An Interview With Leonid Gavrilov And Natalia Gavrilova

Is overpopulation a genuine concern if life extension is achieved? We asked the experts.


Many people are concerned that vastly extended healthy lifespan might lead us to catastrophic overpopulation, and the best way to mitigate this fear is probably to talk to an experienced demographer. To learn more about this and other interesting questions related to life extension, we spoke to Drs. Leonid Gavrilov and Natalia Gavrilova, respectively Principal Investigator and Research Associate at the Center on Aging in Chicago University. Both of them have specialized in the biodemography of aging and longevity and possess nearly endless resumes.

Natalia and Leonid, your field of expertise is the biodemography of aging and longevity. What drew you to this field of research?

This is a scientific approach using demographic data and methods to get insights into the biological mechanisms of aging and longevity. We came to this research area because it allows us to obtain new interesting and meaningful scientific findings despite very limited funding.

Our first scientific publications on this topic were made in 1978 (four articles), so, this year, we celebrate the 40th anniversary of our research effort. In 1991, we published “The Biology of Life Span” in the United States, a book that has received over 600 scientific citations so far.

Assuming that therapies for healthy life extension are never implemented, what would you expect the age demographics to look like over the course of the next hundred years?

By the 2040s, we expect to observe population collapse (depopulation), particularly for people of European ancestry because of their low fertility rate. Life expectancy may stop increasing because mortality rates at ages 100+ will not decrease significantly. The economic and disease burden of an aging population will increase. There will be a strong demand to develop therapies for healthy life extension to resolve all these problems. However, more demographic research is needed to answer this question conclusively.


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Both of you authored a study titled “Demographic Consequences of Defeating Aging”. In that paper, you showed that the 2005 Swedish population wasn’t projected to grow by more than 22%, even given a radical life extension scenario, during the course of a hundred years. Could you summarize why the growth would be so slow despite life extension?

The key to population growth is the fertility level. If the number of children born to one woman is less than two on average, then the chain reaction of explosive population growth is not possible. Instead, the population growth becomes asymptotic, with an upper limit to the final population size.

Is there a reason why you chose Sweden specifically? Can this type of study be done on the global population, and what is required for that?

Sweden was chosen because it has very detailed and accurate demographic data, which is needed for population forecasting. This type of study can also be done on the global population if we find detailed and accurate demographic data on the global population as well as research funding to do this job. Perhaps the Lifespan Extension Advocacy Foundation could sponsor this project.

How much would you expect the world population to grow over the next hundred years, assuming extreme life extension?

We need to do a special study on this topic to answer this question (see above). Also, there is no single answer here but a set of possible scenarios that depend on particular assumptions about future fertility.

Even though there is no real consensus on the matter, there is a widespread belief that the Earth is overpopulated. Do you think that this is correct?

The Earth is overpopulated in some places, and it is abandoned in many other places too. The carrying capacity of the Earth depends on eco-friendly “green” technological progress. It should outpace the challenges of population growth.

Despite the fact that the world population is still growing, according to the UN, the growth rate has been nosediving for almost 60 years now, leading to slower and slower growth. Apparently, some areas, such as Japan, might even experience depopulation. However, some studies suggest that once the human development index reaches high enough levels, fertility goes up again, causing an increase in population. Do you think that this will affect future population growth?

If fertility goes up again, it will affect future population growth. As we said earlier, there is no single forecast but a set of possible scenarios, depending on particular assumptions about future fertility. The future is not fixed, and it depends on the choices we make now.


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Another direction of your research is how different environmental aspects and birth circumstances affect people’s lifespans. Could you please list the factors that were found to be beneficial for a longer life?

We found that people born to young mothers have a higher chance of living to 100 years compared to their brothers and sisters born by the same parents later. We also found that the season of birth is an important predictor of human longevity.

So far, the longevity record belongs to Jeanne Calment, who lived for 122 years. Since 1997, this record has not been broken, and it is somewhat counterintuitive, taking into account all the advancements of medicine. One of the questions we often get from our readers is how much human life can be extended; is there some sort of limit or not? What is your opinion?

This is an open scientific question and a matter of ongoing research efforts. Our most recent studies indicate that over the last 80 years, there has been no significant improvement in human survival after age 100, despite the spectacular progress of medicine during this time period. So, there might be some sort of provisional limit to further life extension.

Has the age of the oldest living person been generally increasing over time?

Yes, with the exception of two longevity outliers (Jeanne Calment and Sarah Knauss), the age of the oldest living person has been generally increasing over time. However, the pace of this longevity progress has declined over time. We will present these scientific findings at the Gerontological Society of America, which will meet in Boston on November 14.

There is no real agreement as to how aging should be classified; do you believe that it should be classified as a disease, classified as a syndrome, or have no medical classification?

Aging is an umbrella term for the totality of processes, each of which contributes to bodily deterioration with age. In other words, any process involved in age-related degradation acts as a component of the aging process. Aging is too broad a concept to be reduced to a single, specific disease. Not every disease is associated with aging, but any disease progression with age is related to aging; aging is the “maturation” of diseases with age.

There is a need for further scientific meetings and discussions with WHO experts to find out whether aging could be classified as a syndrome or have no medical classification.


The field of rejuvenation research has gained a lot of momentum over the past 10 years, and with some luck, the next 10 years might even see some first-generation rejuvenation therapies reaching the clinic. What sort of progress in this field do you expect over the next 50 years?

In our vision for the future, we are encouraged by the prediction of American biogerontologist Steven Austad that a longevity record of 150 years may be reached by 2150. This may happen thanks to future rejuvenation therapies. However, to achieve this, we need a long period of peaceful and prosperous development. The current peaceful situation is fragile, because there is still a risk of accidental nuclear war.

How can the community of people interested in healthy life extension, and society as a whole, help accelerate the pace of aging research and foster the development of therapies to prevent or cure the damages of aging?

The best way to accelerate the pace of aging research and the development of anti-aging therapies is to increase funding for them. Society as a whole can help to do this by advocating for more international collaboration in this area between countries instead of wasting their resources in a mutual arms race.

Thank you so much to both Leonid and Natalia for taking the time to answer our questions. While we can’t promise to sponsor a study on the effect of life extension on the global population, we certainly hope that one day we may at least have the resources that would be required, which may be possible if enough Lifespan Heroes help us out.

About the author
Nicola Bagalà

Nicola Bagalà

Nicola is a bit of a jack of all trades—a holder of an M.Sc. in mathematics; an amateur programmer; a hobbyist at novel writing, piano and art; and, of course, a passionate life extensionist. Nicola produced the Lifespan.io YouTube show - LifeXtenShow until 2021. He is no longer part of the Lifespan.io team having left in 2021 to seek new opportunities and challenges.