Yes, Evolution is a Scientific Theory, Even if You Can't Prove it Wrong

For a theory to be scientific, it must make predictions that can be disproved. The theory of evolution, in which the diversity of life emerges from natural selection operating on random mutations, made several such predictions. At any point in the history of scientific discovery, no one knew whether these predictions would turn out to be true.

Within a couple decades after Darwin proposed his theory, the nature of biological study shifted from trying to distinguish and classify various species of life, to examining the similarities across species in order to understand how they evolved. Why did this shift happen? At any point in this process, one can imagine that scientists might have discovered that examining the common elements of life was a fruitless exercise. Biologists might not have found any vestigial appendages. They might have found that it was rare for closely-related species living in proximity to occupy distinct ecological niches. They might not have found any fossils that appeared to be transitional species between older and newer forms of life. They might have found that fossils gave no indication of the age of geological strata, because life hadn't changed much with time. None of this happened. Instead, Darwin's theory of mutations and natural selection served to make sense of a host of phenomena, in a way that previous theories had not. Scientists adopted Darwin's theory.

However, the success of evolution goes deeper than qualitatively explaining data. It also made predictions about the nature of genetics. First, for a mutation in a parent to survive in the population, it must be able to be transferred in its entirety to a child. Darwin considered this a puzzle, because at the time people generally considered offspring to be a blend of each of their parents. Darwin recognized that if children were a blend, any mutation would end up diluted in future generations of offspring, and it would eventually completely disappear. As it turns out, Darwin was unaware of contemporary experiments that Gregor Mendel was carrying out to understand how the traits of pea plants were inherited. Mendel found that his experiments could be explained if traits came in pairs, and each child received one-half of each pair from each of its parents. He found that traits are not, in general, blended. This means mutations in a gene can be passed whole to the next generation, and natural selection has something to operate on.

Moreover, evolution required there to be a physical way to introduce mutations into genes. One could imagine that if evolution were untrue, we might have found that genetic information was diffused throughout cells in a way that was robust to mutations. Instead, we found that mutations could often be traced to errors in the chromosomes that were copied from the egg and sperm of the parents. Later, we found that the chromosomes themselves contained DNA, and that errors could be introduced into DNA during the copying process by random events within the environment.

Most remarkably, evolution predicts that all life should share the same genetic code. If bacteria, plants, fungi, insects, and animals were all their own special creations, this might not have been the case. However, we now know that the same basic genes encode for similar proteins in all forms of life. Moreover, the genetic code of closely-related species is more similar, as evolution would predict. We share 96% of our genome with apes, but only one-third of yeast genes are found in humans. The fact that yeast and humans share any genes only really makes sense if some form of evolution has occurred.

Finally, evolutionary theory makes a quantitative statement about the age of the Earth, because it takes a very long time for mutations to accumulate and give rise to the vast diversity of species we see now. In the mid-19th century, scientists were just beginning to make claims that the earth was several tens of millions of years old. This was a great break from traditional Western philosophical thinking, which held that God created the Earth only a few thousand years before. If the traditional view were correct, there would not have been time for evolution to occur. Had scientists discovered that the Earth was young, evolution would not have worked as a theory. Instead, radiometric dating shows that the earth is about 5 billion years old, whereas estimating the rate of mutations that is required to explain the genetic diversity under evolutionary theory implies that the earliest form of life appeared around 4 billion years ago. This remarkable coincidence is not a priori necessary, but makes good sense if evolution is correct.

So, in summary, evolution makes several claims that were not known to be true in Darwin's time:

• That all forms of life should share common features: our cells have the same structure as amoeba; our organs are arranged similarly to a pig's.
• That each trait must be passed whole from our parents. Our traits are not a blend of those of our parents.
• That genes are encoded by a physical mechanism that is susceptible to errors, thus generating mutations.
• That, in addition to common features, all species should share varying amounts of genetic code. More closely-related species should have more similar code.
• That the Earth is old enough for evolution through mutations and natural selection to have generated the observed diversity of life.

So could evolution be disproved today? Given the weight of evidence, it is almost impossible to conceive of any new evidence that will emerge that would make us think evolution is wrong. Evolution has been the paradigm for progress in biology and medicine over the last century. We discuss fossils based on their similarity to the species that are their evolutionary ancestors and progeny. We map genomes to trace how species are related. We test drugs on animals that are close enough relatives to assure us that the results are useful. We think in terms of evolution to understand how antibiotic-resistant bacteria develop, and how viruses might change to threaten our health. We understand that we are afflicted with birth defects and genetic diseases because the mutations responsible for evolution usually are harmful. We also know that some genetic mutations, like sickle cell gene in people of African descent, can become prevalent if the evolutionary benefits (resistance to malaria) outweigh the risks (anemia). If evolution were wrong, why would all this make sense?

