Why do the lengths of societal cycles vary?
From biological markers to power structures, many variables shape how we understand the rhythm of societal change.
Epoch Change blog series, No. 6
Dr. Tuomo Kuosa
Tuomo is co-founder and Director of Futures Research at Futures Platform. He holds a PhD from the Turku School of Economics and is an Associate Professor (Docent) of Strategic Foresight at the Finnish National Defence University.
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Throughout world history, many different types and lengths of recurring societal cycles have been identified. One fascinating point of variation lies in the length of generations. Is a generation 15 years, 20–25 years, or even 25–40 years long? And is Generation Z really a distinct generation, or not?
How Long Is a Generation?
In a biological sense, a generation is defined as the period during which children are born, grow up, reach adulthood, and begin having children themselves, which has been roughly 15 years throughout much of human history. Modern social generation theories typically employ this same framework to not only ancient generations but also modern ones to discuss cohorts of people born within the same year range and who share similar cultural experiences.
At the same time, many scholars agree that modern social generations are, from a biological standpoint, actually longer — around 20 to 30 years. For instance, Strauss & Howe use this extended span in their generational theory (See the third article of this series for more information). However, their timing isn’t based solely on biology; it’s tied to identifiable societal turnings.
Due to this division, various social generation theories suggest that the Millennial generation, born between 1980 and 1995, was followed by Generation Z (1996-2010), and further by Generation Alpha (2011-2026). In contrast, Strauss & Howe’s theory of societal changes excludes Generation Z altogether, as it doesn’t fit into their framework of societal turnings.
Ancient scholars such as Ibn Khaldun, Giuseppe Ferrari, and others typically defined generations as lasting 25 to 40 years — far longer than the biological generation, and even longer than Strauss & Howe’s societal turnings. The rationale behind these longer generations may lie in the power dynamics of ancient times. The reign of a king or ruler may have lasted, on average, roughly that time. While one or two biological generations might have come and gone within that period, only the power dynamics between reigns matter from the perspective of war-peace cycles.
Other Reasons Cycle Lengths Vary
Different interpretations of generations are just one factor behind the variation in societal cycle lengths. Another reason is zooming: Some scholars combine shorter cycles into larger ones, and some split longer cycles into smaller phases that describe the maturity of the cycle (e.g. initial growth, stable development, decline).
Cycle lengths also vary because different theories focus on different aspects of the transformation, such as technological ecosystems, generation shifts, hegemony transitions, or war-peace cycles. Assumingly, all such cycles are interlinked and in co-evolution, but they are not totally synchronised except during the strongest transition phases. Yet, it is also fair to say that, e.g. war-peace cycles may vary in length because different scholars interpret, prioritise, and time some events differently.
Assumingly, all such cycles are interlinked and in co-evolution, but they are not perfectly synchronised except during the strongest transition phases. Yet, it is also fair to say that, e.g. war-peace cycles may vary in length because different scholars interpret, prioritise, and time some events differently.
In the next blog, we’ll look even further: to the longest known societal cycles, the 250-year “Mega cycles” that shape what we might call the true epochs of world history.
This article is the sixth instalment in Dr. Tuomo Kuosa’s Epoch Change series. You can find the other articles in this series listed below:
