• Why is Evidence So Important?

    First, sorry for the long time without posting. I have had a truly abysmal illness and work has been crazy. Thank you all for sticking around.

    I had a long discussion with someone yesterday (via Disqus) and I kept asking for evidence of his claims. He replied with things that were not evidence or not discriminatory. In post after post, I talk about the evidence for evolution and the evidence for global warming and constantly ask (nearly beg) for evidence of intelligent design and religion. I always say you can change my mind with evidence and I have changed my mind due to evidence. Skeptics use evidence to form valid conclusions, instead of guessing or just using what we believe to be true. But why is evidence so important?

    Evidence: The available body of facts or information indicating whether a belief or proposition is true or valid (Oxford Dictionary).

    That’s a pretty good definition. Information that tell us whether something is true or not. We don’t just drop an expensive object on the floor, because the body of evidence tells us that gravity will accelerate the object at 9.8 meters per second per second. And the sudden stop when objects hit a floor, tends to damage them. We have a body of facts and information. It’s not just one fact, someone, somewhere, somewhen once let go of an object and it fell and broke. But it’s a huge, almost inconceivable, amount of discrete pieces of information that all point to one fact. When we drop objects, they fall. And they often break. Especially delicate objects like cups and plates.

    In the court room, evidence can be used to establish guilt or innocence of a crime or accusation. It is a body of information that tells us whether someone had a motive, opportunity, the ability to commit a crime. And, even though no one deciding a persons fate in the courtroom was present at the event, there can be such a body of evidence that there isn’t a shadow of a doubt that the person is guilty. But all it takes is one piece of evidence to destroy an entire case. One camera shot from a street cam hundreds of miles away from where the crime took place means that the person wasn’t there and couldn’t have committed the crime.

    The result of something like this is an inference, that is a conclusion reached on the basis of evidence and reasoning. We can’t see gravity. We don’t see a particle that carries the gravitational force (like photons carry electromagnetic force or gluons carry the strong nuclear force). But we infer the existence of a force we call gravity. We have such strong evidence and have used such powerful reasoning that we’re willing to put three men on top of 4,700,000 pounds of explosive fuel and launch them on a three day trip to the moon. Not just once, but nine times. That’s the power of evidence combined with reasoning.

    Evidence is vitally important to our everyday lives. No one goes out to their car and wonders if, today, vaporized gasoline mixed with air won’t explode. Your car may not start, but it’s not because gasoline doesn’t explode under the right conditions. Everything that we do in a technological society (and by that I mean anything more than randomly shoving things in your mouth trying to find food) depends on evidence.  Just knowing whether a fruit is ripe or not depends on evidence.

    Science uses evidence to draw conclusions about how the world works. Science adds some requirements to evidence.

    Scientific evidence is gathered in an extremely painstaking process. Even before evidence is gathered, scientists must carefully plan the steps of their experiments or observations. Many people considered Jane Goodall’s work as not ground-breaking research into chimpanzee society, but inevitably contaminating chimpanzee society. Later, it was shown that even without human presence, chimpanzees could be very violent. Many scientists have been involved in research that has taken decades and every day of every year in those decades, detailed notes are taken, experimental steps are performed in very precise ways using well known methods. This brings reliability to the evidence.

    Scientists take great care in making sure that the evidence that they collect is discriminatory. That is, only one thing could be the cause of the evidence that they collect. Again, experiments are carefully thought out and planned in order to produce results that support a particular idea or reject that idea. Evidence should allow us to choose between two possible results. Either the accused committed the crime or they did not. No one cares that the accused brother is a politician (or they shouldn’t), because that doesn’t establish that the accused did or did not commit the crime.

    A long time ago, humans invented stories about how things came to be in the world. Lightening was the weapon of the gods. Thunder was giants throwing huge boulders at each other. A good harvest was because we threw a bunch of virgins into a volcano. These ‘just-so’ stories match the phenomena, but they are not discriminatory. The stories can be modified in whatever way is necessary to match what is observed.[1] They can’t be used to distinguish between two different ideas about why lightening happens. The process of science though, allows us that ability to distinguish.

    Scientific evidence is objective. Scientific evidence is not, “it feels hot today”. It is “it is exactly 102.6 degrees Fahrenheit at 3:30PM, 10% cloud cover.” When evidence is observed in science, whether observations in the field or in the lab, measurements are taken using devices that are not subject to personal bias. The scientific design of experiment reduces the impact of bias and human introduced error as much as possible. We don’t have a lab student start a stopwatch. Instead, we use an electronic timer that only activates when an object passes it. It, unlike the student, activates in exactly the same way every single time. Even better, equipment like that does not depend on things like country of origin of the scientist or equipment. It does not matter if the scientist has certain biases or beliefs, provided that he or she records the data accurately. That brings up another method by which humans can reduce the impact of bias.

