When our paper on “Underestimating the challenges of avoiding a ghastly future” was published, many people wanted to know more about what might be done to avoid a catastrophic collapse of civilization, as bad news cascades upon us almost daily. Obviously, a long list of individual steps would be needed, but here I want to give my opinion about the requisite scale and speed of a response. The basic cause of the assault on human life-support systems is the scale of the human enterprise – the amount and nature of its aggregate consumption. It can be calculated by combining the number of people, their average per capita consumption, and the technologies and socio-political structures employed to service that consumption (the I=PAT relationship). In thinking about how to eliminate most of the net damage (for that is necessary for long-term sustainability of civilization), one should consider that enterprise’s historical origins and characteristics.
Homo sapiens is genetically and culturally a hypersocial “small-group animal,” one whose “success” however measured relies heavily on cooperation and cleverness. In fact our ancestors out on the African veldt, lacking claws, fangs, armor, and great speed, depended on sociality and IQ for their very survival. For almost all of the several-hundred-thousand-year history of modern human beings, our ancestors existed in relatively equitable tightly-knit groups. They mostly formed units of 50-150 people, the so-called “Dunbar’s number.” The unit size was proposed by anthropologist Robin Dunbar based on studies of primate brain measurements and group sizes. One hundred and fifty or so people is thought to be roughly the maximum size of most hunter-gatherer groups. To a degree, the Dunbar number can, interestingly, be seen today in typical groups of colleagues, lengths of Christmas-card lists, numbers of Twitter contacts and so on, although perhaps somewhat enlarged in complex ways by communications technologies. I attempted to estimate my “Ehrlich number”, which turned out to be in the Dunbar range for close contacts – those where associations were strong and long-lasting, with a larger range increasing to perhaps 600 in expanding shells of diminishing relationship, for other contacts. Clearly, we’re still small-group animals that now as a species is trying to get “comfortable” in groups of thousands, millions, or in some peoples’ minds, billions. And we’re doing an undeniably lousy job of it, and refusing to act on the obvious need for billions to cooperate to steer society away from the cliff..
Our ancestral groups were constantly on the move as people fed themselves by hunting and gathering, surviving on nearby resources until they were overexploited. Leadership tended to go to those best at various tasks – a hunt leader who could bring home the most meat, a healer who knew the medicinal plants, a wise person who settled disputes, and so on. Frequent movement automatically limited “property,” made slavery and servants impractical since every individual had to work and be mobile to obtain food. Racism and xenophobia were near impossible since everyone in a group tended to share most genes, look alike, and speak the same language. Differing groups could simply move away from each other or bud off new groups if internal conflicts arose. In many circumstances, hunter-gatherers had ample leisure time and, compared to those who first practiced agriculture (and many today), led relatively healthy, affluent, and possibly secure lives, though high infant and child mortality kept average life spans shorter than ours today. Adults lived almost as long.
The agricultural revolution, favored by a period of unusual climatic stability, changed all that. Becoming sedentary and developing new technologies (farming, herding, building) allowed one family to feed more than itself. This made possible more specialists – potters, tool-makers, soldiers, shamans, brewers, accountants, kings, and so on. And being settled also made possible more private property, wealth, and poverty. The population explosion was made possible by agriculture and in the last few centuries by improved sanitation and technologies like window screens and insecticides. It occurred at a speed too fast for people to invent social arrangements and ways to maintain vital environmental services that would allow the new large groups to be sustainable in the long term. Instead it created, for the first time in human history, a vast culture gap. In hunter-gatherer groups, all adults were usually in possession of the vast majority of their society’s culture – its non-genetic information. Even the best educated person today does not possess one millionth of one percent of the culture of a modern society. Further, until very recently cultures provided little or no thought of sustainability as global goals. In fact, some people first developed a global view with the first pictures of Earth from space in the mid-20th century. Thus, in an evolutionary blink of an eye, in a few hundred generations – and mostly in the last 10 generations, groups became gigantic. This underlies the fact that humanity is now facing a ghastly future. Indeed, we are on the brink of catastrophe.
