Some of the oldest living things on Earth may lie underground in the form of fungi rather than trees or coral reefs. Despite their widespread presence and ecological role, researchers still lack clear data on typical fungal lifespans or reliable ways to measure age. An opinion paper in Trends in Microbiology explores the challenges of studying fungal longevity and suggests new approaches such as microfluidic devices and extended laboratory trials using genetic markers. Senior author Kristin Aleklett of Lund University notes that it is unclear whether ten years or five hundred years counts as old for different fungal types and growth habits. The visible mushroom is only a minor portion of the organism. Its main structure consists of fine filaments known as mycelium that spread through soil or wood and may link with plant roots. Certain networks are estimated to persist for centuries or longer. Defining the boundaries of a single fungus proves difficult because mycelium constantly branches, expands, reuses older parts and can separate into new networks. This raises questions about what to measure for age, whether age starts at initial formation even after later replacement, and whether separated pieces sharing DNA count as one individual. Unlike animals or trees, fungi cannot be aged by counting rings or birthdays. Scientists often use genetic identification and lab growth rates instead, yet direct observation of expansion and decline over time in natural settings remains limited. Aging patterns also vary across species. Simple yeasts differ from more complex forms, while fungi partnered with plants may match host lifespans and decomposers may persist by moving to new food sources. The authors recommend studying longevity across varied species and conditions rather than seeking one universal figure. They advocate combining genetic tracking, multi-year experiments and new tools to monitor growth in detail. Such insights could improve understanding of fungi that support ecosystems, farming and health. Better knowledge of fungal life cycles, including how they end, would aid efforts to protect biodiversity and ecosystem functions.