Evolution will not be disproved, because it has been an incredibly powerful scientific theory. There are just too many basic facts supporting it.

OK, So I'm an Atheist. Why do I Spend So Much Time Talking about the Bible?

Atheism is more than a counter-Christian (or counter-Islamic) movement. So why do I spend so much time and energy bashing the dominant religions within my culture? If I don't believe in God, why do I bother thinking about religion?

I often discuss Christianity as a means of providing a contrast with Atheism. Some theologians take the view that God allows evil to exist so that his creation would better understand good. In the same vein, criticizing Christianity helps to illuminate the virtues of Atheism. This is useful, because basic tenet of Atheism -- There Is No God -- is negative. By criticizing Christianity, I can explain the problems with believing in God, and how Atheism fares as an alternative. I pick on Christianity because that is the religion with which most people in the West are familiar. Of course, showing one religion has problems does not prove that no religion, much less no possible deity, could be true. It just shows how a choice is possible.

I also have a more general desire to promote a humanistic morality. I point out the flaws in the Bible to explain why one shouldn't use it as a cudgel against those with opposing political or social views. For instance, if you base your opinion of homosexuals on Leviticus, I have news for you. Throughout the Bible, the good Lord seems to endorse (or at least turn a blind eye to) slavery, polygamy, genital mutilation, human sacrifice, and genocide. Today, most of us reject those things as evil. Why then would it make sense to use the Bible as a moral compass? The correct thing to do is to apply the moral compass we've developed over the last few centuries to understanding the Bible.

Of course, challenging a literal interpretation of Biblical morality is not merely the job of an Atheist, but of any humanist. Indeed, many Christians adopt this approach, and have come to terms with the nasty bits of their faith. Perhaps they believe that Jesus has rendered the Old Testament obsolete, so they can focus on the "better" portions of the Bible that relay Jesus's words. Some denominations, such as Anglicans, have gone further and applied modern moral reasoning to embracing women in the priesthood and sanctifying gay marriages. The may believe that the true faith was corrupted by humans. Or, they may decide that the beauty of their faith lets them live with its earlier failings, so long as those failings aren't present now. Telling them, "Look what your book says!" is a bit silly. They know. They've read it too.

That is why, while the counter-Christian rhetoric can be useful, it is necessary to explain that Atheism has its own unique benefits as an outlook on life. Penn Jillette, in a short radio piece that was part of the This I Believe series, was the first person I heard to express this well. If you haven't heard or read his brief essay before, I suggest you stop reading this now and follow the link. If you're interested in other expressions of lack of faith, well, I can share mine...

Atheism appeals to me because takes a step beyond religious humanism. It rejects the premise that there is an unseen Maker of the Universe, and therefore that the Universe has a purpose. By abandoning these assumptions, Atheism is able to make some positive moral contributions.

First, Atheism follows science in demanding that we only believe in the things we can see, experience, and infer by interacting with the physical world. While this might at first seem limiting, the belief in a common reality provides a path toward greater understanding among diverse peoples. Adopting science, rather than canon or subjective spiritual experience, means that reality can be verified by anyone. In principle, it is possible for everyone to come to a shared understanding of reality. Atheism can use science as a common language for communicating across cultures.

Second, Atheism can incorporate scientific advances in our understanding of what it means to be human, and what our place in the universe is. I believe that an Atheism that respects both humanism and science can expand our circles of empathy, which helps to make humans less violent.

Third, Atheism claims that this life is the only one we will ever experience. This demands that we make the most of our mortal lives. Our legacy is how other people will remember us. We will not be redeemed if we harm others. Repentance will not save our souls. There is no higher power whose "will" we can appeal to as justification for our transgressions. Some sins are indeed so egregious, some wounds so deep, that we might never be forgiven. Therefore, we have to think more about how our actions affect others. Looking inward is not enough; we have to look outward. Successfully doing so can make Atheists better people.

Currently, the way that most Americans think about morality is colored by our Judeo-Christian background. I cannot avoid discussing it. I need a contrast to deliver the good news: not believing in God frees me to think about how to better humanity, and to hope that humankind's' capacity for empathy and considerate actions will lead to a better world.

Some Perspective on the Higgs Boson

The discovery of the Higgs Boson is an great success for the Standard Model of particle physics. The Standard Model explains the properties of light; the particles that make up atoms; the slew of other particles that appear for fleeting moments common particles collide, and three of the four fundamental forces in physics (electromagnetism, the weak nuclear force, and the strong nuclear force). It is one of the most well-tested theories in science. Nonetheless, after decades of testing, one key prediction of the Standard Model had yet to be tested. Physicists had not yet confidently detected the Higgs Boson, a particle hypothesized to interact with quantum fields to give other particles mass. As of today, though, physicists working at the Large Hadron Collider have announced that something looking exactly like the Higgs Boson exists. With this, the last prediction of the Standard Model has come nearly to fruition.

