Larry MacPhee: Biology

REvolutionary Thinking

The 200th anniversary of Darwin's (and Lincoln's) birth was Feb. 12, 2009. Happy Birthday Chuck! REvolutionary thinking is applying the Darwinian priniciples of evolutionary biology to the big picture questions that people have always asked. Speculating on these problems in the light of evolution explains things that never made sense before. In the words of the famous geneticist Theodosius Dobzhansky, "Nothing in biology makes sense except in the light of evolution." In order to understand these examples, basic familiarity with evolutionary principles is recommended. Here are the basics.

Teach the Controversy?!

Although evolution is widely accepted among scientists, fewer than four in ten Americans accept evolution. In the public schools, the anti-evolutionists want us to "teach the controversy." Ok, here's the real controversy: A collection of religious zealots want to replace the consensus of scientific facts, gathered with painstaking care and great effort by scientific community over hundreds of years, with their own personal religious beliefs. Letting any special interest group, let alone one so self-righteous, ignorant and misguided, infiltrate schoolboards with the purpose of misinforming our children is dangerous. It is sometimes argued that if scientists are so confident of their ideas, then why do they have to worry about challenges? Several reasons: 1) Fairness: Journalists love to present things as a point-counterpoint but it's not really fair because the scales are so heavily tipped towards science. Giving equal time to nonsense lends it undeserved credibility. 2) Qualifications. Most of the so-called skeptics don't understand the fields they take objection to. It is nearly impossible to find a biologist who doesn't accept evolution as fact, or a climate scientist who disputes human caused climate change, a geologist who questions continental drift, or an astrophysicist who questions the big bang. Sure, they may get quite heated when discussing the details, but the general principles are very well established and unlikely to be overturned. If there was any real doubt, that would not be the case. 3) Salesmanship: Scientists are details people. They are not without humor or charm, but they are rarely very good communicators. A talented salesman, lawyer or preacher can talk circles around a scientist and muddy the waters sufficiently that an audience of lay people will be left confused and uncertain, or worse. 4) Futility: The challenges to scientific findings are generally faith based and not testable by scientific techniques. You can't change a person's mind if they "know" something to be true regardless of the evidence. Debating with them is a losing proposition. If you wrestle with a pig, you're bound to lose because you'll get dirty and the pig will enjoy it.

The Meaning of Life

What is the purpose of life? Surely that's one of the biggest questions people have ever asked. To a biologist, the answer is simple. Life exists to perpetuate itself. The meaning of life is to make it, and to nurture it. Passing one's genes to the next generation, ensuring that those genes live on, and helping your relatives (who carry a similar set of genes to your own) also survive and reproduce is what drives living things. Why? Again, the answer is almost obvious. Because if your ancestors didn't survive and reproduce, and if they weren't really good at it, you wouldn't be here. Against incredible odds, over the unbroken course of 4 billion years, here you are. If you are reading this, your ancestors won life's competitive challenge. Congratulations! Some would say then that life has no greater purpose, and try to depress you. I would disagree. What is more fulfilling than caring for your loved ones, being part of a family, and teaching them what you know? Just ask yourself. Why doesn't money, fame or power bring happiness? True fulfillment and happiness comes only from giving and receiving love. That's how we're wired, people. Embrace it. The only afterlife we can be certain of is the one we give our children. Our genes will live on through them. They are our eternal reward. It's a simpler more honest truth when you stop and think about it.

Crime and Punishment

The author of a recent neurological study of the living brains of convicted psychopaths argues that they differ from the rest of us. If that's the case, can it be long before such techniques are used to screen us all for future bad behavior? It sounds like the plot for a Phillip K. Dick novel. What if we screen a murder suspect and find that he shows these brain activity patterns? Is it confirmation of guilt? Can one's own body be used against him? How does this jive with the right to remain silent to avoid self-incrimination? And if a person is physically incapable of empathy, or remorse, what do we do with him? Is such a person curable? Should we execute someone who is incapable of controlling their actions or just keep them safely away from society while in wait of a cure? Should we treat them as sufferers of an illness or lock them up and throw away the key? If such a screening was available, would you have it done? We are at a stage where the science can tell us things about our future, sometimes with near 100% accuracy, but cannot yet prevent them from happening. Another study shows that while a person can have a genetic predisposition, there may be environmental triggers. If a person with psychopathic tendencies has a healthy childhood, he might live a perfectly normal life. If that same person was abused as a child he might become a monster. These studies do tend to validate the restrictions we, as a society, put on the movements of known sex offenders while we search for a cure. Some loss of liberty is to be expected when one commits a serious crime.

Our Prosthetic Future

There is some crazy stuff going on in the world of prosthetics. There is a Canadian guy who calls himself Eyeborg. He's a bit of a showman! He's got a video camera where a damaged eye should be, and he can broadcast what he sees by WiFi to a nearby monitor. As camera technology improves, he just upgrades his eye. There is a British soldier who was blinded, but uses a video camera to send electrical impulses to his tongue. Somehow, his brain recognizes these signals as visual data and processes it, so he can "see." He describes the images as grainy and black and white, but this just blows me away. There are also some double amputees who have graphite springs that look like hockey sticks, and they can run as fast as any human with ordinary feet. One such guy wants to compete in the regular Olympics, but the IOC isn't sure he should be allowed because he has an unfair "advantage!" Cochlear implants are allowing the deaf to hear, but some deaf people don't consider themselves disabled. We may all feel this way soon. As technology advances and prosthetics continue to improve, will it be long before someone with artificial upgrades is competing with you for a job? What happens when your daughter comes to you with the notion to have her eyes removed so she can replace them with artificial ones that work better than what you gave her? Come on dad, all the cool kids have them! Will humanity split into two groups; the enhanced, who want to be all that they can be, and the unaltered, who resist such artificial improvements? It sounds like the stuff of science fiction, but it's just around the corner.

Does Free Will Exist?

It has been argued that assigning evolutionary-genetic explanations to our bad behavior is to excuse it with a "get out of jail free" card; a modern day version of "the devil made me do it." This is the assertion of Sharon Begley in a recent Newsweek article that assails Evolutionary Psychology. She correctly addresses some of the weaker theories and dutifully knocks them down, but then goes on to throw out the entire approach, claiming that Darwin just has nothing to say on the subject. But Evolutionary Psychology remains valid and valuable as a framework for making predictions which can be tested scientifically by experiment and observation. It's a positive step that these predictions are now being tested and, in some cases, challenged. That's how science works. When we don't find what we predict, we then go back and look at our assumptions, as is done by the researchers she references. We don't throw out the entire field as a misguided, dated, sexist approach to explaining human behavior. That says more about the agenda of the author. But in addition to, apparently, not understanding the scientific method, Begley also misses an important point about humans. While there can be no doubt that our genes sometimes drive us to do things that our conscience tells us not to, humans have a large brain and a long life. We are more capable of learning and are more influenced by our upbringing and experiences than perhaps any other animal. The phenotype, or appearance (including behavior), of an organism is a combination of genes, environment, and the interaction of the two. So while it may be difficult to resist, your fate is not entirely determined by your genes. Whether it's quitting smoking or risking your life to save a stranger, humans are capable of making difficult choices and resisting the selfish urge. Humans are more capable of resisting their biological destiny than any species that lacks long term memory, self awareness, empathy, a conscience, and guilt. Our ability to knowingly make sacrifices for a greater good that we know are not in our personal best interest is unique. It may be that our noblest and most selfless acts occur just because of this non-genetic influence. And if anything separates us from the animals, this is it.

