Continuing down the road of behavioral evolution, Professor Sapolsky discusses....
He begins by covering some elements of grading and the upcoming book and reading assignments. The theme here is that you can optimize behaviors in a manner similar to the physiological optimization that occurs through natural selection. This is also an extension off the Game Theory elements in the previous lecture.
By the mid-70's, field researchers had provided substantial evidence that despite popular belief to the contrary, man is not the only species that kills for non-predatory reasons.
Infanticide is found within groups of langur monkeys, lions, vervet monkeys, mountain gorillas and other species as well. Initial attempts were made to dismiss the events as abnormal, with a variety of reasons to set aside the behavior as psychopathological but not typical of the species.
By the mid-70's, field researchers had provided substantial evidence that despite popular belief to the contrary, man is not the only species that kills for non-predatory reasons.
Infanticide is found within groups of langur monkeys, lions, vervet monkeys, mountain gorillas and other species as well. Initial attempts were made to dismiss the events as abnormal, with a variety of reasons to set aside the behavior as psychopathological but not typical of the species.
Normal....
But as the evidence kept pouring in, the idea that this was abnormal was set aside. Biologists began noticing patterns. It tends to be adult males doing the killing. The actions are not random; the infants are the offspring of other males. It's a competitive strategy that reduces the other guy's reproductive success while improving the killer's since the female no longer has anything to mother and can now move back into the birthing cycle and have his offspring.
There is a formula for this - competitive infanticide occurs when the time between births by the mother is shorter than the average reign for the top male. So the competitive infanticide is there to ensure that he doesn't miss out on the chance to breed with the female when she's busy rearing her offspring instead of mating with him.
The most striking example of how this demonstrates that animals do not operate for the good of the group is that of mountain gorillas. Their numbers are dwindling with approximately 600-700 out there in the wild but they continue to kill their own despite it being against their best interests.
It is, however, highly unlikely that Ishmael would engage in this foolish behavior...
However, when the male replaces a relative, the infanticide is checked by the element of kinship selection and the evolved behavior of supporting, not destroying, the success of relatives.
Females have developed responses to the infanticide. They may spontaneously abort the fetus (rodents), miscarry after being harassed by the new male (wild horses) or even go into pseudo-estrus in which they give off all the signs and even mate with the new guy but without actually giving up the original fetus.
Females will also physically defend their offspring, with the most menacing being the maternal grandmother who has past her prime but still has a genetic stake in the matter. The mother will defend, but not to the point of serious injury. As she ages, her defense will be more vigorous. (Of course these are general patterns and an aggressive male is not guaranteed that things will turn out well for him.)
Kidnapping among savannah baboons is more likely to be seen when the aggressive, high ranking male has been in the troop for a while than when he hasn't since some other baboon's offspring doesn't make a compelling shield.
He then walks through a complicated analysis of dominance hierarchies. In essence, having males is a "risky strategy" in a tournament species because 5% of the males get to produce 95% of the future offspring, so the odds are that a male will not get to mate well. Females tend to mate regardless, so having a female will tend to carry the genes onward at a higher rate. Thus higher ranking females show a greater tendency to give birth to males while lower ranking females have a greater tendency to give birth to females. This is not a choice, but rather reflects some gradual adaptation that's resulted from the males of top ranking females getting to pass on their genes while the lower ranking females' male offspring did not but their daughters did. However, dominance among the males is not based on nepotism, it's based on strength and power, so a male can ascend if he's able to. And the male offspring of a top ranking female may be entirely unsuccessful. My sense is that there isn't a lot to be gained from this section as it's speculative and, of course, the females aren't really choosing to have a male or a female baby; there's simply some tendency that has enabled the offspring of top ranking male-female combinations to be more likely to produce a male. This notion leads into an upcoming topic, which is intersexual competition.
The bias toward more females during times of ecological duress connects directly to the metabolic demands of males being higher than the metabolic demands of females. The tougher it is on the mother, the greater the odds of the fetus not surviving.
Intersexual competition reflects differing interests in the future reproductive success of the female. In tournament species in which the males migrate, they care little about what happens to the female once they are gone and so aggressive elements are sometimes found within their sperm. These elements help increase the odds of generating a successful pregnancy and set the fetus up to be more metabolically demanding. Females, on the other hand, have evolved ways to neutralize these elements as they are costly and dangerous.
