The Edge of Evolution

by Michael J Behe

  The laws of science, as we know them at present, contain many fundamental numbers, like the size of the electric charge of the electron and the ratio of the masses of the proton and electron…. The remarkable fact is that the values of these numbers seem to have been very finely adjusted to make possible the development of life. For example, if the electric charge of the electron had been only slightly different, stars either would have been unable to burn hydrogen and helium, or else they would not have exploded [which allows elements necessary for life to be scattered]…. It seems clear that there are relatively few ranges of values for the numbers that would allow the development of any form of intelligent life.4

  So what are we to make of the flabbergasting fact that the laws of the universe seem set up for our benefit, that “the universe in some sense must have known that we were coming”?5 There are really just two logical responses to anthropic features: 1) We are phenomenally lucky, or 2) our universe was intentionally designed by an intelligent agent. Over the next few sections I’ll consider the design explanation for anthropic features of our universe, and extend the argument far into biology.

  FINELY TUNED PROPERTIES

  Many, many other factors aside from the laws of physics need to be just right before one gets a planet that can nurture intelligent life. For example, not only does the physics of elementary particles have to be right, so do the physics and chemistry of molecules. In other words, having the right value of, say, the charge on an electron so that molecules are stable is just the first, tiny step. The molecules of life have to have other, useful properties, beyond the basics.

  The most famous example is water. Water is such a familiar liquid that most people don’t give it much thought. Yet scientists know it’s unique, and that life without water is virtually unimaginable. Almost all other liquids contract when they freeze. Water expands. Although that seems like a trivial feature, it’s critical for life. If water contracted on freezing, ice would be denser than water, and would sink to the bottom of a lake or ocean, away from warming sunlight. Virtually all the water on earth would likely be frozen solid, unavailable for life. As the geneticist Michael Denton points out in Nature’s Destiny,6 water also has many other properties that suit it to be life’s liquid. Just one further example is that water can dissolve a wide range of substances, such as salts and sugars; very few other liquids can. Of those few other liquids, many are either strongly acidic or strongly basic, or are otherwise unsuited for life. Denton makes a strong case that, in addition to water, many other elements and simple molecules—carbon, oxygen, carbon dioxide, metals, and many more—are as necessary for life as the fundamental constants and laws of nature. So the “anthropic coincidences” needed for life in this universe extend beyond the basic physical laws and constants, well into chemistry.7

  What is the explanation for such a remarkable, unexpected pattern? One great virtue of the design hypothesis is that, without making additional assumptions, it supports all the further anthropic coincidences found more recently in physics and chemistry. After all, an agent who can actually choose and establish the basic laws and constants of the universe is, to say the least, likely to be immensely intelligent and powerful, and so have the ability to further fine-tune nature as necessary. What’s more, if the agent evinces an interest in life, as reflected in biofriendly general laws, then we should expect it would take whatever additional steps would be necessary to achieve its goal of life. The fact that we have discovered life required much more fine-tuning than first supposed fits easily into the design explanation.

  If one admits the possibility of a being who can fine-tune general laws, then there can be no principled objection to ascribing other fine-tuned features of nature to purposeful design. In its 1999 booklet Science and Creationism, the National Academy of Sciences (or at least a committee writing in its name) penned the following lines:

  Many religious persons, including many scientists, hold that God created the universe and the various processes driving physical and biological evolution and that these processes then resulted in the creation of galaxies, our solar system, and life on Earth. This belief, which sometimes is termed “theistic evolution,” is not in disagreement with scientific explanations of evolution. Indeed, it reflects the remarkable and inspiring character of the physical universe revealed by cosmology, paleontology, molecular biology, and many other scientific disciplines [emphasis added].8

  It seems to me likely in this passage the committee was simply trying to make a reassuring gesture toward religious folks, while simultaneously doing what it could to steer the public’s religious beliefs toward those that cause the least trouble for Darwin’s theory. But the committee did not think through the implications of its words. Because if there is indeed a real being who could actually create the universe and its laws, as the committee allows, and if that explanation reflects (that is, is evidentially supported by) “the physical universe revealed by cosmology” and other scientific disciplines, what would stop the being from affecting the universe in other ways if it chose to do so? Would this being that created the universe and its laws have to ask permission of the National Academy to otherwise affect nature? Of course not. Whether it affected the universe in additional ways would be a matter for the evidence—not the committee—to decide. The bottom line is that, if one allows that a being external to the universe could affect its laws, there is no principled reason to rule out a priori more extensive interaction as well.

  The consilience of fine-tuning in physics and chemistry reinforces our confidence in design. It’s reasonable to conclude not only that the universe is designed, but that the design extends well beyond general laws, at least down into particularities of the physics and chemistry of certain molecules.

  FINELY TUNED DETAILS

  In the past few decades it has been gradually realized that anthropic coincidences extend well beyond even the physical and chemical properties of particular compounds such as water. Anthropic coincidences now include a long list of what can only be termed details. And pretty minute details at that.

