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Tyler Volk: I’m Tyler Volk, Professor of biology and Environmental Studies at New York University, Author of several books; Death and Sex, Gaia’s Body, Tour of Physiology of Earth, Meta-patterns Across Space, Time, and Mind.

Question: Why do atoms have such long lives, but organisms die

Tyler Volk: Yeah, well atoms have such long lives because they are made of fundamental particles that themselves are long-lived to infinity. There are some issues about the proton having some kind of a long decay constant, but organisms are dynamical systems made of parts, enzymes that interact very volatility, they have to be rebuilt constantly, the organisms themselves have to have constant inputs of matter and energy in order to carry on to regenerate these complex internal dynamics that they have going all the time. 

Question: On the molecular level, what causes humans to die

Tyler Volk: The body wears down after a while. There are repair mechanisms that we have. You cut your skin; you’ll notice that your skin repairs. You break a bone; the bone repairs. Many of these repair mechanisms, as any of us who are aging know, become less efficient as we get older. And one reason that diseases become more statistically probable as we get older has to do with a general running out of these repair mechanisms; the efficiency of these repair mechanisms that were with us from our birth as human beings, but have themselves a kind of longevity that varies from individual to individual. But you can see, most people when they get to be around 70, 80, or 90, they’re going to look old. There are some certain expectations. So there is some commonality we have as humans as a species in terms of shared genetic capabilities of repair our bodies that wear down over time. 

Question: Why do human beings have so much trouble embracing death?

Tyler Volk: We have a lot of trouble embracing death because we know it’s going to happen and this really flies in the face of our urge to live which we’re coming out of billions of years of organisms being successful at living and passing on progeny and suddenly in the last 30,000 years, 100,000 years, we don’t’ really know, some of the earliest detailed elaborate burials were 30,000 years ago. Human beings not only died, but they know they’re going to die. Of course, the world’s religions have not liked this fact and so try to build up various mythologies about afterlife. But I think the basic reason is just it’s abhorrent to us. We’ve built up the self. We’ve had, for the most part, enjoyable experiences. There’s more to experience. We have loved ones, we have roles in life and suddenly to know that that’s all going to ending; to be snuffed out at some point, really puts in a primal dilemma to our minds 

Question: How do you explain scientific movements to end death

Tyler Volk: Yeah. I think some of these urges to conquer death, or to live a long time, have to do with this primal fear of death itself. Of course, we want to stay healthy, it’s painful to get ill, it’s painful to get old, to have injuries that don’t heal so well, to have permanent pain. So, some of that is overcoming just the sense of un-wellbeing that happens to us. We want medicine to make progress and keep up healthy. 

But the other factor is wanting to live for a long time and maybe forever. It’s not clear what we would do, or how that would affect our lives. Sometimes science fiction writers explore those kinds of themes. But I see that as incredibly natural and I do think it’s going to – not that we’re going to live forever necessarily, I don’t have an informed opinion about that. But from my reading, typically in nature magazines, science magazines and some of the biological findings and also what I see happening with genetics and genomics research in my own Biology Department at NYU, it’s clear that advances are going to be coming to help us fulfill some of these dreams we have had since the upper Paleolithic of living for a long time. 

Question: After researching death for so long, how do you address your own mortality

Tyler Volk: I don’t believe in any afterlife for myself. I don’t think my mind continues after I die. That doesn’t feel particularly good. So, my recourse is to go by who I am, what we have, see myself as a product of billions of years of evolution and during which time this evolutionary process has discovered and utilized in various ways forms of death in support of life. It doesn’t make it something that I look forward to, I definitely do not, but I can see myself part of a larger picture. And I think there’s a lot of gratitude I’ve developed as a result of understanding how death and life are intertwined and doing some of my investigations that I’ve written about in how death and life are closely coupled with each other in the support of life that we know. 

Question: What is the importance of death to evolution

Tyler Volk: Without death, there’s no evolution; at least as far as we know it. One could hypothesize some organism that might live forever that would butt off mutations, but evolution as it works now, operates by organisms dying and the next generations carry on. And those generations, for the most part, have variance in them and then those variants are selected. So you can get a sort of design happening out of evolution over time, or you can get adaptations occurring that did not exist. So, for example, at one point there were no large creatures such as us, or elephants, or dinosaurs, or amphibians walking on land. There were vertebrates called fish in the world’s oceans and then they were about to emerge and to go up on land. The only way that could happen would be many generations dying. Many generations of fish with certain kinds of limbs dying and there were slow variations accumulating to turn those fish into tetrapods, four-legged creatures, that would either being the mud, or in the shallow water and eventually crawl up out of the ocean. So, death has really been an essential ingredient to the evolutionary process. 

