Charles Darwin was not a doctor, although he was the son and grandson of doctors and even attended medical school at the University of Edinburgh, Scotland. He was not a doctor, but he left a legacy of great value to current medicine: the principles of his theory of evolution.
The Tuberculosis Example
The resurgence of diseases that were thought to be eradicated or controlled, such as tuberculosis, is usually associated with the emergence of resistant strains of bacteria. And how can this be explained? What is the relationship of this phenomenon with the theory of evolution? Well, it is easily explained, as long as you understand how evolution, natural selection and competition between infectious agents and drugs work.
The appearance of resistant bacteria is predicted by the theory of evolution, as any population of living beings, faced with a selective agent, and as long as there is hereditary variation and time, will evolve and adapt.
In the case of tuberculosis, the living being is the bacteria Mycobacterium tuberculosis and the selective agent is the antibiotic. If in the population of bacteria there are one or a few individuals with a mutation that allows them to survive the antibiotic and if these individuals reproduce and transmit that mutation to their offspring, the mutation remains in the population and increases in frequency.
The result is that, from generation to generation, the number of resistant individuals increases and the antibiotic loses its effectiveness.
As bacteria have a short lifespan and a high number of individuals per generation, the time required for the entire population to become resistant to the antibiotic may be just a few hours. A much shorter time span than necessary for the development and production of a new antibiotic!
So… What has changed? Why did tuberculosis reappear when it was practically eradicated? What has changed is the proportion of resistant to non-resistant individuals.
Tuberculosis reappeared because the bacterial population M. tuberculosis evolved and adapted to the new environment created with the introduction of certain antibiotics. A new change in the environment – for example the introduction of a different antibiotic – can lead to a decrease in tuberculosis.
But the process is likely to repeat itself, and resistance to the new antibiotic will eventually become prevalent, again leading to the “reappearance” of the disease.
the example of cancer
Medical research in the search for a cure for cancer also benefits from an evolutionary framework and the application of tools that have long been used in evolutionary biology studies, such as the reconstruction of the evolutionary relationships between cancer cells.
Considering that each cell line has its own evolutionary history, by sequencing the DNA of metastases it is possible to identify the origin of cancer.
This procedure has already shown, for example, that malignant cancers considered to be rapidly progressing, such as pancreatic cancer, have, after all, a very long pre-diagnostic history and that, if detected early, can be effectively treated.
On the other hand, the same reasoning that we described for bacteria can be applied to cancer cells to design new strategies in the use of chemotherapy: if malignant tumors are evolving under the action of natural selection, there is competition between more and less malignant tumors ; if the latter slow down the expansion of the former, then controlled doses of chemotherapy may help maintain competition and slow the expansion of more aggressive tumors.
Darwin in medical courses
The integration of evolutionary knowledge into medicine, called 'Evolutionary Medicine' or 'Darwinian Medicine', makes medicine focus on the ultimate, evolutionary causes of disease.
The principle is that natural selection will have shaped the evolution of many human characteristics, so that disease is seen as an adaptive reaction to any disturbance – environmental or physiological – or a by-product of another adaptive response.
Thus, for example, metabolic diseases, such as type II diabetes, or food intolerances, such as the lactose intolerance syndrome, can be better understood if they are placed in a context of recent changes in our diet and energy requirements; the beginning of agriculture and sedentarization will take about 10 thousand years, a short period of time from an evolutionary perspective.
Is evolutionary medicine the solution to the disease? The evolutionary perspective places the disease as part of the human being's history, which, in turn, leads to the formulation of new questions, relating to the 'conventional' medical perspective.
Perhaps in the search for answers to these questions, new ways to fight diseases can be found.
Darwin day
As we have seen, Darwin's importance goes far beyond the work he developed during his lifetime and which today help us to better understand the origin and diversification of living beings.
It has very valuable implications in different areas fundamental to society.
In return, all over the world events are organized to commemorate your birthday, on February 12th, known as Darwin's Day.
*text adapted from Vila J, Campos R (2013). Evolutionary medicine. In Fields R (ed.). A book about evolution. CIBIO, Research Center for Biodiversity and Genetic Resources. Porto, Portugal. pp 111-114. Free distribution [https://www.dropbox.com/s/t2iw0czeobtid5g/Um%20livro%20sobre%20evolucao.pdf]
Author: Rita Campos
With a degree and a PhD in Biology from the University of Porto, she is currently a post-doctoral researcher at the Center for Research in Biodiversity and Genetic Resources (CIBIO/InBIO).
The general objective of your research is to try to better understand biodiversity by analyzing the patterns of its genetic variability.
Since 2009 he has dedicated part of his time to non-formal education and science communication projects.
He is particularly interested in the themes of biological evolution and biodiversity and in developing projects that involve the active participation of the public.
She is a founding member of the Portuguese Association of Evolutionary Biology (APBE) and its Education and Dissemination Nucleus (NEDE-APBE).
Science in the Regional Press – Ciência Viva
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