Müller & Schumann (M&S) approach substance use through a broad interdisciplinary approach that spans evolutionary theory, neuroscience, and psychology. They focus on the idea of “drugs as instruments” as a concept that both illuminates substance use and can unite these different areas of research. This dual approach – broad integration and specific concepts – should be applauded and emulated.
Their use of evolutionary theory to analyze drug use and understand the links between use behavior, neurobiological impacts, and mental states represents an important step forward in evolutionary analysis of substance use and abuse. Like neurobiological and psychological research, evolutionary approaches have largely focused on trying to explain addiction, rather than on the more widespread behavior of substance use. M&S show the importance of focusing on drug use itself and help move the evolutionary debate forward by going much further than the simplistic argument that people use drugs because they “create fitness benefits.”
With drug instrumentalization, M&S focus on mental states, which then help in achieving behavioral goals. As they put it, drinking coffee can help with driving a car better. The combination of mental effects and behavioral goals can lead to a variety of benefits, ranging from improved social interactions to coping with stress and euphoria. This focus on functional use is important because it opens research up to a range of uses and meanings for drugs that better reflect reality, rather than simply reducing drug use to either self-medication or getting high (Lende et al. Reference Lende, Leonard, Sterk and Elifson2007).
Drugs can provide concrete adaptive benefits, however, not simply changes in mental states. For example, moderate alcohol use is associated with improved cardiovascular benefits over the life span. Steroid use can improve competitive ability, often with negative mental benefits. Adaptive benefits can also play an important role in reinforcement of drug use. Survey research among adolescent drug users in Bogotá, Colombia, examined how many times respondents had been involved in agreeable sexual situations and had won competitions or fights as a result of substance use. Using a summary variable of evolutionary benefits (the sum of both sexual and competitive benefits), addicted individuals reported 2.76 total benefits versus 0.98 benefits for non-addicted individuals (p<0.001, two-tailed t-test) (Lende Reference Lende, Trevathan, Smith and McKenna2007). Evolutionary theory focuses on competition and reproduction, and drug use can provide adaptive benefits.
In future work, M&S can improve their overall evolutionary analysis in other ways. When considering the evolution of the adaptive mechanisms underlying substance use, a basic distinction can be drawn between approach behaviors and consummatory behaviors (Lende & Smith Reference Lende and Smith2002). Both foraging and sexual reproduction involve the basic adaptive problem of finding food or mates and then eating the food or engaging in mating. Different neural and bodily mechanisms underlie these two dimensions of the basic adaptive problem. Instrumentalization folds these two dimensions into one learning process. However, the structure of the adaptive problem indicates that evolution has probably produced a more complex learning architecture, and substance use will differently relate to seeking and consumption behaviors and effects.
M&S's focus on niches and flexible responding is useful, and it can be augmented by closer consideration of adaptive scenarios and changes over evolutionary time. For humans, niche construction has been argued as a way to buffer humans against selection pressures. The drug instrumentalization view represents one major way humans might be able to create a cultural niche that lowers selection pressures, thus creating adaptive lag (Laland & Brown Reference Laland and Brown2006).
Evolutionary medicine often focuses on evolutionary discordance, the difference between modern environments and the environments in which we evolved, for example, taste buds that evolved to taste sweetness in low-sugar environments and are now faced with an abundance of sugar. M&S propose that today in industrial societies we face many different microenvironments, often requiring large shifts in behavioral strategies with short transition times. Given the time lag in initial drug effects and the length of time many drugs remain in the system, it is not clear that drugs can fulfill the proposed function. Moreover, it is also not clear that there is an environmental mismatch. Decades of research on hunter-gatherer societies have continually emphasized their social and linguistic complexity and the enormous variation in their foraging strategies.
The importance of social and cultural forces in human evolution dates back at least 2 million years, and most likely longer, given strong evidence for chimpanzee cultural/behavioral traditions. New research on neural plasticity, including evidence that culture directly shapes neural function, indicates that a compartmentalized and isolated view of mental function is also biologically inaccurate. Flexible local responding, directly shaped by local sociocultural dynamics, looks like a key to understanding human evolutionary history. This makes an approach that locates instrumentalization solely at the psychological and internal level at odds with evolutionary and neurobiological research.
Drug use takes place in specific social contexts and is shaped by cultural meanings and social expectations. A full account of instrumentalization cannot rely solely on a psychological process of changing internal states; drugs are often used for external social reasons, and social learning mediates the specific effects drugs have. Neuroanthropology, which integrates the insights of neuroscience and psychology with social and cultural anthropology, offers an enriched way to understand how people engage in drug use (Lende Reference Lende2005).
Neuroanthropology can also be used to examine specific neural mechanisms that play a role in involvement with drugs. Alongside instrumentalization, processes of attention and incentive salience (“wanting drugs”) mediate how people use drugs and offer ideas about how individuals move from use to abuse (Lende Reference Lende2005). Individuals might have an instrumental idea about substance use, for example, using alcohol to relax. However, social dynamics can oblige use irrespective of an individual's goal – the toast at a start of a meal to celebrate coming together. Even with instrumentalization, involvement matters in shaping the actual behavior pattern: say, seeking out alcohol to relax and hence kicking off the start of a family meal with its celebratory toast.
