Is Our Species Destined To Self Terminate?
I’ve been thinking. Are Homo Sapiens the first self-terminating species? Homo genocide? Homo omnicide?
FFS—what’s wrong with us? Some folks have developed narratives they believe encapsulate our predicament perfectly and are obsessed with specific frames and concepts. People hope that sharing a truthful narrative can get most people on their side and change the world. That’s a tall order. I’m obsessed with peace, health, and thriving in a beautiful world, teaming with life.
Please watch this video and listen carefully to what these young people have to say. Try to understand their struggle and appreciate what they are sacrificing to do what they know is right.
We are experiencing a “biological annihilation.”
We are what we are. If we want to be something else, we must become revolutionary revolutionaries, build a culture very different from what we’ve had throughout history, choose a radically different path, and, by the grace of God, let evolution do the rest. I’d love to see us living within the constraints of nature as benevolent stewards and protectors of Life/Gaia, but I’m not sure it’s in our nature to do so. Maybe Nature’s self-care systems are better without us.
Gaia hypothesis
The Gaia hypothesis, also known as Gaia theory or Gaia principle, proposes that all organisms and their inorganic surroundings on Earth are closely integrated to form a single and self-regulating complex system, maintaining the conditions for life on the planet. The scientific investigation of the Gaia hypothesis focuses on observing how the biosphere and the evolution of life forms contribute to the stability of global temperature, ocean salinity, oxygen in the atmosphere and other factors of habitability in a preferred homeostasis. The Gaia hypothesis was formulated by the chemist James Lovelock and co-developed by the microbiologist Lynn Margulis in the 1970s. Initially received with hostility by the scientific community, it is now studied in the disciplines of geophysiology and Earth system science, and some of its principles have been adopted in fields like biogeochemistry and systems ecology. This ecological hypothesis has also inspired analogies and various interpretations in social sciences, politics, and religion under a vague philosophy and movement.
The Gaia theory posits that the Earth is a self-regulating complex system involving the biosphere, the atmosphere, the hydrospheres and the pedosphere, tightly coupled as an evolving system. The theory sustains that this system as a whole, called Gaia, seeks a physical and chemical environment optimal for contemporary life.[1] Gaia evolves through a cybernetic feedback system operated unconsciously by the biota, leading to broad stabilization of the conditions of habitability in a full homeostasis. Many processes in the Earth's surface essential for the conditions of life depend on the interaction of living forms, especially microorganisms, with inorganic elements. These processes establish a global control system that regulates Earth's surface temperature, atmosphere composition and ocean salinity, powered by the global thermodynamic desequilibrium state of the Earth system.[2] The existence of a planetary homeostasis influenced by living forms had been observed previously in the field of biogeochemistry, and it is being investigated also in other fields like Earth system science. The originality of the Gaia theory relies on the assessment that such homeostatic balance is actively pursued…
Revisiting James Lovelock’s theory as it approaches 50.
I was a young scientist then, and I had a different idea about Earth’s feedback mechanisms. Jim, like most good scientists, accepted my criticism without rancor, but we were clearly on different sides of the issue. The Gaia Hypothesis was having a powerful impact on the environmental movement by encouraging people to think of the Earth holistically, as a kind of super-organism that protects us and deserves our protection. I had to agree, though, with the scientists Ford Doolittle, Richard Dawkins, and Stephen Jay Gould, that a planet or planetary ecosystem cannot evolve like an individual organism, and is unlikely to have developed in such a way as to stabilize the Earth system. As Jim’s famous hypothesis approaches its 50th anniversary, it has lasting value. But to understand Earth’s long-term climate stability, we need to look past Gaia.
Now, I said Earth’s climate is “relatively” stable. It’s important to begin with that qualifier because many geoscientists, including me, believe the oceans may have frozen completely over at least three times during Earth’s history. These so-called “Snowball Earth” events are thought to have occurred during the Late Proterozoic, around 600-800 million years ago, and also in the early Proterozoic, around 2.3 billion years ago. Life made it through these events, however, and there is good evidence that life has been continuously present on Earth’s surface since at least 3.5 billion years ago. Earth itself is more than 4.5 billion years old, having formed shortly after the formation of the sun.
Why should it be considered surprising that Earth has been inhabited for this long? What intrigued Lovelock, along with astronomer Carl Sagan, who co-wrote a paper about it back in 1972, was that the sun is thought to have increased significantly in luminosity over this time interval. To be precise, the sun was about 30 percent dimmer 4.5 billion years ago, and it has brightened more or less linearly since then. All other things being equal, this implies that Earth’s surface should have been completely frozen prior to about 2 billion years ago. But it wasn’t—the Snowball Earth glaciations were brief, and the two best-documented episodes occurred somewhat later. Although the geologic record of the early Earth is rather spotty, climate during the first half of Earth’s history appears to have been, if anything, even warmer than today.