The Probability of Life

People often wonder if there is life out there in the universe. While this is purely a speculative exercise, what can we infer? Let's start with the assumption that life arose on Earth by a natural process and that no miracle happened. If it happened here by natural means, then there's no reason it couldn't happen elsewhere. How likely that is depends on what the process is, and on the number of planets in the universe where conditions are favorable. Here's what we know. The Earth formed about 4.5 billion years ago, and life was detectable as early as 3.9 billion years ago, so life appeared relatively quickly after the planet cooled. The early Earth was very different from the present one. There were periods of heavy asteroid bombardment that kept the surface molten and made life impossible for the first few hundred million years, but eventually the crust cooled and became a "primordial soup" of chemicals. There was little oxygen, but water, methane, ammonia and hydrogen were abundant. There was an atmosphere, lots of lightning, more intense radiation, strong tidal forces from a closer moon, and probably freeze thaw cycles at least in some places. Almost certainly, there was heterogeneity. When scientists simulate those conditions in the lab, amino acids are produced over a short period of time. Amino acids are the building blocks of proteins, and that's what living things are made of, so we're on the right track. But how organic molecules assembled into more complex forms and gained the ability to self-replicate is still a hot topic in biology and there is not a single accepted theory that explains it all. Scientists have also, to date, been unsuccessful at creating living things, though there are some promising projects. However, once molecules gained the ability to self-replicate, then Darwinian selection acts to favor the ones that do it most effectively and major leaps forward would naturally occur. At what point these molecules become "living" depends on your definiton of life, but we are well on our way towards it. So yes there is probably life out there in the universe, and possibly even elsewhere in our solar system on the moons of the gas giants, under the ice around geothermal vents. But intelligent life? Intelligence at more or less the same level as our own alive at the same time as us? An alien intelligence capable of communicating with us? An intelligence enough like our own that we would understand anything they tried to communicate? Intelligence advanced enough to cross the void of interstellar space and visit us? The odds on those bets are increasingly slim. Let's remember that for the next two billion years or so after life first appeared, there was nothing more complex than a single celled bacterium. And while we've only been capable of sending radio messages to other star systems for about 100 years, and have only taken our first baby steps to nearby worlds, we have come dangerously close to wiping ourselves out with weapons of enormous destructive capacity. Would an alien intelligence that has managed not to destroy itself even want to talk to us or let us become aware of their existence?

Getting Sick

Viruses don't have brains, but they act in very clever ways. Think about the common cold. When you are in the grips of the cold, your head is stuffed up, your eyes are red, your nose is running, you are sneezing and coughing, and you have a sore throat and possibly congestion. Not a pretty picture. Anyone who doesn't want to catch your cold should steer clear, right? Well, it turns out they're probably too late. The infectious stage happened before you displayed any symptoms at all. By the time your body reacted to the invasion, the stage where you have lots of physical symptoms, the virus has already leaped to its next host. You wouldn't kiss someone with mucus running out of their nose, right? A virus that spreads before it causes you to develop many physical symptoms is going to be more successful than one that trys to spread after you look ill.

Endosymbiosis

Some people get the creeps when they think about organisms that live on us or in us. But what's really incredible is that there are organisms in our cells that long ago became a part of us! Inside the cells of virtually all complex organisms are little structures called mitochondria, commonly referred to as the "powerhouse" of the cell. Plants have additional structures called chloroplasts, which are more like nature's version of the solar panel. Mitochondria and chloroplasts, two of the most important cellular organelles, have an intriguing origin. They resemble in many ways the more primitive single-celled bacteria. They are double membraned structures which contain their own unique DNA; distinct from the DNA of the nucleus. The outer membranes of the mitochondrion and chloroplast resemble those found in eukaryotic or complex cells, while the inner membranes resemble those found in prokaryotic or primitive bacterial cells. The DNA of the mitochondrion forms a ringed chromosome characteristic of bacterial DNA. It is now generally accepted that these organelles, vital to the survival of the cells that house them, originated from the incomplete consumption or invasion of single celled creatures millenia ago. These single celled organisms were adopted by the cell and became an integral part of the multicellular organism, reproducing themselves when the greater cell divides. The theory of Endosymbiosis, first ridiculed but now widely accepted, proposes that the complex eurkaryotic cells found in multicellular organisms arose from symbiotic associations of simpler prokaryotic organisms. Without the energy producing mitochondria and the photosynthetic chloroplasts none of the eukaryotes, the "higher" animals, plants, and fungi, would exist. We owe it all to the lowly bacteria that live within us and nourish us.

Mitochondrial Eve

There's an interesting consequence of "anisogamy," the difference in the size of the male and female sex cells or gametes. The sperm is generally tiny compared to the egg, and when they fuse, the DNA of the sperm is injected into the egg but the rest of the sperm cell is discarded. The sperm cell is merely a highly specialized delivery vehicle that, once it's mission is complete, is no longer needed. In contrast, the fertilized egg is the cell that will divide repeatedly to become the baby. That means that while baby gets nuclear DNA in equal parts from mom and dad, baby only gets mitochondria (and mitochondrial DNA) from mom. So what? Historically, Westerners have always made a big deal out of male children because they carry on the family name, while daughters take the name of their husband at marriage. The lineage of the daughter is therefore harder to trace. But with mitochondrial DNA it's the opposite. We can trace maternal lineages back thousands of years because your mitochondria came from your mom unchanged, and hers came from her mom, and so on. Over generations, the occasional mutation gets introduced and new lines appear. So we can compare maternal ancestral lines quite easily and use this data to determine historical paths of migration and colonization. The most recent common matrilineal ancestor of us all lived in Africa about 200,000 years ago.

The Domestication of Dogs

Recent studies have cast doubt on the origins of our pets and farm animals. The old idea, that humans captured and tamed wild animals, gradually breaking their wild spirit, sounds plausible but apparently it doesn't work very well. In truth, it's more likely that the animals "decided" to join forces with us. In a new book that summarizes research on the domestication of the wolf, it becomes clear that what happened with dogs is a better general theory of domestication. Wolves that feared humans stayed clear of them, while those that were more tolerant of our presence spent more time in our viscinity during those hunter-gatherer caveman days. Why? Because humans are wasteful, and leave lots of scraps around their campsites that a wolf can enjoy rather than hunt for his food. Over generations, these scrap heap wolves became more and more tolerant of humans, because those who were least timid and least aggressive towards humans got the most scraps and had the most pups. Natural selection gave this offshoot from the wolf family tree an alternative survival strategy. It makes perfect sense that dogs would eventually become our helpers. Prosperous humans produce more table scraps. Apparently it worked. Today there are many more dogs in the world than their are wolves.

