suspected to have water and an atmosphere, and its temperature fluctuates between 0 and 40 degrees Celsius.[8]

Confirmation of the rapid origination of life on Earth
The Earth formed 4.6 Gyr ago and rocks began to appear 3.9 Gyr ago. Life emerged quickly thereafter 3 Gyr ago. Some estimates show that life emerged in as little as 600 million years after the formation of rocks.[9]

Growing legitimacy of panspermia theories
There is a very good chance that we inhabit a highly compromised and fertile Galaxy in which ‘life seeds’ are strewn about. The Earth itself has been a potentially infectious agent for nearly 3 billion years.

Evidence has emerged that some grains of material in our solar system came from beyond our solar system. Recent experiments show that microorganisms can survive dormancy for long periods of time and under space conditions. We also now know that rocks can travel from Mars to Earth.[10]

Discovery of extremophiles
Simple life is much more resilient to environmental stress than previously imagined. Biological diversity is probably much larger than conventionally assumed.

Developing conception of a biophilic Universe in which the cosmological parameters for the existence of life appear finely tuned
As scientists delve deeper and deeper into the unsolved mysteries of the Universe, they are discovering that a number of cosmological parameters are excruciatingly specific. So specific, in fact, that any minor alteration to key parameters would throw the entire Universe off kilter and result in a system completely unfriendly to life. The parameters of the Universe that are in place are so specific as to almost suggest that spawning life is in fact what the Universe is supposed to do. [11]

Cosmological uniformitarianism implies that that anthropic observation need not be and cannot be specific to human observers, but rather to any observer in general; in other words, the Universe can support the presence of any kind of observer, whether they be here on Earth or on the other side of the cosmos.

Confirmation of the early potential for intelligent life
My own calculations have shown that intelligence could have first emerged in the Universe as long as 4.5 Gyr ago -- a finding that is consistent with other estimates, including those of Lineweaver and David Grinspoon.[12]

Refinement of evolutionary biology, computer science and systems theories
Evolution shows progressive trends towards increasing complexity and in the direction of increasing fitness. There has also been the growing acceptance of Neo-Darwinism.

Advances in computer science have reshaped our conception of what is possible from an informational and digital perspective. There is the growing acceptance of systems theories which take emergent properties and complexity into account. Game theory and the rise of rational intelligence add another level to this dynamic mix.

Development of sociobiological observations as they pertain to the rapid evolution of intelligent life and the apparent radical potential for advanced intelligence
Exponential change. Moore’s Law. Kurzweil’s Law of Accelerating Returns. Steady advances in information technologies. Artificial intelligence. Neuroscience. Cybernetics, and so on.

And then there is the theoretic potential for a technological Singularity, digital minds, artificial superintelligence, molecular nanotechnology, and other radical possibilities. There is also emerging speculation about the feasibility of interstellar travel, colonization and communication.

In other words….
There are more stars in the Universe than we can possibly fathom. Any conception of ‘rare,’ ‘not enough time’ or ‘far away’ has to be set against the inability of human psychology to grasp such vast cosmological scales and quantities. The Universe and the Milky Way are extremely old, our galaxy has been able to produce rocky planets for quite some time now, and our earth is a relative new-comer to the galaxy.

The composition of our solar system and the Earth itself may not be as rare as some astronomers and astrobiologists believe. These discoveries are a serious blow to the Rare Earth Hypothesis – the idea that the genesis, development and proliferation of life is an extremely special event[13]. It’s also a blow to Brandon Carter’s anthropic argument which takes a very human-centric approach to understanding cosmology, suggesting that our existence as observers imposes the sort of Universe that only we can observe.