  In Rare Earth: Why Complex Life Is Uncommon in the Universe geologist Peter Ward and astronomer Donald Brownlee present a powerful argument that, as the title suggests, planets like ours may be exceedingly rare in the universe, in fact so rare that, although the authors think other planets may sport primitive bacterial life, ours may be the only planet able to support intelligent life. If that’s the case, then, like a pool shark setting up a trick shot, the agent who set up the universe for intelligent life would have had to pay attention to all the details needed to produce an appropriate planet.

  (Ward and Brownlee themselves think the earth was lucky, not designed: Given the size of the universe, getting one or a relative handful of planets physically like earth may be possible just by chance. However, that thinking overlooks problems with the origin of life and evolution by random mutation. If the subsequent evolution of intelligent life—even on a suitable planet—is itself enormously improbable, the “lucky” line of reasoning breaks down. In that case there would be just one or a few earthlike planets, but terrible odds against any of them developing intelligent life. We would have no good reason to expect life to develop on a single earth.)

  Not only do the laws and chemical properties have to be right, but planets have to form in the right location with the right mix of ingredients. That’s very difficult to do. If the earth were a bit closer to the sun, it would be too hot to support intelligent life. Venus is 68 million miles from the sun. The earth is 93 million miles away. On Venus temperatures are high enough to melt lead. If the earth were a little farther from the sun, water would freeze. Daytime temperatures on Mars, which is about 140 million miles from the sun, average about—80°F. The so-called “Goldilocks effect,” where a planet can’t be located where it’s too hot or too cold, has led to the notion of a “habitable zone”—a narrow region in a solar system that has more of the necessary, but still far from sufficient, conditions for li
fe.

  The concept of a habitable zone applies to galaxies, too. It turns out that large swaths of a typical galaxy are quite hostile to life. Regions that are either too close to a galaxy’s center or situated in a band of a spiral galaxy get fried by high doses of X-rays emanating from colliding stars and supernovas. Regions too far from the center of a galaxy have a different set of problems, as Ward and Brownlee explain.

  The outer region of the galactic habitable zone is defined by the elemental composition of the galaxy. In the outermost reaches of the galaxy, the concentration of heavy elements is lower because the rate of star formation—and thus of element formation—is lower. Outward from the centers of galaxies, the relative abundance of elements heavier than helium declines. The abundance of heavy elements is probably too low to form terrestrial planets as large as earth…. [O]ur planet has a solid/liquid metal core that includes some radioactive material giving off heat. Both attributes seem to be necessary to the development of animal life: The metal core produces a magnetic field that protects the surface of the planet from radiation from space, and the radioactive heat from the core, mantle and crust fuels plate tectonics, which in our view is also necessary for maintaining animal life on the planet. No planet such as Earth can exist in the outer regions of the galaxy.9

  Decades ago the late astronomer Carl Sagan derided the Earth’s location as a galactic backwater. But with the progress of science we now see that a planet suitable for life can’t be too close to the center of things. Far from being a backwater, Earth’s location is ideal for complex life.

  A planet in the right region of a solar system, in the right region of a galaxy, in a universe with the right kinds of laws to produce chemicals with the right kinds of properties—this is all necessary for life, but still very far from sufficient. The planet itself has to be not too big and not too small, with enough but not too much water, the right kind of minerals in the right places, a core active enough to power plate tectonics but not so active as to blow everything apart, and much, much more. Some of these factors considered in isolation may be less improbable, others more improbable, but all are critical. If any one of them were missing, intelligent life would be precluded.

  FINELY TUNED EVENTS

  To get a better feel for the extreme fine-tuning required to produce intelligent life, consider the critical role played in the formation of the earth by a unique event—that is, by a singular occurrence that is not simply a “law,” or a “property,” or even a “detail.” Instead, like a cluster of pool balls bouncing just so, it results from the dynamic interplay of multiple, apparently unrelated factors.

  Consider the entwined origin of the earth and moon. The question of how the moon originated puzzled astronomers for centuries. In recent years a radical proposal has emerged as the most likely contender. Billions of years ago, as the nascent earth itself was forming, a large body roughly the size of Mars struck our then-undersized planet. It proved to be a spectacularly accurate, glancing blow. The tremendously energetic, not-quite-head-on impact caused the two bodies to melt. The dense molten metal cores of the two orbs combined and sank into the interior of the now-larger earth, while chunks of the rocky crust of both were ejected into space, later to coalesce into a stable, orbiting moon. As Ward and Brownlee remark, “To produce such a massive moon, the impacting body had to be the right size, it had to impact the right point on Earth, and the impact had to have occurred at just the right time in the Earth’s growth process.”10

  The moon that resulted from that seemingly serendipitous, unique event contributes in a variety of critical ways to making our planet livable, for example by stabilizing the earth’s tilt—that is, the angle formed by earth’s axis of rotation compared to its orbital plane—which allows earth’s climate to avoid extreme, life-killing fluctuations. In short, without that singular collision in space when the solar system was young, as well as the laundry list of necessary conditions that preceded it and the plethora of happy results that flowed from it, earth would be uninhabitable, no matter that it was otherwise in the right location.