Restoring a Fishery

An interesting thing has happened in some of our better managed fisheries. While the fish remain numerous and the population healthy, year after year the average fish length has been decreasing! Modern technology helps us to be very good at catching fish so it would be safe to assume that fish are simply being caught before they reach a large size. But something more subtle is happening. Regulators, with good intentions, have imposed minimum size limits that protect fish from capture until they have a chance to reproduce, thereby allowing the fishery to be sustainable. One way to do this is to require that the holes in the nets fishermen use are large enough that small fish can escape. The minimum size limit is set somewhere beyond the size of first reproduction. But there is an unintended consequence; it creates selective pressure that favors reproduction at a smaller size and earlier age. This has caused the stock to evolve in a way that, while it continues to thrive, makes it less desirable to us commercially. A recent study of the silverside showed that not only does this happen but it can be reversed. The key is to modify the regulation so that fish beyond a maximum size cannot be taken. This will keep the largest fish alive and reproducing most successfully, driving selection back in the opposite direction. But how to not catch the big fish may be a bigger practical challenge, since fish are generally dead when they come up in the nets and we can't just throw the big ones back.

Living at Elevation

Scientists have been studying human adaptations to living at high elevation. Both the native Tibetans and the Peruvians are far better at it than someone who's ancestors are from lower elevations. But more interesting is the finding that the Tibetans are significantly better at it than the Peruvians. Why? They've been doing it for a much longer period of time, and have accumulated a bigger bag of evolutionary tricks. Remember that human population originated in Africa, spread out across Europe and Asia, and only "recently" (between 15 and 20 thousand years ago) migrated across the land bridge connecting Asia to Alaska, ultimately reaching South America. So compared to the people living in the Andes, the people of the Himalayas had a really big head start.

A Cure for the Common Cold

The common cold has been tough to beat. Its trick is that it keeps mutating, changing its exterior appearance so that our immune system fails to recognize it from one time to the next. But it may be that the long sought cure for the common cold is not far off. Scientists have been busily sequencing the DNA of cold viruses and they have found that while the parts of the genome that code for its superficial appearance evolve rapidly and allow the virus to hide from our immune system, there is a core sequence that is remarkably conservative. Targeting medicines at this critical part of the virus will be more effective, since it cannot change these sequences and continue to replicate. So the virus can camouflage itself any way it wants but we'll be able to spot it by something more akin to a heat signature. If it can't hide, our immune system will take care of the rest.

Survival of the...Cutest? ...the Spiciest?

Normally, when we think of survival of the fittest, we imagine that the strongest or the fastest or the toughest will be the most successful and leave behind the most progeny. But remember, one must both survive and reproduce and ensure the survival of one's children in order to successfully pass along one's genes. It's no use being tough if you never get to mate, and it's no use producing a lot of babies that all get eaten. There are an amazing variety of strategies for success. One particularly odd way of achieving high "fitness" is to hitch one's cart to another successful species. Think of the guinea pig. This small furry creature which originated in the Andes mountains of South America has become a favorite small pet because it is gentle, cute and makes sounds that are pleasing to people. On its own, the guinea pig would not be nearly as numerous as it is today, but as long as humans enjoy keeping them as pets, the humble guinea pig has a fabulously successful survival strategy; be cute. Chili peppers have a similar strategy. Many plants produce nasty substances to make them less palatable to predators. Originally, the capsaicin (the spicy stuff) in chili oils was designed to discourage grazing mammals from eating the fruits of the chili plant. But humans discovered that, in small doses, adding spices to food makes it more tasty. The chili plant is now grown all over the world just because people like to eat it. So humans carry a whole collection of species along with them. For a while, horses had it really good because they were so useful to humans, but their luck has turned. And it's not all positive. Rats, cockroaches and mosquitoes are also far better off because of humans. We have brought them with us to the the four corners of the earth.

Why can't we eradicate the diseases for which we have vaccines?

We beat smallpox but, in general, we have not been very successful at eradicating diseases that we can easily immunize against. Why? At least one reason is human behavior. When vaccination efforts are relatively successful, as they are with polio, whooping cough, and measles, we drive the frequency of the virus to such low numbers that most people today don't remember what awful diseases they were, because they have never encountered them. That makes final eradication difficult because it lowers the fear factor, as people either don't bother to, or forget to, or decide not to, get vaccinated. Getting the last few percent vaccinated is very hard. In these cases, the disease finds safe harbor and can bounce back. There are also certain situations where, if everyone makes a small sacrifice, everyone wins big. But getting everyone to play along is hard. The temptation, of course, is to forego the sacrifice but collect the rewards. This can work for a while but if too many people do it or if you get caught the game is up. If we could vaccinate everyone against measles, we could eliminate the disease from the face of the earth. There is a small risk of harm from a measles vaccination and there is a great risk of harm if one contracts the measles. Therefore, if most people get vaccinated, there is no penalty for failing to get vaccinated and there may even be a small benefit. However, if too many people start cheating, then at some point the risk of catching the measles rises above the risk associated with vaccination. This little lesson should remind us of an important point. Individuals don't do things for the common good; they do them for their own good. Natural selection works on the individual, not the group. Those who best take care of themselves and their close relatives pass along the most genes. Selflessness may be noble, but it's not a winning strategy.

Herd Immunity

Vaccination is a good thing. However, the very young, the immune compromised, and the very old cannot be vaccinated because of their undeveloped or weakened immune systems. For an additional small percentage of vaccinated people, the vaccine fails to work so they would also be vulnerable. Finally, there are those who seek a religious exemption and opt out of vaccination. Those for whom the vaccine has failed, and those who are unvaccinated, rely on something we call herd immunity. Just as a herd might shield its most vulnerable members from attack by encircling them, the vaccinated population can protect the unvaccinated and reduce their risk of infection. However, when the percentage of the population that is vaccinated drops only a few percentage points below 100% the viruses can find refuge and an outbreak of disease can occur. During the 1990s, reports began to surface that thimerosal, which used to be an ingredient in the MMR vaccine, was linked to autism. The research that led to these news reports, which got wide circulation in the media, was later determined to be either deeply flawed or fabricated, but the fear that they caused has resulted in mainstream public suspicion about vaccines. That suspicion has led to a lower vaccination rate and the breakdown of herd immunity in a number of incidents since, and experts predict it will be years before the damage done can be repaired. For those of you who think that getting vaccinated is risky, how do you feel about contracting polio or giving it to someone you care about?