Keeping Earth habitable over long time periods requires that various feedback mechanisms must have been in operation. Specifically, one needs negative feedback to counter the climatic cooling induced by the faint young sun. Earth’s climate system includes numerous feedback processes, some negative and some positive. Two of the easiest climate feedbacks to understand are those involving water vapor and ice albedo. (The term “albedo” simply means reflectivity.) Water vapor is a greenhouse gas that helps to warm Earth’s surface. Its concentration in the atmosphere increases with surface temperature; hence, warmer surface temperatures lead to more water vapor, which in turn leads to warmer temperatures—a positive feedback loop. Conversely, colder surface temperatures should lead to less water vapor, and to even colder temperatures. So the water vapor feedback makes the faint young sun problem worse, not better. The same is true of ice albedo feedback: colder temperatures create more snow and ice, which reflect away more of the sun’s rays, and this leads to still colder temperatures.
Earth’s climate system must contain negative feedback loops, as well. If it didn’t, the system would be perpetually unstable. The most fundamental negative feedback loop is the link between surface temperature and the outgoing infrared radiation. As Earth’s surface heats up, it emits more infrared radiation. But emission of infrared energy cools the surface, and so this is a negative feedback. This feedback is so basic that it is often overlooked. But this is what keeps our climate stable on a day-to-day or year-to-year basis.
The infrared radiation-surface temperature feedback loop is not enough to stabilize Earth’s climate over long time scales, though, because the system is forced by long-term changes in solar luminosity, or brightness, amplified by the positive feedback loops. We need a negative feedback loop that stabilizes climate over long time scales.
To set out some alternative views of humanity's relationship to, and responsibility for, the earth
To show how different biblical texts can be used to support some of these alternative perspectives
To invite consideration of how scientific and religious perspectives relate to one another
Stewardship is a prominent and influential Christian perspective on environmental ethics, but it is not the only proposal. Some alternative models of the relationship between humans and the environment are introduced below. They are not listed in any order of priority or preference, and other alternatives also exist.
As usual, let me provide some more context.
Then Came People
Early Hominid Tool Use and Extinction
Complex tool use distinguishes Homo sapiens from other animals. Chimpanzees and other primates use simple tools like sticks and stones; the earliest evidence of more complex tool-making dates back to about 3.3 million years ago, associated with Australopithecus afarensis and Kenyanthropus platyops—primarily sharp-edged stones used for cutting and scraping.
The exact reasons for the extinction of these early hominids are complex and multifaceted. They likely involved a combination of factors, such as climate change, competition with other species, and environmental changes. Extinction is a natural part of evolution, and many hominid species have come and gone over millions of years.
We have a hard time considering our mortality, much less our species’ extinction.
What tools, concepts, models, and methods we need to find all this out are in a library at our fingertips, waiting for us to dive in and learn if we’re interested.
Australopithecus afarensis existed for a surprisingly long time, considering the often tumultuous nature of evolution and environmental change. Fossil evidence indicates they thrived for at least 900,000 years, between approximately 3.85 and 2.95 million years ago. To put that in perspective, our species, Homo sapiens, has only been around for roughly 300,000 years. So, Australopithecus afarensis existed over three times longer than we have! This longevity suggests a successful adaptation to their environment in Eastern Africa. They survived and reproduced over many generations, a testament to their resilience and adaptability.
Australopithecus afarensis was exceptionally efficient at walking upright, which freed their hands for carrying food, tools, and infants, which must have been advantageous in their environment. Evidence suggests they had a diverse diet, including fruits, leaves, and possibly meat, which must have been crucial during periods of rapid environmental change. We don’t have definitive proof that they likely lived in social groups, but that would have offered protection from predators and increased their chances of survival.
“Lucy” is commonly thought to have no language or speech abilities. It is likely, however, that communication was very important, and they may have been as vocal as modern chimpanzees.
Reconstructing the vocal tract
The base of Lucy’s skull was ape-like in shape. This indicates that she, and others of her species Australopithecus afarensis, had an ape-like vocal tract. Chimpanzees, for instance, have a vocal tract with a high larynx and a short pharynx. This limits the range of sounds that they are able to produce. Lucy’s sound range would probably have been restricted in the same way.
Like all species, Australopithecus afarensis eventually went extinct. The exact reasons are still debated, but they likely involved a combination of factors like climate change, competition with other species, and changes in their food sources. However, their long reign highlights their successful adaptation and provides valuable insights into human evolution. Isn’t it wonderful that we have so many marvelous tools to study our natural history?
“Furthermore, Australopithecus afarensis was an edge species,” adds Sussman. They could live in the trees and on the ground and could take advantage of both. “Primates that are edge species, even today, are basically prey species, not predators,” Sussman argues.
