I've pondered Dawkins' selfish gene since reading about it in college. Unless I've lost my recall over the years (which is possible; college was toward the end of the prior millennium), the selfish gene theory was that evolution is optimized neither for the individual life form nor the community of conspecifics, but for the genes themselves. Individuals and communities are simply ways the genes get there.
Your closing sentence is true, no matter if evolution optimizes for communities, individuals, or the genes.
Hi Josh. I don't know if you recall, but we met last week when you presented on the IPAK Director's Webinar. I am the mast cell researcher who was talking with you about exosomes. I haven't been able to find an email address for you. Can I send something to you here on your Substack email address or is there another email address you prefer? Thanks, Diane Kane.
So might we call it the "Enlightened Self-Interest" gene?
I never read "Sex and the Single Girl". I think there was eventually a movie, too. I was young, and then I was busy.
Thank you for the pleasantly presented insights, Josh, you have used a deft touch in this essay, which may have taken a lot of time and re-reads/re-edits to accomplish.
It's a privilege to be able to evaluate science in many fields, to write poetry, teach yoga, play chamber music, advocate politically for freedom. I'm fortunate indeed to enjoy this life. I don't have a salary, and I think I could never do the variety of things I do if someone was paying me.
Yes, much ado is made about the cost of sex to individual fitness: passing on only 50% of your genes instead of 100%. It seemed like quite the mystery to me when first hearing of it as an undergrad. I don't know why I didn't notice then, and no one seems to notice now, that (on average) those paying that cost only have to make 50% of the parental investment in their offspring. So isn't it a wash and therefore not really much of a mystery? Am I missing something?
In addition to the "cost of males", there's also the breakup of well-adapted combinations of genes. The most successful gene combinations are prevented from keeping themselves together.
Hmmm, a possibility to be sure, but aren't you overstating it to say "prevented"? I don't have a good quantitative sense of how frequently crossover mutations occur, or translocations either. (Though someone must.) But surely it's a possibility that such combinations remain intact.
The more I think about it, the more complicated I find assessing this risk to be. It's going to be different for different types of combinations. If the nature of the combination is to have 2 loci a certain distance apart, then what happens in meiosis with the slightly mismatched pair of chromosomes? I would think there'd be a 50/50 shot of retention.
If by "gene combinations" you also mean allele combinations, then we're talking about simple Mendelian probabilities, which would be far from 'prevention'. In either case, I would think the selective value of the combination would give it a leg up too. Say at locus A there are alleles b and c of equal fitness, and at locus X there are alleles y and z of equal fitness, but there's something special about b z individuals. Well, I was going to say there's still a 25% chance the combination remains, but even this has layers of complication... whom do you mate with, do the fitness advantages accrue to heterozygous as well as homozygous individuals...? Anyway, in such a situation, c and y are rapidly driven to extinction, rendering the breakup concern moot. I guess you might call that selfish genes cooperating with one another.
I also wonder about r-selected versus k-selected species. Maybe there's a meaningful difference there. The former's shotgun approach makes it more likely Some offspring retain the combination. Maybe mosquito's are fine, but whales have something to worry about. But of course in the real world, sex is everywhere; k-selected and r-selected species alike. The only multicellular organism believed to have reverted to exclusively asexual reproduction, bdelloid rotifers, are pretty r-selected I'd say.
Then we have the possibility, that a lost combination could reconnect again. Yeah, I think it's quite the can of worms you've opened here, Josh. My guess is that the selective advantage of the combination outweighs the risk of its loss. But doing the math on that is above my pay grade.
Mammals of both sexes tend to make substantial parental investment in their offspring, but what about flies or turtles or salmon? Other than birds and mammals, most animals lay eggs and then have nothing more to do with them. So why don't both sexes lay eggs? Why aren't they hermaphrodites, like worms or snails or starfish?
The theory I heard, which seems reasonable to me, was that there was dispersive selection for gamete size. Sexual reproduction initially did not have males and females of course, and gamete size exhibited a gaussian distribution. Small gametes may have been selected for due to motility, and larger ones for the higher parental investment. Gametes of average size had the worst of both worlds. How we would test that theory, I don't know. But I consider it reasonable speculation.
I don't recall ever hearing anything about selective forces influencing hermaphroditism. Maybe it'll come to me though. :)
I've pondered Dawkins' selfish gene since reading about it in college. Unless I've lost my recall over the years (which is possible; college was toward the end of the prior millennium), the selfish gene theory was that evolution is optimized neither for the individual life form nor the community of conspecifics, but for the genes themselves. Individuals and communities are simply ways the genes get there.
Your closing sentence is true, no matter if evolution optimizes for communities, individuals, or the genes.