Imprinted genes are genes that have different manifestations depending on which parent they came from. In classic Mendelian genetics, a combination of Aa and AA treats the A's as similar, but with imprinted genes it actually matters whether the A came from the father or mother because the gene will behave differently. Through the process of methylization, the gene's behavior will be altered based on its origin. If you get it from one parent it will be active, if from the other it will be silenced. When you look at imprinted genes that are active if they come from the father, they all tend to be genes that promote fetal growth. If from the mother, they tend to slow down fetal growth. For example, one of the genes codes for insulin like growth factor. Not hard to see how that fits in. The female's version makes for a less responsive receptor for the insulin like growth factor. Another example is choriocarcinoma, which is a cancer of the uterus that can happen if the male's sperm has aggressive growth factors and the female has no counterbalancing genes; this leads to unchecked growth which is bad. Pregnancy hyperglycemia is another example as the fetus is trying to get lots of sugar from mom but mom may have an active gene that checks that (hypoglycemia will occur if she does not). These types of imprinted genes are not typically seen in pair bonding species. Humans are again right in the middle.
Next up is the fun topic of...sperm competition? Yes, research into fruit flies shows that another strategy that's out there is the sperm carrying a toxin that kills off other males' sperm. Sadly for the females, the toxins are also potentially toxic to them. Thus we see females have evolved ways to counteract this.
Exogamy impacts the behavior of animals as well. There is variation in who leaves (females in chimps and gorillas, males in baboon troops) and that influences what happens within the group. For example, chimp groups can be highly aggressive and even genocidal toward other groups ("outsiders" or "them") because the males are all related by kinship ties and thus get along much better than they would if there was male exogamy.
Professor Sapolsky then makes an interesting point that relates to the later lectures on aggression: One of the scariest things in the world is when all the males in a given group start getting along really well with each other. Aggression toward the others often follows.
This relates to military techniques that aim to create a sense of kinship among the troops. This makes them a band of brothers that will cooperate with each other, though it can have divisive effects as well, such as was seen in the Vietnam War, because the group may agree to disagree with orders and commands from above, the hierarchical other.
Next we return back to Group Selection 2.0. The "Marlin Perkins" version of group selection was defined by individuals acting for the good of the species. The newer version differs. In this form of group selection, the following happens:
A bio-geographic (or other) event occurs that separates out a subset from a larger group. This smaller subset soon becomes more inbred than the larger whole, simply as a by-product of being a smaller group. This translates into having a higher degree of relatedness, which introduces the whole business of kin selection. Because these guys are more closely related, they will work together more as a group and will end up outcompeting the original group members when they are reunited. This is called a founder effect.
Another scenario is demonstrated through the example of two chickens, one that's highly aggressive and one that's more laid back. When competing one on one, the more aggressive chicken will lay more eggs, but there's the drawback in which a group of aggressive chickens will harass each other and thus impair their own breeding while the calmer group will lay more eggs because as a group they cause less grief for each other.
Professor Sapolsky moves on to discuss criticisms of the ideas of evolutionary biology. The first criticism rests on the notion of heritability and the associated notion that the behaviors are genetically received, inevitable and produced. The next notion is that of adaptiveness, which suggests that all behaviors have evolved because they are adaptive (beneficial). The third principle is that the changes are gradual.
The molecular view challenges the notion of heritability. While the evolutionary biologist argues that the trait is commonly seen among groups and has emerged because it is inherited and beneficial, the molecular folks say show me the gene, establish the direct connection.
Adaptiveness is attacked as the adaptationist fallacy. Everything is reduced down to a just so story in which the best story wins. He notes that to honestly assess it, you must keep the context in mind. Squid aren't so great as swimmers compared to fish, but they kick butt compared to mollusks, which is where they started. Nevertheless we have the concept of spandrels (courtesy of Stephen Jay Gould and Richard Lewontin), suggesting that some evolved elements just came along for the ride.
There is a formula for this - competitive infanticide occurs when the time between births by the mother is shorter than the average reign for the top male. So the competitive infanticide is there to ensure that he doesn't miss out on the chance to breed with the female when she's busy rearing her offspring instead of mating with him.
The most striking example of how this demonstrates that animals do not operate for the good of the group is that of mountain gorillas. Their numbers are dwindling with approximately 600-700 out there in the wild but they continue to kill their own despite it being against their best interests.
