MODULE #1: Biology: The Study of Life
Limitations of the Scientific Method
At the end of the previous section, we said that if a theory survives the scientific method and becomes a scientific law, it is “reasonably trustworthy.” Why did we say “reasonably?” Aren't all scientific laws completely trustworthy? If a hypothesis survives scientific scrutiny and becomes a theory, and the theory goes through more significant scientific scrutiny and becomes a law, isn't it 100% reliable? No, it is not. You see, in order to test hypotheses and theories, scientists must gather data. In order to gather data, they must perform experiments and make observations. Since these experiments and observations are designed and performed by imperfect humans, the data collected might, in fact, be flawed. As a result, even though there might be an enormous amount of data supporting a scientific law, if the data are flawed, the law is most likely wrong! In addition, it is simply impossible, even after centuries of experimentation, to test all implications of a scientific law completely. Thus, even though years and years of experimentation exist in support of a scientific law, some clever person somewhere might devise an experiment that produces data which contradict the law. Thus, scientific laws can be demonstrated false when the experiments that support them are shown to be flawed or when someone finds a new kind of experiment that contradicts the law. Both of these situations occur frequently in the pursuit of science, and they are best studied by example.
Scientific laws are constantly being overthrown due to the fact that it is impossible to test them completely. For example, prior to 1938, it was considered scientific law that the coelacanth
(see' luh kanth), a type of fish, was extinct. After all, many fossils of the fish had been uncovered, but no live specimen had ever been found, even after much searching. Since almost 100 years of searching for this fish never turned up a live specimen, the hypothesis that it was extinct was eventually accepted as a theory and then as a scientific law. All scientists agreed: the coelacanth was extinct. Imagine their surprise when, in 1938, a live coelacanth was found in the net of a fishing boat off the coast of South Africa! We now know that the coelacanth is relatively plentiful in the western Indian Ocean. In this case, then, a scientific law was overthrown due to the fact that it was impossible to test it completely. One would think that since 100 years of careful searching for the coelacanth had never turned up a live specimen, the law stating that it was extinct should be rather reliable. However, no one had looked carefully enough in the Indian Ocean off the coast of Africa, and therefore a scientific law turned out to be quite wrong!
Scientific laws are also overthrown because the experiments that support them are flawed. For example, in about 350 B.C., the famous Greek philosopher Aristotle observed that if a person left meat out in the open and allowed it to decay, maggots would appear on the meat within a few days. From that observation, he formed the hypothesis that living maggots were formed from nonliving meat. We call this idea spontaneous generation, and Aristotle postulated that this is how many life forms originate. He made many other observations that seemed to support his hypothesis. For example, he showed that eels have a similar smell and feel as the slimy ooze at the bottom of rivers. He considered this evidence that eels spontaneously formed from the ooze.
As time went on, many more experiments were performed that seemed to support the hypothesis of spontaneous generation. As a result, the hypothesis was quickly accepted as a theory. Of course, the experimentation did not stop there. As late as the mid-1600s, a biologist named Jean Baptist van Helmont performed an experiment in which he placed a sweaty shirt and some grains of wheat in a closed wooden box. Every time he performed the experiment, he found at least one mouse gnawing out of the box within 21 days. Think about it. A hypothesis that was formed around 350 B.C. was quickly accepted as a theory due to the fact that all experiments performed seemed to support it. Experiments continued for a total of 1,900 years, and they all seemed to support the theory! As a result of this overwhelming amount of data in support of the theory of spontaneous generation, it became accepted as a scientific law.
About that same time, however, Francesco Redi, an Italian physician, questioned the law of spontaneous generation. Despite the fact that this law was universally accepted by the scientists of his day, and despite the fact that his fellow scientists laughed at him for not believing in the law, Redi challenged it. He argued that Helmont could not tell whether the mice that supposedly formed from a sweaty shirt and wheat grains had gnawed into the box or out of the box. He said that in order to really test this law, you would have to completely isolate the materials from the surroundings. That way, any life forms that appeared would have definitely come from the materials and not from the surroundings. He performed experiments in which he put several different types of meat in sealed jars and left them to decay. No maggots appeared on the meat. He claimed that this showed that maggots appear on meat not because they are formed by the meat, but instead because they get on the meat.
Of course, the scientists of his day said that by sealing the jars, Redi was cutting off the air supply, which would stop the maggots from forming. Thus, Redi redesigned his experiment. Instead of sealing the jars, he covered them with a fine netting. The netting was fine enough to keep insects out but allow air in. Still, no maggots formed on the meat, even long after it was decayed. What these experiments showed was that the previous experiments which purportedly demonstrated that maggots could form from decaying meat were simply flawed. If one were to adequately isolate the meat from the surroundings, maggots would never form.
