Over the last decade, an increasing number of clinical trials and investments have focused on technologies striving to increase human longevity—to increase our lifespan. Just today, the UK-based startup Juvenescence closed a $100 million Series B round. These researchers and investors have made incredible scientific strides in determining the causes and effects of ageing on the human body, and what steps we can take to prevent it.

But despite this exciting scientific progress, something about trying to lengthen our lifespan just feels wrong to me. No, I’m not religious, so it’s not based on an objection to humans playing God. But longevity research makes me feel uniquely wary, like humans are approaching a kind of science that is best left alone.  

Before I analyze my own discomfort with the topic, let’s talk a bit about the existing technologies. Laura Deming, founder of The Longevity Fund, a VC focused on longevity research, has a wonderful summary of the field as it stands. The major areas of research include (among others) senolytics, using drugs to destroy ageing cells; parabiosis, providing blood transfusions from younger, healthier individuals; telomeres, which are genetic sequences found on the ends of chromosomes whose lengths are correlated with cell longevity; as well as areas of regenerative medicine such as stem cells and organ regeneration. Through manipulating these systems, scientists have found pathways to extend years of life and also to improve the long-term health, mostly in mice and, in some cases, in non-human primates. If transferable to humans, these technologies could target the pathways that result in ageing and rewire them to prevent degenerative processes.

It is important to realize that much of this discussion relies upon what the definition of ageing is. The Gompertz-Makeham law of mortality suggests that ageing is the exponential increase of the age-dependent component of mortality risk over lifespans. J. B. S. Haldane, Peter Medawar, and George C. Williams developed the evolutionary theory that ageing was the result of a lack of selection pressure, because while an inherited mutation that negatively impacted your ability to have children would be selected out over time, mutations that only appear after an age at which most reproduction has already occurred will not experience the same selection pressures. Dr. Jonathan Flacker, amongst others, has argued that ageing shouldn’t be classified as a disease because the very idea of a disease suggests that it is not a normal condition, while ageing is ubiquitous to humankind.

Regardless of how we define it, ageing doesn’t occur in a health vacuum. Nine traits associated with ageing have been identified, but rather than just correlating to the life-history of humans, many of these traits can also result in debilitating diseases, such as Alzheimer’s and cancer. So while these areas of research are targeting the ageing process, they could also potentially target the many diseases associated with ageing. Which brings us to an important point of distinction:

Are we extending our years, or our healthy years?

I believe that many scientists would say, both. Aubrey de Grey, a leading researcher in longevity, has suggested that his research could eventually offer an additional thirty years to the average 60-year old, but with the body of a 30-year old. In other words, live to 90, but without the same level of health degeneration. This seems a lot less controversial than suggesting humans could, for example, live for 1,200 years.

Although, perhaps even the idea of a “right” age to die is a product of fantasy. Just looking at the number of deaths prevented by the invention of vaccines demonstrates that we have been comfortable manipulating human life expectancy for decades. Because the average life expectancy at birth for American men was 40 in 1900, does that mean we should have stayed there? The housefly lives for an average of 28 days; the Greenland shark can live for 400 years; it’s unclear if the Ocean quahog ages at all. Why should I determine that human life expectancy as it stands now is somehow the natural way things should be?

But I can’t stop the off-putting feeling that the idea of extending the human lifespan gives me. Perhaps as an evolutionary biologist I just have a feeling that progress comes through the cycle of death and procreation, and to escape parts of that process are to prevent the progress of our species. Or perhaps it is the sense that there are millions of people around the world experiencing significantly shortened lifespans than others, and research should be focused on equalizing the playing field before we make the extremes any larger. If we find a way to extend our lifespans, will only the wealthy be able to afford it? Could we end up creating two separate species, those who live longer and those who don’t?

Or perhaps, as a nonreligious person, my hesitation arises from the feeling that this life is precious and valuable because it is all we get. And if we start artificially extending that timeline, we are risking the loss of the pressure that ultimately drives us to be good people. Is the awareness of our shared mortality the last thing keeping people accountable to one another? Does the promise of forever make us less accountable for the choices we make?

I would never disagree that the investigation of diseases like Alzheimer’s should be a priority, and if we classify that as a kind of longevity research, then there are kinds of longevity research that I heartily agree with. Maybe I am stating the obvious, but I am much more invested in these technologies curing the diseases associated with ageing rather than treating ageing as a disease in and of itself. Haven’t we read too many classic tales—The Picture of Dorian Gray comes to mind—about the risks of humans attempting to surpass their own mortality?

The progress on longevity is incredible, and I hope with all my heart that it delivers cures to devastating age-related diseases. But I would be lying if I said there wasn’t something about the search for the fountain of youth that makes me feel like as if we, as a species, are overstepping our bounds.