Abstract
Despite being an affable strategy of adaptive expectation, the transmission of cultural information can result in unintended changes in the information. This is known as “mutation” in the theory of cultural evolution. The occurrence of information mutations in local medical systems may be greater in some situations. For example, “vegetable complexes” can be used as good study models to show a greater accumulation of mutations due to the variation in the mixtures and combinations of information. Here, we tested the following hypotheses: (H1) medicinal plants in plant complexes generate a greater accumulation of mutations than isolated plants in local medical systems; (H2) information on the medicinal function of the plant species generates a greater proportion of mutations than information on the parts of plants used medicinally; (H3) plants in plant complexes perceived as less efficient undergo more information mutational events; and (H4) changes in information on plant complexes are more random (mutation) than intentional (guided variation). We conducted the study in the Lagoa do Junco community, state of Alagoas, Northeast Brazil. For data collection, we used semistructured interviews to address the use of isolated medicinal plants and plant complexes. Additionally, we assessed the informants’ perceptions about the effectiveness of the plants used in these preparations. We found that the mutation rate was higher when isolated plants were used than when plant complexes were used (), and it was also higher for function than for parts of the medicinal plants (). No relationship between the mutations and perceived efficiency of the plants () was observed, and changes in information were more random (mutation) than intentional (guided variation) (). From an evolutionary perspective, greatly varying information, such as that on plant complexes, did not explain a greater accumulation of mutations. Thus, we suggested that further studies that include other evolutionary parameters that may cause the accumulation of information mutations must be conducted.
1. Introduction
The use of plants for medicinal purposes is considered one of the main strategies adopted by human populations to cure or alleviate various diseases [1, 2]. This shows that the existence of diseases has led people to experiment with natural resources present in the environment, contributing to the formation of local medical systems [3]. In this context, the local medical system is a set of perceptions that humans have about diseases and the methods and resources they use to treat health problems [3, 4].
In local medical systems, isolated medicinal plants or plant mixtures or preparations, herein referred to as plant complexes, can be used. The plant complexes include the “bottled,” “syrups,” and “lickers” [5]. Various local populations produce these complexes as home remedies with the function of curing or alleviating one or more diseases [6, 7]. The use of plant complexes dates back many centuries [6]. The practice of using them preferentially for the treatment of diseases, even in the presence of other local options, has become popular [8–10].
The use and production of plant complexes in local medical systems result from the social transmission of information among individuals [8, 11]. However, cultural information is not always reliably transmitted, allowing errors to occur often [12, 13]. Thus, according to the theory of cultural evolution, errors that occur during the transmission of cultural information are called cultural mutations [14]. The errors that occur randomly during the transmission of cultural information are called “information mutations” (information is changed unintentionally) [14]. On the other hand, the errors that occur when information is intentionally altered by individuals are called “guided variations” [14]. Therefore, although the transmission of cultural information plays a key role in cultural evolution, the emergence of certain mutations can lead to failed exchanges of information in social systems because the occurrence of these mutations implies the establishment of behaviors that do not contribute to individual survival (poorly adapted cultural traits) [12, 14, 15].
In the case of information mutations, since local medical systems are characterized as social information systems permeated by the exchange of cultural information [12], the establishment of this process in these systems depends on a set of main factors including (I) incomplete transmission of information [13] (only parts of complex or varied information can be transmitted or assimilated in the minds of individuals); (II) concealment of information [12] (the information transmitted socially among individuals is not always verified after being acquired, favoring people to learn what to do without understanding the reasons for it) [16]; and (III) confusion of the types of information (although the human mind is largely adaptive, its associative authenticity can be counterproductive, leading people to transmit probable information instead of adequate information) [17].
Based on the aspects mentioned above, information mutations may occur when plant complexes are used in local medical systems. These preparations are produced using a combination of widely varying information on medicinal plants and other specific elements [9, 18] in a single event of cultural information transmission, implying a greater probability of the occurrence of information mutations. Thus, in this work, we sought to investigate whether plant complexes functioned as points of accumulation of information mutations in local medical systems. For this, we tested four hypotheses concerning the process of mutation of information. The first hypothesis (H1): the use of medicinal plants in plant complexes tends to generate a greater accumulation of information mutations than the use of isolated plants in local medical systems. Additionally, we expected other factors in the local medical system to contribute to the greater occurrence of information mutations. The second hypothesis (H2): information on the medicinal function of plant species generates a greater amount of mutations than information on the parts of plants used as medicine. In local medical systems in the caatinga environment (seasonal dry forest), the information on the medicinal function of plants tends to vary more than the information on the parts of plant species used by individuals. When this occurs, the use of several plants in plant complexes can cause a “causal mismatch” (unintentional combination of information) [19]. When several plants are used together, there may be a lack of understanding of the real medicinal function of the plants that are included in these preparations.
