There are several physiological situations that at another time were the subject of speculation and controversy, but which, over time, have managed to permeate the minds of all human beings and no one denies the phenomenon anymore, despite the fact that they carry greater risks than those usually that today some groups refuse to accept certain therapies, for example, vaccines. Let’s give several examples.
The fertilization and generation of a new individual. Many years ago there was a theory, generated by Aristotle, that sperm mixed with menstrual blood to create a new individual and the argument in favor was that, for this reason, menstruation stops during pregnancy. Another theory said that what happened is that the new individuals already existed in a microscopic form in the semen and that the role of the woman was only to incubate that individual so that it would grow to the point of being born. Evidence that sperm and egg combine to form a new individual had to wait until microscopes powerful enough to observe the phenomenon were developed. It is interesting that, despite the fact that the vast majority of humanity has never seen the phenomenon under a microscope, as my grandmother would say, “with her own eyes”, today everyone accepts it as real. I don’t know of any sect that denies it and promotes a different theory for fertilization.
The blood circulation. Before William Harvey published his book “De motu cordis et sanguinis in animalibus” the prevailing theories were that the arteries carried air from the lungs to the tissues or that, in effect, the heart expelled blood, but that this remained in the tissues. There was no concept that the arterial and venous circulation are connected by capillaries, because the appropriate instrument was not available to see them. Again, despite the fact that most of humanity has never seen a capillary, I don’t know of any group that defends the non-existence of capillaries and still believes that the arterial circulation is not connected to the venous one.
Blood test
Microorganisms as disease-causing agents. Hundreds of diseases remained without apparent cause for years and were attributed to deities and not to those responsible, which are microscopic organisms, which, again, have not been seen by most humans. However, I also do not know of a group of people who deny that tuberculosis or syphilis is caused by a microorganism. In this part, what is still missing is for the population to understand the difference between viruses, bacteria and fungi.
Although it was issued by Darwin 170 years ago, we are still in transition to the theory of natural selection of species, since there are still those who do not accept it (or do they not understand it?). In this case, the necessary evidence to show it had to come from the submicroscopic world, with the discovery of the structure of DNA, which makes it very easy for anyone who wants to see how this process works. The recent appearance of the SARS-CoV-2 virus and the diversity of mutations that have made it capable of continuing to infect humans through natural selection, is evidence that has occurred before everyone’s observation in real time. I am confident that one of the positive consequences of the pandemic is that it allowed us to see natural selection in action and with this we can move towards a more rational and less ignorant society.
Dr. A.S. Gerardo Shrimp
National Institute of Medical Sciences and Nutrition Salvador Zubirán and
Biomedical Research Institute, UNAM