Small-group attitudes remain prominent in blocking effective responses to the existential threats humanity faces. No doubt they are a major reason we have both a fascination with diversity (is it the attraction of novelty?) and a problem with diversity (the aversion to “others”?). Those attitudes are behind our constant associations in groups smaller than the entire human species, that is, groups with which we easily identify. Not only nations and ethnic groups, but also religions and other cults, genders, professions, clubs, gangs, sports participants and fans, political parties, social and economic “classes” (castes), and on and on. Almost all of these entities carry the same seeds that allow belief in myths (that are different from other groups’ myths), failure to seek an evidence-based worldview, and, sometimes, promoting intergroup dissension and even violence. Almost all of them hinder the widespread cooperation that will be required to change the direction of cultural evolution in response to worldwide existential threats. Indeed, responses of a cultural system can be counterproductive. MAGA and BREXIT are potentially disastrous examples on the international scene. In view of the rate of environmental deterioration so far, and projected future rates, humanity faces semi-conflicting needs. It must make monumental changes and do it at an unprecedented pace. But it must succeed despite long-evolved structures that today create daunting barriers to success. These range from fractured media and inadequate education systems to rapacious corporations and the confusion of money and wealth with quality and value. Since environmental deterioration and associated threats are products of the expansion of the human enterprise resulting from agricultural and industrial revolutions, to stop the downhill slide global civilization requires another revolution — a survival revolution. And the scale of change must match, if not exceed, that of each of the revolutions that have generated the decay of humanity’s life-support systems.
The first element of such a revolution would be to generate broad understanding of the need for and nature of the required rapid change. The human enterprise today can be seen as two gigantic interacting complex adaptive systems (CASs), biophysical and cultural. Each CAS contains many random elements and is “self-organized.” In the safest prediction of their trajectories, as they race toward collapse in the years ahead, they will display many emergent features, often emerging at unpredictable times, places, and scales. The first major pandemic in a century was anticipated, but its arrival remained unpredictable, as was the election of an autocrat as the 45th president of the United States just before the pandemic arrived. The necessary preconditions for both were, however, known, and ignored. Thus, the eventual emergence of a virus pandemic like that of SARS-CoV-2 was foreseen by many, but its timing, characteristics, and intersection with who was in power when it emerged was not predictable. Also predictable was the possibility of political turmoil in a nation of escalating financial inequity, a broken educational system, persistent structural racism, increasing costs of climate disruption, and declining democracy with little understanding of the political system by citizens who believed occasional voting was adequate participation. The recent interactions of the CASs, especially in the United States, produced a vast tragedy, leading to hundreds of thousands of deaths from the virus and immense physical, emotional, and economic suffering. I emphasize that it was the interaction between the biophysical CAS (covid-19) and the cultural one (Trump) that caused the vast tragedy.
Despite the difficulty of foreseeing the emergent properties of a CAS, it is usually possible to predict its long-term fate. Einstein’s brain, like all human brains, was a CAS, but at the age of 16 even he could not predict the emergence of special relativity a decade later. Nonetheless he could easily predict the ultimate fate of that entire CAS when he died. Similarly, despite the unpredictability of many events along the way, since physical growth of the human enterprise cannot continue forever on a finite planet, or even in a finite universe, we can confidently predict the future of the interaction. Growth must at some point cease, and then shrinkage will likely begin, although exactly how swiftly or gradually or how it will manifest itself remains uncertain.
What does seem near certain is that, as presently constituted, the daydream believing priesthoods of economics, business, and politics, and many pundits of public culture will fail to face the evident human prospect and thus not recommend prosocial responses. The world-destroyers will likely continue to meet at Davos annually until they succeed. They haven’t grasped that the last few hundred years of worshiping money, economic growth (despite its lack of connection to happiness or well-being), and uncontrolled markets has been a mistake in terms of its effect on the future well-being of our species. This period never was a “normal” to which society could return. Markets will develop in any large-scale human society, but vast markets and large corporations (if permitted to persist) will need extremely careful monitoring and close control. Without it, present day gigantic and technologically advanced societies won’t have a chance of shrinking gradually and safely to the point where they might be sustainable for the long term and be reasonably democratic.
The market’s lack of historical knowledge, empathy, and predictive ability, the inevitably uneven flow of information, and many other factors mean we must implement vast reforms in how we deal with each other and humanity’s life-support systems. Indeed, history suggests that financial gains and losses are a poor choice as the central organizing principle of a civilization. Uncontrolled markets and temporary corporate-maneuvered successes primarily benefit a limited portion of human society. The “successes” are based on a one-time resource bonanza, the dominance of private property over public good, massive ignoring of negative externalities, and the “successes” (like exploiting fossil energy and inventing weapons of mass destruction) are now spelling doom for the whole enterprise.
Against this background, how should we small-group animals respond to the threat of a ghastly future? Unfortunately, the required changes are far larger than those put in place immediately after Pearl Harbor in the United States, which dramatically (but temporarily) changed patterns of consumption. The scale of the transformations that formed the industrial revolution is closer to what is needed. In my view the only response with a chance of long-term success is to greatly reduce the size of the human enterprise, and to do it humanely and equitably. The imperative is to recruit almost everyone into an unprecedented effort.
