In her new book, Sarah Hrdy's explores the natural history of paternal care, describing the underlying behavioral endocrinology and speculating on its evolutionary origins.
> Despite all our knowledge of human nature, it is unclear just how naturally brutish man is, how much this has change over our history (plenty to suggest we’re less violent than our ancestors but it’s debated)
I thought we actually have decent grounding here.
For hunter gatherer males before agriculture, the rate is something like 30-50% chance of violent death in their lifetime. If you put it in terms of violent deaths per 100k, they're averaging about 1030. Some of the most warlike HG tribes we've seen historically top at 1500.
> and how much the male proclivity for violence varies over the population.
For more recent non-state hunter gatherers 1800 - today they've come down to ~520.
Here's a table I made showing rates for one of my own substack posts:
And of course for modern states like Europe and the US, if you include homicides we're at rates between 0.2 (Japan), ~1 (most of Europe), and ~7 (USA) today.
This overall narrative arc of progressively reducing violence is basically the narrative in Stephen Pinkers Better Angels of our Nature.
> It seems like there could have been and still be a lot of things that domesticate and/or pacify men so that we act less troglodytian.
Yes, have you read Richard Wrangham's *The Goodness Paradox?* It's about our self-domestication as a species. Amazingly readable and accessible book, like most of his books. I think a combination of this and Geoffrey Miller's *The Mating Mind* covers the forces making us less troglodytian. Broadly, it's sexual selection for hundreds of thousands of years, then the Tyranny of the Cousins for a few hundred thousand.
This is directly contrasted with our confreres the Neanderthals, and our likely-ancestors H Heidelbergensis, who were not domesticated and so had massively higher testosterone, and likely much higher reactive aggression. This led to them having much lower group sizes, and our self domestication was like a super weapon that led to us wiping them (and every other) hominin species out in our last out-migration from Africa after the Cognitive Revolution 50kya.
I wrote about this in a different substack post, but don't want to seem like I'm spamming your comment section, so won't leave a link to any of them unless asked.
In terms of Neanderthal violent death rates per 100k, it's difficult to estimate, but if you count hunting accidents, it would be significantly higher than ours - they were more or less obligate carnivores, the majority of their diet was meat according to dentin studies, and so they had to hunt for food much more often than H Sap did, and their life expectancy was quite a bit shorter than H Sap hunter gatherer life expectancies. Contemporary HG's like the Hadza live to their mid 70's, and adult Neanderthals lived to their early 40's or so on average (so that's not the typical "medieval people only lived to 40" misunderstanding driven by high infant mortality), and the majority of skeletal remains found have signs of injury or violent death.
Thanks for the comments and the table is useful. I'll respond to a few points here.
>I thought we actually have decent grounding here.
This will depend on your prior beliefs and the amount of skepticism you'd like to apply to the claims. I think I'm generally satisfied with the "Better Angels" model and Wrangham's domestication/purging of brutes theory. But with all claims that rely on historical dataset, it is easy for a critic to point to things like ascertainment bias or other possible issues with the numbers. Also, the environment has changed substantially over the course of human history (social, climate, pop size, etc) which can make it difficult to put a number on what the natural rate of human violence is. I think it's safe to say that nature is "red in tooth and claw" and that Hobbes is more correct than Rousseau, but I was trying to gesture at uncertainty about the intensity of our devilish side.
>Yes, have you read Richard Wrangham's *The Goodness Paradox?* It's about our self-domestication as a species. Amazingly readable and accessible book, like most of his books. I think a combination of this and Geoffrey Miller's *The Mating Mind* covers the forces making us less troglodytian. Broadly, it's sexual selection for hundreds of thousands of years, then the Tyranny of the Cousins for a few hundred thousand.
I'm familiar with these books and obviously many other evo-psych theories and research. This Fatherhood book by Hrdy directly critiques the traditional sexual selection theory of paternal care and downplays kinship theories a bit. She prefers a "social selection" model which of course is still ultimately mediated by sexual selection but the vector that's relevant to selection in her view is social status as understood as being a good and generous group members (reputation). Her evidence for this is fairly thin as it relies on extrapolations about available calories across the Pleistocene, but she draws on examples of how other animals share parental/care duties in harsh conditions.