Racism

Why are humans so nasty to people who are different, and why are we so good at spotting people who aren't like us? A lot of it has to do with our evolutionary history as a species. Humans spread out of Africa in small bands of closely related individuals. They hunted and gathered and gradually settled into an agricultural way of life. At this point in our history, it was highly adaptive to be afraid of strangers because they were potential competitors. Strangers might kill you, enslave you, rape you or take your possessions if they had the ability to do so, and encounters with others were likely met with great caution. The more different these others were from you, either in looks, beliefs, language, or customs, the less likely they shared your genes. Meanwhile, your tribe was comprised of your close relatives and descendants. As you spread your genes, you spread your looks, your beliefs, your customs, your language, so meeting people like yourself was less of a threat. This also explains why intermarriage with nearby clans made sense. The more you mixed your genes with your neighbors, the more you and they would be assured of peaceful relations and the preservation of your genetic legacy. Eventually these loose organizations of like peoples formed our modern nation states as a way to protect themselves, and conflicts continue to arise where different groups clash. While we have less to fear from those who are different from us in the modern world, it still helps to explain the instinctive negative reactions people have toward immigrants and those who don't speak our language or share our faith or our cultural practices.

Living in Space

Astronauts who spend even short periods of time living in space come home with reduced bone density and diminished musculature. The Americans and the Russians have wasted decades and millions of dollars studying the negative effects of low gravity on astronauts and developing remedies to treat them. Why is this a completely wrong-headed approach? Would you push an astronaut out an airlock without a spacesuit and expect her to live? Of course not. Because humans don't adapt to extreme environments. Humans adapt the environment to meet their needs. We are fabulously successful as a species because we use technology to change the rules. Neil Armstrong is not evolutionarily distinct from a caveman, but his technology is far superior. A walking human is among the least efficient locomotors, but a human on a bicycle is among the most efficient. We don't try to breathe the dissolved O2 from water or extract it from the thin air of Mount Everest. We bring bottled air with us. In airplanes we pressurize the cabin to 1 atmosphere. We have not developed a greater tolerance for cold by evolving fur; instead we wear clothing and live in heated shelters. So if we don't try to live without air or heat or standard atmospheric pressure, why then, in space, should we try to live without gravity for more than brief periods of time? Sure we might enjoy brief forays in zero G the way we enjoy a dip in the pool. But we won't live there. Instead, we will need to create artificial gravity by spinning our ships to produce centripetal force. It will be expensive and technically difficult, but that's what it's going to take.

Turning up the heat on cancer

Radiation and chemotherapy are the most common of the orthodox cancer treatments. They shrink tumors by scrambling the DNA of dividing cells, and cancer cells are among the most rapidly dividing. Unfortunately, the treatment can be as bad as the disease; radiation and chemo are also tough on rapidly dividing normal cells such as those found in the bone marrow, so they wipe out your immune system. Even if you survive the cancer, you are left with a severely compromised immune system and are vulnerable to all sorts of normally not too dangerous infections. But dating back to the 19th century, it has been observed that sometimes people who develop a high fever see their cancers remiss. Could it be that a coincidental infection jump starts the immune system into hunting for abnormal cells, which knocks out the cancer too? This is a very promising find. If we could artificially induce fever by introducing a benign foreign agent that triggers the full blown immune response, our own bodies might be capable of identifying and destroying abnormal cancerous cells. Maybe we could even plant these triggers in the cancerous tumors to help the immune system zone in on the problem.

Parent-Offspring Conflict

It has never been harder to be a parent or a teen. For purely biological reasons, parent-child conflict during the teen years is increasing. In pioneer days, people got married in their teens and started their own families around the same time that they matured physically. This worked well. But modern teens are victims of two forces that pull them in opposite directions. Improving nutrition has been causing teens to physically mature at earlier and earlier ages. It gives a whole new meaning to the term "developed nations." It is now common for girls to become reproductively mature before the age of 10. Earlier physical maturity means not just earlier interest in sexual activity but earlier challenges to parental authority. But emotional maturity, good judgment, and a complete education, so necessary in our complex modern world, are developing later because they are products of time and money rather than nutrition. Teens are chafing against parental rules and demanding independence at earlier ages than ever before, but they remain financially dependent upon their parents for longer than ever before, often into their late 20s. Teens live in a world relatively free of natural dangers, and with few real responsibilities, yet they crave independence, adventure and excitement. They complain of boredom but lack common sense and good judgment. They live in a consumer culture and have no money. As a result, they often create their own trouble for stimulation. And they start earlier every year.

What to do with teens? A modest proposal ;)

Many of the problems with teens are caused by opposing forces (earlier physical maturity and longer financial dependency) that put stress on both the teens and their parents. So what could be done? We could try to suppress physical maturity, preserving children in a more childlike state until they are older and more educated. But that would still be hard on parents, who would have "dependents" longer. Or we could try to shorten financial dependence. Rather than sending kids directly off to college after high school, what if we required a period of work experience? After all, many college freshmen have no idea what they want to do with their lives and many only manage to accumulate massive debt and mediocre grades. But the modern world seems too dangerous for high school graduates to be living out on their own, cooking meals, driving, working, and paying bills. And while it would give them freedom, working a crappy job and trying to be self-sufficient lacks excitement and doesn't give them real responsibility. I think perhaps we need an exchange program with the Almish. We could embed our teens with birth control and send them off to the farm to live a simpler life, working the fields and tending the animals. Let them have all the (safe) sex they want, and all the responsibility and hard work they can handle. But no alcohol, drugs, guns, iPods, cars, nightclubs or shopping malls. And if, after a few years of that, they want to return to the modern world and work or go to college, I think they'll be more ready. If the farm isn't the place for everyone, a new Civilian Conservation Corps, the Peace Corps, a stint doing International Relief, a non-military version of the National Guard (Disaster Relief and Aid) or Teach for America might be excellent alternatives. Giving teens true responsibility and channeling all that energy would pay huge dividends.

Lactose Intolerance

Lactose is the sugar found in milk and other dairy products. Humans, being mammals, have evolved to drink milk from their moms. It's natural. It's good for you. It gives you an immune system boost. But many of us wean by the age of 2 and almost all of us do by age 5. During most of our evolutionary history, that was the last time we saw milk, so the genes that code for the production of lactase, the enzyme that breaks down milk sugars, are designed to shut down permanently once milk is no longer a major part of our diet. Without lactase, consuming dairy products leads to unpleasant abdominal cramping because we can't digest the milk sugars. In asian and african cultures, where commercially available dairy products are not common, this continues to be the case. But in cultures where humans have a long tradition of raising animals for milking, there is a prevalent mutation on chromosome 2 which prevents the shutoff of the genes that code for lactase. Humans who have evolved in pastoral settings are much more likely to have this mutation, which confers the very useful ability to digest dairy products.