It is, however, highly unlikely that Ishmael would engage in this foolish behavior...
However, when the male replaces a relative, the infanticide is checked by the element of kinship selection and the evolved behavior of supporting, not destroying, the success of relatives.
Females have developed responses to the infanticide. They may spontaneously abort the fetus (rodents), miscarry after being harassed by the new male (wild horses) or even go into pseudo-estrus in which they give off all the signs and even mate with the new guy but without actually giving up the original fetus.
Females will also physically defend their offspring, with the most menacing being the maternal grandmother who has past her prime but still has a genetic stake in the matter. The mother will defend, but not to the point of serious injury. As she ages, her defense will be more vigorous. (Of course these are general patterns and an aggressive male is not guaranteed that things will turn out well for him.)
Kidnapping among savannah baboons is more likely to be seen when the aggressive, high ranking male has been in the troop for a while than when he hasn't since some other baboon's offspring doesn't make a compelling shield.
He then walks through a complicated analysis of dominance hierarchies. In essence, having males is a "risky strategy" in a tournament species because 5% of the males get to produce 95% of the future offspring, so the odds are that a male will not get to mate well. Females tend to mate regardless, so having a female will tend to carry the genes onward at a higher rate. Thus higher ranking females show a greater tendency to give birth to males while lower ranking females have a greater tendency to give birth to females. This is not a choice, but rather reflects some gradual adaptation that's resulted from the males of top ranking females getting to pass on their genes while the lower ranking females' male offspring did not but their daughters did. However, dominance among the males is not based on nepotism, it's based on strength and power, so a male can ascend if he's able to. And the male offspring of a top ranking female may be entirely unsuccessful. My sense is that there isn't a lot to be gained from this section as it's speculative and, of course, the females aren't really choosing to have a male or a female baby; there's simply some tendency that has enabled the offspring of top ranking male-female combinations to be more likely to produce a male. This notion leads into an upcoming topic, which is intersexual competition.
The bias toward more females during times of ecological duress connects directly to the metabolic demands of males being higher than the metabolic demands of females. The tougher it is on the mother, the greater the odds of the fetus not surviving.
Intersexual competition reflects differing interests in the future reproductive success of the female. In tournament species in which the males migrate, they care little about what happens to the female once they are gone and so aggressive elements are sometimes found within their sperm. These elements help increase the odds of generating a successful pregnancy and set the fetus up to be more metabolically demanding. Females, on the other hand, have evolved ways to neutralize these elements as they are costly and dangerous.
Imprinted genes are genes that have different manifestations depending on which parent they came from. In classic Mendelian genetics, a combination of Aa and AA treats the A's as similar, but with imprinted genes it actually matters whether the A came from the father or mother because the gene will behave differently. Through the process of methylization, the gene's behavior will be altered based on its origin. If you get it from one parent it will be active, if from the other it will be silenced. When you look at imprinted genes that are active if they come from the father, they all tend to be genes that promote fetal growth. If from the mother, they tend to slow down fetal growth. For example, one of the genes codes for insulin like growth factor. Not hard to see how that fits in. The female's version makes for a less responsive receptor for the insulin like growth factor. Another example is choriocarcinoma, which is a cancer of the uterus that can happen if the male's sperm has aggressive growth factors and the female has no counterbalancing genes; this leads to unchecked growth which is bad. Pregnancy hyperglycemia is another example as the fetus is trying to get lots of sugar from mom but mom may have an active gene that checks that (hypoglycemia will occur if she does not). These types of imprinted genes are not typically seen in pair bonding species. Humans are again right in the middle.
Next up is the fun topic of...sperm competition? Yes, research into fruit flies shows that another strategy that's out there is the sperm carrying a toxin that kills off other males' sperm. Sadly for the females, the toxins are also potentially toxic to them. Thus we see females have evolved ways to counteract this.
Exogamy impacts the behavior of animals as well. There is variation in who leaves (females in chimps and gorillas, males in baboon troops) and that influences what happens within the group. For example, chimp groups can be highly aggressive and even genocidal toward other groups ("outsiders" or "them") because the males are all related by kinship ties and thus get along much better than they would if there was male exogamy.
Professor Sapolsky then makes an interesting point that relates to the later lectures on aggression: One of the scariest things in the world is when all the males in a given group start getting along really well with each other. Aggression toward the others often follows.
