Science fiction author and physicist David Brin has pointed out a theoretical reason why we might expect anti-aging therapies that work in mice to fail in humans: the human lifespan is already a ridiculous outlier. Life spans vary with size, metabolism, and other factors, but one thing tends to hold constant: most mammals have a lifetime of about one billion heartbeats. Humans get a whopping 2.5 times that. An intervention would have to more than double a mouse’s lifespan just to catch up with whatever it is that evolution has already done to humans—if there are any simple mechanisms that can cause a mammal’s body to increase its lifespan, humans are probably already pushing them to their limits.
If you’re referring to median lifespan, we already know that many factors increase lifespan by up to 10-15 years in humans cumulatively: exercise, fasting, diet and so on. So it is highly likely that therapies (e.g. mTOR inhibitors) that potentially act through similar pathways will extend median lifespan.
In terms of maximal lifespan, I’m not sure of the strength of those theoretical reasons in light of mechanisms of aging such as cellular senescence, which is known to strongly contribute to the aging phenotype in mice and humans and which can be removed in humans now (2020 study).
Evolution is not optimizing for lifespan...only on gene transmission. So in general, I think arguments along the lines of ‘as humans we are hitting our natural limit of lifespan’ are poorly substantiated.
Science fiction author and physicist David Brin has pointed out a theoretical reason why we might expect anti-aging therapies that work in mice to fail in humans: the human lifespan is already a ridiculous outlier. Life spans vary with size, metabolism, and other factors, but one thing tends to hold constant: most mammals have a lifetime of about one billion heartbeats. Humans get a whopping 2.5 times that. An intervention would have to more than double a mouse’s lifespan just to catch up with whatever it is that evolution has already done to humans—if there are any simple mechanisms that can cause a mammal’s body to increase its lifespan, humans are probably already pushing them to their limits.
If you’re referring to median lifespan, we already know that many factors increase lifespan by up to 10-15 years in humans cumulatively: exercise, fasting, diet and so on. So it is highly likely that therapies (e.g. mTOR inhibitors) that potentially act through similar pathways will extend median lifespan.
In terms of maximal lifespan, I’m not sure of the strength of those theoretical reasons in light of mechanisms of aging such as cellular senescence, which is known to strongly contribute to the aging phenotype in mice and humans and which can be removed in humans now (2020 study).
Evolution is not optimizing for lifespan...only on gene transmission. So in general, I think arguments along the lines of ‘as humans we are hitting our natural limit of lifespan’ are poorly substantiated.