Dear reader, this post will be completed in some hours; I'm posting it now because I'm participating in justwrite.club and I don't want to forfeit $1k. I'll remove this note when it's done. That said, the sections that are below are real; what I'm still doing is adding the "coming soon" sections. ----
Or: The payload lens on Darwin
Tl;dr: What is the most natural teleological shorthand to use, when thinking about evolution?
The “gene-centered view” of e.g. Dawkins says: genes are “trying” to increase the number of exact copies of themselves. And organisms are “vehicles” genes use to survive.
The “payload lens” (which I’ll be pitching) says: adaptive payloads (such as eyesight or fair meiosis) are “trying” to become deeper, stabler attractor basins that can team up with other adaptive payloads. And genes are “vehicles” these payloads use to survive.
Epistemic status: I haven’t done much of a lit search, so I’m claiming neither that any of this is original nor that it is vetted/established; I’m laying it out partly because I want to be able to build on it in some later essays about what we humans are (and what some possible AIs might be) other than optimizers. (However, I don’t mostly get to that here; and I hope this stuff may also be interesting in its own right.)
Angles on Darwin
Darwinian evolution (as operationalized by Lewontin in his 1970 paper The Units of Selection, which helped organize the field) is the theory that intricate adaptations (such as those in Earth’s living organisms) tend to arise when a process satisfies three principles:
Variation (organisms vary)
Differential reproduction (different variations have different reproductive odds)
Heredity (new organisms resemble their parents more than they resemble random population members, including in reproductive success).
Lewontin stresses that these principles can apply at any of several levels, e.g. genes, cells, gametes, organisms, or populations.
My business in this essay will be to contrast two such concretizations: “genes as replicators,” which is the standard lens associated with Williams and Dawkins, and “adaptive payloads as replicators”, which I have not personally seen in the literature. I will ask how much sense each lens lets us make of the living world.
Genes as replicators
DNA strands can be copied with high fidelity, so that a given chunk of functional DNA (a “gene”) is often exactly preserved from parent to child. Such genes are a natural and common way to concretize 1-3. Under this lens, 1-3 becomes:
Variation: DNA sequences vary
Differential reproduction: DNA sequences reproduce when their organisms reproduce, and some sequence-variants help their organisms reproduce more than others do
Heredity: a copied sequence matches its parent sequence, apart from rare mutations.
Following others, I will call this lens the gene-centered view. I believe this lens captures much, but far from all, of the ways 1-3 can help account for life’s variety.
Adaptive payloads as replicators
Adaptive payloads are innovations that make their organisms better at reproducing, such as eyesight, fair meiosis, or a preference for eating sugars. Adaptive payloads also constitute what Daniel Dennett calls “design work.”[1]
We can get an alternate concretization of Darwin’s 1-3 by taking adaptive payloads as our replicators. Under this lens, 1-3 becomes:
Variation: Adaptations vary across organisms (e.g, different organisms have more or less functional eyesight)
Differential reproduction: adaptive payloads reproduce (noisily) when their organisms reproduce; their organisms reproduction depends partly on the payloads’ presence
Heredity: the adaptations in the offspring bear a noisy resemblance to the adaptations in the parent.
Adaptive payloads are not copied exactly, as genes are; but they nonetheless possess enough parent-child resemblance to satisfy “heredity” in Lewontin’s sense. (Being a “replicator” in this sense does not require exact copying.)
I will call this the “payload lens.”
It is well-established that the gene-centered view is useful; I will spend this essay arguing that the payload lens carries some additional value (though the reverse is also true; the genes lens is irreplaceable).[2]
Example: eyesight
Consider eyesight. More exactly, consider the progression over time that eyesight has in a particular lineage – a progression across many millions of years from the first eyespots to primitive eyes to more effective, robust eyes that work in various particular contexts.
The payload lens makes it easier to notice some facts about eyesight’s trajectory.
Eyesight is a stable attractor
Let’s jump in in the middle of the story, by attending to eyesight in a particular population of raccoons (say).
Imagine some process messes intermittently with some raccoons’ eyesight – perhaps there’s a new attractive food source that contains a vision-impairing toxin. Or perhaps this population recently began mating with a new population of quasi-raccoons that had previously been separated by a mountain range and the new gene-combinations sometimes fail to make fully functional eyes.
In this context, evolution won’t have to look through as many new mutations before it finds one that can counter the trouble (since this is a simpler change; fixing a previously-working machine is easier than building a machine from scratch). Also, existing variants that help with the new circumstance may quickly approach fixation (since a previously-working machine that is slightly broken offers strong selection gradients toward fixing the machine).
Thus, the presence of useful eyes will cause selection toward more robust eyes. Importantly, this rapid selection toward robust eyes happens mostly because eyesight is already present; animals with no eyes might evolve eyesight, but the selection would be far slower.
Eyesight is thus a stable attractor (and this is easy to describe in terms of “eyesight,” i.e. when focusing on eyesight as an adaptive payload, and hard to describe in terms of genes directly, since e.g. “restores eyesight” could happen via any of thousands of genes).
