The Argument from Antiquity is a logical fallacy that is used very commonly in support of various types of alternative medicine. The fact that a particular treatment has been used for hundreds or thousands of years says nothing about the efficacy or safety of that treatment. Treatments used before scientific understanding of biology and medicine were invented by trial and error at best and were often based on profound ignorance or misunderstanding of the processes involved. At the time they were invented, all medicine veterinary or human, was in the same category. Some of the treatments used for many years were dangerous and harmful (bleeding, treatment with toxic heavy metals, etc.). Some treatments are "safe" and cause no toxicity or side effects because they have no effect at all. Some of these treatments may have survived for exactly this reason-they were safer than some treatments simply because they had no effect other than a placebo effect.
A recent paper provides another reason to be skeptical of traditional treatments. In this paper, the authors have developed a mathematical model to show how medical treatments can spread in populations. They included variables for the efficacy of the treatment, conversion and abandonment rates for the treatment, death rate due to the disease, and other variables. When they ran the calculations, they found that ineffective treatments were often more culturally fit than effective treatments. The main reason for this is that an ineffective treatment is often demonstrated more frequently than an effective treatment. This results in a larger number of people adopting the treatment, even if many of them later abandon it. In many cases the recruitment rate was much greater for ineffective treatments and the ineffective treatments had a greater cultural fitness than effective treatments.
This model is very interesting in that it shows how ineffective treatments can develop and persist in a population often better than effective treatments do. This is not earthshaking news to skeptics, and the model does not take into account other factors such as tradition or religious ideas that can also help ineffective treatments to survive. Herbal medicines are one of the most plausible traditional medical treatments, and some traditional herbs have been developed into modern medicines (aspirin is a good example). This model shows why even plausible treatments such as traditional herbs need to be evaluated scientifically before being accepted as an effective treatment. People are likely to favor ineffective treatments. The authors were able to apply their model to both human and veterinary treatments, and even self treatment by non-human primates.