Considering the evidence that, over time, individuals began memorizing more relevant information from an adaptive point of view due to the limited capacity of the human brain to store complex information about the environment [20], we proposed the third hypothesis (H3): medicinal plants in plant complexes perceived as less efficient suffered the highest number of information mutational events. Furthermore, we proposed the fourth hypothesis (H4): information changes that occur when plant complexes are used are more random (mutation) than intentional (guided variation). Learning information from others, compared to intentionally creating, innovating, or changing information (guided variation) [21], is a faster and less costly adaptive strategy [22].
2. Materials and Methods
2.1. Study Area
The study was conducted in the “Lagoa do Junco” community located in the municipality of Santana do Ipanema in the state of Alagoas, Northeast Brazil [23]. The municipality of Santana do Ipanema has a population of 48,232 inhabitants and is located in the mesoregion of the Sertão Alagoano, 207 km from the state capital Maceió [23]. “Lagoa do Junco” has a semiurban population, characterized as one of the largest urban and popular neighborhoods in the municipality. Totally 188 individuals (63 families), of which 144 individuals were over 18 years old, resided in this community. In the locality, there are some commercial establishments and public spaces, such as a school, a municipal creche, churches, and a municipal health post, in which individuals from the community can access health services. Additionally, a forest, from where individuals obtain and use natural resources and medicinal plants, surrounds the community. This community was selected for the study because it is comprised of people who produce plant complexes that are used traditionally and supplied to local markets and other neighboring locations in the region.
2.2. Ethical and Legal Aspects
The realization of this study included instructions from the Resolution (466/12) of the National Health Council for research with human beings. The study proposal was sent to the Research Ethics Committee (CEP) and approved under number CAAE: 97380918.9.0000.5207 of the University of Pernambuco (UPE). Additionally, it was submitted to the Biodiversity Authorization and Information System (SISBIO), which provided proof of registration under number 64841-1 for the collection of botanical material from the study site. Those who agreed to collaborate with the data in this study were invited to sign the Free and Informed Consent Form (ICF).
2.3. Data Collection
The data for this study were obtained from September 2018 to June 2019. For data collection, we conducted semistructured interviews [24] of all people who were over 18 years old and agreed to participate in the research. Thus, 120 people were interviewed (corresponding to 82% of the adult population). To investigate their knowledge on local medicinal plants, we applied the free listing technique [24], according to which the informants were asked to list the names of all plants, used for medicinal purposes, known to them. Following that, we conducted semistructured interviews to address the use of plants individually and in plant complexes. For each plant mentioned by the informants, we asked certain questions including the following: (1) For what disease or diseases is this plant indicated? (2) What are the symptoms related to this health problem? (3) What parts of the plant are used for the treatment? (4) How is the medicine prepared? (5) Of the plants that were mentioned, are any of them used in association with others? (6) If so, what other plants are used? (7) What health problems can be treated using this mixture? (8) From whom did you obtain this knowledge?
2.4. Plant Collection and Identification
Following the semistructured interviews, the guided tour technique [24] was used to collect the botanical material, and the informants were invited to indicate the medicinal plants that were within or near their properties. For this, we collected specimens with their reproductive materials and identified the collected material with the help of botanical specialists. Exsiccated specimens were deposited at the Institute of Agricultural Research of Pernambuco-IPA.
2.5. Local Perception of the Efficiency of Medicinal Plants
After conducting semistructured interviews, we conducted a new stage of data collection in the community. Individual forms were provided to each interviewee, who mentioned using plant complexes, to collect information related to the perceived effectiveness of medicinal plants. We asked each participant to place the plants used in each type of plant complex in the order of their efficiency in treating the indicated diseases, and this resulted in the classification of more and less efficient plants. Additionally, we checked whether possible changes in information were random (mutation) or intentional (guided variation). For this, we assessed the information obtained from individual apprentices (person who acquired information from a specific individual in the local medical system) and transmitters (person who was mentioned as a transmitter of information by the individual apprentices in the local medical system).
2.6. Classification of Information Mutation and Guided Variation
To identify the presence of possible information mutations, we compared the information units (IUs) obtained from the person who learned the information with those obtained from the person who transmitted the information. An IU was the association of the therapeutic target with the plant species and the part of the plant used [25]. For example, “pain–Lippia alba–leaf,” “pain–Myracrodruon urundeuva–bark,” and “cut–Myracrodruon urundeuva–leaf.” For this assessment, we analyzed and compared the data collected in the interviews of the apprentices with that of the transmitters. Mutation was considered when: (1)—the therapeutic target (disease) within the IU indicated by the apprentice was different from that indicated by the transmitter and (2)—when the part of the plant used within the IU indicated by the apprentice was different from that indicated by the transmitter. To avoid misinterpretation of the local therapeutic indications, we referred to the symptoms of each disease mentioned by the informants.