Finally, the Universe appears capable of spawning radically advanced intelligence – the kind of advanced intelligence that transhumanists speculate about, namely post-Singularity, post-biological machine minds. Given intelligent life's ability to overcome scarcity, and its tendency to colonize new habitats, it seems likely that any advanced civilization would seek out new resources and colonize first their star system, and then surrounding star systems. Indeed, estimates place the time to colonize the Galaxy anywhere from one million to 100 million years.[14]

The fact that our Galaxy appears unperturbed is hard to explain. We should be living in a Galaxy that is saturated with intelligence and highly organized. Thus, it may be assumed that intelligent life is rare, or, given our seemingly biophilic Universe, our assumptions about the general behaviour of intelligent civilizations are flawed.

A paradox is a paradox for a reason: it means there’s something wrong in our thinking.

So, where is everybody?

Part II: The Fermi Paradox: Advanced Civilization Do Not...

Part III: The Fermi Paradox: Possible Solutions and Next Steps

---

[1] Hart, M. H. "An Explanation for the Absence of Extraterrestrial Life on Earth," Quarterly Journal of the Royal Astronomical Society, 16, 128-135 (1975).

[2] This list, which is not intended to be a complete re-affirmation of the Fermi Paradox, was inspired and partly adapted from: Ćirković , Milan M. and Bradbury, Robert J. "Galactic Gradients, Postbiological Evolution and the Apparent Failure of SETI", New Astronomy, vol. 11, pp. 628-639 (2006).

[3] "How many stars are there in the Universe?" European Space Agency, Space Scientist, February 23, 2004: http://www.esa.int/esaSC/SEM75BS1VED_index_0.html.

[4] Hanson, R. 1999, “Great Filter,” (preprint at http://hanson.berkeley.edu/greatfilter.html).

[5] See Harvey Mudd and S. E. Levine: “Mass of the Milky Way and Dwarf Spheroidal Stream Membership.”

[6] Gonzalez, G., Brownlee, D., and Ward, P. 2001, “The Galactic Habitable Zone: Galactic Chemical Evolution,” Icarus 152, 185-200; Lineweaver, Charles H., Fenner , Yeshe, and Gibson, Brad K. 2004, “The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way.”; M. Noble , Z. E. Musielak , and M. Cuntz: 2002, "Orbital Stability of Terrestrial Planets inside the Habitable Zones of Extrasolar Planetary Systems"

[7] "A Rush of New Planets," Astrobiology Magazine: Jun 02, 2007: http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=2351

[8] "All Wet? Astronomers Claim Discovery of Earth-like Planet," Scientific American, April 24, 2007: http://www.sciam.com/article.cfm?articleID=25A261F0-E7F2-99DF-313249A4883E6A86&chanID=sa007

[9] See Stephen J. Mojzsis: http://spot.colorado.edu/~mojzsis/

[10] Raulin-Cerceau, F., Maurel, M.-C., and Schneider, J. 1998, “From panspermia to bioastronomy, the evolution of the hypothesis of universal life,” Orig. Life Evol. Biosph. 28, 597; "Encore: Great Debates Part VI," Astrobiology Magazine, Aug 19, 2002: http://www.astrobio.net/news/article254.html

[11] The Wikipedia entry on the Fine Tuning argument has some good links and references: http://en.wikipedia.org/wiki/Fine-tuned_universe

[12] Dvorsky, George: 2006, “When Did Intelligent Life First Emerge in the Universe?” http://sentientdevelopments.blogspot.com/2006/06/when-did-intelligence-first-emerge-in.html;

[13] Ward, P. D. and Brownlee, D. 2000, Rare Earth: Why Complex Life Is Uncommon in the Universe (Springer, New York). Lineweaver, Charles H., Fenner , Yeshe, and Gibson, Brad K. 2004; Grinspoon, David, Lonely Planets, Ecco; 1st edition (November 4, 2003).

[14] Ćirković , Milan M., 2003: "On the Importance of SETI for Transhumanism." As it pertains to reframing the Fermi Paradox, Ćirković recommends Lytkin, Finney, and Alepko (1995; for Tsiolkovsky), Jones (1985; for Fermi), Viewing (1975), and Hart (1975), (Tipler 1980), Boyce (1979).

William Crawley interviews Peter Singer