The possibility of evolved death has fascinated me. The idea came about when I learned that fires are sometimes an integral part of certain ecosystems. This had me wondering if mechanisms of mortality could evolve. In fact, throughout nature there are seemingly cases where this is true and many more cases where it might be true. From the origin of life, to the origin of death, join me on a journey into the psychedelic nature of evolution as I ponder whether we have evolved to die!
While watching a video from Science Magazine about how fires can help increase the biodiversity of an ecosystem, a question emerged in my mind:
Did we evolve to die?
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Before we explore this, there are two concepts that tie into this question that led me to wonder about this possibility. This topic ties into my recent fascination with the concepts of adaptive radiation and The Phoenix Effect. Adaptive radiation is a sudden diversification of species to fill niches, often occurring after mass extinction events. Normally, occupied niches tend to check each other and create a system that is stable, with only slow changes in evolution. These occupied niches essentially block adaptive radiations from occurring. The most glaring example of an adaptive radiation that people are familiar with is the extinction of the dinosaurs which gave rise to a radiation of the mammals.
As for The Phoenix Effect, it is essentially analogous to an adaptive radiation of the mind. It is the notion that psychedelic drugs induce their most influential effects by reverting the mind’s development so that we are like a child or even a newborn infant again. The psychedelics may strip away the conditioning that we have acquired from the environmental influences, at least for some duration of the their effects. This can allow for habits, addictions, compulsions, and traumatic conditioning to dissolve in such a way that we can see what life was like without the influence of these things. The effects of psychedelia are often described as a mind death and rebirth, like a mind extinction event that may spur a subsequent cognitive adaptive radiation.
Moving back to the idea that fires promote biodiversity in an ecosystem, it is essentially analogous to the adaptive radiation. Most aptly, this effect is literally about the ecosystems partially burning down, where biodiversity may rebirth itself, like a phoenix. The fires may essentially prevent any single organism from “monocropping” itself throughout the entire ecosystem.
Why might we evolve to die though?
Death itself may originally have been something that is inevitable, especially for individual cells. In the same way that cells reproduce, multicellular organisms reproduce. This is a kind of genetic attempt at ‘immortality’, though not the immortality of the cell or the organism. Instead, the genes live on, albeit not forever as we see many extinctions, but at least much longer. While some genes meet their extinction, the chemical process of life is still continuing for what seems to be 3.7 billion years.
Even the cells in our own body reproduce and die, even while our organism lives on. This is particularly interesting. It seems to suggest that we could live longer, but our bodies die still yet. Why, then, do we die? After all, something that lives longer might even be able to reproduce more times than if life was shorter. Of course, having children later often has consequences, but presumably we could develop adaptations that resist those problems too.
Many have argued that the selection pressure to survive after reproduction diminishes because the genes have already passed on. The first pressure that may enhance the longevity of the parent is, well, parenting. Parenting can enhance the reproductive success of the offspring by providing protection and support, and surviving longer as a parent can extend the amount of support the parent gives. In humans, it has been proposed that longevity has evolved from grandparent support (Kim et al 2012). Some researchers have suggested that sociality of a species may promote the evolution of longevity (Lucas & Keller 2020). Furthermore, isolated social animals sometimes die faster, like in the case of humans (Holt-Lunstad et al 2015) and in the case of ants (Koto et al 2015). It is important to note that ants can live on their own but this appears to stress them and induce side effects that reduce longevity, which is similar with humans as well.
These are selection pressures to extend life, but what about selection pressures to die?
Selection Pressures For Death
What are fires, but a chaotic blight of energetic death to living systems? It isn’t that fires kindle biodiversity, but rather it is death that kindles biodiversity. Fire is just a means for death. While natural selection may not seem to select an ecosystem for biodiversity directly, there are still benefits that a biodiverse ecosystem has compared to one that lacks biodiversity. Look at the case of monocropping, where humans will breed a plant species to be entirely clone-like. There are major downsides to this, specifically the entire harvest of plants can easily share the vulnerability to a disease and all die. This is actually happened with the common banana which got Panama disease that threatened the species existence.
I actually started to wonder if biodiversity somehow could be selected for. There is an argument that flammability actually evolved (Pausas et al 2016). The case of fires enhancing biodiversity could be related to the way that environmental change seems to accelerate evolution (Cameron et al 2013). This may be like a small-scale adaptive radiation from the sudden destruction of niches or the sudden addition of untouched niches. It could be that being flammable is better than becoming a monocrop. It is possible that biodiversity is selected for because of the way that complex ecosystems would outlive and thrive more than an ecosystem that lacks biodiversity. For example, a loss of biodiversity is thought to play a role in the ongoing Holocene extinction, where the drop in biodiversity is resulting in a loss of natural capital (the soil, air, water, and so on). In this sense, gene-level selection could occur alongside ecosystem-level selection. The total collapse of an ecosystem means the end for the genes inside the ecosystem.