Each individual apprentice and transmitter, who presented divergent information, was notified of their information transmitted during the semistructured interviews. We then asked some inductive questions including the following. (1) You mentioned that you use this mixture to cure the disease X. However, can this mixture be used to cure another type of disease? If so, which one? (2) Have you ever used this mixture to cure another disease in the past? If so, which one? (3) You mentioned that you use parts of certain plants X and Y in this preparation. However, can other parts of plants X and Y be used in this preparation? If so, which ones? It was then possible to compare the IUs obtained from the person who learned the information with those obtained from the person who transmitted the information, verifying whether the divergence was random (mutation) or intentional (guided variation).
2.7. Data Analysis
To assess whether information mutations occurred more frequently in plant complexes than in isolated plants, we calculated the number of times information mutations occurred in individual plants and plant complexes. Then, the average mutation rates for individual plants and plant complexes and the difference in the averages were calculated. Finally, using the Monte Carlo technique, we created a hypothetical null scenario, in which the differences between the averages were simulated 1000 times at random to obtain greater credibility of the statistical results. The differences between the real averages were considered significant when the probability of occurrence was less than the random probability generated by the null scenario (). We used the same procedure to compare (1) the average mutation rate with the average guided variations in plant complexes; (2) the average mutation rate considering the part of the plant used with the average mutation rate considering the medicinal function (treated disease).
To determine whether the perceived efficiency of plants in the plant complex affects the occurrence of mutation, we developed a generalized linear model (GLM) using the binomial family. The dependent variable was the occurrence (1) [or not (0)] of mutation of cultural information, while the independent variable was the value of the order of the perceived efficiency of the plant. Considering that each plant complex has a different size (variety in the number of plants inserted in each complex), a factor that directly affected the calculation of the effect of the independent variable in a multilevel GLM was used to consider the variable differences of the complexes. Thus, we verified the effect of efficiency on the mutation rate of random information of each plant complex and tested the existence of an explanatory trend in the GLM, compared with the null model, using ANOVA analysis. All analyses were performed in the R development environment [26] using “lme4” package [27] for multilevel analysis.
3. Results
In the present study, we identified 52 medicinal plant species used alone or in association (Table 1). Of the 120 individuals interviewed, 108 mentioned that they produced or used some type of plant complex. We identified and divided 141 types of plant complexes (Table 2) into five categories: 7 types of medicinal baths (plants immersed in water to obtain decoctions to be used topically), 39 types of teas (plants immersed in water to obtain decoctions to be used orally), 26 types of bottled medicine (plants mixed with alcoholic or sweetened substances to form a preparation to be used through closed containers), 64 types of “lambedor” (plants immersed in sweetened substances to obtain decoctions), and 5 types of syrups (plants immersed in honey to obtain decoctions) (Table 2).
Contrary to our expectations, the results showed a higher mutation rate in isolated plants than in plant complexes; hence, the average mutation rate was significantly higher () for isolated plants (mean = 0.45; standard deviation (SD) = 0.89) than for plant complexes (mean = 0.24; SD = 0.54). Additionally, our analysis showed that the average mutation rate was significantly higher () for function (mean = 0.56; SD = 0.99) than for plant parts (Mean = 0.11; SD = 0.4).
The results indicated that the perceived efficiency of plants in plant complexes was not a reliable variable to explain the existence of information mutations because the inclusion of this variable did not generate a better explanatory model than the null model (χ2 = 1.71; ). Thus, perceived efficiency was not a factor that affected the information mutation rates (Table 3). We also observed that the mean of change was significantly higher () for mutations (mean = 0.24; SD = 0.52) than for guided variations (mean = 0.03; SD = 0.16).
4. Discussion
4.1. Does the Use of Medicinal Plants in Plant Complexes Cause a Greater Accumulation of Information Mutations than the Use of Isolated Plants?
In general, some studies [28, 29] have shown that many of the plant complexes used in traditional medicine consist of various medicinal plants. We expected that this fact would make the transmitted information more susceptible to changes during the information transmission process. However, the information on these preparations was more conservative than the information on isolated medicinal plants.
Studies that specifically address the different types of individual learning are necessary to explain the mechanisms that may cause information on plant complexes to become more conservative than information on isolated medicinal plants. These mechanisms include obtaining information on (I) isolated medicinal plants and (II) plant complexes. For instance, since plant complexes are produced using a combination of plants and specific elements, information on these preparations could be acquired from “prestigious individuals” in the local medical system. Prestigious individuals have a high social status due to their personal experiences and generally become models for other people who imitate their behaviors and follow their traditional customs and knowledge. In this case, information on plant complexes is less susceptible to variation because there would be no other sources “competing” for the transmission of the same information. In contrast, the acquisition of information on isolated medicinal plants can take place through different learning pathways, such as from parents to children (vertical), between individuals of the same generation (horizontal), and between individuals with no kinship (oblique) [14]. This would increase the chances of inheritance of information with mutations [21].