Question: Why are cells constantly being recycled in our bodies

Tyler Volk: Cells are dying in our bodies all the time. The rates that they die and are replaced vary depending on what organ we’re looking at. So, for example, the skin – the cells in the skill are turned over approximately every month of time. New cells are migrating outward and old cells are sloughed off. And that makes some sense. The skin is subject to a lot of wear and tear and abrasion; it is in contact with a harsh environment. So for the skin to have some kind of way to renew itself is very essential to having a border around our bodies. Organs, such as the brain and the heart, the cells there – many of those cells, either aren’t intended to die, they don’t really have turnover. And some part of the brain it is being discovered, the cells do have turnover, but clearly the places such as the brain and the heart in which the interconnectivity of the cells and the cells working together, is really crucial in those organs that turnover is a lot less. 

So the body, through the evolutionary process, has tuned death in a kind of adaptive manner to insure that these organs are healthy depending on what function these organs have to play. 

There’s also a role of death in development that all large creatures that we know, have. A really good example is our hand with our five fingers. The fingers do not grow as stems of a tree might grow in which they start small and they just grow outward. You might think that happens that they are starting – of course they’re small in the womb. But instead, the hand starts off as like a paddle. Sort of a thick, very thick ping-pong paddle. And the fingers in this embryonic stage are formed by the cells in between dying off. So the first extension of the fingers is formed by a developmental form of death. It’s a programmed death. This is death being controlled. It’s not just the turnover that I described earlier of the skin turning over, but these cells die in between. And they don’t die and then fall away. They die and are reabsorbed into the hand, and so it’s a form of recycling. But the formation of the hand; and this is true of the human hand, the mouse hand, there’s many examples of this. And if there is not controlled, what’s called programmed cell death, very precisely sculpting the developing organism, it’s been show that these organisms can die that death is absolutely essential in the early developmental process. 

Question: How is death essential to life? 

Tyler Volk: Yeah. One thing I write about is the fact that there’s not just one death, there’s different forms of death. There’s the death of our bodies that has to do with the essence of us being a large multi-cellular creature, a metazoan having to do with the slowing down of the repair mechanisms. But there’s also a lot of death inside our bodies as we live. The death of our cells, skin cells are always sloughing off, internal cells are dying, cells that are abhorrent; go through a kind of suicide program. So, there’s a lot of death inside our bodies all the time going on that is essential to our life. And this is somewhat of a different death from the death of our bodies as large organisms. 

And then there’s also death on small scales, in bacteria, that either have to do with running out of nutrients that is an inadvertent form of death, but there’s also kinds of bacteria which are multi-cellular, and they can program cell death as they go into reproductive phases. So, one issue about death that I find particularly fascinating is that there is not just one kind of death, but death has been really incorporated into life in various forms depending on what scale of nature we’re looking at. 

Tyler Volk: Yeah. One thing I write about is the fact that there’s not just one death, there’s different forms of death. There’s the death of our bodies that has to do with the essence of us being a large multi-cellular creature, a metazoan having to do with the slowing down of the repair mechanisms. But there’s also a lot of death inside our bodies as we live. The death of our cells, skin cells are always sloughing off, internal cells are dying, cells that are abhorrent; go through a kind of suicide program. So, there’s a lot of death inside our bodies all the time going on that is essential to our life. And this is somewhat of a different death from the death of our bodies as large organisms. 

And then there’s also death on small scales, in bacteria, that either have to do with running out of nutrients that is an inadvertent form of death, but there’s also kinds of bacteria which are multi-cellular, and they can program cell death as they go into reproductive phases. So, one issue about death that I find particularly fascinating is that there is not just one kind of death, but death has been really incorporated into life in various forms depending on what scale of nature we’re looking at. 

Question: How does the human lifespan compare to our closest primate relatives

Tyler Volk: Our closest primate relatives are the chimpanzees and gorillas, with the chimpanzees being closer to us genetically. They’re natural life spans are approximately half of ours. And that’s of some interest because the chimpanzees are a bit smaller than use in body mass and the gorillas are larger than us in body mass. We can’t know for sure the lifespan of the last common ancestor of humans and chimpanzees, but there would be some – you might guess that it would be half of what our current lifespan is. 