The predators living at the same time as Australopithecus afarensis were huge and there were 10 times as many as today. There were hyenas as big as bears, as well as saber-toothed cats and many other mega-sized carnivores, reptiles and raptors. Australopithecus afarensis didn’t have tools, didn’t have big teeth and was three feet tall. He was using his brain, his agility and his social skills to get away from these predators. “He wasn’t hunting them,” says Sussman. “He was avoiding them at all costs.”
Approximately 6 percent to 10 percent of early humans were preyed upon according to evidence that includes teeth marks on bones, talon marks on skulls and holes in a fossil cranium into which sabertooth cat fangs fit, says Sussman. The predation rate on savannah antelope and certain ground-living monkeys today is around 6 percent to 10 percent as well.
Sussman and Hart provide evidence that many of our modern human traits, including those of cooperation and socialization, developed as a result of being a prey species and the early human’s ability to out-smart the predators. These traits did not result from trying to hunt for prey or kill our competitors, says Sussman.
“One of the main defenses against predators by animals without physical defenses is living in groups,” says Sussman. “In fact, all diurnal primates (those active during the day) live in permanent social groups. Most ecologists agree that predation pressure is one of the major adaptive reasons for this group-living. In this way there are more eyes and ears to locate the predators and more individuals to mob them if attacked or to confuse them by scattering. There are a number of reasons that living in groups is beneficial for animals that otherwise would be very prone to being preyed upon.”
Life begets Life. As long as there is life and “life energy,” various life forms will evolve under ever-changing conditions. We don’t have to worry about that. We need to worry about how our grandchildren will live and what kind of world they inhabit.
Ardipithecus ramidus aobiology of Earlynd the Pale Hominids
Hominid fossils predating the emergence of Australopithecus have been sparse and fragmentary. The evolution of our lineage after the last common ancestor we shared with chimpanzees has therefore remained unclear. Ardipithecus ramidus, recovered in ecologically and temporally resolved contexts in Ethiopia’s Afar Rift, now illuminates earlier hominid paleobiology and aspects of extant African ape evolution. More than 110 specimens recovered from 4.4-million-year-old sediments include a partial skeleton with much of the skull, hands, feet, limbs, and pelvis. This hominid combined arboreal palmigrade clambering and careful climbing with a form of terrestrial bipedality more primitive than that of Australopithecus. Ar. ramidus had a reduced canine/premolar complex and a little-derived cranial morphology and consumed a predominantly C3 plant–based diet (plants using the C3 photosynthetic pathway). Its ecological habitat appears to have been largely woodland-focused. Ar. ramidus lacks any characters typical of suspension, vertical climbing, or knuckle-walking. Ar. ramidus indicates that despite the genetic similarities of living humans and chimpanzees, the ancestor we last shared probably differed substantially from any extant African ape. Hominids and extant African apes have each become highly specialized through very different evolutionary pathways. This evidence also illuminates the origins of orthogrady, bipedality, ecology, diet, and social behavior in earliest Hominidae and helps to define the basal hominid adaptation, thereby accentuating the derived nature of Australopithecus.
Homo sapiens as a Self-Terminating Species
A growing body of evidence, unfortunately, supports my concern about Homo sapiens being a self-terminating species. Our impact on the planet is undeniable, with human activities driving the sixth mass extinction event, climate change, and widespread environmental degradation. Humans have been laying waste to habitats for a very long time. Is it in our genes? The urgency of this situation cannot be overstated. We also have weapons of mass destruction and insist on making war over resources necessary to sustain a global consumer economy based on perpetual growth on a finite planet. It pains me that so few people pay attention to the limits we live within.
Terms like “Anthropocene, Plantationocene, Capitalocene, Anthrobscene, Misanthropocene, and Chthulucene” have been proposed to describe the current geological epoch, characterized by significant human impact on the Earth’s systems. Our misuse of natural resources, reliance on fossil fuels, and propensity for conflict pose serious threats to our survival and the survival of countless other species. We should know better by now.
Invoking 'the Anthropocene' signals a paradigm in which humans have fundamentally altered the biosphere in ways that are deeply problematic. But does designating the epoch in this manner constrain us toward mainly negative outcomes?
Contemporary societies have a tendency to name things based more on what has been lost than what’s actually transpiring in real time. As such, a new suburban development might be dubbed something bucolic-sounding like “Quail Meadows,” after the quail have been chased off and the meadows turned into building pads. Many North American landmark names follow similar logic.
The pronouncement by a blue-ribbon working group that we are living in “The Anthropocene” (denoting fundamental human interventions in the planet’s biophysical processes) fits within this framework. Up to now, the naming of historical epochs has always been done with the benefit of hindsight, but the Anthropocene revealed itself contemporaneously — and perhaps nostalgically.