We know such a transformation can’t be accomplished simply by greatly increasing the dissemination of scientific evidence. Human minds function through both reason and emotion; and emotions often tend to be more powerful. Individual success, personally and reproductively, has depended on cooperation within hyper-social groups, and in the days of hunting and gathering, that usually meant close physical relationships with others. As a result, decision-making was likely always dependent to some degree on emotion. Indeed, contrary to the training of most scientists, policy debates are often not settled by evidence, which in fact may be overwhelmed by individual emotions and preconceptions, and by the views of leaders or of friends or peers in networks. For example, evidence has not been the main factor in determining attitudes toward climate disruption. In one study, “twenty-seven variables were examined by synthesizing 25 polls and 171 academic studies across 56 nations. Two broad conclusions emerged. First, many intuitively appealing variables (such as education, sex, subjective knowledge, and experience of extreme weather events) were overshadowed in predictive power by values, ideologies, worldviews and political orientation.”
On the evidence side, it’s clear that a revision of educational systems from top to bottom is essential, including, especially, awakening university curricula out from Aristotelian slumber. Emotion may be key to much decision-making, but reason and education supply things to decide about. If institutions like Stanford could be dragged into the 20th century (sic) and developed dramatically altered curricula focused on the new world they would influence other institutions, especially those charged with elhi education. But things need to go much farther than that. If the culture gap is to be narrowed at critical points, society must dispose of the idea that education is a process of pouring knowledge into individuals in the first two decades of life, essentially filling up a limited vessel. Education in a rapidly changing world needs to be viewed as a life-long critical process. People cannot be expected to take any action on problems they don’t understand or, indeed, they’ve never even heard of. Overpopulation is the paradigmatic example where continuous education backed by emotion-focused messaging is necessary. Many think that “too many people” is itself an impossible idea. Others believe that there are too many of the wrong kind of people, especially people who are poor or have the wrong skin color. Correcting such views should start in kindergarten and continue through old age as advances in understanding both genetic and cultural evolution clarify the demographic situation and nature of human diversity. As people have learned more, various steps taken, some supported by governments, have brought birth rates down in many areas while adding to the recognition of serious problems of inequity. These include developing modern contraceptives, seeing the finite nature of the planet in photos from space, installing family planning programs, focusing more educational effort on girls, the poor, and minorities and international discussions of womens’ reproductive rights. Does the record with population control and civil rights, both successes and failures give us clues about what actions in other areas might increase sustainability?
Reduced birth rates in diverse nations following international discussions suggests such discussions can help. So can reinforcing the hopeful gradual trend of more women taking political leadership positions. International discussion, especially the United Nations World Conferences on Women, starting in 1975, helped this along. More recently a 2020 report on the catastrophic decline in biodiversity by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) attracted a great deal of attention. Governments of the UN member nations agreed on supporting the IPBES program results through their national environmental programs. More than 33,000 articles across 158 countries in 50 languages covered the report, with comments by the Pope, Al Gore, Hillary Clinton, and Greta Thunberg. That, like the attention given to the UN World Conferences on Women is encouraging, but the total absence of discussion of the need to shrink the scale of the human enterprise was not. Even though it is obvious that absent this consideration most of the planet’s remaining biodiversity, including innumerable critical microorganisms, will disappear and the status of women become moot. But on the other hand, the impressive international report supplies talking points that those already concerned can use to help persuade others.
One thing that concerned citizens can do now is to join the MAHB (mahb.stanford.edu), whose mission is to get civil society to press for the needed revolution, and help to persuade others to focus on dealing with civilization’s existential threats. Progress on meeting those rapidly escalating threats through governmental action has mostly been depressingly slow, and, as in the case of the IPCC, recommendations from official bodies too conservative. The MAHB is just one non-governmental organization (NGO) trying to deal with humanity’s existential problems. Some of them, like the Natural Capital Project, directly seek cures to extremely serious existential problems. NatCap’s goal is “a world in which people, governments, investors, and business recognize the values of nature in supporting human well-being, and routinely incorporate them into decision-making.” But even the best of the NGOs face the prospect of too little or too late – they serve as models for major action, but there is as yet no sign of such action. Human beings have a tendency to assay situations in terms of goals, motives, aspiration and the like, when we should focus on results if any — measurable reductions in threats.
Individuals can, of course, take personal actions like stopping at one child, eating less meat, and using less plastic. But given that we are hypersocial animals I think we must focus more on collective political action, including much strong and loud but peaceful protest. That will be much more important in moving to a reduction in the scale of society, and necessarily moving there rapidly. And it can be done in a way that matches our evolved preferences, working in relatively small groups.
