The notion of “ancient knowledge” is a common theme among anti-vaccers and alternative health practitioners. It generally takes one of two basic forms. Either they claim that something is right/effective/safe because our ancestors thought so and they were somehow privy to some “ancient knowledge” that we don’t have access to today, or they argue that a treatment is safe/effective because it has been used for many generations and has stood the “test of time.” Conversely many of them argue that we shouldn’t use vaccines and modern pharmaceuticals because they have not passed this arbitrary test of time. These arguments are, however, appeal to antiquity fallacies. The fact that something is old or has been used for a long time does not in any way shape or form demonstrate that it is safe, effective, etc. So anytime that someone makes one of these arguments, they are committing a logical fallacy and according to the rules of logic, you must reject their argument. Nevertheless, let’s briefly look a bit closer.
These arguments are particularly absurd because the history of science is nothing if not a steady debunking of ancient ideas. Geocentrism, the idea that nature is made of four elements (earth, water, air, fire), alchemy, etc. were all ancient ideas that were later debunked and replaced by science. So the fact that something is ancient clearly does not validate it. To be clear, I’m not suggesting that the fact that many ancient ideas have been refuted means that all ancient ideas are wrong (that would be just as flawed as the logically invalid argument that we shouldn’t trust science because it has been wrong in the past). Rather, I am saying that you cannot assume that something is true/effective/safe just because it is ancient. You have to actually test it scientifically, and you have to accept the results of those tests.
The “test of time” argument is similarly flawed. There are thousands of ancient medical treatments that were used for countless generations before science came along and discredited them. Leeches are a good example. We used them for hundreds of years before we realized that draining a sick person’s blood was a bad idea (note: we do still use leeches medicinally today, but not for the same thing that they were used for historically). Similarly, tobacco was common in Native American medicine and was adopted by European explorers, yet today we know that it is extremely dangerous (Charlton 2004); note: it is a myth that there was once a scientific consensus that smoking was safe. The reality is that the tobacco companies had paid off a handful of scientists, but the scientific consensus was and is that it’s dangerous).
When you think about it, it is, of course, not surprising that many things would be used medicinally for countless generations without anyone realizing that they don’t work. Imagine that in some village, someone gets sick, eats an herb, then gets better just by his/her body healing itself. It will appear that the herb worked because the person took the herb, then got better (this is known as a post hoc ergo propter hoc fallacy). As a result, every time that someone in that village gets that ailment, they will take that herb. Sometimes, it simply won’t work and the person will get worse, but other times, the placebo effect will kick in and the person will get better. Additionally, in many cases, the sick person’s body will simply heal itself, thus giving the appearance that the herb works. Every one of these “success stories” will serve to affirm the villagers’ belief that the herb works, and it will get used from one generation to the next.
The only way to actually tell whether or not the herb works, however, is to test it scientifically with proper controls. In order to know if it actually has healing properties, you have control for confounding factors, and you need to know the background recovery rate (i.e., how many people heal because of the placebo effect, their own body’s healing abilities, etc.). Then, and only then, can you say whether or not the herb works. That is really my fundamental point in all of this. The fact that something is ancient or has been used for many generations does not automatically mean that it works, and making that assumption is logically invalid. Carefully controlled studies are the only way to tell for sure.