    The double blind study is on in which the person (say a doctor) who is interacting with an experimental group (say some patients) doesn’t even know who is the control group and who is the experimental group. Since the doctor doesn’t know, then any biases he or she might have are reduced significantly.

    Both of these methods increase the reliability of the evidence. Scientific evidence is not someone’s opinion, but it should be same for everyone, everywhere, provided that they setup the experiment or observations the same way. I say that with the understanding that some things are just not repeatable. We can’t just hold the 2012 presidential election again, even if we wanted to. To much has changed about everything that influences elections.

    As I just mentioned, scientific evidence is repeatable. An object falling on Earth (in a vacuum) accelerates at 9.8 m/s^2. If you go to Venice and drop a pebble or New York and drop a penny, the acceleration is the same. Like I said, some things aren’t really repeatable, but in a general way, they can be. A great example of this is Richard Lenski’s work with the bacterium Escherichia coli. Over 20 years or so, some of his bacteria evolved a new trait. Lenski, however, kept samples every couple of hundred generations (about 3 days) and froze them. He was actually able to go back to various frozen samples of bacteria from tens of thousands of generations in the past and have them begin growing again. He found that some groups evolved the same trait. Even biological evolution can be a repeatable piece of evidence.

    Evidence that is repeatable, even under controlled conditions is very valuable evidence. It shows that we are witnessing a real thing. It’s not an accident or a random event.

    The word random has a variety of confusing interpretations, so let me take a moment to be clear. The strike location of a single bolt of lightening is random. However, it is a repeatable, controllable event. We have a significant amount of evidence that tells us when and where lightening strikes are likely to happen (rain storms, for example) and when they are not likely to happen (sunny days with no clouds). We understand how lightening forms (flow of electrons as raindrops fall through clouds) and can create and even direct lightening. For example, since we have evidence that lightening is really finding the most efficient path to the ground, we can create a very efficient path (say by launching a rocket trailing copper wire into a cloud) and direct where the lightening flows. So, while a lightening strike is a random event. The understanding that we have is that lightening itself is not a random event.

    This applies to many things that people might say is random. In reality, it’s probably more accurate to say that it is random within very tight constraints. Any card you draw out of a standard deck will be random, but you will never draw the 23 of trains.

    Finally, and possibly most importantly, scientific evidence is repeated. That’s part of the nature of science.  Someone does something and other (who don’t believe him or her) copy the experiment and see if the evidence really is valid evidence. It so happens that a very good example of this happened recently. Richard Muller was attempting to show that global warming wasn’t real. So he got the data and analyzed it himself. He replicated the results and confirmed that the Earth really is getting warmer.

    This is why scientific evidence is so important. It is reliable, because great efforts are undertaken to make it reliable. Evidence like this is not opinion. It’s not a guess. It’s evidence.

    Now, with evidence, comes a conclusion. And we’re back to that inference I mentioned above. Using reason, we collect as much evidence as we can, and decide which conclusion is more likely. Again, this isn’t a case of just slapping down a bunch of data and then saying “x is true”. That’s not science. For example, a fairly recent anti-GMO paper was widely touted as evidence that GMOs caused horrible cancer. Until people actually read the paper. The simple conclusion was that the researcher used rats that have been bred for decades to get cancers and die in two years time. When those rats, got cancer and died, this was “evidence” that GMOs caused cancer.

    This is the same as saying that most people who drown, drown in water. Therefore water is very dangerous and should not be drunk. That experiment failed almost every statement I made about scientific evidence. The author is notoriously anti-GMO. The experiments were not repeatable, except that the rats die after two years, but that’s whether they are given GMO feed or not. It was not objective. It was not discriminatory. In several trials, the control rats, those fed non-GMO feed, died more frequently than the GMO fed rats.

    Let’s say that a friend of yours says that it is raining. You know your friend and know that they are not a compulsive liar. You have little reason to doubt your friend, so you grab an umbrella. The claim is not unprecedented (unless you live in the high Andes). Therefore, you may be willing to accept your friends claim without evidence. 

    But let’s say your friend says that they saw Bigfoot. That’s a huge claim. There have been many hoaxes and fakes over the decades. While you know your friend isn’t a compulsive liar, you still shouldn’t believe them without a significant amount of evidence. For Bigfoot, let’s face it, we’re going to need a body or a live animal. That’s the only evidence that would be acceptable. Anyone with $500 can get a computer that is perfectly capable of making high quality fake photographs, even high quality fake video. With a little effort, someone could easily get gorilla hair and footprints have been faked for over 60 years.

    Is the evidence repeatable? Can you go back to where your friend saw the animal and see it again? Is the evidence objective? Do you have a variety of experts with primate anatomy and behavior knowledge? Do they agree that it was Bigfoot?  How much evidence is there?

    Any lawyer will tell you that personal testimony is about the worst kind of evidence that exists. Humans, as we’ve talked about, are biased, confused, and unable to judge simple things. For example, how long is a road stripe on US highways? It’s 10 feet long with a 30 foot gap between them. Consider the following. You probably can remember three people you saw today. Now, what color were their shoes? Are you sure? Let’s say the police think one of your friends was involved in a crime, but they only have a photograph of the shoes? Are you willing to stake you and your friend on you remembering what color their shoes were?