There was a debate between Dawkins and Margulis, captured on Youtube for posterity:
https://www.youtube.com/watch?v=YJ-sZHHx7O0
Hi Josh. I don't know if you recall, but we met last week when you presented on the IPAK Director's Webinar. I am the mast cell researcher who was talking with you about exosomes. I haven't been able to find an email address for you. Can I send something to you here on your Substack email address or is there another email address you prefer? Thanks, Diane Kane.
So might we call it the "Enlightened Self-Interest" gene?
I never read "Sex and the Single Girl". I think there was eventually a movie, too. I was young, and then I was busy.
Thank you for the pleasantly presented insights, Josh, you have used a deft touch in this essay, which may have taken a lot of time and re-reads/re-edits to accomplish.
;-)
You have such a wide range of interests, Josh. Wonderful!
It's a privilege to be able to evaluate science in many fields, to write poetry, teach yoga, play chamber music, advocate politically for freedom. I'm fortunate indeed to enjoy this life. I don't have a salary, and I think I could never do the variety of things I do if someone was paying me.
My error
Lynn Margulis, thank you.
Lynn Margulis was married to Carl Sagan as a young grad student. They had a son, Dorion, who co-authored my book on aging.
https://scienceblog.com/484749/preface-cracking-aging-code-josh-mitteldorf-dorion-sagan/
I have the book he co-wrote with his mother.
Thanks for the tip!
btw, on the topic: https://twitter.com/CrocodileChuck/status/1834844699372536274
Yes, much ado is made about the cost of sex to individual fitness: passing on only 50% of your genes instead of 100%. It seemed like quite the mystery to me when first hearing of it as an undergrad. I don't know why I didn't notice then, and no one seems to notice now, that (on average) those paying that cost only have to make 50% of the parental investment in their offspring. So isn't it a wash and therefore not really much of a mystery? Am I missing something?
In addition to the "cost of males", there's also the breakup of well-adapted combinations of genes. The most successful gene combinations are prevented from keeping themselves together.
Hmmm, a possibility to be sure, but aren't you overstating it to say "prevented"? I don't have a good quantitative sense of how frequently crossover mutations occur, or translocations either. (Though someone must.) But surely it's a possibility that such combinations remain intact.
The more I think about it, the more complicated I find assessing this risk to be. It's going to be different for different types of combinations. If the nature of the combination is to have 2 loci a certain distance apart, then what happens in meiosis with the slightly mismatched pair of chromosomes? I would think there'd be a 50/50 shot of retention.
If by "gene combinations" you also mean allele combinations, then we're talking about simple Mendelian probabilities, which would be far from 'prevention'. In either case, I would think the selective value of the combination would give it a leg up too. Say at locus A there are alleles b and c of equal fitness, and at locus X there are alleles y and z of equal fitness, but there's something special about b z individuals. Well, I was going to say there's still a 25% chance the combination remains, but even this has layers of complication... whom do you mate with, do the fitness advantages accrue to heterozygous as well as homozygous individuals...? Anyway, in such a situation, c and y are rapidly driven to extinction, rendering the breakup concern moot. I guess you might call that selfish genes cooperating with one another.
I also wonder about r-selected versus k-selected species. Maybe there's a meaningful difference there. The former's shotgun approach makes it more likely Some offspring retain the combination. Maybe mosquito's are fine, but whales have something to worry about. But of course in the real world, sex is everywhere; k-selected and r-selected species alike. The only multicellular organism believed to have reverted to exclusively asexual reproduction, bdelloid rotifers, are pretty r-selected I'd say.
Then we have the possibility, that a lost combination could reconnect again. Yeah, I think it's quite the can of worms you've opened here, Josh. My guess is that the selective advantage of the combination outweighs the risk of its loss. But doing the math on that is above my pay grade.
"Well adapted" this century may be "poorly adapted" a century before or after...
"The times, they are a changin'."
Mammals of both sexes tend to make substantial parental investment in their offspring, but what about flies or turtles or salmon? Other than birds and mammals, most animals lay eggs and then have nothing more to do with them. So why don't both sexes lay eggs? Why aren't they hermaphrodites, like worms or snails or starfish?
The theory I heard, which seems reasonable to me, was that there was dispersive selection for gamete size. Sexual reproduction initially did not have males and females of course, and gamete size exhibited a gaussian distribution. Small gametes may have been selected for due to motility, and larger ones for the higher parental investment. Gametes of average size had the worst of both worlds. How we would test that theory, I don't know. But I consider it reasonable speculation.
I don't recall ever hearing anything about selective forces influencing hermaphroditism. Maybe it'll come to me though. :)
Janet Margulis agrees with you re: evolution as co-operation.
I don't know Janet Margulis. Lynn Margulis was one of the most outspoken critics of the selfish gene dogma from 1970 until her death.