The Paradox of Human Intelligence
Homo sapiens are paradoxical animals with unique intelligence, creativity, complex consciousness, and capacity for innovation that have allowed us to develop complex tools, build civilizations, and successfully control and manipulate natural systems and materials to a fantastic degree. However, throughout history, we have developed destructive technologies and unsustainable practices that threaten our existence. No other animal is like this. Where do the vices, unusual behavioral traits, and deadly “sins” come from? Tens of thousands of books and stories have tried to answer that question. The problem of evil is still a mystery.
Perhaps our species should be called “Homo apex predator” or “Homo exploiter and killer,” considering our propensity towards exploitation, violence, and environmental destruction.
But we are proud and want to be wise, loving, kind, caring, compassionate, and creative. We want to be good. We want to be heroes fighting for what’s right. Do we have a negativity or positivity bias? Our psychology is of a different order than other mammals. Our sublime stories have reflected our creative, love of beauty, and destructive (some might say evil) attributes. Homo paradox might be an apropos descriptive. But really, our consciousness is nothing like other species, and why is this? Mysteries beget mysteries.
The Need for Change
It’s not enough to be a mystic and commune with spirits; our species’ challenges are immense and require a commitment to the mundane world. Otherwise, we are too destructive to continue evolving for long. Our intelligence and capacity for cooperation offer us hope and something to work for. We must recognize our self-destructive path and take collective action to change course. We must understand the limits and constraints imposed by “human nature” and Great Nature and radically reconfigure our way of life, accounting for sustainable energy sources and renewable resources, protecting biodiversity, and promoting peace and cooperation. We must fight to create a better world, or the opportunity to develop it will disappear.
The earliest evidence of complex tool-making: Harmand, S. et al. (2015). 3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya. Nature, 521(7552), 310-315.
Human evolutionary scholars have long supposed that the earliest stone tools were made by the genus Homo and that this technological development was directly linked to climate change and the spread of savannah grasslands. New fieldwork in West Turkana, Kenya, has identified evidence of much earlier hominin technological behaviour. We report the discovery of Lomekwi 3, a 3.3-million-year-old archaeological site where in situ stone artefacts occur in spatiotemporal association with Pliocene hominin fossils in a wooded palaeoenvironment. The Lomekwi 3 knappers, with a developing understanding of stone’s fracture properties, combined core reduction with battering activities. Given the implications of the Lomekwi 3 assemblage for models aiming to converge environmental change, hominin evolution and technological origins, we propose for it the name ‘Lomekwian’, which predates the Oldowan by 700,000 years and marks a new beginning to the known archaeological record.
Anthropocene: Crutzen, P. J. (2002). Geology of mankind. Nature, 415(6867), 23.
Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines
The population extinction pulse we describe here shows, from a quantitative viewpoint, that Earth’s sixth mass extinction is more severe than perceived when looking exclusively at species extinctions. Therefore, humanity needs to address anthropogenic population extirpation and decimation immediately. That conclusion is based on analyses of the numbers and degrees of range contraction (indicative of population shrinkage and/or population extinctions according to the International Union for Conservation of Nature) using a sample of 27,600 vertebrate species, and on a more detailed analysis documenting the population extinctions between 1900 and 2015 in 177 mammal species. We find that the rate of population loss in terrestrial vertebrates is extremely high—even in “species of low concern.” In our sample, comprising nearly half of known vertebrate species, 32% (8,851/27,600) are decreasing; that is, they have decreased in population size and range. In the 177 mammals for which we have detailed data, all have lost 30% or more of their geographic ranges and more than 40% of the species have experienced severe population declines (>80% range shrinkage). Our data indicate that beyond global species extinctions Earth is experiencing a huge episode of population declines and extirpations, which will have negative cascading consequences on ecosystem functioning and services vital to sustaining civilization. We describe this as a “biological annihilation” to highlight the current magnitude of Earth’s ongoing sixth major extinction event.
The Rise of r/K Selection—Do Homo sapiens Fit?
The r/K selection theory has a fascinating and somewhat controversial history in ecology. While initially popular, it faced criticism and has been largely replaced by more nuanced life history theory.
MacArthur and Wilson (1967) introduced r/K Selection terminology based on their island biogeography work. They proposed that species could be broadly categorized into two strategies:
r-selected species prioritize high reproductive rates (r), often with small body size, short lifespans, and minimal parental care (e.g., insects, rodents), and thrive in unstable environments. K-selected Species invest in fewer offspring (K) with larger body sizes, longer lifespans, and greater parental care (e.g., elephants, humans) and thrive in stable environments near carrying capacity.
In the 1970s and 1980s, ecologists and biologists widely used r/K selection to explain life history patterns across various taxa. It provided a simple framework for understanding how organisms allocate resources to growth, reproduction, and survival.
r/K Fall from Grace
By the early 90s, several studies challenged the predictive power of r/K selection. Stearns (1992) argued that many species didn’t fit neatly into either category and that life history traits often varied independently rather than as a cohesive strategy.