    This is why evidence is so important. It gets rid of the confusion and biases of people. It allows us to discriminate between choices (conclusions) in a real way, not in a biased way. It provides the basis of understanding the real world as it is, not as we wish it was or even as we think it is.

    Six hundred years ago, everyone knew the Earth was flat. Five hundred years ago everyone knew the Earth was the center of the universe. But those things aren’t true. They never have been. It took reliable evidence to disprove what everyone “knew” to be true. We have the same problems today. People use common sense to know things about the universe that simply aren’t true. People use feelings and beliefs to know things about the universe (and other people) that simply aren’t true.

    Some scientific concepts with mountains of evidence are questioned because some people don’t like the results of that evidence. Well, the evidence doesn’t care what people think. It just is. Whether someone likes it or not is not a fault of the evidence, it is the fault of the biased human mind.

    Let’s be clear there is an unimaginable amount of evidence that evolution happens, common descent is true, and mutation plus natural selection (and some other well known processes) are the cause of the diversity of life around us.

    There is a huge amount of evidence that the Earth is warming and that humans are the direct cause of this by burning (and spilling) fossil fuels.

    There is a huge amount of evidence that genetically modified organisms are safe as food for animals including humans are actually less damaging to the environment than some other forms of agriculture.

    There is a huge amount of evidence that vaccines are safe, do not cause autism, and are vitally important for the well-being of our world.

    The evidence is real. And it is good, solid, reliable, repeatable, unbiased, objective evidence that easily discriminates between conclusions. Therefore, the conclusions based on that evidence are solid. Does that mean you can’t question them? Of course, not. Question all you like, but when you see good evidence, then you must accept it. If you cannot, then you can’t understand the real world. I love fantasies, but we don’t live in one.


    [1] Which is one reason that creationism (including intelligent design) are not science.  Over the years, I have observed that any time a truly major discovery is announced in biology, a week or so later, a creationist has determined that creationism/id “predicts” that discovery or that the discovery is perfectly in-line with creationist thinking. This is the same as the just-so stories. It’s telling that no creationist has ever used their ideas to predict a feature of biology in advance of it being discovered.

    Category: CultureEducationfeaturedScienceSkepticism


    Article by: Smilodon's Retreat

    • http://www.skepticink.com/incredulous Edward Clint


      Minor point, but in the US at least, a court never establishes anyone as innocent of a crime. You can only be found guilty or not guilty, and “not guilty” really means “in so far as the evidence compels”. This is not a trivial point because you can beat criminal charges for an alleged action, be found “not guilty” and subsequently be found legally liable for wrong-doing in a civil case. This is precisely what happened with OJ Simpson, for example. But no civil case could have such an outcome had the state already declared you “innocent”.

      • SmilodonsRetreat

        Crud. Spent the whole thing trying to talk very precisely, but messed that up. Blech.


          Don’t feel bad. It is a difficult distinction to make, especially when compared to scientific procedure. A significant difference between law and science is that law generally demands answers NOW. There is no waiting for 20, 30 … 100 years for new evidence or new types of evidence to come along to decide who committed a crime. The Scots have a more nuanced system where a jury can answer “not proven” but even that is dependent on a standard (beyond reasonable doubt) that is not quantifiable. On the other hand, evidence in court can establish someone’s innocence (DNA eviidence is a good example) to such a degree that, even after they have been convicted, we release them after years of incarceration or on the verge of being put to death. So, it’s not quite correct to say that evidence in court never establishes anyone is innocent.

    • cazimir


      The evidence for this is exactly nothing. Remember that every time you write on the topic evolution.

      “Evolution: Loss of function mutation helps prevent heart attacks, say researchers”

      “Is this Darwinian evolution in action? No, because loss of function is the opposite of gain in function, which is what Darwin’s theory (natural selection acting on random mutation) proposes to explain.

      Loss of function is a form of evolution, but is resources are very limited. The problem is, as Jonathan Bartlett kindly writes to say,

      If we destroy enough genes we can make a human! If we burn enough buildings we can make a city, and if I comment out enough code I can write a program. I can build a company if only I can fire enough employees, and I can invent new machines by taking an axe all my prototypes.”


      • SmilodonsRetreat

        The evidence for it is in every post that I make about mutations. You don’t get it because you purposefully ignore the actual research.

        Mutation causes diversity. There are 3000+ HLA-B alleles in the human population. How did they get there? Mutation.

        Diversity is the key to resisting the selection process. Especially when the environment changes.

        Heck, just look at the genetic/evolutionary algorithms. Yes, selection removes 90-95% of the genomes every generation, yet mutation and sexual reproduction keep the diversity so high that there is a continuing improvement in the genome for the particular function.