These experiments sent shock waves throughout the scientific community. A scientific law, one which had been supported by nearly 1,900 years of experiments, was wrong! Of course, many scientists were simply unwilling to accept this. Yes, they agreed, perhaps maggots did not come from decaying meat, but surely there were some types of organisms that could spontaneously generate from nonliving things.
In the 1670s, some scientists thought that Anton van Leeuwenhoek had found such organisms. He had fashioned his own microscope and had used it to study water. As a result, he discovered the world of microorganisms.
Microorganisms – Living creatures that are too small to see with the naked eye
In the next module, we will begin studying this fascinating world in more depth. For right now, you just need to know that because these creatures cannot be seen without the aid of a microscope, scientists prior to 1670 had no idea that they existed.
Leeuwenhoek and many others showed that microorganisms did, indeed, seem to generate spontaneously. For example, in the mid-1700s, John Needham did experiments very similar to Redi's. Needham made a liquid broth of nutrient-rich material such as chicken broth. Such broths were called “infusions,” and Needham showed that if you boiled an infusion for several minutes, you could kill all microorganisms in it. If you then put a cork in the flask that held the infusion, microorganisms would appear in the infusion within a few days. Needham concluded that since he had put a cork in the flask, the infusion was isolated from the surroundings. These experiments were hailed as support for the beleaguered law of spontaneous generation.
Lazzaro Spallanzani, a contemporary of Needham, did not like Needham's experiments. He thought that either Needham did not boil the infusion long enough to completely kill off the microorganisms or that Needham's corks allowed air to leak into the flask, bringing microorganisms in with it. Spallanzani repeated Needham's experiments, but he boiled the infusions for a long time and sealed the flasks by actually melting their openings shut. That made a truly airtight seal. In these experiments, no microorganisms formed. Of course, those who still held to the law of spontaneous generation argued that once again, without air, nothing could live. Thus, by completely sealing the flask before the infusion was boiled, Spallanzani cut off the process of spontaneous generation.
In 1859, however, the great scientist Louis Pasteur finally demonstrated that even microorganismsms cannot spontaneously generate. In his experiments, illustrated in Figure 1.4, Pasteur stored the infusion in a flask that had a curved neck. The curved neck allowed air to reach the infusion, but because microorganisms are heavier than air, any microorganisms present would be trapped at the bottom of the curve. When Pasteur repeated Needham's experiments in the curved flask, no microorganisms appeared. In a final blow, Pasteur even showed that if you tipped the flask once to allow any microorganisms that might be trapped to fall into the infusion, microorganisms would appear in the infusion. Thus, Pasteur showed that even microorganisms cannot spontaneously generate.
Click for an animation about Louis Pasteur's experiment
The point of this rather long discussion is simple. Even though a scientific law seems to be supported by hundreds of years of experiments, it might still be wrong because those experiments might be flawed. All of the experiments that were used to support the law of spontaneous generation were flawed. The scientists who conducted the experiments did not adequately isolate them from the surroundings. Thus, the life forms that the scientists thought were being formed from non-living substances were, in fact, simply finding their way into the experiment.
These two discussions, then, show the limits of science and the scientific method. First, even scientific laws are not 100% reliable. Most likely, some of the things that you learn in this book will someday be proven to be wrong. That is the nature of science. Because it is impossible to fully test a scientific law and because laws are tested by experiments that might be flawed, scientific laws are not necessarily true. They represent the best conclusions that science has to offer, but they are nevertheless not completely reliable. Of course, if you are working with something that is a theory, it is even less reliable. Thus, putting too much faith in scientific laws or theories will end up getting you in trouble, because some of the laws and many of the theories that we treasure in science today will eventually be shown to be wrong.
Well, if scientific laws are not 100% reliable, what is? The only thing in the universe that is 100% reliable is the Word of God. The Bible contains truths that will never be shown to be wrong, because those truths come directly from the Creator of the universe. So much misery and woe have come to this earth because people put their faith in something that is not reliable, like science. In the end, they are spiritually deprived because what they believe is, to one extent or another, wrong (Romans 1:21-25). Those who put their faith in the Bible, however, are not disappointed, because it is never wrong.
If science isn't 100% reliable, why study it? The answer to that question is quite simple. There are many interesting facts and much useful information not contained in the Bible. It is worthwhile to find out about these things. Even though we will probably make many, many mistakes along the way, finding out about these interesting and useful things will help us live better lives. Because of the advances made in science, wonderful technology like vaccines, the television, and the computer exist. Thus, there is nothing wrong with science. In fact, it is even a means by which we can celebrate the awesomeness of God. When we learn how well the world and its organisms are designed, we can better appreciate the gift that God has given to us in His creation. The problem occurs when certain people who are enamored with science end up putting too much faith in it. As a pursuit of flawed human beings, science will always be flawed. Because the Bible was inspired by One who is perfect, the Bible is perfect. As long as we keep this simple fact in mind, our study of science will be very rewarding!