Side question: Did humans help bring about the Holocene extinction by not dying enough and monocropping themselves and their favorite domesticated species of plants and animals across the globe?
Microorganisms took very long to evolve multi cellularity. What if this is because immortality was a first focus? There was a 2 billion year period before multicellularity evolved, which seems quite an extreme amount of time for what seems to be a simple transition. Perhaps the organisms of this period were in some kind of homeostasis or maybe they were evolved to be almost immortal. It is thought that the evolution of predation in unicellular microorganisms may have inspired multicellularity to evolve as a defense mechanism (Bengtson 2017). This may have played a role similar to fire in boosting the biodiversity of the ecosystem. Predators are in some sense a living fire, metaphorically of course. Predation may also be one of the earlier forms of evolved dying, except that it is not self-death.
Before predation, it may be that the unicellular life would multiply endlessly, to the point of catastrophic extinction events. The lifeforms may totally consume their resources and create massive stockpiles of byproducts that are toxic to themselves. The first stages of the evolution of life may have involved reactions to these problems. It has been argued that anaerobic life came first on Earth and then eventually they produced so much oxygen as a byproduct that it was toxic to themselves (Fischer et al 2016). This is thought to have created the selection pressure that gave rise to aerobic organisms. During this time period, these kinds of self-extinctions may have been one of the first evolutionary pressures in general.
The evolution of predation may have been critical in generating stable ecosystems and helping to prevent the overuse of resources by the prey species. Predation, fires, and other death mechanisms may also help keep lifeforms in check and promote biodiversity. During the Cambrian explosion, Animalia diversified and colonized the Earth. It is thought that this is because of the emergence of predation in animals (Fox 2016), which turned on the evolutionary arms race that drove rapid evolution.
As for selection pressures for the evolution of death, consider the case of the black widow. During mating, the female spider will often consume the male after intercourse. This urge to consume the male may evolve in the female because it enhances the possibility of spreading her genes and having her children. The researcher Andrade has argued that there is sexual selection for adaptive suicide in the male spider (Andrade 1996). Meanwhile, further research showed that males often resist this destiny, sometimes by mating with younger females who tend not to eat them (Biaggio et al 2016). In this case, the species may have conflicting pressures for and against dying, depending on whether it is the male’s or female’s genes. Though, we aren’t like black widows. We don’t eat our mates. Not many species take on this strategy, but it does show that a selection for death is at least possible.
One of the stranger selection pressures for death comes from the fact that the mature organisms would be occupying niches and competing with their own youth. The mature organisms would hypothetically have built up more power and experience overtime and dominate over the youth, unless they evolved the tendency to become frail and face death. The death cycle allows for the old generations of humans and all organisms to submit to the new generations, to allow them to reign and take over the niches that their ancestors occupied in the ecosystem. Parenting and grandparenting may be one way in which a species can overcome this selection pressure by helping instead of competing. Shorter life cycles in animals may be especially selected for in environments of scarcity, where the competition is much stronger. In fruit flies, an experiment found that evolution favored shorter lifespans in the case of dangerous environmental conditions, as defined by high extrinsic mortality rates (Stearns et al 2000).
This idea that the old die to make way for the new generations was proposed by Weismann in the late 1800s (Weismann 1882). The idea has been termed programmed aging and is controversial. More recently, Idan Solon has proposed the term ‘genetic bandwagoning‘ to refer to the case in which an individual forfeits some or all of its’ resources like mates, territory, or food, to neighbor individuals that may be of superior quality (Solon 2019). Idan continues to argue that blind altruism may evolve through these mechanisms. He also argues that there could be an evolution of suicide in the case of genetic bandwagoning. This is similar to the idea of grandparenting, except the support that is given by the dying individual is the removal of the self, which might ordinarily infringe on others.
As mentioned previously, socialization may often select for longevity because the animals support each other’s fitness. On the other hand, being a burden to others might select for suicidal ideation (de Catanzaro 1995). This might suggest we evolved to feel like a burden and that this feeling is geared towards adaptive suicide. One argument for evolved suicide in humans relies on the idea of kin selection. Kin selection is where genes that don’t produce fitness benefits for the individual organism can help genetically related organisms who also hold these genes as to help these genes pass on through the other organism. Kin selection is often explored as an explanation for the evolution of altruism. The extreme case of this may be eusocialism, in which species such as ants have evolved entire castes that do not breed and thus live purely as self-sacrificial for the sake of the queen. So the argument is that altruistic suicidal acts can evolve through kin selection (Lankford 2015). This includes the idea of genetic bandwagoning as well as self-sacrifice in other ways, such as in battle to defend your family, like soldier ants.