Question: This is the natural lifespan

Tyler Volk: Let’s make a distinction that we’re not talking about the infants dying – small children dying of diseases or death by predator, but the natural lifespan in normal, almost perfect circumstances. So looks throughout history, there’s always been people who have made it to age 80 or so, or longer, even though the average life expectance at birth, given all factors, given diseases, predators, and then the diseases of aging and senescence, even those have been more prevalent, the natural lifespan has been approximately the same as it is today. The maximum – the natural maximum lifespan, which is different from life expectancy at birth which can vary even in different countries today. Russia right now has a relatively low life expectancy, people in Africa have a relatively low life expectancy, Japan has the highest life expectancy of any nation now. So, there’s variations, but take those individuals into relatively equal healthy environments and they’re all going to live close to the same age. 

Question: And this natural life expectancy has not gone up

Tyler Volk: Right. The natural life expectancy has not gone up very much. However, since the diseases, some of the diseases that modern medicine is tackling, such as heart disease and cancer, become more and more the diseases that we are dying from in elderly age, we can be expected to live longer without trying to genetically go in and manipulate our metabolisms in some ways. There’s a lot of work being done on what is called caloric restriction. 

There’s a lot of research being done on what is called caloric restriction. Animals that are given reduced calorie diets, and yet have the essential nutrients that they need, live longer. We haven’t been able to do the experiments on human beings yet. There are people out there attempting to do this by themselves. You can get books and join organizations to try to enhance or help you – how you can make recipes that satisfy your hunger and have caloric restriction. 

I’m saying this to show that there are probably going to be ways that science is going to understand this natural demise, this metabolic demise of our repair mechanisms that set up our natural lifespan that has kept it pretty constant for a long time. And we’re probably going to bring that forward. We’re going to live longer lives I really think. I don’t know if it’s right around the corner, that’s hard to judge. You’ve had people on your show that are saying what they think it’s going to be. But just from reading the literature, it’s clear that these kinds of advances are going to happen. 

Question: Why do lifespans vary across species

Tyler Volk: I find it really fascinating to consider why certain species of mammals live longer than other species of mammals. For example, we live longer than dogs, dogs live longer than mice. Often there’s a tendency, or trend, that the large creatures live longer. But you might try to say, from an evolutionary viewpoint, that it would serve creatures well to live for a long time. They can reproduce more, let’s say if they live for longer, and therefore can pass on their genes for even a longer period of time. But we know that there’s a large variation in when creatures senesce and what the average lifespan is. And it turns out, there’s two ways of looking at this. One is to go down deep into the organism and ask, why are the cellular repair mechanisms breaking down when they do; a couple years in the case of some small mammals. For us it’s many decades, 70, 80, 90 years. But the other way to look at it is that these cellular repair mechanisms themselves must be subject to evolution. We know that these repair mechanisms vary among creatures. 

It’s been shown that birds, for example, have better cellular repair mechanisms than mammals do. The current reasoning has to do with the ecological niche that a certain creature lives within as a member of its species. And if that niche allows the possibility for many of the individuals to live long lives, then it has been worthwhile for the evolutionary process to build in better repair mechanisms for its cells to allow it to live longer. So, if I go back to the example of birds, the phrase that’s sometimes used in the technical literature for birds and why the birds live so much longer than the mammals of the same body mass is the phrase, “fly now, die later.” And the idea being that birds in the trees and in flying have very good predator escape mechanisms that make it worthwhile for the birds to have cellular repair mechanisms inside their bodies that allow this longevity for a certain body mass to occur. 

And what I find fascinating here is that there is a tuning of the creature’s niche, or environmental lifestyle and the possibilities that that lifestyle has for longevity and the very internal, deep internal, cellular repair mechanisms. The enzyme repair mechanisms issues about oxidative stress that either facilitate that longevity or cut the life short. One particular example I think is very telling is the case of the several species of the Pacific Salmon that live in the Northwest United States, Canada, and in Alaska. These salmon are born in upstream fresh water streams, or rivers. Very quickly, they go down to the saltwater oceans so they have a transition from fresh water to saltwater ocean. They live in the ocean for typically two to three years, depending on the species. They find their way back through a process somewhat mysterious, but maybe having to do with the water chemistry of their birth stream. They find they’re way back to their birth stream and at that point, the males and the females undergo some physiological changes. Their bodies turn more red, they bolt out – the males, the jaws get very bulked out. And if you look at what’s happening hormonally in them, it’s like they’re on an incredible dose of steroids. They’re revved up for this upstream swim that we see dramatic pictures of where they’re swimming these rapids and can they hop this dam or not, or do they have ladders to go up. 

