See how the spiky back could be a runaway feature?
Until some other species takes over your ecological niche.
I seem to remember hearing about a gene in mice that would ensure that it always gets copied into the offspring if present (leading to rapid growth in the gene pool) but had the unfortunate effect that homozygotes are sterile.* Under random mating, you can calculate the population levels at which the gene frequency is stable,** but under non-random mating, a group where 50% of the parents have this gene could totally annihilate itself (as it would be possible to ensure that every child in the next generation is a carrier, and thus the generation after that will be totally sterile).
But consider this gene without a drawback: if one parent has at least one copy, then the child will, and if both parents each have at least one copy, then the children will have two copies, but the gene is fitness neutral in all permutations. Then we can calculate how many generations it will take for the gene to reach fixation, given random mating.
*Suppose the mechanism was that it would break the other chromosome. This means you’re the only option—unless the other chromosome had the exact same idea, and now there aren’t any functional chromosomes.
**As it turns out, the heterozygote advantage and homozygote disadvantage are both so strong that the only stable levels are 0 and 1. If you drop the heterozygote advantage to something more likely, like a heterozygote having a 55% chance of passing it on to a child, then you get a more interesting answer.
The important thing is not to calculate if it is a net positive or net negative, but rather what happens?
This is a fundamentally mistaken way of looking at evolution. The only important thing is whether it is a selective advantage or disadvantage! Populations roll down the selection gradient, and the assumption that population sizes are the same from year to year is a feature of mathematical models, not reality.
You are good at lowering the probability I give to this hypothesis, and I thank you for that, but it is stil not 0.
First about the second point—my point is more like selective advantages do not mean the fitness of the group, or even the fitness of the parents to be maximized, but solely that of the propagation of the gene in descendants. So, from that angle, a gene killing some parents but still making an animal more sexually succesful can still confer a selective advantage. Depending on the ratio of this two of course. My point is precisely that on the whole it can be hugely destructive for the group.
Of course, and now back to your first point, this weakens the group. This would happen with a spiky back but here is where my metaphor stops being useful. It is intelligence. It begins with the ecological dominance—social competition model. The group was all right before intelligence. Surely a weaker but smarter group can compensate for the group level weakening?
My point is pulling an Occam here. Our best hypothesis is that an unknown factor X launched a runaway IQ based competition inside the hominid species. What if factor X is intelligence itself, basically it killing mothers, thus making the sexual competition of males more vivid? Surely such a reduction of factors is worth pondering? And as a side-effect, whatever group level weakness it would cause wrt other species, they would resolve that because of this intelligence, which according to EDSC was not formerly necessary, but at this point became useful for keeping other species at bay?
And if this all at least sounds not-impossible enough to invest resources into pondering or testing, it could generate a Great Filter hypothesis, namely that intelligence needs to be advantageous for the offspring but at some level harmful to parents (dangerous birth, maternal care) to launch such an arms race, it would basically predict that any alien species without the special difficulties of Earth mammals and their problems of pushing a big head through a vagina would not have this arms race.
I’m not sure, but I think your model assumes intelligence is mostly (entirely?) useful for males. Actually, females also have a complex bunch of roles, since they need to take care of themselves and their children and make alliances to get help from both males and females.
You might be interested in Mother Nature by Sarah Hrdy.
Actually it is notable that women and men have such similar intelligence. Women and men are quite easy to distinguish physically in a variety of ways, but there is probably way ( I don’t believe one has been discovered) to reliably distinguish a woman from a man based purely on how their minds work. Minds are a lot more like livers, kidneys and eyeballs (effectively identical in each sex) than like body shape, genitals or hair distribution. I haven’t heard this said before, but this would seem to suggest that minds are NOT primarily to get us laid, that they do not evolve from sexual selection, but rather arise from natural selection (survival of the fittest).
Of course, but “useful” is different from “increases reproductive fitness”, and the basic assumption is that the selective pressure of intelligence came from competition inside the species. It is sort of difficult for me to imagine what kind of competition can happen between ancestral females to increase reproductive fitness (and not simply to have a better life, these two are different things). Let’s assume for now it is not for higher quantity of children, nor for higher quality sperm thus the genetic quality of children (it does not really require much of a competition, it is cheap), what else is left? Largely the upbringing and life of those children. Am I on the right track there that it is more about what happens to the children once they are born? Are the get resources invested by the genetic father, by the tribe, by the chieftain, by the queen, by whoever, what status they get and so on? As this sounds vaguely possible for I just don’t know to visualize it. (Sort of Cersei Lannister situation, push children into high status positions?)
I have to check on this, but I think competition can go all the way to low status female’s children being killed. Even if it doesn’t go that far, less access to food/more stressed mothers mean that the children of a low status mother are more likely to be less capable adults.
Yep, higher-status female apes sometimes kill lower-status female apes’ babies. One of the reasons why female cliques are so important even when females typically do not use them to kill other adult females.
In humans, you see how some women have the instinct to touch other women’s babies, and how those mothers are usually scared like shit. Touching other womens’ babies is a female status move. -- That’s because as a female ape you couldn’t realistically defend yourself and your baby from a group of female apes; you would be completely in their mercy. So another female ape touching your baby reminds you of your relative positions in the tribe.