Political Systems

Which socio-political system works most like Darwinian evolution? Not democracy. Not communism or totalitarianism. It's the free market! A purely capitalist system allows the most nimble, the most clever, the most powerful, and the most ruthless to prosper. In a purely capitalist nation, there would be no entitlement programs like medicare and social security. The rich would have excellent healthcare and a comfortable retirement, and the poor would have none. There would be no corporate bailouts. If a company was struggling, it would be allowed to die or be absorbed by a stronger one. That's natural selection. Except for nepotism, it would be every man, woman and child for him/herself, and the only alliances would be ones of convenience. There would be lots of treachery but no ethical dilemmas. Laws would be made by the powerful to benefit themselves. The police would serve and protect those who paid them. Applying evolutionary principles to the way we choose to behave (Social Darwinism) is a scary concept. But if we're trying to understand why capitalism works so well, it's simple. It's survival of the fittest. Capitalism does not require that all men are created equal, nor that they have equal rights. Inequality isn't a problem in a capitalist system; it's the incentive. Want more than your neighbor has? Then beat him and collect your reward! And what country embodies this contradiction of ruthlessly selfish capitalism on the one hand with selfless Christianity and egalitarian democracy on the other? America! It's no wonder we're conflicted!

Modern Ailments: Part I

Why is it that, in this age of incredible medical advances, people seem to develop illnesses that were unheard of in the past? Cancer, arthritis, heart disease and Alzheimer's seem to be running rampant. REvolutinary thinking may explain some of it. One argument is that, because we are all living longer, problems that appear later in life like heart attack and stroke, arthritis, cancer, and Alzheimer's, rarely manifested in the past because something else always got us first. If I was born in an earlier age, I would have died of an appendicitis at age six. How about you? Has modern medicine ever saved your life? More than a few people who would have died of infection or injury or in childbirth, or of plague, malaria, scarlet fever, or dysentery, are now living long enough to develop cardiovascular disease, arthritis and Alzheimer's. As the old saying goes, "If it ain't one thing, it's another!"

Modern Ailments: Part II

Ok, so living longer might explain why certain health problems appear to be on the rise. But what about the diseases that affect children? Something else is going on there. One fascinating theory, sometimes referred to as the "hygiene hypothesis," is that our environment has become too clean, and the result is a rise in autoimmune disorders. Our immune system was designed to attack foreign bodies that invade us. But in a world where our water contains no microbes, our food is free of parasites and our infections are eradicated with antibiotics, the immune system seems sometimes to find itself all dressed up with no place to go. Without anything to do, it turns on the body or overreacts to things that really aren't much of a risk, like pollen or peanuts or your organs! A recent study showed that people living with multiple animals in the house have fewer pet allergies. In Mexico, people drink the water all the time, but Americans who drink it get gastrointestinal distress. Another study showed that respiratory problems and allergies are far worse among inner city residents. Less than 100 years ago, almost everyone lived on a farm in a dirty, biotic mess of manure and dander. Is it the urban smog, or do we all need to spend our formative years exposing ourselves to dirt, germs, and other unsanitary stuff in order to train our immune systems on what to attack? A remedy that has shown promise is to introduce relatively harmless flatworms into patients with auto-immune sensitivity to give the body's defenses something real to fight.

Hidden Causes of Disease

People used to think that stomach ulcers were caused by stress and diet. If you got ulcers, you had to change your lifestyle; no more stress and no more spicy foods. That's the way it was for years, and it was a life sentence. Even with those lifestyle changes, people could control ulcers but not eliminate them. Then it was discovered, to the disbelief of the medical establishment, that people who got ulcers had a particular bacterium in their gut, called Helicobacter pylori. If you had it, your risk of ulcers was far higher than if you didn't. With a short course of antibiotics, H. pylori can be eliminated and presto, no more ulcers. How many more lurking invisible microbes, either with us now or exposed to us in the past, could be the root causes of our ailments? What if you could get a vaccination against cancer? There is strong evidence that exposure to certain viruses can cause specific types of cancer later in life. The most recent case, for which there is now a vaccination, is cervical cancer. If a girl is vaccinated against HPV (Human pappiloma virus) before she becomes sexually active and is exposed, she can ward off this cancer. Although the pro-abstinence people consider it controversial, the science is solid. The vaccination is 100% effective against the strains of HPV that cause 70% of cervical cancers. Update: This work was just awarded a Nobel prize in 2008!

Male Promiscuity

In the animal world, there are many different mating systems, but polygamy (one male mates with many females) is far more common than monogamy (one male, one female) or polyandry (one female, many males). Males of almost every species will attempt to mate just about whenever the opportunity arises. By now, most of the women reading this are nodding knowingly. Females are, with rare exception, far more choosy. And now the men are nodding. Why are males so promiscuous? Why are females so choosy? The amount of energy it takes to produce a sperm cell is far less than that required to make an egg. If both sexes have a roughly equivalent amount of energy dedicated to reproduction, then it is the way that energy is apportioned that differs. Think of it this way. A male has 100 pennies (sperm) to gamble on 100 matings and a female has a dollar coin that she has to bet all at once on a single mate. This is further accentuated in birds and mammals, where fertilization is internal (and where the female is almost always the incubator). And to protect her greater initial investment, the female is more committed to costly parental care. Does it start to seem a bit more obvious why women are the "rate limiting step" in reproduction? In a word, it's "anisogamy."

Antibiotics

Back in the 1950s, it seemed there was nothing a shot of penicillin wouldn't cure. So why are our antibiotics less effective than they used to be? When we catch a cold, the doctor will typically start by prescribing a cough medicine and a decongestent to treat the symptoms, leaving the cold to run its course. If the symptoms last more than a week, then a secondary bacterial infection like Streptococcus may be involved, and the doctor will then prescribe antibiotics. Antibiotics are useless against viruses like the common cold but people demand them, invoking the "just in case it's bacterial" argument. So where's the harm? If they've got a virus, it will clear on its own and if it's a bacterium, they nip it in the bud, right? Well, partly. But what's good for the individual is bad for the group. The more we expose an antibiotic to the bacterial population at large, the sooner a resistant strain will arise by mutation and spread by natural selection. So it's important to use our antibiotic ace-in-the-hole only when we really need it. And when we resort to antibiotics, we need to use overwhelming force. When people start to feel better, they sometimes prematurely stop taking the antibiotic. This kills the weakest of the bacterial strains in their body but leaves the more resistant strains alive to reproduce and spread. The best example of this is Tuberculosis, which we nearly eradicated. Resistant strains have evolved in the homeless population where follow up treatment is difficult, and these killer strains are now spreading through hospital wards like wildfire. So avoid antibiotics until you need them, and, when you get them be sure to finish the prescription! If you don't kill it, you make it stronger! Taking a class of antibiotics out of circulation for a while can also help by relaxing selection. If there is any cost to being resistant, the resistant strains will die out in favor of the wild type and the antibiotic will then have renewed effectiveness. And the desperation strategy is to create a cocktail of many different classes of antibiotics when we encounter the toughest bugs, in the hope that throwing everything against them will work. Let's hope so, because if it doesn't we're all in trouble.