>This is directly contrasted with our confreres the Neanderthals, and our likely-ancestors H Heidelbergensis, who were not domesticated and so had massively higher testosterone, and likely much higher reactive aggression. This led to them having much lower group sizes, and our self domestication was like a super weapon that led to us wiping them (and every other) hominin species out in our last out-migration from Africa after the Cognitive Revolution 50kya.
I think more recent evidence suggests a more complex story. There is new strong evidence that many Neanderthal groups were incredibly isolated so there was a high-level on consanguinity. This of course is unlikely to be adaptive. Additionally, there is new evidence that the Neanderthal admixture to our lineage was likely much more substantial than the remaining ~2% that lingers today. This suggests that Neaderthals that did mingle with modern human groups were able to cooperate to some degree.
> But with all claims that rely on historical dataset, it is easy for a critic to point to things like ascertainment bias or other possible issues with the numbers.
Ah, sure. But it's not just ethnographies, it's also things like how many skeletons show evidence of violent death and such.
> I think more recent evidence suggests a more complex story. There is new strong evidence that many Neanderthal groups were incredibly isolated so there was a high-level on consanguinity. This of course is unlikely to be adaptive. Additionally, there is new evidence that the Neanderthal admixture to our lineage was likely much more substantial than the remaining ~2% that lingers today. This suggests that Neaderthals that did mingle with modern human groups were able to cooperate to some degree.
I think this fits in, though. The reason N's were more inbred *was* the smaller group sizes and likely higher reactive aggression.
Human HG's generally have larger group sizes and larger group affiliations - you have your immediate clan, but you also have your tribe and your people that you share a language with, and HG's generally get together in larger aggregates and pair up with more mating diversity at those times.
If N's were more reactively aggressive, this would be hard. Most N group sizes were basically "1 or 2 families," and it's likely they explicitly followed the "alpha dominating the group" thing we got away from via domestication and Cousin Tyranny. If this is the case, and an N supergrouping requires a bunch of alphas to put away their clubs and all make nice, that's obviously harder from the beginning, and more volatile and hard to sustain, and so the lower genetic diversity.
The H Sap + N admixture is fun, too. Deep time is a big space, and groups of H Sap and N's were living side by side for hundreds of thousands of years in the Levant and Europe, so we can't really say with authority that there was any one dynamic. But I'd point out that things like a "Yamnaya model of admixture" is just as plausible as H Sap and N's cooperating and trading mates. Indeed, David Reich once pointed out that the majority of N + H Sap breedings were N male + H Sap female - this is at least suggestive of a "Yamnaya model of admixture," if not dispositive. Because if it's two groups getting together in the spirit of amity and exchange, wouldn't you expect women to change hands on both sides, as often happens in HG's historically?
>Ah, sure. But it's not just ethnographies, it's also things like how many skeletons show evidence of violent death and such.
I'm referring to more than just methodology. There is a survival bias to what is available to dig up (i.e. the preservation of remains isn't a random process), and the areas that are accessible for professional digs are not random either (ascertainment bias). There is also some noise/expert judgement in the forensic analysis of remains of course. It's hard to know exactly how this should cause us to adjust our understanding of the data we have. I'm inclined to believe in the signal. I'm just highlighting the level of uncertainty here.
>I think this fits in, though. The reason N's were more inbred *was* the smaller group sizes and likely higher reactive aggression.
I think there are a lot of inputs on this other than T levels. T levels alone aren't the best predictor of reactive aggression either. I think there is evidence of isolation due to social, geographical, and climate factors. And again, there was also substantial intermixing that occurred in more than one location. We know this because we have hybrid remains who are verified as not ancestral to us.
>David Reich once pointed out that the majority of N + H Sap breedings were N male + H Sap female - this is at least suggestive of a "Yamnaya model of admixture,"
I actually haven't see this claim for Reich, but I'm not sure how much it would mean for our lineage because of low fertility in hybrid males. The next generation after mixing would require Sapien males. In the Dwarkesh pod, he entertain the idea that a Neander group was perhaps successive introgressed by waves of humans from NE Africa/N. East and this created modern humans.