Another clue is the potential usefulness of narratives and entertainment in changing behavior by appealing to emotions. A prominent example is the Sabido methodology – using television and radio entertainment to bring about social change. Polls have shown that soap operas with stories that include women’s rights and reproductive issues change attitudes in a prosocial way. One need not do scientific polling to see the potential power for change in poet laureate Amanda Gorman’s inauguration presentation, Karole Armitage’s environmental dance performances, the large and growing MAHB art community, Darryl Wheye and Don Kennedy’s “science art” efforts, or an athlete’s “taking the knee” during the national anthem.
But, of course, there is a need to find ways to avoid censorship of speech while restricting the spread of disinformation. In my view, and that of many of my colleagues, Fox “News” helped President Trump murder hundreds of thousands of Americans by supporting the criminal gang and spreading misinformation about the politics and science of Covid-19. It was a large-scale equivalent of shouting, “Fire!” in a crowded theatre, and some of the shouters themselves paid for it with their lives. But what should be done to avoid fake news interfering with a survival revolution? Should our view become the only acceptable one? Will attempts to counter fake news be viewed as unacceptable censorship. Issues like this seem to call for new forums, especially involving social scientists and members of civil society to hash out the best strategies for increasing the chances of revolutionary success – basically ensuring long term well-being for individuals and societies. I think much more broad discussion of “what to do” is critically important to orchestrate time-sensitive decision-making. How, for example, are political units to be organized and governed? Humanity is far too numerous and has already altered the biosphere to the degree that a return to hunter-gatherer economics and politics is not a viable choice, even if it became widely desired. Political change will be necessary to start the survival revolution, and it won’t be easy, as I have learned in a lifetime of failures.
It is surely time to reexamine our governance systems in light of the current existential threats and expand the reexamination to a global discussion, especially since the current upsurge of fascism could make the future even more ghastly. In today’s context, reexamination may seem insanely idealistic and totally impractical – but we must ask, is it as insane and impractical as letting Earth’s average surface temperature exceed an increase of 6ºC , continuing to exterminate pollinator populations, or allowing the human sperm count to approach zero?
Obviously huge effort will be required to deal with the practical issues, an effort already well under way among academics. These, for instance, range from reducing climate disruption and designing and implementing an economic system not impossibly based on perpetual growth to ending the chemical industry’s pumping of poisons into the environment and securely abolishing weapons of mass destruction. Hopefully, wide discussions would be generated of more esoteric topics like “Is there an optimal level of diversity for a given society?” or “Considering the uneven global distribution of resources, and the virtual absence of serious efforts to reduce national inequities, are borders ethical?”
It is, of course, not clear whether any sustainable cultural system can be devised for a newly technologically powerful small-group animal like modern Homo sapiens, struggling to live in groups of billions. How can we get the needed actions in time when, in the most overpopulated large nation, millions of people, many with automatic weapons, feel wearing a mask to slow the spread of SARS—CoV-2 is an infringement on their liberty? The rapid roll-out of the Biden-Harris administration’s plans to deal with the coronavirus pandemic could supply a meso-scale example of the needed full-scale roll-out of a multi-decade plan to re-engineer human society. But how do we make clear that the required changes are much larger than those put in place in a nation preparing to recover from criminal leadership while facing a pandemic, economic disaster for many, and gross inequity. Can not just Americans but a substantial fraction of the global population come to realize that the scale of the transformations in the industrial revolution is what is required for a survival revolution? To be frank, while I’m hopeful, I’m not optimistic.
In summary, the biggest question is how to get from where we are to where we want to go? That means the first task is to get a substantial portion of society to understand where we are, humanity’s current situation, to recognize the growing barriers to sustainability. Then if people can agree they want to go to a peaceful and equitable future world where everyone has a reasonable level of well-being, change their efforts, discourse, and institutions to make determining how to respond to the human predicament society’s collective primary goal. This is obviously an extremely daunting challenge, demanding revision of many of the most basic assumptions of today’s maladaptive cultures. Once that’s agreed upon, the next goal is even tougher — making the changes. But it has long seemed to me that the very least we should do is try to reach it. Nothing is more impractical for humanity than not developing a massive and clever response and instead plunging on to experience a ghastly future.
Paul R. Ehrlich
 Partially extracted from my memoir “Out on a Limb” (in review).
 Bradshaw CJ, Ehrlich PR, Beattie A, Ceballos G, Crist E, Diamond J, Dirzo R, Ehrlich AH, Harte J, Harte ME. 2020. Underestimating the challenges of avoiding a ghastly future. Frontiers in Conservation Science 1:9.