Diet and Exercise

Throughout most of our evolutionary history as humans, food has been scarce and it took a lot of tough physical work like farming, fishing or hunting to fill the larder. Let's look at fat. Fat is not intrinsically bad. We need fat for nervous system development and cell membranes, and we store excess energy in fat for times when food is scarce. When our ancestors came across fat, our caveman bodies told us to eat all we could get, because it might be a long time until the next big feast. But in our modern world, which has appeared in the evolutionary blink of an eye, we are still listening to our old programming. What has changed is that it's hard to refuse those once scarce fats and simple sugars that are present in every meal, and the portion sizes seem to keep getting bigger. Since food is never scarce, we never burn those stored fats. The world has never seen such nutritional abundace as we have in the west. And we have never been less active. Between our car culture, our desk jobs, and all the modern conveniences, most of us get winded going up a flight of stairs or walking the groceries from the car to the house. We are paying for our "prosperity" with a whole new collection of afflictions like obesity, heart disease, poor circulation, back pain, and diabetes. And for many of those who do exercise, it's costing a small fortune at the local fitness club! So act like a caveman for better health; exercise heavily, avoid excess, eat foods in season, eat foods produced locally, and embrace the slow food movement. There was a recent study that showed rats kept near starvation and exercised heavily lived somewhat longer than their well fed and poorly exercised brethren. But as the joke goes, "Would we actually live longer or would it just seem longer?"

Longevity: Part I

Human population just passed 7 billion in October of 2011. There are more people alive today than in all of human history combined but, even after factoring for that stunning statistic, there are proportionally more people living past 100 years than ever before. Why? In the longevity discussion, people used to wonder what would happen to quality of life if people lived longer. Would we just be decrepit for longer, or would we be able to push back the onset of the symptoms of aging, a term gerontologists refer to as "senescence"? The answer seems to be that, with some exceptions, 50 really is the new 40, 60 is the new 50 and so on! It also appears that once people pass 90, their odds of dying soon actually decline for a while. Think of it this way. If you have a serious defect, then it will catch up with you eventually. But if you don't, or if it is repaired medically, then you may only die when your parts finally wear out. That seems to be what's happening with the very old. Why we wear out at all is the discussion for Part II.

Longevity: Part II

Why do we age? Are there any organisms that don't? It is often useful to look at exceptions to develop a better understanding of the rule. Humans reproduce over a fairly long period of time, care for their young for an equally long time, and senesce gradually. But what about salmon, or squid, or mayflies? They save it all up, and reproduce over a very short period of time, and then immediately die. Why is that? The evolutionary theory of aging proposes that your body has to hold you together long enough to pass your genes along successfully. Once that job is finished, you, the container of your genes, become irrelevant. So the genes that help to keep us alive long enough to reproduce are favored, but the genes that keep us alive beyond that point are not. And the genetic defects that harm us before we reproduce are selected against, while those that harm us later in life are not. For the big bang reproducers, death is more abrupt than for organisms that reproduce over a longer span of time, and for those that care for their young past the age of last reproduction. So could we devise a strategy that would allow us to live longer? It's already been done, and that's the topic of Part III.

Longevity: Part III

The trick to creating longer lived organisms has already been figured out. We could do it with humans. In fact, we're already doing it without meaning to. With a concerted effort, we could probably double lifespan within 20 generations, without knowing anything more than we know right now about medicine. The reason is that we don't need to know why it works. It's a black box. If we knew why it worked, then we could do even more to extend life, using gene therapy and other biotechnologies. But that comes later. So how do we do it? Simple, at least in theory. Extend the date of first reproduction for everyone in the population. By doing so, we prevent any deleterious genes that express during that extension period from being passed to the next generation, because they kill the owner before he/she reproduces. Keep advancing the age of first reproduction for each generation and, before you know it, we're all living longer and healthier. With fruit flies, it only took only 20 generations for the flies to live twice as long, and there's no reason to think it would work differently with mice or humans. The reason I say we're already doing it, to some degree, is that, in the modern world, careers increasingly push women to delay reproduction from the teens and 20s into the 30s, 40s, and even early 50s. But while we cannot and should not attempt this with humans, and besides which it would take a long time, we can do it with mice in the lab. We can get 4 generations per year out of mice, and mice are physiologically very much like us, so most of what works for the mice will work for us. So first create some long lived lines, and then look at the physiology, biochemistry and genetics of why they're living longer. Then work out the therapies for ourselves. It's being done, and it's guaranteed to work. Now the next big problem is what to do with 7 billion people who live twice as long!

Homosexuality

If homosexuality is heritible then how can it persist, since homosexuals should pass along fewer, if any, genes to the next generation? A new evolutionary theory of male homosexuality has been recently proposed that might just explain it biologically. What if there was a gene or genes that caused its owners to be more attracted to men than those who didn't carry it? Such a gene would be passed down to both male and female children. Men with this gene would be more attracted to men than the average man, but women with this gene would be more attracted to men than the average woman. If that was the case, then although gay men would not pass along these genes, the sisters of gay men would have more than the average number of children, and that would preserve this gene in the population. It's all hypothetical, of course, but it seems that someone checked the reproductive output of the female relatives of gay men, and this may indeed be the case.

REvolutionary Thinking: Future Topics

• Why there tend to be equal numbers of males and females.
• Childbirth, c-sections, and "advanced maternal age"
• Orthodontia: Why are our mouths so crowded with teeth?
• Population size and rates of evolution.
• Why babies look like their fathers, and why people say they do.
• Why a good looking young women might prefer an older man.
• Why people in small towns are so friendly.
• Face recognition in babies, monkeys, and machines.
• Skin color and human origins
• Why spotting a terrorist isn't so easy as racial profiling
• Why inbreeding isn't always a bad thing
• Nature nurture and identical twin studies
• Autism on the rise?

Why Darwin is still controversial

As a biologist, I have often wondered why so many people are so bothered by evolution. The evidence is overwhelming and there is near unanimity among scientists. There is hardly another theory that is so elegant and so intuitive. But it's overly simplistic to imagine that so many people are tied to a literal translation of scripture. After all, most people don't go around taking an eye for an eye and a tooth for a tooth. If they did, we'd meet a lot more toothless and eyeless people. I used to think that it was a failure to grow up intellectually. Galileo was excommunicated for trying to displace the Earth from the center of the universe, so it must be hard for some to accept that man is just another inconsequential creature that came up from the primordial ooze. If we're not special, then maybe there's no purpose? Or is it just a lack of imagination? But how can we not see reflections of ourselves in the great apes? In their hands, their expressions, their physiology. Or is it that, because they look like people but act like animals, they embarrass us and make a mockery of our higher aspirations? But there are some very smart people from both ends of the political spectrum who take issue with the idea that our genes make us who we are. They just don't want it to be true. Because if genes, rather than our upbringing, control our actions then free will is in jeopardy and education is futile. To the liberals, this is unsettling because it argues for capital punishment rather than incarceration and reform. To the conservatives, it is disturbing because it would be pointless to suppress homosexual tendencies. Some people have a visceral fear of atheism because they think religion keeps us in line. If we were all atheists and evolutionists, wouldn't there be anarchy? Darwin said look out for yourself and that undermines the very fabric of civilization. Why should I fight for my country? Why shouldn't I take the last portion of food, or steal from your shop, or park in the handicapped spot, or hit on your wife? So long as I don't get caught. Dangerous thoughts.