Until some other species takes over your ecological niche.
I seem to remember hearing about a gene in mice that would ensure that it always gets copied into the offspring if present (leading to rapid growth in the gene pool) but had the unfortunate effect that homozygotes are sterile.* Under random mating, you can calculate the population levels at which the gene frequency is stable,** but under non-random mating, a group where 50% of the parents have this gene could totally annihilate itself (as it would be possible to ensure that every child in the next generation is a carrier, and thus the generation after that will be totally sterile).
But consider this gene without a drawback: if one parent has at least one copy, then the child will, and if both parents each have at least one copy, then the children will have two copies, but the gene is fitness neutral in all permutations. Then we can calculate how many generations it will take for the gene to reach fixation, given random mating.
*Suppose the mechanism was that it would break the other chromosome. This means you’re the only option—unless the other chromosome had the exact same idea, and now there aren’t any functional chromosomes.
**As it turns out, the heterozygote advantage and homozygote disadvantage are both so strong that the only stable levels are 0 and 1. If you drop the heterozygote advantage to something more likely, like a heterozygote having a 55% chance of passing it on to a child, then you get a more interesting answer.
This is a fundamentally mistaken way of looking at evolution. The only important thing is whether it is a selective advantage or disadvantage! Populations roll down the selection gradient, and the assumption that population sizes are the same from year to year is a feature of mathematical models, not reality.
You are good at lowering the probability I give to this hypothesis, and I thank you for that, but it is stil not 0.
First about the second point—my point is more like selective advantages do not mean the fitness of the group, or even the fitness of the parents to be maximized, but solely that of the propagation of the gene in descendants. So, from that angle, a gene killing some parents but still making an animal more sexually succesful can still confer a selective advantage. Depending on the ratio of this two of course. My point is precisely that on the whole it can be hugely destructive for the group.
Of course, and now back to your first point, this weakens the group. This would happen with a spiky back but here is where my metaphor stops being useful. It is intelligence. It begins with the ecological dominance—social competition model. The group was all right before intelligence. Surely a weaker but smarter group can compensate for the group level weakening?
My point is pulling an Occam here. Our best hypothesis is that an unknown factor X launched a runaway IQ based competition inside the hominid species. What if factor X is intelligence itself, basically it killing mothers, thus making the sexual competition of males more vivid? Surely such a reduction of factors is worth pondering? And as a side-effect, whatever group level weakness it would cause wrt other species, they would resolve that because of this intelligence, which according to EDSC was not formerly necessary, but at this point became useful for keeping other species at bay?
And if this all at least sounds not-impossible enough to invest resources into pondering or testing, it could generate a Great Filter hypothesis, namely that intelligence needs to be advantageous for the offspring but at some level harmful to parents (dangerous birth, maternal care) to launch such an arms race, it would basically predict that any alien species without the special difficulties of Earth mammals and their problems of pushing a big head through a vagina would not have this arms race.
I’m not sure, but I think your model assumes intelligence is mostly (entirely?) useful for males. Actually, females also have a complex bunch of roles, since they need to take care of themselves and their children and make alliances to get help from both males and females.
You might be interested in Mother Nature by Sarah Hrdy.
Actually it is notable that women and men have such similar intelligence. Women and men are quite easy to distinguish physically in a variety of ways, but there is probably way ( I don’t believe one has been discovered) to reliably distinguish a woman from a man based purely on how their minds work. Minds are a lot more like livers, kidneys and eyeballs (effectively identical in each sex) than like body shape, genitals or hair distribution. I haven’t heard this said before, but this would seem to suggest that minds are NOT primarily to get us laid, that they do not evolve from sexual selection, but rather arise from natural selection (survival of the fittest).
Of course, but “useful” is different from “increases reproductive fitness”, and the basic assumption is that the selective pressure of intelligence came from competition inside the species. It is sort of difficult for me to imagine what kind of competition can happen between ancestral females to increase reproductive fitness (and not simply to have a better life, these two are different things). Let’s assume for now it is not for higher quantity of children, nor for higher quality sperm thus the genetic quality of children (it does not really require much of a competition, it is cheap), what else is left? Largely the upbringing and life of those children. Am I on the right track there that it is more about what happens to the children once they are born? Are the get resources invested by the genetic father, by the tribe, by the chieftain, by the queen, by whoever, what status they get and so on? As this sounds vaguely possible for I just don’t know to visualize it. (Sort of Cersei Lannister situation, push children into high status positions?)
I have to check on this, but I think competition can go all the way to low status female’s children being killed. Even if it doesn’t go that far, less access to food/more stressed mothers mean that the children of a low status mother are more likely to be less capable adults.
Yep, higher-status female apes sometimes kill lower-status female apes’ babies. One of the reasons why female cliques are so important even when females typically do not use them to kill other adult females.
In humans, you see how some women have the instinct to touch other women’s babies, and how those mothers are usually scared like shit. Touching other womens’ babies is a female status move. -- That’s because as a female ape you couldn’t realistically defend yourself and your baby from a group of female apes; you would be completely in their mercy. So another female ape touching your baby reminds you of your relative positions in the tribe.