For someone who has examined 361 studies and 73 books on societal collapses, Danilo Brozović’s conclusion on what must happen to avoid today’s world imploding is both disarmingly simple and a daunting challenge: “We need dramatic social and technological changes.”The collapse of past civilisations, from the mighty Mayan empire to Rapa Nui (Easter Island), has long fascinated people and for obvious reasons – how stable is our own society? Does ever-growing complexity in societies or human hubris inevitably lead to oblivion? In the face of the climate crisis, rampant destruction of the natural world, rising geopolitical tensions and more, the question is more urgent than ever.“More and more academic articles are mentioning the threat of collapse because of climate change,” says Brozović at the school of business at the University of Skövde, Sweden. The issue of collapse hooked him after it was raised in a project on business sustainability, which then led to his comprehensive review in 2023.The field is not short of extreme pessimists. “They believe what we are doing will eventually cause the extinction of the human race,” says Brozović. Some say today’s challenges are so great that it is now time humanity comes to terms with extinction, and even build a vault containing our greatest cultural achievements as a record for some future – perhaps alien – civilisation. Others, using data on deforestation and population, rate the chance of catastrophic collapse at 90% or more.Most scholars are more optimistic, if not actually optimists. Brozović says: “They say collapse for us will just be the end of life as we know it today. There will be less globalisation and a lower standard of life, affecting public health very negatively.”This raises the question of what is meant by collapse: most agree it is the loss of complex social and political structures over a few decades at most. But by this definition, many classic collapses, misinterpreted in the rear-view mirror of history, may actually be better described as transformations. He says: “In the last 10 years or so, people are asking did the Rapa Nui society collapse or did it reinvent itself?” he says.The search for explanations of societal collapse has been a long one, going back at least to Thomas Malthus’s An Essay on the Principle of Population and Edward Gibbon’s History of the Decline and Fall of the Roman Empire, which blamed decadence and barbarian invasions.Today, collapses are seen as the result of combined factors, such as environmental problems, disease, political or economic turmoil, religious crises and soil exhaustion, even if one factor might precipitate the collapse.Brozović says: “But there is one theory of collapse that stands out as the most frequently invoked: Joseph Tainter’s theory of complexity.” Tainter’s theory was published in 1988 and has since been described as “peak complexity”.Brozović says: “He says the main function o