(Of course, it is stable only so long as it is useful; when e.g. naked mole-rats move into a niche without light, entropy gradually disrupts the payload. The “eyesight attractor” requires constant selection to preserve its adaptive payload.)
The eyesight of Theseus
The “ship of Theseus” is a ship from a famous thought experiment; the ship stayed arguably “itself” across a huge period of time, even as every piece of it eventually wore out and was replaced.
Eyesight is a kind of “ship of Theseus”; its “stable attractor” nature can be preserved across huge periods of evolutionary time, and despite massive changes to the genes that initially supported it.
Or, well, that’s a theory-driven approximation. To attempt empirical accuracy:
The opsin family (a family of photosensitive proteins) has been conserved since before eyes’ beginnings. This does not much fit the payload lens. Early on, evolution found a good method for turning light into a rapid signal within a cell – a method that did not lead easily into an attractor of much better methods – and it has kept that method.[fn: Although, evolution didn’t get opsins from nowhere; opsins evolved from previous sensor-proteins that cells used to detect chemicals, and the thing where a previous payload (G-protein-coupled receptors) made it easier for this new payload (vision) to arise… does remind me of the payload lens. See [name of later section in this essay about payloads giving each other toeholds]]
The Pax6 gene (a “master control gene” that activates many other genes that together build eyes) is also highly conserved: if a mouse version of Pax6 is expressed in a fruit fly’s leg, the fruit fly forms an additional fruit fly eye on its leg. That is: the small thousands of genes involved in eye-formation in the mouse, and the small thousands of genes involved in making quite different fruit-fly eyes in the fruit fly, are still triggered by genes similar enough that copy-pasting the mouse one works on the fruit fly. I believe this does fit the payload hypothesis, as ~any change to the function of the Pax6 gene would cut off huge chunks of the “eyesight” payload at once.
Most other things do get substituted out over time. (E.g. our distant ancestors had four cone opsin classes, for color vision; our ancestors lost two of these while nocturnal, but then Old World primates got a new one by duplicating-and-mutating one of their existing ones. Or, for another example: many birds swapped out most of the ancestral crystallins used to make their transparent eye-lenses for a new one called δ-crystallin while retaining the same eye-shape and design; this new one was a recruited copy of a metabolic gene.)[3]
So, eyesight is a partial “ship of Theseus”, where most planks can be substituted out but Pax6 can’t (lest the whole ship lose its function) and opsins can’t (because they’re already quite optimized, and there doesn’t seem to be a hill-climbable path from there to a different and better solution)
Several more sections coming soon, please check back in some hours
"Design work" here means "stuff (such as a watch, or an intricate bit of biological function) that must be the result of some sort of "research and design"-type process, such as a human engineer, biological evolution, or memetic trial and error across a large population.
Dennett's concept originates (in some sense) in William Paley's famous thought experiment in which a man, walking across a heath, happens upon a watch and infers, as he looks at the intricate ticking gears (even without having seen a watch before), that there must somewhere be a watch-maker. Dawkins later riffed off this thought experiment by referring to evolution as a "blind watch-maker," as did Dennett with his notion of "design work," which he uses to describe anything that visibly contains R&D.
To see at once that the genes lens is great, notice e.g. that we today see no life without nucleic acid sequences – evolution has not produced lineages that can thrive and produce offspring without genes.
Apparently biologists have a term for a related sort of substitution – “developmental system drift,” as introduced by True and Haag, 2001; the authors’ claim, like mine, is that sometimes selection pressures cause aspects of a phenotype to remain stable despite substantial changes in genes. (Unlike me, the authors know lots of biology and can root their generalizations in empirics.)
Dear reader, this post will be completed in some hours; I'm posting it now because I'm participating in justwrite.club and I don't want to forfeit $1k. I'll remove this note when it's done. That said, the sections that are below are real; what I'm still doing is adding the "coming soon" sections.
----
Or: The payload lens on Darwin
Tl;dr: What is the most natural teleological shorthand to use, when thinking about evolution?
The “gene-centered view” of e.g. Dawkins says: genes are “trying” to increase the number of exact copies of themselves. And organisms are “vehicles” genes use to survive.
The “payload lens” (which I’ll be pitching) says: adaptive payloads (such as eyesight or fair meiosis) are “trying” to become deeper, stabler attractor basins that can team up with other adaptive payloads. And genes are “vehicles” these payloads use to survive.
Epistemic status: I haven’t done much of a lit search, so I’m claiming neither that any of this is original nor that it is vetted/established; I’m laying it out partly because I want to be able to build on it in some later essays about what we humans are (and what some possible AIs might be) other than optimizers. (However, I don’t mostly get to that here; and I hope this stuff may also be interesting in its own right.)
Angles on Darwin
Darwinian evolution (as operationalized by Lewontin in his 1970 paper The Units of Selection, which helped organize the field) is the theory that intricate adaptations (such as those in Earth’s living organisms) tend to arise when a process satisfies three principles:
Lewontin stresses that these principles can apply at any of several levels, e.g. genes, cells, gametes, organisms, or populations.
