IT WAS as if someone had turned back time. Once-faltering paws gripped objects with renewed strength. Hearts and livers regained their youthful vitality. Fuzzy memories sharpened. And according to Steve Horvath’s experiments, the biological age of his rats had been cut in half. “I was stunned,” he says.
Horvath, an anti-ageing researcher at the University of Los Angeles, California, and his colleagues saw these startling effects in 2020 after injecting old rats with blood extract from younger rodents. And they are not alone. A growing number of labs are reporting findings that indicate we might have been thinking about ageing the wrong way.
Rather than the result of the accumulation of wear and tear as time ticks by, ageing could be driven by the forces that build our bodies in the uterus and maintain them after we are born. In youth, they help us, but a failure to switch them off brings the deterioration of old age. This new view offers a deeper understanding of what ageing actually is and the possibility of slowing or even partly reversing it.
While the processes that drive ageing are a matter of debate, biogerontologists do agree on one thing – what it looks like: the progressive decline in physical function that most creatures experience with the passage of time. They have catalogued the cellular changes accompanying this decline, which include crumbling chromosome ends, damaged and unstable genomes and changes in the way that cells sense nutrients.
For many years, biologists have favoured the idea that these hallmarks were the result of damage such as that wrought by reactive molecules called free …