It is important to note that it isn’t clear that human suicide benefits the fitness of other family members, as this is quite a traumatic event that might harm fitness of family members. Though it is also important to note that this is something people would not likely be comfortable talking about, as it is clearly upsetting and if someone were to express that there were benefits to a family member’s suicide, they would be seen as antisocial or sociopathic. Because of this, we aren’t likely to hear much about any possible positive impacts of familial suicide in human culture.
Speaking of adaptive suicide and extreme altruism, there has been a recent rise in environmentalist death cults and ideologies that propose that human influence on the Earth’s ecosystems must be stopped or at least reduced. One such cult is known as the Voluntary Human Extinction Movement. This would suggest that it isn’t purely an evolved pattern, but even a rationalized perspective that many humans take on. There are people who believe that reducing the population will ultimately help us as a species or help the entire planet of ecosystems that we influence.
Another possibility in the evolution of death is that inheritance generates a selection pressure for earlier death. You could imagine that wealthy families who’s children receive inheritance during the prime times of their lives might be able to breed better and reap many benefits or get a head-start over the competition at the very least. A positive selection for earlier death in parents or grandparents could exist in these cases, though due to the nature of tragedy and its’ impact on mental health there may be drawbacks as well. Due to this it is probably that grandparent deaths are more beneficial than parent deaths in this case. In the case of the gene-level evolutionary process here, it may be that parents who die earlier will be less invasive in the lives of the children, thus allowing a better chance for the childrens genes to pass. This would be kin selection as well.
This pattern has echoes in distant unrelated animals. In one species of spider, the newborns eat the mother (Junghanns et al 2019), which may serve multiple roles. It gives the spiders a similar head-start like the case of inheritance and it removes the mother from the ecosystem. Another related pattern that has been argued to be evolved in other species is adaptive suicide. This has been observed in bumble bees that have contagious infections (Poulin 1992). They will often leave the hive and die somewhere else rather than risk the death of the entire colony.
An even stranger case is semelparity, which refers to a breeding pattern in which the organism dies abruptly after breeding. This famously happens with salmon, but it also happens in some obscure mammals. When salmon die after breeding, the pools that contain the eggs are in some sense fertilized with nutrients for the progeny. It was observed that the dead salmon decompose to allow algae to thrive, which the salmon babies feed on (Kline et al 1997). So the Salmon who die in these breeding pools will be more likely to pass on their genes than surviving ones. This is another case of evolved inheritance.
Pandemics might be like fires.
What if the propensity to unleash pandemics upon other overly ‘monocropped’ species has evolved like the way flammability has evolved? It has been said recently that humans pushing onto nature is a contributing factor for the ongoing pandemic. Perhaps when species like bats harbor various dangerous contagious pathogens it may help to maintain ecosystems from total collapse by annihilating some of the species that has become too prevalent. This could be a kind of anti-homogenization mechanism for ecosystems, much like the role of fires. Such systems like this would certainly outlive a system without such mechanics. By hosting contagions, an organism can weed out invasive species that are colonizing the ecosystem.
In the case of the ongoing pandemic, it has been argued that human farming and land use has increased the risks of exposure to pandemic contagions like we face today. This idea isn’t new, as it has been argued that the loss of biodiversity should give rise to zoonotic diseases even 6 years earlier (Morand et al 2014). It could be that zoonotic illness leads to increased biodiversity and helps check overpopulating species that further induce a loss of biodiversity. In this case, ecosystems that have zoonotic illnesses may outlive ecosystems without such illnesses. As one redditer put it: in the same way the body produces antibodies to fight off infections, the ecosystems produce viruses to fight off overgrowths of species that become too prevalent. Could a Gaia immune system have evolved?
Culture needs radiation too.
I’ve recently explored the idea of memetic adaptive radiations and how pandemics (that disrupt culture, but without killing everyone) could promote such memetic evolutionary events. Rather than a pandemic exterminating and disrupting the many addictive ways of life we cling onto, death itself may clean away the cultural niches to allow the culture of the youth to radiate onto society. Pandemics may be like memetic and in some cases biological infernos. In Adaptive Radiation: Beyond Evolution I argued that the Renaissance came after the plague, a memetic extinction event, as an adaptive radiation of culture. Something I overlooked was that we might have evolved a mechanism for niche holders to be erased, because of the benefit that allowing the youth to claim their place in the light of the ecosystem has. Rather than a plague that disrupts the habitual flow of daily society, it is biological death. With each cycle, death allows us to undergo a micro-renaissance.