  The bottom line is that the “fine-tuning” of our universe for life is not at all just a matter of the basic laws and constants of physics. Fine-tuning reaches deeply into ostensibly small details of the history of our solar system and planet, and includes unique, dynamic events. Without attention to such small details, mere fine-tuning of general physical laws would be futile. The strong nuclear force might be perfect, the charge on the electron just right, but if the end result of the undirected playing out of general laws were a lifeless asteroid where the earth should have been, why bother?

  If there really does exist an agent who tuned the general laws of nature with the goal of producing intelligent life, then it’s reasonable to think the agent would have taken whatever further steps were necessary to achieve its goal. And, to science’s great surprise, in the past century it has discerned an ever-lengthening list of essential steps. If the design hypothesis is a leading contender as an explanation for the fine-tuning of the laws of the universe, then by the same reasoning it also must be regarded as a leading explanation for the finer physical, chemical, and astronomical details and events that make life possible. Arranging for a happy collision between two astronomical bodies is not obviously more difficult than arranging the right values for the fundamental constants of nature, so there is no principled reason to allow the possibility of design in the one case but withhold it in the other.

  THE ORIGIN OF LIFE AS A FINELY TUNED EVENT

  The laws and constants of the universe are finely tuned to allow life. So, too, are the physical and chemical properties of elements such as carbon and simple compounds such as water. So, too, is earth’s location in the galaxy and solar system. So, too, are details of the earth’s size, composition, and history.

  So, too, as the geneticist Michael Denton has forcefully argued in Nature’s Destiny, are the more complex categories of the molecules of life. The physical and chemical properties of DNA, protein, lipids, and other substances are superbly fit for the roles they play in the cell. No other kinds of molecules are known that could plausibly fill those roles. What’s more, shows Denton, the complex molecules of life harmonize in multiple ways with many levels of nature. For example, the strength of the electric charge allows both the strong (covalent) and the weak (noncovalent) chemical bonds necessary for proteins to work. Denton makes the case that one would be hard pressed to find a category of biomolecule or basic feature of life that isn’t finely tuned.

  Here I want to extend the rubric of “fine-tuning” even further to embrace the origin of life. Just as astronomers for decades beat their collective heads against the wall trying to envision a comparatively orderly, lawlike scenario for the origin of the moon, only to come up empty, so, too, have origin-of-life researchers for decades beat their heads against a wall trying to come up with a comparatively lawlike scenario for the origin of life, only to come up empty. The current model for the origin of the moon is not lawlike in the least, no more than a trick pool shot is lawlike. In isolation it can only be described as utterly random. But in context, seen from the point of view of producing life, seen as another part in a purposeful arrangement of parts, it is one in an extensive series of anthropic coincidences, very finely tuned to yield life.

  Similarly, there currently is no plausible lawlike model for the origin of life. In his exploration of the question of the origin of life in The Fifth Miracle, the physicist Paul Davies argues that something completely different is needed:

  When I set out to write this book I was convinced that science was close to wrapping up the mystery of life’s origin…. Having spent a year or two researching the field I am now of the opinion that there remains a huge gulf in our understanding. To be sure, we have a good idea of the where and the when of life’s origin, but we are a very long way from comprehending the how.

  This gulf in understanding is not merely ignorance about certain technical details, it is a major c
onceptual lacuna…. My personal belief, for what it is worth, is that a fully satisfactory theory of the origin of life demands some radically new ideas.11

  I suggest that the origin of life is best viewed not as lawlike, but as one more of the long, long chain of anthropic “coincidences” very, very finely tuned to yield life. In this view the origin of life was a unique event, like the origin of the moon, and was purposely arranged. For example, just as the origin of the moon involved a particular body of a particular mass traveling at a particular speed and particular angle at a particular time, and so on, so might the origin of life have involved an extensive string of particulars. Perhaps a particular molecule in a primeval ocean hit another at a particular angle when, say, a particular hydroxide ion was close enough to catalyze a particular reaction, and the product of that reaction underwent a long string of other unique, particular events to yield the first cell. Although at the time the molecules may have been following standard physical laws, no law or general conditions were sufficient to cause the origin of life. It was simply a finely tuned, unique event—undoubtedly much, much more finely tuned than the origin of the moon, but another finely tuned event nonetheless.

  Although that view might strike some people as strange, if we admit the possibility of an agent who can choose and implement the laws of physics for the universe, then there is no principled reason to think that implementing much greater fine-tuning would be beyond it.

  If the origin of life is a finely tuned event, then research directed at uncovering some reproducible set of generic conditions that would yield life will continue to prove futile, as it has for the past half century. Nonetheless, with the abandonment of the fruitless “lawlike” origin-of-life paradigm, science might productively take up an approach similar to that of astronomers studying the unique conditions needed to explain the origin of the moon. The Nobel laureate Francis Crick once remarked, “An honest man, armed with all the knowledge available to us now, could only state that in some sense, the origin of life appears at the moment to be almost a miracle, so many are the conditions which would have had to have been satisfied to get it going.”12 Investigation of those very many, unique, anthropic, fine-tuned conditions needed to start life could keep scientists busy for many years.