Abstract Life history theory tries to explain how evolution designs organisms to achieve reproductive success. The design is a solution to an ecological problem posed by the environment and subject to constraints intrinsic to the organism. Work on life histories has expanded the role of phenotypes in evolutionary theory, extending the range of predictions from genetic patterns to whole-organism traits directly connected to fitness. Among the questions answered are the following: Why are organisms small or large? Why do they mature early or late? Why do they have few or many offspring? Why do they have a short or a long life? Why must they grow old and die? The classical approach to life histories was optimization; it has had some convincing empirical success. Recently non-equilibrium approaches involving frequency-dependence, density-dependence, evolutionary game theory, adaptive dynamics, and explicit population dynamics have supplanted optimization as the preferred approach. They have not yet had as much empirical success, but there are logical reasons to prefer them, and they may soon extend the impact of life history theory into population dynamics and interspecific interactions in coevolving communities.
Reznick et al. (1990) found that guppies exhibited life history variation within populations, suggesting that environmental factors could override any fixed r/K strategy.
Critics pointed out that r/K selection oversimplified complex ecological interactions and neglected factors like density dependence, fluctuating environments, and trade-offs between life history traits.
The evolution of population dynamics in a stochastic environment is analysed under a general form of density-dependence with genetic variation in r and K, the intrinsic rate of increase and carrying capacity in the average environment, and in σe2, the environmental variance of population growth rate. The continuous-time model assumes a large population size and a stationary distribution of environments with no autocorrelation. For a given population density, N, and genotype frequency, p, the expected selection gradient is always towards an increased population growth rate, and the expected fitness of a genotype is its Malthusian fitness in the average environment minus the covariance of its growth rate with that of the population. Long-term evolution maximizes the expected value of the density-dependence function, averaged over the stationary distribution of N. In the θ-logistic model, where density dependence of population growth is a function of Nθ, long-term evolution maximizes E[Nθ]=[1−σe2/(2r)]Kθ. While σe2 is always selected to decrease, r and K are always selected to increase, implying a genetic trade-off among them. By contrast, given the other parameters, θ has an intermediate optimum between 1.781 and 2 corresponding to the limits of high or low stochasticity.
The Emergence of Life History Theory
Life history theory encompasses a broader range of factors influencing an organism’s life cycle, including:
Age and size at maturity
Reproductive effort and frequency
Offspring size and number
Lifespan and senescence
The Life history framework acknowledges that organisms face trade-offs in resource allocation. For example, investing more in reproduction might come at the cost of reduced lifespan or growth. Can we manage trade-offs for good reasons and to good effect?
While r/K selection is no longer the dominant paradigm, its core ideas about resource allocation and environmental influences remain relevant to the broader context of life history theory.
Biogeography was stuck in a "natural history phase" dominated by the collection of data, the young Princeton biologists Robert H. MacArthur and Edward O. Wilson argued in 1967. In this book, the authors developed a general theory to explain the facts of island biogeography. The theory builds on the first principles of population ecology and genetics to explain how distance and area combine to regulate the balance between immigration and extinction in island populations. The authors then test the theory against data. The Theory of Island Biogeography was never intended as the last word on the subject. Instead, MacArthur and Wilson sought to stimulate new forms of theoretical and empirical studies, which will lead in turn to a stronger general theory. Even a third of a century since its publication, the book continues to serve that purpose well. From popular books like David Quammen's Song of the Dodo to arguments in the professional literature, The Theory of Island Biogeography remains at the center of discussions about the geographic distribution of species. In a new preface, Edward O. Wilson reviews the origins and consequences of this classic book.
This book is the first comprehensive summary of life-history evolution, a field that holds a central position in modern ecology, evolution, and population biology. The book offers an up-to-date description of the analytical tools used in evolutionary explanation: demographics, quantitative genetics, reaction norms, trade-offs, and phylogenetic/comparative analysis. It goes on to discuss the evolution of such major life-history traits as age and size at maturity; clutch size, reproductive investment and size of offspring; reproductive lifespan; and aging. This is an essential text for biologists wishing to understand the evolution of the life cycle and the causes of phenotypic variation in fitness. It is additionally the only book available designed specifically for teaching the subject, with problems and discussion questions at the end of each chapter.
Reznick, D., Bryga, H., & Endler, J. A. (1990). Experimentally induced life-history evolution in a natural population. Nature, 346(6282), 357-359.