It is important to consider the finding that, over time, due to great information diversity, human memory systems have evolved, allowing certain information that is more relevant from the adaptive point of view to be more easily memorized [30]. Thus, we suggested the need for further studies that will assess the differences in the perceived importance of the use of isolated medicinal plants and plant complexes. If the use of plant complexes is perceived more important, this can be considered a determining factor of the information on these preparations being more conservative.
4.2. Does the Information on the Medicinal Function of Plant Species Generate a Greater Amount of Mutations than Information on the Parts of Plants Used Medicinally?
The lower mutation rate for information on the parts of plants used medicinally could be explained by the pattern of use of plant species in the local medical system because only stem, bark, and leaves of plants were used medicinally. Thus, since several plants are used together in plant complexes, there may be a lack of understanding of the real purpose of each plant part in these preparations or that transmitted information was more susceptible to judgment errors [17].
4.3. Do Medicinal Plants in Plant Complexes Perceived as Less Efficient by People Suffer the Highest Amount of Information Mutational Events?
Over time, individuals had to filter out information relevant to their survival due to the limited capacity of the human brain to store complex information about the environment [20, 30]. Thus, we expected that the information on plants that were considered more efficient by informants would be more conservative than that on plants that were considered less efficient by informants. However, although some plants in the local medical system were perceived as more efficient than other plants, the perceived efficiency did not influence the occurrence of information mutations. Thus, modification of information occurred, regardless of the importance of the information.
4.4. Are Changes in Information on the Use of Plant Complexes More Random (Mutation) than Intentional (Guided Variation)?
Our results indicated that the changes in information occurring in the system were random, and thus, information transmission was an uncontrollable process [14]. This randomness occurred due to the following mechanisms: (I) concealment of information [12]—information transmitted socially among individuals was not verified, since the people enjoyed transmitting information to other individuals, regardless of whether the information was correct or altered [12, 16]; (II) incomplete transmission of information [13]—since plant complexes are produced using a wide variety of plants and specific elements, only parts of the information on these preparations were memorized and transmitted; and (III) confusion of the different types of information—due to the great variety or complexity of information, altered and/or inadequate information was transmitted [17].
It was found that the exchange of cultural information among individuals was often associated with “trade-offs” (cost and benefit) [21]. Although guided variation favored individuals to adapt to their personal experiences better, learning information from others, compared to intentionally creating, innovating, or changing information, is a faster, more adaptive, and less costly strategy [22]. Therefore, there is a need for further studies that specifically address the preferences of the people in the local medical system between obtaining information and creating their own information.
5. Conclusions
This study highlighted the occurrence of information mutations in local medical systems and showed that the transmission of knowledge on medicinal plants was one of the main factors of this process. Consequently, it may contribute to the establishment of poorly adapted local cultural traits. However, we found that greatly varying information that must be transmitted did not explain the greater accumulation of information mutations because the occurrence of greater or fewer information mutations might be influenced by other evolutionary factors during the transmission of knowledge. This requires further scientific investigation. Therefore, we suggested that future studies that address the establishment of information mutations in local medical systems and the understanding of this evolutionary process by considering other responsible parameters, such as perceived importance and cultural validation, must be conducted. Accumulation of maladaptive information in local medical systems must be studied further.
5.1. Limitations
This study has some limitations. We did not have specific questions for people experienced with medicinal plants and plant complexes, and this made it impossible to identify prestigious individuals. Consequently, a robust analysis of the relationship between the acquisition of information from these individuals and the occurrence of mutations could not be performed. Thus, we suggested that future studies that assess whether the transmission of information from these individuals significantly influences the occurrence of mutations in the system must be conducted.
Data Availability
The data used to support the findings of this study are available from the corresponding author upon request.
Conflicts of Interest
The authors declare no conflicts of interest regarding the publication of this article.
Acknowledgments
The authors are grateful to the Lagoa do Junco community, in particular, to all individuals who agreed to corroborate with the data obtained from this study. This work was funded by the Coordination of the Improvement of Higher Education Personnel (CAPES), under finance code 001. The authors acknowledge the contribution of the INCT Ethnobiology, Bioprospecting and Nature Conservation, certified by CNPq, with financial support from FACEPE (Foundation for Support to Science and Technology of the State of Pernambuco (Grant number: APQ-0562-2.01/17)).