The Scientific Creed

All of science is founded on a leap of faith. Does this surprise you? It surprised me when I first began to think about it. Here it is. Scientists accept, without direct evidence, the assumption that "the universe is governed by a set of consistent and knowable physical laws." That means that these laws apply from one day to the next and from one place to another. As our knowledge of these physical laws grows, through observation and experiment, we should be able to make increasingly accurate predictions about the world around us. Conversely, the more accurate our predictions, the more validation we have that we correctly understand the system. Take, for example, the law of gravitation that gives us our understanding of planetary motion. We understand this system well enough that we can aim a space probe at the location where a planet will be years from now when the probe finally arrives there across the great void of space and land it safely on the planet's surface. This is the power of science. And while not all systems are as well understood as planetary motion, we continue to make advances. Of course, with things like weather, or earthquakes, or human behavior, there are so many more variables that predicting future actions is increasingly difficult. But not impossible. And while the initial leap of faith was data free, science has advanced our knowledge of the world in more tangible ways than any other "belief system." This is validation of the original assumption upon which all of science stands.

Science and the Law

The way people investigate crimes is quite different from the scientific method. In crime investigation, a prime suspect is identified and then evidence is gathered to attempt to link that suspect to the crime. Yes, the suspect is innocent until proven guilty, but that's the goal; find enough evidence to prove the suspect's guilt beyond a reasonable doubt. Other lines of inquiry will not generally be followed unless the prime suspect's guilt cannot be proven. Even if the suspect did it, and you know he did it, you must have proof. Without a body, for example, there's no proof of murder; only a missing person. Ok, so what about science? Scientists set up hypotheses and then conduct experiments to test them. They don't seek to prove a hypothesis, but only to test it. If a well conducted experiment fails to confirm the hypothesis, the scientist doesn't try harder to prove it but, rather, rejects it and frames a new hypothesis. Scientists also generally don't speak about proof; rather they speak of confidence in a result. A clever lawyer knows this and can use it to try to manipulate a jury. Does a sample of DNA recovered from the crime scene prove that suspect X was there? To a scientist, no it doesn't; that's a decision for the jury. The scientist might say that the probability of a match between subject X's DNA sample and the sample gathered from the crime scene is, say, 1/1,000,000. But that's not absolute proof. There's still a 1/1,000,000 chance that the match was a coincidence. That's a level of confidence. While it might be enough to convict, it's not the same as proof. The scientist would also have no opinion about how the DNA sample got to the crime scene, and would acknowledge the possibiliy of sample contamination or even the possibility that the sample was planted there. A good lawyer who understands the way science works can find a lot of ways to undermine the credibility of a scientific expert witness. Scientists are never sure; they're only confident.

Science and the Press

Much of what the press covers is sensational. You might note that the local news always leads off with a scary sounding story that threatens the personal safety of you or your loved ones. That grabs your attention. The media loves a controversy, and the less reputable news outlets aren't above fabricating one just to grab headlines. Here's the media formula for a juicy story: You find two groups with opposite opinions, no matter how valid, and give them equal time. If everyone agreed, that wouldn't be very exciting. What you're really hoping for is a fur fight! Fair and balanced reporting seems like a good thing. After all, it's the tagline of Fox news, that paragon of unbiased reporting! The point/counterpoint approach works great in the media. Present one side, and then the other. Give them equal time. That sounds fair. The problem is that in science, consensus is built by independent verification of results, and by building upon accepted knowledge. Put a scientist up, on the one hand, to defend the idea that the dinosaurs were killed off by a giant asteroid strike and put a crackpot up, on the other side, who says that aliens killed the dinosaurs. It's anyone's guess who's going to be more convincing in a 5 minute segment to an uninformed audience. What the audience doesn't know is that millions of scientists and their independently derived research back the scientist in the chair, but that guy with the thick glasses and ill-fitting suit often won't be as charismatic, or as good with words, or as well practiced in front of the camera as the crackpot. When the subject is less absurd, it may be even harder for an uneducated audience to tell who's credible. Although the evidence for human caused global warming is very strong, it's pretty easy for a smooth talker to discredit the scientist in the chair, who has lost us all with details that are tedious or incomprehensible, by just reminding the audience how cold it was last winter and questioning the poor scientist's common sense. The audience laughs, and concludes that either one could be right. And climate scientists everywhere sigh in despair.

Science and the Charlatans

Is red meat bad for you? Can zinc cure your cold? Are anti-oxidants protection against cancer? Which diet will help you lose the most weight? Why are so many people so easily confused by medical advice? Here are some of the problems: 1) The news media likes to scare you because that's the best way to get your attention. 2) Even a well-educated lay person generally won't understand the science involved. 3) Con artists and spin doctors are very convincing with their talking points because it's what they do for a living. 4) People want simple, easy answers that require no effort and science rarely provides them. 5) It's all to easy to be fooled by someone who tells you what you want to hear. Ok, so how can you separate good science from quackery? It's actually pretty easy if you, or the media, are willing to do a little homework. You just need to find out who's paying for the research. If it's the "Tobacco Growers Board of America," you can be pretty sure they're not going to come down too hard on cigarettes. If it's the National Institute of Health or the National Academy of Sciences, or an article that appears in a good peer reviewed scientific journal, you can be pretty sure it's valid. But what about a report from the "Herbal Remedies Research Council" or the advocacy group, "Citizens for Healthy Choices"? Some of these groups are named deliberately to conceal their true identities. In most cases however, you only need to follow the money. If a company that sells a product is funding the research that finds its own product theraputic, be skeptical. That's a conflict of interest that raises questions about motives. Conspiracy theories are also often employed. Sales people will say things like, "This promising cancer fighting drug, which is inexpensively extracted from a common garden weed, is of no interest to the big drug companies because they can't patent it." And, of course, the deeper the conspiracy, the harder it is to find evidence of its existence! Finally, there's the "grain of truth" trick. Often, if trying to fool you, the first thing a con artist will tell you is something that is absolutely true and easily verifiable. This establishes credibility. But beware the next thing they tell you, which will probably be much harder to confirm, particularly if they have something to gain by convincing you. If you think it's easy to tell science from spin, read up on the tragedy of DHMO in our water supply and consider signing the petition to have this dangerous substance more strictly regulated.