Cultural evolution may be facilitated by biological death as well. The old humans of the earth accumulate power over their lifetimes and have the ability to control much of culture and society. Their dominance looms over the youth, often times until their death. From the ashes of their death, the youth can establish their cultural movements and political influence over the world. Without death, the addictive mental patterns of the aged would dominate over the culture of the youth.
As another example for how cultural and memetic niches block out radiations of new memes, consider the case of TV shows or podcasts. We only have so much time in our lives, so we naturally find ourselves having to limit how much media we can consume. We must reject other media that we have no time for. People will often favor their favorite shows and podcasts as opposed to new mysterious shows and podcasts for which they haven’t tried. People would rather binge watch the new episodes of familiar shows than to try an unknown one. Once we run out of content, there is a gaping hole and this is when an opportunistic meme can take its’ place. This is one of the challenges that content creators face. They must compete against larger memetic organisms that already dominate the memetic ecosphere like the dinosaurs that loomed over the smaller mammals. The extinction of popular shows may leave people searching for a replacement.
We evolved to undergo cycles of birth, life, and death. Rather than a pandemic, rather than a fire, perhaps we have evolved to die. Death may be a built-in ‘fire’ that allows for micro-renaissances to emerge from the ashes. Then it hit me: The Phoenix Effect may really be a general pattern in the systems of life. Things burn to the ground and something new emerges.
A selection for evolvability.
Interestingly, the faster that life gives birth and dies, the faster it can cycle through new renaissances and the faster it can evolve. This faster cycling may be favorable in an arms race against other species. So it may be that the earliest lifeforms were not evolved to die as much, but only to reproduce and select for longevity to the point of reproduction. Up until competition set in and a spiral of an accelerating evolutionary arms race set in. Consider the fruit fly study mentioned earlier. The fruit flies didn’t only evolve faster death cycles, but they also had accelerated development so that they could reproduce at an earlier age too. This occurred in the face of danger and mortality risk, which might represent pressures from predators in the real world. So it could be that predatory pressures would accelerate evolution to aide in the arms race against the predators. There is some evidence now that evolution may select for faster evolvers, which some researchers have argued that one way involves viruses altering out DNA through horizontal gene transfer (nonsexual) (Rice University 2007).
This pattern of selection for accelerated evolution is often said to be a selection for evolvability. In the earliest days of life on Earth, the lifeforms may have not yet evolved for evolvability, thus why multicellularity took so long to evolve. Then eventually predation and mechanisms of death may have become some of the earliest evolvability selections. Ecosystems may be described as a balanced system of lifeforms that mutually enhance evolvability in each contributing species.
Side Note: Most fascinatingly, shorter lifespan cycles like those observed in the flies may select for learning ability, due to the need to learn and adapt faster before death occurs (Liedtke & Fromhage 2019). One may need enhanced learning in order to complete everything fast enough in the life cycle. Perhaps a compressed lifespan accelerates many aspects of life, from development, to learning, to reproduction, and even death itself.
Moving back to the idea of sacrificing the old for the youth, it almost seems like humans have taken a strange turn in which the old enslave the youth for their own long-lasting lives. That is, until the youth turns against the old for exploiting them for work. This pattern of enslaving the youth resembles what ants have achieved as well. Some queen ants will live up to 30 years and have many children throughout (Centitas 1998). The worker/slave children only live for 1-2 years in contrast.
So, what does it really mean to evolve to die? It essentially means that we may have the lifespan and aging that we do because of naturally selected genes. In some sense, we may be programmed to live longer or die younger. It seems that we are not headed for immortality, as that would cause evolution to cease entirely. The cycles of birth and death may be an important part of evolutionary systems. The cycle of life and death is a form of immortality at the gene-level that allows many adaptive elements to be reset (the mind/learning) while retaining the capacity for new adaptations to unfold.
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Maybe we shouldn’t fear death. Perhaps we should religiously submit to the higher order of nature (very debatable)(also what does that even mean??). We may be too naïve to think that we can resist the system. If we resist, then we may stop evolution. It would potentially be a monocropping of memetics and of genetics, a stasis and a stagnation of evolution. Is that the ultimate goal of life for us?
Should we stop this cycle?
Here is a bit by the great Alan Watts
Our lives may be programed with death via multiple means. Recurrent extinction events may have led to the evolution of bizarre checks and balances that are geared towards controlling how extinctions play out. Evolution could be more complex than we currently imagine it to be, which is something that fascinates me very much. I hope it fascinates you too.
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Citations
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Cameron, Tom C., et al. Eco‐evolutionary dynamics in response to selection on life‐history. Ecology letters 16.6 (2013): 754-763.
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