This relates to military techniques that aim to create a sense of kinship among the troops. This makes them a band of brothers that will cooperate with each other, though it can have divisive effects as well, such as was seen in the Vietnam War, because the group may agree to disagree with orders and commands from above, the hierarchical other.
Next we return back to Group Selection 2.0. The "Marlin Perkins" version of group selection was defined by individuals acting for the good of the species. The newer version differs. In this form of group selection, the following happens:
A bio-geographic (or other) event occurs that separates out a subset from a larger group. This smaller subset soon becomes more inbred than the larger whole, simply as a by-product of being a smaller group. This translates into having a higher degree of relatedness, which introduces the whole business of kin selection. Because these guys are more closely related, they will work together more as a group and will end up outcompeting the original group members when they are reunited. This is called a founder effect.
Another scenario is demonstrated through the example of two chickens, one that's highly aggressive and one that's more laid back. When competing one on one, the more aggressive chicken will lay more eggs, but there's the drawback in which a group of aggressive chickens will harass each other and thus impair their own breeding while the calmer group will lay more eggs because as a group they cause less grief for each other.
Professor Sapolsky moves on to discuss criticisms of the ideas of evolutionary biology. The first criticism rests on the notion of heritability and the associated notion that the behaviors are genetically received, inevitable and produced. The next notion is that of adaptiveness, which suggests that all behaviors have evolved because they are adaptive (beneficial). The third principle is that the changes are gradual.
The molecular view challenges the notion of heritability. While the evolutionary biologist argues that the trait is commonly seen among groups and has emerged because it is inherited and beneficial, the molecular folks say show me the gene, establish the direct connection.
Adaptiveness is attacked as the adaptationist fallacy. Everything is reduced down to a just so story in which the best story wins. He notes that to honestly assess it, you must keep the context in mind. Squid aren't so great as swimmers compared to fish, but they kick butt compared to mollusks, which is where they started. Nevertheless we have the concept of spandrels (courtesy of Stephen Jay Gould and Richard Lewontin), suggesting that some evolved elements just came along for the ride.
These spandrels would be decorated, but for all that they weren't put there for adaptive purposes. They are simply inevitable when arches are brought together. As Francois Jacob put it "Evolution is a tinkerer."
Next the critique becomes more interesting as Sapolsky notes that the larger argument is that the theory is heavily saturated with elements of competition and outcompeting the others at every level, with the winner being, by definition, the best and most worthy and most fit. All of this fits in with rather nicely with the world view and SES of the people advancing these arguments, each of whom was a Southern white male.
On the other hand, competition may not be the most important element. Russian biologists viewed the issue from a collective viewpoint and had a greater respect for the impact of external elements, such as the environment.
Gould and others suggested that gradualism was possibly a flawed concept. Instead they suggested that punctuated equilibrium makes more sense. In this scenario, most of the time nothing is happening and there isn't really much impact from all this competition stuff. Then a genetic change of some sort occurs and a massive change follows and then things return back to normal.
Politics comes into play as well, with issues ranging from male domination, sexual aggression, social stratification and more and the question of the extent to which these are a reflection of natural order.
On the other hand, the gradualists were Northeastern Marxists. And the world they want it to be fits smoothly into the notion of dialectical materialism.
Next the critique becomes more interesting as Sapolsky notes that the larger argument is that the theory is heavily saturated with elements of competition and outcompeting the others at every level, with the winner being, by definition, the best and most worthy and most fit. All of this fits in with rather nicely with the world view and SES of the people advancing these arguments, each of whom was a Southern white male.
On the other hand, competition may not be the most important element. Russian biologists viewed the issue from a collective viewpoint and had a greater respect for the impact of external elements, such as the environment.
Gould and others suggested that gradualism was possibly a flawed concept. Instead they suggested that punctuated equilibrium makes more sense. In this scenario, most of the time nothing is happening and there isn't really much impact from all this competition stuff. Then a genetic change of some sort occurs and a massive change follows and then things return back to normal.
Politics comes into play as well, with issues ranging from male domination, sexual aggression, social stratification and more and the question of the extent to which these are a reflection of natural order.
On the other hand, the gradualists were Northeastern Marxists. And the world they want it to be fits smoothly into the notion of dialectical materialism.