Science and the Silver Screen

Why are there so few accurate portrayals of scientists on TV and in the movies? What effect does this have on recruitment of scientists and trust in scientific results? In the 1950s, during the darkest days of the cold war, when everyone was doing duck and cover drills and building bomb shelters in preparation for coming nuclear attack by the Soviets, the launch of Sputnik rejuvenated American interest and investment in science. But possibly because of the very invention that ended World War II, and the "better living through chemistry" era that followed, the image of scientists as good guys has been tarnished.In the decades since the '50s, things have only gotten worse for the public image of scientists. Unfortunately, not that many Americans actually know scientists, so the image that is portrayed in entertainment has gone unchallenged and has become an unflattering stereotype. In my own memory, the most flattering portrayal of a scientist is the professor from Gilligan's Island. Can you make a list of the negative stereotypes commonly employed in the portrayal of scientists and college professors? Do the following words make an appearance? Naive? Obsessed? Absent-minded? Mad? Geeky? Dorky? Awkward? Dishevelled? Misguided? Anti-social? Now try to come up with some portrayals of scientists and professors in current entertainment. How do they fare? Are scientists ever the heroes or merely the dupes of the bad guys, if not the evil bad guys themselves? Clearly people, scientists have got an image problem. Why would anyone aspire to be a dork or a sociopath?

Correlation vs. Causation

People are really good at spotting patterns. So good in fact that we sometimes see things that aren't really there. Sometimes events are correlated, and that can lead us to the false conclusion that they are directly connected. A rooster crowing is correlated with the sunrise, but the rooster has no influence whatsoever on whether or not the sun comes up. And even though the sunrise is more important to the rooster than vice versa, we could also trick the rooster into crowing by manipulating light levels. So, really, it's not that the sun itself is affecting the rooster so much as the light it produces and the regularity of day/night cycles. There is no direct causation between sun and rooster, but there is correlation. In addition to frequently mixing up correlation with causation, we also sometimes make even simpler mistakes like reversing cause and effect. Is it watching television that makes us obese, or is it just that if you're obese you're likely to watch more television? Or is it the ads for junk food on the television, or that if there was nothing good on television you'd be out jogging? Don't think it's easy to tease all these things apart!

Limitations of Scientific Inquiry

Science has changed human life dramatically in the last 100 years, but there are some things science is unable to resolve. If something can't be measured or observed, either directly or indirectly, it is outside the realm of scientific inquiry. One case is the impossibility of proving a negative. Let's use a silly example. Science can't prove that the Easter Bunny doesn't exist. Part of the problem is that absolute proof is elusive, but there's a bigger issue here. If one fails to find evidence of the existence of the Easter Bunny, it could always be argued that he's (is the Easter Bunny a he?) invisible. Or perhaps you can only see him if you believe in him. Or perhaps your experiment was imperfect and if you had only done this or that differently you would have found him. Clearly if the Easter Bunny held a public press conference, there would be definitive proof of his existence, but what if he doesn't want to be found? To put it cleverly, "Absence of evidence is not evidence of absence." The best you could say is that there is no scientific evidence of his existence, and conclude that therefore the Easter Bunny is unlikely to exist. However, when all those chocolate rabbits appear on Easter Sunday, I'm sure a lot of kids and dentists would beg to differ! And they've got evidence!

Occam's Razor

Scientists try to generate the simplest possible hypotheses that explain the evidence. If there are several competing explanations and all do an equally good job in other respects, accept the one that makes the fewest assumptions. That's Occam's Razor. It's a good rule because the best explanations usually have what scientists refer to as "elegance." Good explanations are clean and satisfying. It's not that the simplest explanation is always the best, but we shouldn't add complexity to an explanation unless it improves the predictive power.

Control and Treatment

A well designed experiment has a control and a treatment group. If you didn't have a control, you couldn't say for sure that it was treatment that caused a change. Perhaps the change is caused by time? For example, a cold typically lasts about a week. If you don't have a control group to compare to, you might reach the false conclusion that your treatment cured the cold when all that happened was that the infection ran its course and the body healed itself. But if the treatment group has reduced symptoms or gets better faster than the control group, you're on much better footing to argue that your remedy is effective. Ideally these control and treatment groups are as similar to each other as possible; they should be selected randomly from the same population. If the groups are heterogeneous, you can't tell whether it was the treatment or some other difference between the groups that caused the observed change. For example, you woudn't want the control group to be all men and the treatment group to be all women, just in case women and men respond differently to either the disease or the medicine. A good experiment also uses large sample sizes. This

The Double Blind

Generally, it's best if the subjects of the experiment, particularly if they are human, don't know which group they're in. In the best designed experiments, neither do the people collecting the data. This makes it less likely that the subjects or the experimenters will intentionally or inadvertantly bias the results.

The Placebo Effect

When conducting an experiment on the effectiveness of a drug, for example, the control group might receive a placebo, or fake treatment, in order to ensure that the physical act of taking a pill or the confidence that they are being treated by a promising new drug wasn't what was making the patients feel better. However, occasionally, something interesting happens. In rare cases, the people taking the placebo do better than another test group that got no placebo. The best scientific explanation for this is that the patient's own optimism or belief in the treatment had a physical effect. A good example is when someone gets better because he believes that the people praying for him made a difference and that God interceded on his behalf. While science can't refute this explanation, a scientist would prefer to do a controlled study where one group of patients was prayed for and another group was not, and neither the control nor the treatment groups knew the nature of the experiment. This would eliminate the possibility of the subject influencing the test.

Type I and Type II

In statistics, there are two kinds of errors. You can detect a relationship that doesn't exist. This is sometimes referred to as a "false positive" or Type I error. Or you can fail to detect a relationship that does exist. This is referred to as a "false negative" or Type II error. Take for example, a pregnancy test. If you are not pregnant and the test says you are, that's Type I. If you are pregnant and the test says you're not, that's Type II. This is the trade-off between power and robustness. A test is powerful if it is very good at detecting relationships. Powerful tests sometimes give a false positive but rarely produce a false negative. Robust tests sometimes produce a false negative but rarely give a false positive. So if you want to be very certain that you have detected something real, even though it might take longer, pick a robust test. If you want to be very certain that you don't miss anything, even if it might be nothing, pick a powerful test. What approach would you take if you were searching for cancer cures? How about looking for WMDs in Iraq? Or being pregnant? Or seeking the death penalty?

Precision and Accuracy

Precision and accuracy have two quite different meanings. Precision is about repeatability whereas accuracy is about closeness to truth. In the figure on the left, the shooter has moderately good accuracy (all arrows hit the target) but poor precision (because they are scattered). In the center figure, the shooter has poor accuracy (not hitting the bulls eye) but good precision (all shots hit the same region). In the figure on the right, the shooter has both good precision and good accuracy. Both accuracy and precision are important. In the case of the center figure, it might be possible to improve accuracy without reducing precision by instructing the archer to shoot slightly lower and to the left. What could we do to improve the precision of the shooter on the left? Perhaps shooting from a stable platform would help? A broken wristwatch is accurate twice a day while a wristwatch with good precision might be exactly 12 minutes and 19 seconds fast all day long.