Thanks, interesting take on Father Time. I've just started reading Father Time when I came across your post. I've read several books of Sarah Blaffer Hrdy, she's a great scholar and an inspiring writer. Sarah Blaffer Hrdy: “Human males may nurture their young a little, a lot, or not at all” (Mothers and Others, 2009: 162). I am very curious how her journey got Hrdy from this universal truth to this point that you mention: "My unexpected finding is that inside every man there lurk ancient caretaking tendencies that render a man every bit as protective and nurturing as the most committed mother. After all: “Of all the casts of characters in this melodrama the role of the father is the most subject to creative script variation” - David Lancy (The Anthropology of Childhood - Cherubs, Chattel, Changelings, 2022: 131).
It seems the softening of Hrdy's view of the innate care capacities/proclivities of men began in the 2010s. It appears to be in response to two major lines of research: 1) live brain imaging (fMRI) studies of the parents of newborns and 2) behavioral endocrinology studies in humans of prolonged exposure to children (I link to the famous PNAS study which was also popularized by Jo Henrich in The WEIRDest People in the World). It seems her experiences watching millennial fathering practices in America firsthand also motivated her rethinking.
As my review hopefully highlights, I am persuaded by the latter evidence but not impressed by the former. And in her speculation about how selection has shaped male parenting, I think she's invested a bit too much in marginal phenomenon. It seems the sexual selection dynamics (i.e. differential parental investment - a theory pioneered by her post-doc advisor) is still likely most of what is going on (past and present) and we're just talking about changes in the human niche and what status is/means.
From a genetic perspective, it is of course very plausible that there is a substrate for care/parenting shared by both sexes. It would be interesting to know what the genetic architecture of that substrate is (in the autosome) and how the presence of a Y chromosome and a lack of a second X chromosome is likely to modify the expression of that care substrate. We may also learn how much natural variation there is in care/parenting abilities/proclivities. I'm sure some insight can already be already gleaned from the genetics/GWAS literature, but I haven't investigated.
The endocrine response appears to be an adapted response to prolonged proximity to babies. Happens in any human being. In animals, this can also be replicated but it often a lot harder to trigger. Hrdy describes attempts to sensitize male mice to unrelated pups in the book. Most of the time the unrelated male mouse just kills and cannibalizes the pup. Hrdy's account does not entirely explain why infanticide is seemingly so rare in humans compared to the animal kingdom and even near ape relatives (e.g. chimps).
> Despite all our knowledge of human nature, it is unclear just how naturally brutish man is, how much this has change over our history (plenty to suggest we’re less violent than our ancestors but it’s debated)
I thought we actually have decent grounding here.
For hunter gatherer males before agriculture, the rate is something like 30-50% chance of violent death in their lifetime. If you put it in terms of violent deaths per 100k, they're averaging about 1030. Some of the most warlike HG tribes we've seen historically top at 1500.
> and how much the male proclivity for violence varies over the population.
For more recent non-state hunter gatherers 1800 - today they've come down to ~520.
Here's a table I made showing rates for one of my own substack posts:
https://imgur.com/a/J1bcPPG
And of course for modern states like Europe and the US, if you include homicides we're at rates between 0.2 (Japan), ~1 (most of Europe), and ~7 (USA) today.
This overall narrative arc of progressively reducing violence is basically the narrative in Stephen Pinkers Better Angels of our Nature.
> It seems like there could have been and still be a lot of things that domesticate and/or pacify men so that we act less troglodytian.
Yes, have you read Richard Wrangham's *The Goodness Paradox?* It's about our self-domestication as a species. Amazingly readable and accessible book, like most of his books. I think a combination of this and Geoffrey Miller's *The Mating Mind* covers the forces making us less troglodytian. Broadly, it's sexual selection for hundreds of thousands of years, then the Tyranny of the Cousins for a few hundred thousand.
This is directly contrasted with our confreres the Neanderthals, and our likely-ancestors H Heidelbergensis, who were not domesticated and so had massively higher testosterone, and likely much higher reactive aggression. This led to them having much lower group sizes, and our self domestication was like a super weapon that led to us wiping them (and every other) hominin species out in our last out-migration from Africa after the Cognitive Revolution 50kya.
I wrote about this in a different substack post, but don't want to seem like I'm spamming your comment section, so won't leave a link to any of them unless asked.