Müller & Schumann (M&S) approach substance use through a broad interdisciplinary approach that spans evolutionary theory, neuroscience, and psychology. They focus on the idea of “drugs as instruments” as a concept that both illuminates substance use and can unite these different areas of research. This dual approach – broad integration and specific concepts – should be applauded and emulated.
Their use of evolutionary theory to analyze drug use and understand the links between use behavior, neurobiological impacts, and mental states represents an important step forward in evolutionary analysis of substance use and abuse. Like neurobiological and psychological research, evolutionary approaches have largely focused on trying to explain addiction, rather than on the more widespread behavior of substance use. M&S show the importance of focusing on drug use itself and help move the evolutionary debate forward by going much further than the simplistic argument that people use drugs because they “create fitness benefits.”
With drug instrumentalization, M&S focus on mental states, which then help in achieving behavioral goals. As they put it, drinking coffee can help with driving a car better. The combination of mental effects and behavioral goals can lead to a variety of benefits, ranging from improved social interactions to coping with stress and euphoria. This focus on functional use is important because it opens research up to a range of uses and meanings for drugs that better reflect reality, rather than simply reducing drug use to either self-medication or getting high (Lende et al. Reference Lende, Leonard, Sterk and Elifson2007).
Drugs can provide concrete adaptive benefits, however, not simply changes in mental states. For example, moderate alcohol use is associated with improved cardiovascular benefits over the life span. Steroid use can improve competitive ability, often with negative mental benefits. Adaptive benefits can also play an important role in reinforcement of drug use. Survey research among adolescent drug users in Bogotá, Colombia, examined how many times respondents had been involved in agreeable sexual situations and had won competitions or fights as a result of substance use. Using a summary variable of evolutionary benefits (the sum of both sexual and competitive benefits), addicted individuals reported 2.76 total benefits versus 0.98 benefits for non-addicted individuals (p<0.001, two-tailed t-test) (Lende Reference Lende, Trevathan, Smith and McKenna2007). Evolutionary theory focuses on competition and reproduction, and drug use can provide adaptive benefits.
In future work, M&S can improve their overall evolutionary analysis in other ways. When considering the evolution of the adaptive mechanisms underlying substance use, a basic distinction can be drawn between approach behaviors and consummatory behaviors (Lende & Smith Reference Lende and Smith2002). Both foraging and sexual reproduction involve the basic adaptive problem of finding food or mates and then eating the food or engaging in mating. Different neural and bodily mechanisms underlie these two dimensions of the basic adaptive problem. Instrumentalization folds these two dimensions into one learning process. However, the structure of the adaptive problem indicates that evolution has probably produced a more complex learning architecture, and substance use will differently relate to seeking and consumption behaviors and effects.
M&S's focus on niches and flexible responding is useful, and it can be augmented by closer consideration of adaptive scenarios and changes over evolutionary time. For humans, niche construction has been argued as a way to buffer humans against selection pressures. The drug instrumentalization view represents one major way humans might be able to create a cultural niche that lowers selection pressures, thus creating adaptive lag (Laland & Brown Reference Laland and Brown2006).
Evolutionary medicine often focuses on evolutionary discordance, the difference between modern environments and the environments in which we evolved, for example, taste buds that evolved to taste sweetness in low-sugar environments and are now faced with an abundance of sugar. M&S propose that today in industrial societies we face many different microenvironments, often requiring large shifts in behavioral strategies with short transition times. Given the time lag in initial drug effects and the length of time many drugs remain in the system, it is not clear that drugs can fulfill the proposed function. Moreover, it is also not clear that there is an environmental mismatch. Decades of research on hunter-gatherer societies have continually emphasized their social and linguistic complexity and the enormous variation in their foraging strategies.
The importance of social and cultural forces in human evolution dates back at least 2 million years, and most likely longer, given strong evidence for chimpanzee cultural/behavioral traditions. New research on neural plasticity, including evidence that culture directly shapes neural function, indicates that a compartmentalized and isolated view of mental function is also biologically inaccurate. Flexible local responding, directly shaped by local sociocultural dynamics, looks like a key to understanding human evolutionary history. This makes an approach that locates instrumentalization solely at the psychological and internal level at odds with evolutionary and neurobiological research.
Drug use takes place in specific social contexts and is shaped by cultural meanings and social expectations. A full account of instrumentalization cannot rely solely on a psychological process of changing internal states; drugs are often used for external social reasons, and social learning mediates the specific effects drugs have. Neuroanthropology, which integrates the insights of neuroscience and psychology with social and cultural anthropology, offers an enriched way to understand how people engage in drug use (Lende Reference Lende2005).
Neuroanthropology can also be used to examine specific neural mechanisms that play a role in involvement with drugs. Alongside instrumentalization, processes of attention and incentive salience (“wanting drugs”) mediate how people use drugs and offer ideas about how individuals move from use to abuse (Lende Reference Lende2005). Individuals might have an instrumental idea about substance use, for example, using alcohol to relax. However, social dynamics can oblige use irrespective of an individual's goal – the toast at a start of a meal to celebrate coming together. Even with instrumentalization, involvement matters in shaping the actual behavior pattern: say, seeking out alcohol to relax and hence kicking off the start of a family meal with its celebratory toast.