LIFE-HISTORY theory predicts that reduced adult survival will select for earlier maturation and increased reproductive effort; conversely, reduced juvenile survival will select the opposite1#150;5. This is supported by laboratory studies6-10 and comparative data from natural populations11-15. Laboratory studies may support a theory, but cannot assess its importance in natural populations, and comparative studies reveal correlations, not causation16. Long-term perturbation experiments on natural populations resolve both problems. Here we report the findings of a long-term study of guppies (Poecilia reticulata), in which the predictions of life-history theory are supported. Life-history differences among populations of guppies are closely associated with predator species with which guppies live13,17-21. The predators apparently alter age-specific survival because they are size-specific in their choice of prey21-23. Crenicichla alta (a cichlid), the main predator at one class of localities, preys predominantly on large, sexually mature size classes of guppies22-24. Rivulus hartii(a killifish), the main predator at another class of localities, preys predominantly on small, immature size classes. Guppies from localities with Crenicichla mature at an earlier age, have higher reproductive effort, and have more and smaller offspring per brood than those from localities with just Rivulus. These differences are heritable, and correspond with theoretical predictions17-19. To prove that predation caused this pattern, we perturbed a natural population of guppies by changing predation against adults to predation against juveniles. This resulted in significant life-history evolution in the predicted direction after 11 years, or 30-60 generations.
Revisiting Reznick et al. 1990
In a 1990 paper in Nature, David Reznick, Heather Bryga and John Endler, showed, through an 11-year experiment on a natural population of guppies in Trinidad, that predators can cause significant life-history evolution. Twenty-six years after the paper was published, I spoke to David Reznick about its making, the influence it had on its career and what we have learnt since about life-history evolution in guppies.
Pianka, E. R. (1970). On r- and K-selection. The American Naturalist, 104(940), 592-597. (An early influential paper on r/K selection)
Scientific theories evolve as new evidence and perspectives emerge. r/K selection may have fallen out of favor, but it played a crucial role in shaping our understanding of life history evolution and paved the way for more nuanced theories.
We are uniquely complex creatures, so much of what we call “human nature” is a mystery. To glimpse what we are requires immense scholarship across many domains of inquiry.
Biological Domain
To understand our genetic makeup, how genes influence behavior, and how they interact with the environment, we must explore areas like evolutionary psychology, behavioral genetics, and neurogenetics. The brain is the seat of our thoughts, emotions, and behaviors, but it is also embodied. Studying its structure, function, and development is essential for understanding human nature—fields like cognitive, affective, and behavioral neuroscience. Endocrinology (hormones), immunology (how the immune system interacts with behavior), and chronobiology (biological rhythms) help us understand how biological processes influence our behavior and well-being.
In this month's episode of Brain Science I explore two big picture questions: What does it mean to claim that the Mind is "embodied?" and How does this change our understanding of our place in the world? The conversation was inspired by the book "Out of the Cave: A Natural Philosophy of Mind and Knowing" by Mark L Johnson and Donald M Tucker.
Psychological Domain
Studying attention, language, memory, and decision-making helps us understand how our perception, thinking, learning, memory, and problem-solving work. Studying cognitive, social, and moral development can help us understand how humans change dramatically across their lifespans. We are inherently social creatures. Social cognition, group dynamics, and persuasion are essential to interacting with others, forming relationships, and behaving in groups. We all have unique personalities with characteristic thoughts, feelings, and behavior patterns. Studying individual differences helps us understand the diversity of human nature. We must also understand mental disorders and their causes. And all of these explorations only scratch the surface.
The neurobiology of human social behavior: an important but neglected topic.
The past few decades have produced important advances in our understanding of how the brain regulates emotion and cognition. In comparison, research on the neuroscience of human social behaviour is a relatively neglected topic in spite of the importance of social interactions for mental health. In this editorial, I give examples of some of the experimental approaches that have been used to study the neural substrates of human social behaviour in the hope that this will stimulate more researchers to become involved with this fascinating and important topic.
Humans are inherently social. We are not special in this way; it is hard to think of any animal for whom the regulation of social behaviour is not important. Something akin to social behaviour may even occur in organisms lacking a nervous system. For example, Science recently published an article titled “Genetic determinants of self identity and social recognition in bacteria.”1 Different animals, including humans, share many of the same types of social behaviour such as affiliation and aggression, the establishment of hierarchy and territoriality. This can be the case even in species, such as ants, with a primitive brain. Although we may share some of the broader aspects of our social behaviour with more primitive species, human social behaviour is obviously more complex but no less important for our health and survival. Given the importance of social interactions for humans, it is not surprising that most psychiatric disorders involve some disruption of normal social behaviour, and that in several disorders abnormal social functioning is one of the central symptoms. Examples are autism, social anxiety disorder, borderline personality disorder and schizotypal personality disorder.
Despite the importance of social interaction, our understanding of the neural factors that control social behaviour is limited. Human social neuroscience is receiving increasing attention, but much of the current work concerns social cognition. For example, studies on the activation of different brain areas in response to faces with different expressions are interesting and important, but they are not central to the regulation of actual social behaviour. If response to faces was an essential determinant of social interaction, then blind people would not be able to form adequate social relationships and the use of text messaging would not be nearly as widespread as it is.