In terms of Neanderthal violent death rates per 100k, it's difficult to estimate, but if you count hunting accidents, it would be significantly higher than ours - they were more or less obligate carnivores, the majority of their diet was meat according to dentin studies, and so they had to hunt for food much more often than H Sap did, and their life expectancy was quite a bit shorter than H Sap hunter gatherer life expectancies. Contemporary HG's like the Hadza live to their mid 70's, and adult Neanderthals lived to their early 40's or so on average (so that's not the typical "medieval people only lived to 40" misunderstanding driven by high infant mortality), and the majority of skeletal remains found have signs of injury or violent death.
Thanks for the comments and the table is useful. I'll respond to a few points here.
>I thought we actually have decent grounding here.
This will depend on your prior beliefs and the amount of skepticism you'd like to apply to the claims. I think I'm generally satisfied with the "Better Angels" model and Wrangham's domestication/purging of brutes theory. But with all claims that rely on historical dataset, it is easy for a critic to point to things like ascertainment bias or other possible issues with the numbers. Also, the environment has changed substantially over the course of human history (social, climate, pop size, etc) which can make it difficult to put a number on what the natural rate of human violence is. I think it's safe to say that nature is "red in tooth and claw" and that Hobbes is more correct than Rousseau, but I was trying to gesture at uncertainty about the intensity of our devilish side.
>Yes, have you read Richard Wrangham's *The Goodness Paradox?* It's about our self-domestication as a species. Amazingly readable and accessible book, like most of his books. I think a combination of this and Geoffrey Miller's *The Mating Mind* covers the forces making us less troglodytian. Broadly, it's sexual selection for hundreds of thousands of years, then the Tyranny of the Cousins for a few hundred thousand.
I'm familiar with these books and obviously many other evo-psych theories and research. This Fatherhood book by Hrdy directly critiques the traditional sexual selection theory of paternal care and downplays kinship theories a bit. She prefers a "social selection" model which of course is still ultimately mediated by sexual selection but the vector that's relevant to selection in her view is social status as understood as being a good and generous group members (reputation). Her evidence for this is fairly thin as it relies on extrapolations about available calories across the Pleistocene, but she draws on examples of how other animals share parental/care duties in harsh conditions.
>This is directly contrasted with our confreres the Neanderthals, and our likely-ancestors H Heidelbergensis, who were not domesticated and so had massively higher testosterone, and likely much higher reactive aggression. This led to them having much lower group sizes, and our self domestication was like a super weapon that led to us wiping them (and every other) hominin species out in our last out-migration from Africa after the Cognitive Revolution 50kya.
I think more recent evidence suggests a more complex story. There is new strong evidence that many Neanderthal groups were incredibly isolated so there was a high-level on consanguinity. This of course is unlikely to be adaptive. Additionally, there is new evidence that the Neanderthal admixture to our lineage was likely much more substantial than the remaining ~2% that lingers today. This suggests that Neaderthals that did mingle with modern human groups were able to cooperate to some degree.
> But with all claims that rely on historical dataset, it is easy for a critic to point to things like ascertainment bias or other possible issues with the numbers.
Ah, sure. But it's not just ethnographies, it's also things like how many skeletons show evidence of violent death and such.
> I think more recent evidence suggests a more complex story. There is new strong evidence that many Neanderthal groups were incredibly isolated so there was a high-level on consanguinity. This of course is unlikely to be adaptive. Additionally, there is new evidence that the Neanderthal admixture to our lineage was likely much more substantial than the remaining ~2% that lingers today. This suggests that Neaderthals that did mingle with modern human groups were able to cooperate to some degree.
I think this fits in, though. The reason N's were more inbred *was* the smaller group sizes and likely higher reactive aggression.
Human HG's generally have larger group sizes and larger group affiliations - you have your immediate clan, but you also have your tribe and your people that you share a language with, and HG's generally get together in larger aggregates and pair up with more mating diversity at those times.
If N's were more reactively aggressive, this would be hard. Most N group sizes were basically "1 or 2 families," and it's likely they explicitly followed the "alpha dominating the group" thing we got away from via domestication and Cousin Tyranny. If this is the case, and an N supergrouping requires a bunch of alphas to put away their clubs and all make nice, that's obviously harder from the beginning, and more volatile and hard to sustain, and so the lower genetic diversity.