Discovering the Higgs Boson is also a fantastic validation of the scientific method. Thomas Kuhn summarized how science works in his Structure of Scientific Revolutions. Most of work in science is spent probing scientific paradigms like the Standard Model, in order to confirm that the various predictions within the paradigm are correct. The search for the Higgs Boson, and before that for the W and Z bosons (found in 1983) and the top quark (found in 1995) , fit perfectly into Kuhn's interpretation of scientific work. Theoretical physicists worked out the implications of their theory, and predicted new particles. Experimental scientists then designed and built experiments that would be able to infer that the particles existed. Finding the Higgs registers as a great success for the hard work of science, because physicists found what they were looking for.

Finding the Higgs Boson also is an enormous triumph for the Large Hadron Collider (LHC). Measuring the Higgs Boson (or ruling out its existence) is one of the main goals of the LHC. The LHC will hopefully still make other discoveries - it might find evidence for a slew of additional "supersymmetric" particles, or hints of extra dimensions - but none of those are required by currently accepted theories. Therefore, building a $9 billion experiment just to look for them would have been risky, and possibly controversial. The search for the Higgs justified the LHC. Finding the Higgs validates the design decisions that went into building the LHC.

So, the Higgs Boson justifies our continued use of the Standard Model; it gives us confidence in the scientific method; and it can be used to justify the building of the Large Hadron Collider. However, there is a real sense in which the Higgs Boson poses a problem for physicists.

This is captured well in a piece in Wired, How the Discovery of the Higgs Boson Could Break Physics. The problem is that in science, the only way to push theories into truly new territory is to discover the ways in which they are wrong. Scientists already have a lot of reasons to believe the Standard Model is wrong. It's quantum mechanical nature cannot be reconciled with the smoothly-curved space-time of General Relativity. It provides no explanation for the origin of the dark matter that appears to holds galaxies together. It also provides no explanation for the dark energy that is causing the expansion of the space-time of the Universe to accelerate. Finally, the model includes several "free parameters," or numbers that have to be assigned arbitrarily to explain the masses of some particles and the strengths of the fundamental forces. Finding the Higgs Boson does not help address any of those problems, and it closes off one possible route to discovering something new.

The Big News discovery of the Higgs Boson has also led to media reports that distort the meaning of the discovery. I'm afraid this is because some clever physicist decided to call the Higgs Boson "the God Particle," and it stuck. It probably seemed like a good marketing move, but in the end it suggests the particle has an outsized importance in the theory.

The New York Times called the particle a Holy Grail, which I guess is meant to reflect the fact that the discovery is a Big Deal. I have a personal dislike of that hackneyed phrase, but I would also object because, as I said above, the really big deal would be the discovery of something unexpected.

Both The New York Times and The Daily Beast referred to the Higgs Boson as a Key to Life. Even an otherwise informative and well-written essay in Science News took this tack:

In fact, the Higgs is responsible for the structure of the universe as we know it. It's the Higgs that makes physical reality the way it is, with atoms, chemical reactions and life. No Higgs, no molecules. No planets. No people.

While that's technically true, this is misleading in a few ways. First, the paragraph ignores the philosophical distinction between the reality of our Universe and physicists' model for the Universe. Our existence is a given. The Standard Model is how we try to understand the facts of our existence. If the Higgs Boson had not been found, it would not have undermined reality, but our model.

Second, the paragraph implies that the Higgs Boson is the key to everything in the Standard Model. In fact, it is no more central to the Standard Model than any other particle, field, or force. That paragraph could have as easily read, "The electron is responsible for the structure of the universe as we know it..." If the Higgs had turned out not to exist, reality would not have been affected. Instead, we would have found that our model was not a complete description of the Universe. The Higgs is not special because nothing works without it (that's true of all the particles), but because it was the last particle to remain undiscovered.

Finally, there seems to be a mistaken notion that physicists have come closer to understanding the nature of life by finding the Higgs Boson. This, to me, is laughable. Physicists understand how individual particles interact with each other, in pairs and groups of a few. Physicists now have access to the computational power to approximately understand simple molecules. However, physicists are still generally flummoxed when they try to calculate how proteins fold. Physicists are almost completely lost when they try to understand life. True, they can measure the structure of DNA, and contribute to decoding the genome, measure the electrical chemical reactions in neurons, examine the balance of hormones, and determine how the blood transports oxygen. However, having models for the components of a living being is not the same as understanding life. The interesting parts of life are not addressed by finding the Higgs Boson: understanding how life originated, how it became so diverse and complex, how it developed consciousness.

Finding the Higgs Boson is a big accomplishment for particle physicists. It is, however, just a small step for understanding.