Study Explains Growing Genetic Impact on Human Lifespan Over Time - Video

How much of a person’s lifespan is determined by genetics has long been debated. For decades, research suggested that genes account for about 20-25% of how long people live, with the remaining influence coming from lifestyle, environment, and healthcare. However, a new study published in Science suggests that the genetic contribution to lifespan may be significantly higher.

Researchers argue that earlier estimates did not fully consider how causes of death have changed over time. In the past, many deaths occurred due to external factors such as infections, accidents, and poor sanitation. In modern, developed societies, most deaths are now linked to ageing and age-related diseases like heart disease and dementia.

To better understand genetic influence, scientists analyzed large datasets of Scandinavian twins, excluding deaths from external causes. They also examined twins raised apart and siblings of centenarians in the United States. When deaths caused by accidents and infections were removed, the genetic contribution to lifespan increased sharply to around 50–55%.

This increase does not mean that genes have suddenly become more powerful. Instead, environmental risks have reduced. As living conditions improve, differences in lifespan increasingly reflect biological ageing processes, which are more strongly influenced by genetics.

Researchers explain this using the example of height. In the past, poor nutrition limited growth, but today most people reach their genetic height potential. As a result, height now appears highly genetic—not because nutrition no longer matters, but because environmental differences have narrowed.

The same principle applies to lifespan. Heritability is not fixed and depends on population conditions. Even today, about half of lifespan variation is still shaped by lifestyle, healthcare, environment, and random biological events.

The study highlights that genes and environment work together. Understanding how they interact may help explain why some people live much longer than others and guide future research into healthy ageing.

REFERENCE: Max Kozlov,Longevity is in the genes: half of lifespan is heritable, Nature, (2026). https://doi.org/10.1038/d41586-026-00300-w