The most extensive knowledge on the neurobiology of human social behaviour concerns one particular aspect of social behaviour: aggression.2,3 Research on aggression has led to the use of selective serotonin reuptake inhibitors (SSRIs) for the treatment of impulsive aggression,4 an illustration of how social neuroscience can lead to treatments for disordered social behaviour. However, aggression, although an important societal problem, does not feature prominently in many disorders even though it is required for the diagnosis of intermittent explosive disorder. Furthermore, overt aggression is not a common part of everyday social interactions.
Research on the neurobiology of less extreme forms of social behaviour than aggression is limited. Two examples of how research on animals is starting to be applied to human social behaviour follow. In some species of monkeys, serotonin can influence both agonistic-affiliative behaviours and hierarchy. Although low levels of serotonin increase aggressive behaviours, as in humans, increasing serotonin function enhances prosocial behaviours such as grooming other animals.5,6 Increasing serotonin function also helps a male to achieve dominant status.7 Similar results have been reported in a few studies involving humans, carried out both in the laboratory and in everyday life. In the laboratory, healthy participants receiving an SSRI were rated more dominant and more cooperative during a mixed motive game8 and showed more affiliative behaviours during a dyadic puzzle task requiring cooperation.9 On the other hand, acute tryptophan depletion to lower serotonin levels caused reductions in the level of cooperation shown by participants when playing the prisoner's dilemma game.10 Acute tryptophan depletion also changed behaviour in an ultimatum game in which players had to decide whether to accept or reject fair or unfair monetary offers from another player. Participants with low serotonin levels rejected a greater proportion of unfair offers, but not fair offers.11 This result was consistent with a lowered level of affiliation. In studies investigating social behaviour in everyday life, social behaviour can be studied using an ecological momentary assessment methodology (discussed recently in this journal12) that measures behaviours along 2 axes, agreeable–quarrelsome and dominant–submissive. In crossover studies comparing placebo with the administration for 2 or 3 weeks of tryptophan to increase serotonin, increased serotonin was associated with decreased quarrelsomeness and increased dominance among healthy participants,13 and with decreased quarrelsomeness and increased agreeableness among participants with high trait hostility.14 In both studies, participants were not able to guess, better than by chance, when they were taking tryptophan and when they were taking placebo, indicating that participants were unaware that their behaviour was changed by tryptophan.
Oxytocin is another compound that has been shown to influence social behaviour in animals, and its effect on humans has been tested recently. Animal studies have shown that oxytocin is involved in the formation of bonds between mates and between mothers and their offspring, including the use of aggression in the protection of these relationships.15 In laboratory studies involving healthy humans, intranasal administration of oxytocin altered behaviour in a way that indicated increased trust in others.16,17
In the past, one of the limiting factors in the study of the neurobiology of human social behaviour was the limitations in the methods for measuring social behaviour. In the past, this usually depended on peoples' own global assessment of their behaviour. The few studies described previously give an indication of the scope of the methodology that is now available for studying human social behaviour both in the laboratory and in everyday life. So far, most studies have looked at the effects on dyadic interactions. Future studies should also look at group interactions, both within groups and between groups. Group behaviour is an important component of human social behaviour and may differ in some ways from dyadic interactions. Social psychologists have studied what they term the interindividual–intergroup discontinuity, which refers to the fact that groups are sometimes more competitive or aggressive than individuals. This has been demonstrated in mixed-motive situations18 with a test based on Milgram's19 obedience research in which groups acting as teachers delivered significantly more severe shocks than individuals acting as teachers20 and in the prisoner's dilemma game in which groups were more competitive than individuals.21 Furthermore, discussion between groups was characterized by a higher frequency of fear and greed statements than discussion between individuals. How the manipulation of different neurotransmitters might affect these results is not known but should definitely be researched.
The techniques for the study of human social behaviour are available. There are a wide variety of drugs that target different neurotransmitter systems and are available for use in experimental research involving humans. What seems to be lacking at the moment are researchers willing to combine both in their research.
It’s fantastic that we can do this research and continue learning about Great Nature, of which we are part and parcel.
What else?
Anthropology
Sociology
History
Philosophy
If only more people were deeply interested in learning more about who we are, where we came from, and how to live well while ensuring a healthy future for all life forms.
Environmental Domains
Studying the relationship between humans and their environment, including how we impact the planet and how it impacts us, is crucial for understanding our place in the world. But too many believe we are separate from Nature, operating under God’s rules, and are more concerned with favors, the hereafter, or liberation from rebirth than justice, health, happiness, peace, and our future. I am not saying that stories don’t help with that, but there is also a great deal of meaning in an evidence-based understanding of our Nature works.