 E.g., https://www.washingtonpost.com/climate-environment/2021/01/25/ice-melt-quickens-greenland-glaciers/
 Ehrlich PR, Holdren J. 1971. Impact of population growth. Science 171:1212-1217.
 Dunbar RIM. 1993. Coevolution of neocortical size, group size and language in humans. Behavioral and Brain Sciences 16:681 – 735; Goncalves B, Perra N, Vespignani A. 2011. Validation of Dunbar’s number in Twitter conversations. arXiv preprint arXiv:1105.5170; Wellman B. 2012. Is Dunbar’s number up? British Journal of Psychology 103:174-176. ome argue that hunter-gatherer groups were mostly smaller, or that people may feel comfortable with 200 or more. Who is much concerned whether the number could instead be 75 or 200?
 Indeed, barriers to such movement have been hypothesized as being central to the evolution of states (Webb MC. 1988. The first states: how — or in what sense — did “circumscription” circumscribe? American Behavioral Scientist 31:449 – 458.)
 Sahlins M. 1972. Stone Age Economics. Aldine.
 The amounts and causes of violence before agriculture is much debated (e.g.., Gat A. 2000. The human motivational complex: Evolutionary theory and the causes of hunter-gatherer fighting. Part I. Primary somatic and reproductive causes. Anthropological Quarterly:20-34. Allen MW, Jones TL. 2014. Violence and warfare among hunter-gatherers. Left Coast Press. Bowles S. 2009. Did warfare among ancestral hunter-gatherers affect the evolution of human social behaviors? Science 324:1293-1298. Eerkens JW, Carlson T, Malhi RS, Blake J, Bartelink EJ, Barfod GH, Estes A, Garibay R, Glessner J, Greenwald AM. 2016. Isotopic and genetic analyses of a mass grave in central C alifornia: Implications for precontact hunter‐gatherer warfare. American Journal of Physical Anthropology 159:116-125). Evidence is often lacking, and the possibility exists that levels of violence themselves evolved over the half-million or more years (depending on your definitions) of hunting and gathering leading up to a mere few thousand years of early agriculute.
 Ehrlich PR. 2010. The MAHB, the culture gap, and some really inconvenient truths. PLoS Biology 8 e1000330.
 Locher, F. 2019. Neo-Malthusian environmentalism, world fisheries crisis, and the global commons, 1950s–1970s. The Historical Journal:1-21.
 Levin S. 1999. Fragile Dominion. Perseus Books.
 Easterlin RA. 2015. Happiness and economic growth–the evidence. Pages 283-299. Global handbook of quality of life, Springer.
 [Bakan, 2020 #11779]
 Bechara A, Damasio AR. 2005. The somatic marker hypothesis: A neural theory of economic decision. Games and Economic Behavior 52:336-372.
 E.g., Lord CG, Ross L, Lepper MR. 1979. Biased assimilation and attitude polarization: The effects of prior theories on subsequently considered evidence. Journal of Personality and Social Psychology 37:2098.
 Hornsey MJ, Harris EA, Bain PG, Fielding KS. 2016. Meta-analyses of the determinants and outcomes of belief in climate change. Nature Climate Change 6:622-626.
 The Montreal Protocol on substances that deplete the ozone layer was a prominent exception.,
 Mandle, L, Z Ouyang, J Salzman and GC Daily, Eds. 2019. Green Growth that Works: Natural Capital. Island Press (published in Chinese, Science Press of China).
 Ryerson WN. 2008. The effectiveness of entertainment mass media in changing behavior. Population Media Center.
 E.g., an example by an economist who I and my colleagues enjoy working with: Goulder L, Hafstead M. 2017. Confronting the climate challenge: US policy options. Columbia University Press. A very recent example by another economist colleague and friend is the report to the British government on the economics of biodiversity by Sir Partha Dasgupta (https://bit.ly/3jA0Qlw). These, other friends who practice the dismal science, and my economist daughter and son-in-law demonstrate that not all economists pose threats to civilization.
 Brown JH, Burger JR, Burnside WR, Chang M, Davidson AD, Fristoe TS, Hamilton MJ, Hammond ST, Kodric-Brown A, Mercado-Silva N. 2014. Macroecology meets macroeconomics: Resource scarcity and global sustainability. Ecological engineering 65:24-32.
 Ehrlich PR, Blumstein DT. 2018. The Great Mismatch. BioScience 68:844-846.
 I am grateful to Corey Bradshaw, Dan Blumstein, Joan Diamond, Gretchen Daily, Avinash Dixit, Anne Ehrlich, Larry Goulder, John Harte and Lee Ross for helpful comments.