They go upstream and the males and females mate. The females lay the eggs in these little depressions in the sediments, and then the males and females all die. They do not go back downstream to say, live another year and come back upstream. And you might think that what’s happening is a real waste of these salmon. It’s been shown that they add some nutrients to the stream water, but they’re not dying to add nutrients to the upstream waters, they’re dying because what’s happened to their bodies has put such stress on their bodies that they’ve done this incredible swim and put all their efforts into getting to a place to mate and into mating. And this is a wonderful example of how it’s important for these organisms to remain healthy up until sex, up until successful sex and reproduction and then it’s possible to die. Senecessence is, it’s possible just after sex. If there were senecessence before sex, that creature is out of the evolutionary game, obviously. But you could have death following right on the heels of sex and in the case of the salmon, this has occurred in evolution. So, we can see here that there is a tuning between death and when senecessence that happens and the ecological, or environmental, circumstances that have resulted in various adaptations in the case of Pacific Salmon. A really dramatic case. 

Question: How do the dead pervade our ecosystem

Tyler Volk: Walk in the woods and the whole forest floor is filled with the litter of the trees, the dead material from the trees that’s fallen down to the forest floor and is feeding the creatures in the soil. There’s a lot of life in the soil, many species of bacteria we don’t yet know, a lot of worms, other creepy crawly things in the soil. They’re basically living on the ****, the dead material that’s coming from above either in the form of dead parts of plants, entire plants, dead animals, waste products from animals, mushrooms rise and then die and fall back to the forest floor. And so the whole ecosystem is working by the efficient recycling of the dead. We can put a number on that in the following way. We can put a number on how the recycling of the dead actually enhances life. We can see it happening on the forest floor, but I’ll just walk you through the number. 

The total amount of carbon that photosynthesizing plants and algae require on an annual basis is about 100 billion tons of carbon that they incorporate, they either pull it in from the ocean water in the case of algae, or pulling it in from the air going into the leaves of plants, in the case of trees and other plants on land; about 100 billions tons of carbon a year. We can ask, what if plants had to rely on, what if the plants and algae had to rely on new carbon that was coming up from deep going into the atmosphere and ocean from volcanoes, from the dissolution of rocks that contain carbon? And that amount is about one-half of a billion tons per year. So, where the photosynthesizers to rely on this carbon coming up from deep that’s fresh going up into the ocean and atmosphere? That’s only ½ billion tons per year. Current abundance, the beautiful abundance of green life on the planet is requiring about 100 billion tons of carbon per year. So, it’s a 200 to one ratio. And they get this 199 parts over the half billion tons that come up fresh from below from the recycling of organisms. From our breaths, from the breaths of the elephants, the eagles, from the breaths of the snakes, from the breaths of the bacteria, or the gases being put out as waste products from bacteria. That’s really the bulk of this recycling, from the bacteria in the ocean and the soil. 

And so, one can say that from the efficient recycling of the dead and the fact that the creatures that are putting forth Co2, such as ourselves, are living on the dead because we are going to eat animals that ate the plants. So, there’s death to support our bodies, that this webbing of nature in which death becomes life and life becomes death around and around, enhances life we can say approximately 200 times. There’s approximately 200 times more life on the planet with this networking of life and death that happens. 

Question: How large of a role do decomposed human bodies play in this

Tyler Volk: Humans are part of this, but we are relatively small in terms of our bodies decomposing and going into the cycle. The big carbon fluxes are really in the realm of all plants, the bacteria in the soil. We are creating more and more carbon fluxes – we are putting more and more of the earth’s carbon fluxes in these earth cycles under our own control with taking over 10% of the planet, using 10% of the planet for agriculture and another 10% to 20% for grazing of various kinds and the fisheries. So, with our population, we are bringing more of this death and life cycle under control. The actual contributions of our bodies dying, of course, are relatively small compared to these larger pictures.

Recorded on: February 22, 2010
 

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