Listen to Carl Sagan. We are still struggling with the same issues he was concerned about.
My feeling Charlie is that it’s it’s not that pseudoscience and superstition and new-age so-called beliefs and fundamentalist zealotry are something new they’ve been with us for as long as we’ve been we’ve been human, but we live in an age based on science and technology with formidable technological powers science and technology are propelling us forward at accelerating rates that’s right and if we don’t understand it, by we I mean the general public if it’s something that oh I’m not good at that I don’t know anything about it then who is making all the decisions about science and technology that are gonna determine what kind of future our children live in just some members of Congress but there’s no more than a handful of members of Congress with any background in science at all and the Republican Congress has just abolished its own office of Technology Assessment the organization that gave them bipartisan and competent advice and Science and Technology they say we don’t want to know don’t tell us about science surprising it’s the danger of all this I mean you know this is not the thing there’s two kinds of dangerous one is what I just talked about that we’ve arranged a society based on science and technology in which nobody understands anything about science and technology and this combustible mixture of ignorance and power sooner or later is gonna blow up in our faces I mean who is running the Science and Technology in a democracy if the people don’t know anything about it and the second reason that I’m worried about this is that science is more than a body of knowledge it’s a way of thinking a way of skeptically interrogating the universe with a fine understanding of human fallibility if if we are not able to ask sceptical questions to interrogate those who tell us that something is true to be skeptical of those in authority then we’re up for grabs for the next charlatan political or religious who comes ambling along it’s a thing that Jefferson laid great stress on it wasn’t enough he said to enshrine some rights in a in a constitution or a Bill of Rights the people had to be educated and they had to practice their skepticism and their education otherwise we don’t run the government the government runs us. —Carl Sagan
Thanks to super-smart computer algorithms, let’s look at some domains of inquiry relevant to our relationship with our environment. We all process information with tools, just like we process food with tools. We use a lot of energy and materials to do this, which profoundly impacts our environment and habitat. My bad! I’m constantly wondering if we can use these tools in a sustainable, habitable way. One day, perhaps, we won’t have these tools anymore and will rely on simpler tools we craft from natural materials by hand.
Tools of the Wild: Unveiling the Crafty Side of Nature
Once considered a uniquely human activity, tool use has been spotted across diverse species. It’s time to rethink what tools reveal about their users’ intelligence and evolution.
Biotic and Abiotic Interactions
Population Ecology
Community Ecology
Ecosystem Ecology
Biogeochemistry
Ecophysiology
Spatial and Temporal Scales:
Landscape Ecology
Global Ecology
Paleoecology
Human Impacts and Conservation:
Conservation Biology
Environmental Science
Restoration Ecology
Sustainable Development
Tools and Techniques:
Ecological Modeling
Remote Sensing
Field Ecology
Molecular Ecology
5. Interdisciplinary Connections:
Environmental Economics
Environmental Sociology
Environmental Ethics
It’s, wait for it, interdisciplinary
These domains are interconnected. If we want to understand our nature, we must study it all. If we're going to understand the social and cultural factors that contribute to violence, we need to understand the biological basis of aggression, etc.
Humans are complex creatures full of contradictions. Are we curious enough about what things are and how they work, about system dynamics, stocks and flows, biology, complexity, science, physics, and all the rest of it to learn what’s necessary to build a culture focused on health, well-being, and posterity? We seem too prone to distraction, entertainment, and “emotional highjack” to focus on things we need to learn. It’s far easier to listen to someone with power tell us what to believe and fit in.
Even if we had a complete and detailed understanding of our nature, developing a culture with the agency to favor certain “traits” over others would be complex and take generations. We would have to change the way we do things radically. How does one kind of human/culture create a different type of human/culture that would live much differently than we do now? Refering to isolated groups of hunter-gatherers as an example doesn’t consider that no group remains isolated and is, therefore, inevitably influenced by other groups sooner or later unless purposely kept in isolation by a group with the power to do so. We will not magically turn into hunter-gatherers living a simpler way in harmony with Nature’s limits as benevolent protectors of life without a critical number of revolutionary revolutionaries willing to sacrifice their lives to take power from Homo destroyer of worlds.
How do we reconcile POWER with peaceful living in harmony with Nature? Power over people is the crux of our predicament. Empowering people is a necessity.
We have no problem sacrificing blood and treasure for our current ideological beliefs, obsessions, and addictions. And look, we’re still in the same predicament we’ve been in for thousands of years.
Who wants to be a revolutionary rebel when history has clearly shown us what we have become and what our preferences seem to be? What will level the “playing field,” giving rise to a different type of person who will have the power to educate humanity about its better nature and profound responsibilities? Who will sacrifice for that?
It’s something to think about before the lights go out.
