Epistolution Musing №12: Why Do We Grow Old?
Dear Friends,
This letter is part of a weekly series of brief thoughts I would like to share with you, either because I’ve come across your related work in biology or because you’re a person I like. I discovered an interesting problem in 2019, a problem I can’t forget. Epistolution is the unknown biological mechanism that purposefully activates genetic influences and applies them to problems. Clear examples of epistolution include embryonic development, wound healing, regeneration, cancer, learning, memory, creativity, swarm intelligence, and the placebo effect.
Recap: One of the most difficult phenomena to explain in all of biology is actually not the growth of life, but the decline of life. Senescence is not the inescapable fact that we grow older chronologically, but rather the unnecessary enfeeblement that time brings to most organisms. Biological aging is distinct from chronology; there are many examples where the two do not match. And every organism is derived in a material way from the cells of its ancestors…the process of life is indefinitely prolonged by a part of a parent becoming a part of a child. Senescence doesn’t benefit us, so why do we fail to remain juvenile as time passes? In this section I explain why epistolution solves the problem of senescence.
From a selectionist perspective the problem with senescence is this: Why should an organism, which is motivated only to replicate its genes, develop into a senescing organism rather than maintaining its reproductive juvenility indefinitely? It can’t simply be that “parts wear out.” Biological parts are regenerative in principle, that’s what separates life from nonlife. Some organisms, like certain jellyfish or hydra or planaria, do not age at all but remain continually regenerative or can even age in reverse, regressing into juvenile morphologies when resources are scarce. Some large organisms like oak trees become continually less likely to perish the older they are, which is the mathematical actuary’s definition of youth. From this perspective the problem is very hard. Why shouldn’t we use all the resources we gain in order to grow ourselves younger, fitter, and more productive? Why shouldn’t the organisms that have been around the longest have grown to be the most irresistibly sexy?
From an epistolutionist perspective the problem looks very different. Umwelts are what control development, not genome sequences. This means that juvenility or senescence is a consequence not of what is written in the code but of how the code is interpreted by the umwelt. Biologically old cells and young cells contain the same genomes. So why would the cell, which is intending to incumulate (take in and make a part of oneself) as much knowledge as possible, choose to interpret its genome in a way that hinders that process of learning more and more? Juveniles can learn with fluidity; as we age we all become stiffer and more inflexible. It is hard to teach an old dog new tricks. Age defeats the mind as well as the body.
The answer, ironically, is probably good old-fashioned antagonistic pleiotropy. This is the idea that genes have slightly different effects in old organisms than they do in young organisms. Since all organisms are young at some point but only a few grow old, there is declining selection pressure for genes that benefit old organisms at the expense of benefiting young ones. But this explanation doesn’t really solve the problem from a selectionist perspective. Antagonistic pleiotropy relies on a distinction between a young and an old organism, a distinction which presupposes what we are trying to explain, the difference between young and old. From a selectionist perspective, genes should combine during development to increase fitness and that’s it. If the only purpose of life were to replicate genes then there would be no pleiotropy with respect to replication of genes. The organism would simply develop into the best replication vehicle it could build and then stop changing. We have to remember that genes are not individual units of Darwinian selection. Selection is only applied at the level of the phenotype, so any phenotype that continued to use its resources to become more fit rather than less fit would be selected for, and senescence would be selected against. Genes themselves do not senesce; they are immortally generated again and again through replication. If selectionism were true there would be no way for plieotropy to develop, so from selectionist’s point of view, senescence is an unsolved puzzle. This is ironic because the antagonistic plieotropy theory was invented by selectionists.
From an epistolutionist’s very different perspective, antagonistic pleiotropy makes much more sense. Cells, although they may be epistevolvers, are also entirely dependent on their genomes to perform their functions. Another way of saying it is that umwelts are dependent on utilizing the inflexible genome in order to produce life. Since the genome can only hold a finite number of genes, and that number is constrained by the time and energy required for replication, the space in the nucleus, competition between genes, and many other factors like that, it is inevitable that the genome will contain pleiotropic genes, and indeed even pleiotropic attractors. This is necessary because it is inevitable that the umwelt will change as an organism develops. There is no way for an organism to both incumulate knowledge and also retain the same umwelt for all its cells. Incumulation, unlike replication, by definition transforms the phenotype. No matter what the mechanism of epistolution turns out to be, one thing we can know for sure is that it changes cellular function, therefore the umwelten of cells. So introducing the prime mover of knowledge in the place of survival and reproduction actually makes the idea of antagonistic pleiotropy into a good explanation rather than a poor one. If we leave selectionism behind, we can have our antagonistic pleiotropy.
Living systems are inherently self-repairing, and therefore immortal in principle. The astonishing thing about solving biological aging in light of epistolution is that the key to living indefinitely in a youthful state will be learning the principles by which everything we know can be intentionally forgotten, or transformed from settled knowledge into uncertainty. Learning is important to a good, long life, but forgetting may be even more so.
Be Kind, and Be Brave,
Love, C