The H Sap + N admixture is fun, too. Deep time is a big space, and groups of H Sap and N's were living side by side for hundreds of thousands of years in the Levant and Europe, so we can't really say with authority that there was any one dynamic. But I'd point out that things like a "Yamnaya model of admixture" is just as plausible as H Sap and N's cooperating and trading mates. Indeed, David Reich once pointed out that the majority of N + H Sap breedings were N male + H Sap female - this is at least suggestive of a "Yamnaya model of admixture," if not dispositive. Because if it's two groups getting together in the spirit of amity and exchange, wouldn't you expect women to change hands on both sides, as often happens in HG's historically?
>Ah, sure. But it's not just ethnographies, it's also things like how many skeletons show evidence of violent death and such.
I'm referring to more than just methodology. There is a survival bias to what is available to dig up (i.e. the preservation of remains isn't a random process), and the areas that are accessible for professional digs are not random either (ascertainment bias). There is also some noise/expert judgement in the forensic analysis of remains of course. It's hard to know exactly how this should cause us to adjust our understanding of the data we have. I'm inclined to believe in the signal. I'm just highlighting the level of uncertainty here.
>I think this fits in, though. The reason N's were more inbred *was* the smaller group sizes and likely higher reactive aggression.
I think there are a lot of inputs on this other than T levels. T levels alone aren't the best predictor of reactive aggression either. I think there is evidence of isolation due to social, geographical, and climate factors. And again, there was also substantial intermixing that occurred in more than one location. We know this because we have hybrid remains who are verified as not ancestral to us.
>David Reich once pointed out that the majority of N + H Sap breedings were N male + H Sap female - this is at least suggestive of a "Yamnaya model of admixture,"
I actually haven't see this claim for Reich, but I'm not sure how much it would mean for our lineage because of low fertility in hybrid males. The next generation after mixing would require Sapien males. In the Dwarkesh pod, he entertain the idea that a Neander group was perhaps successive introgressed by waves of humans from NE Africa/N. East and this created modern humans.
Thanks, interesting take on Father Time. I've just started reading Father Time when I came across your post. I've read several books of Sarah Blaffer Hrdy, she's a great scholar and an inspiring writer. Sarah Blaffer Hrdy: “Human males may nurture their young a little, a lot, or not at all” (Mothers and Others, 2009: 162). I am very curious how her journey got Hrdy from this universal truth to this point that you mention: "My unexpected finding is that inside every man there lurk ancient caretaking tendencies that render a man every bit as protective and nurturing as the most committed mother. After all: “Of all the casts of characters in this melodrama the role of the father is the most subject to creative script variation” - David Lancy (The Anthropology of Childhood - Cherubs, Chattel, Changelings, 2022: 131).
It seems the softening of Hrdy's view of the innate care capacities/proclivities of men began in the 2010s. It appears to be in response to two major lines of research: 1) live brain imaging (fMRI) studies of the parents of newborns and 2) behavioral endocrinology studies in humans of prolonged exposure to children (I link to the famous PNAS study which was also popularized by Jo Henrich in The WEIRDest People in the World). It seems her experiences watching millennial fathering practices in America firsthand also motivated her rethinking.
As my review hopefully highlights, I am persuaded by the latter evidence but not impressed by the former. And in her speculation about how selection has shaped male parenting, I think she's invested a bit too much in marginal phenomenon. It seems the sexual selection dynamics (i.e. differential parental investment - a theory pioneered by her post-doc advisor) is still likely most of what is going on (past and present) and we're just talking about changes in the human niche and what status is/means.
From a genetic perspective, it is of course very plausible that there is a substrate for care/parenting shared by both sexes. It would be interesting to know what the genetic architecture of that substrate is (in the autosome) and how the presence of a Y chromosome and a lack of a second X chromosome is likely to modify the expression of that care substrate. We may also learn how much natural variation there is in care/parenting abilities/proclivities. I'm sure some insight can already be already gleaned from the genetics/GWAS literature, but I haven't investigated.
What about biologic data on human adoptive parents both male and female as well as any adoptive animal data?
The endocrine response appears to be an adapted response to prolonged proximity to babies. Happens in any human being. In animals, this can also be replicated but it often a lot harder to trigger. Hrdy describes attempts to sensitize male mice to unrelated pups in the book. Most of the time the unrelated male mouse just kills and cannibalizes the pup. Hrdy's account does not entirely explain why infanticide is seemingly so rare in humans compared to the animal kingdom and even near ape relatives (e.g. chimps).