My business in this essay will be to contrast two such concretizations: “genes as replicators,” which is the standard lens associated with Williams and Dawkins, and “adaptive payloads as replicators”, which I have not personally seen in the literature. I will ask how much sense each lens lets us make of the living world.
Genes as replicators
DNA strands can be copied with high fidelity, so that a given chunk of functional DNA (a “gene”) is often exactly preserved from parent to child. Such genes are a natural and common way to concretize 1-3. Under this lens, 1-3 becomes:
Following others, I will call this lens the gene-centered view. I believe this lens captures much, but far from all, of the ways 1-3 can help account for life’s variety.
Adaptive payloads as replicators
Adaptive payloads are innovations that make their organisms better at reproducing, such as eyesight, fair meiosis, or a preference for eating sugars. Adaptive payloads also constitute what Daniel Dennett calls “design work.”[1]
We can get an alternate concretization of Darwin’s 1-3 by taking adaptive payloads as our replicators. Under this lens, 1-3 becomes:
Adaptive payloads are not copied exactly, as genes are; but they nonetheless possess enough parent-child resemblance to satisfy “heredity” in Lewontin’s sense. (Being a “replicator” in this sense does not require exact copying.)
I will call this the “payload lens.”
It is well-established that the gene-centered view is useful; I will spend this essay arguing that the payload lens carries some additional value (though the reverse is also true; the genes lens is irreplaceable).[2]
Example: eyesight
Consider eyesight. More exactly, consider the progression over time that eyesight has in a particular lineage – a progression across many millions of years from the first eyespots to primitive eyes to more effective, robust eyes that work in various particular contexts.
The payload lens makes it easier to notice some facts about eyesight’s trajectory.
Eyesight is a stable attractor
Let’s jump in in the middle of the story, by attending to eyesight in a particular population of raccoons (say).
Imagine some process messes intermittently with some raccoons’ eyesight – perhaps there’s a new attractive food source that contains a vision-impairing toxin. Or perhaps this population recently began mating with a new population of quasi-raccoons that had previously been separated by a mountain range and the new gene-combinations sometimes fail to make fully functional eyes.
In this context, evolution won’t have to look through as many new mutations before it finds one that can counter the trouble (since this is a simpler change; fixing a previously-working machine is easier than building a machine from scratch). Also, existing variants that help with the new circumstance may quickly approach fixation (since a previously-working machine that is slightly broken offers strong selection gradients toward fixing the machine).
Thus, the presence of useful eyes will cause selection toward more robust eyes. Importantly, this rapid selection toward robust eyes happens mostly because eyesight is already present; animals with no eyes might evolve eyesight, but the selection would be far slower.
Eyesight is thus a stable attractor (and this is easy to describe in terms of “eyesight,” i.e. when focusing on eyesight as an adaptive payload, and hard to describe in terms of genes directly, since e.g. “restores eyesight” could happen via any of thousands of genes).
(Of course, it is stable only so long as it is useful; when e.g. naked mole-rats move into a niche without light, entropy gradually disrupts the payload. The “eyesight attractor” requires constant selection to preserve its adaptive payload.)
The eyesight of Theseus
The “ship of Theseus” is a ship from a famous thought experiment; the ship stayed arguably “itself” across a huge period of time, even as every piece of it eventually wore out and was replaced.
Eyesight is a kind of “ship of Theseus”; its “stable attractor” nature can be preserved across huge periods of evolutionary time, and despite massive changes to the genes that initially supported it.
Or, well, that’s a theory-driven approximation. To attempt empirical accuracy:
So, eyesight is a partial “ship of Theseus”, where most planks can be substituted out but Pax6 can’t (lest the whole ship lose its function) and opsins can’t (because they’re already quite optimized, and there doesn’t seem to be a hill-climbable path from there to a different and better solution)
Several more sections coming soon, please check back in some hours
"Design work" here means "stuff (such as a watch, or an intricate bit of biological function) that must be the result of some sort of "research and design"-type process, such as a human engineer, biological evolution, or memetic trial and error across a large population.
Dennett's concept originates (in some sense) in William Paley's famous thought experiment in which a man, walking across a heath, happens upon a watch and infers, as he looks at the intricate ticking gears (even without having seen a watch before), that there must somewhere be a watch-maker. Dawkins later riffed off this thought experiment by referring to evolution as a "blind watch-maker," as did Dennett with his notion of "design work," which he uses to describe anything that visibly contains R&D.
To see at once that the genes lens is great, notice e.g. that we today see no life without nucleic acid sequences – evolution has not produced lineages that can thrive and produce offspring without genes.
Apparently biologists have a term for a related sort of substitution – “developmental system drift,” as introduced by True and Haag, 2001; the authors’ claim, like mine, is that sometimes selection pressures cause aspects of a phenotype to remain stable despite substantial changes in genes. (Unlike me, the authors know lots of biology and can root their generalizations in empirics.)