so better not marry those SYTs if you want sons.
Go for the ugly broads instead.
http://alphadominance.com/?p=1126
In a recent posting the subject of sexual conflict came up, which is in essence the propagation of antagonistic goals by one of the sexes’ gametes at the expense of the other. This can set up sexual biases in certain lineage’s offspring. Sexual bias need not always be antagonistic however, sometimes both genders are served by having more sons or daughters.
The idea that such biases occur based on the fitness of the parents to optimize their reproductive potential with whatever genetic cards they’ve been dealt is called the Trivers-Willard hypothesis:
In evolutionary biology, the Trivers-Willard hypothesis proposes that, if parents have information on their offspring, it is more beneficial to invest in the sex that gives them the greatest reproductive payoff (‘grand-offspring’) with increasing or “marginal” investment, and that the “optimal” avenue of investment may differ according to the parent’s condition. It was formally put forth by Robert Trivers and Dan Willard.
For example, in species where some males may mate with multiple females and other males achieve few or no matings (polygynous species), parents in good condition can have many more grand-offspring if they produce and invest in sons rather than daughters, because their good-condition sons have an increased chance of mating with multiple females—a huge reproductive benefit—whereas daughters will experience smaller benefits from being in good condition.
On the other hand, the offspring of parents in poor condition are also likely to be in poor condition (all else being equal), so (among polygynous species) parents in poor condition will have more grand-offspring if they produce and invest in daughters rather than sons, because those daughters are likely to achieve at least some mating success (i.e. from the good-conditions males of other parents), whereas sons in poor condition may be outcompeted by other males and end up with zero mates (i.e. those sons will be a reproductive dead-end).
Thus, the Trivers-Willard hypothesis predicts greater investment in males by parents in good condition and greater investment in females by parents in poor condition (relative to parents in good condition). The hypothesis was used to explain why, for example, Red Deer mothers would produce more sons when they are in good condition, and more daughters when in poor condition. In polyandrous species where some females mate with multiple males (and others get no matings) and males mate with one/few females (i.e. “sex-role reversed” species), these predictions from the Trivers-Willard hypothesis are all reversed: parents in good condition will invest in daughters in order to have a daughter that can outcompete other females to attract multiple males, whereas parents in poor condition will avoid investing in daughters who are likely to get outcompeted and will instead invest in sons in order to gain at least some grandchildren.
One can define “good condition” in multiple ways, such as body size, low parasite loads, or dominance, which has also been shown to affect the sex of offspring, with dominant females birthing more sons and non-dominant females birthing more daughters. This effect has been found in macaques (Macaca sylvanus) where males born to high-ranking females have greater reproductive success than those of low-ranking females. Consequently high-ranking females give birth to a higher proportion of males than those who are low-ranking (Kuesterl & Arnemann 1992).
The Trivers-Willard hypothesis rests on certain assumptions:
1. Parental condition influences offspring condition;
2. Differences in offspring condition will persist into adulthood;
3. Being in good condition increases the mating success of one sex more than it does the other sex.
Evolutionary biologists predict a Trivers-Willard effect where these conditions hold, and no effect when these conditions do not hold. In polygynous species where some males have multiple mates and others have none (i.e. greater variance in mating success among males than females), being in good condition affects males more than females. This is reversed in polyandrous species, and possibly in species where condition is based on social status and males disperse.
No direct biochemical explanation of how the effect occurs has yet been given.
This reflects the core of the argument for why a woman should want to raise her son by an Alpha to adopt the reproductive strategy of his father. Since Alpha traits are largely genetically endowed, she stands to squander a major boost to her reproductive fitness if she successfully raises him to relate to women as a Beta “nice guy” instead. On the other hand if his father was a Beta this may represent his best opportunity at reproductive success. For non-Alpha fathers, daughters may present the best reproductive opportunity as they are likely to reproduce with either an Alpha or a Beta father but may be better endowed by a Beta father who passes on genes for less masculine characteristics and lower testosterone levels. The lesson here is that certain traits in offspring are more desirable than others and the choice hinges on parental reproductive fitness.
If this hypothesis holds in humans, we should see sexual biases in the offspring of parents with identifiable traits that would confer a reproductive advantage on their offspring, and indeed this is precisely what we find:
The generalized Trivers–Willard hypothesis (gTWH) [Kanazawa, S., 2005. Big and tall parents have more sons: further generalizations of the Trivers–Willard hypothesis. J. Theor. Biol. 235, 583–590) proposes that parents who possess any heritable trait which increases the male reproductive success at a greater rate than female reproductive success in a given environment will have a higher-than-expected offspring sex ratio, and parents who possess any heritable trait which increases the female reproductive success at a greater rate than male reproductive success in a given environment will have a lower-than-expected offspring sex ratio. One heritable trait which increases the reproductive success of daughters much more than that of sons is physical attractiveness. I therefore predict that physically attractive parents have a lower-than-expected offspring sex ratio (more daughters). Further, if beautiful parents have more daughters and physical attractiveness is heritable, then, over evolutionary history, women should gradually become more attractive than men. The analysis of the National Longitudinal Study of Adolescent Health (Add Health) confirm both of these hypotheses. Very attractive individuals are 26% less likely to have a son, and women are significantly more physically attractive than men in the representative American sample.
So there you have it gents. The most desirable gender of offspring hinges on the traits of the parents. If both are large and masculine female offspring will suffer reduced reproductive fitness, but males will benefit. If both are attractive with more effiminate features, or diminuitive, daughters will be the better bet. Like most areas of biology niche specialization confers benefits.
Go for the ugly broads instead.
http://alphadominance.com/?p=1126
In a recent posting the subject of sexual conflict came up, which is in essence the propagation of antagonistic goals by one of the sexes’ gametes at the expense of the other. This can set up sexual biases in certain lineage’s offspring. Sexual bias need not always be antagonistic however, sometimes both genders are served by having more sons or daughters.
The idea that such biases occur based on the fitness of the parents to optimize their reproductive potential with whatever genetic cards they’ve been dealt is called the Trivers-Willard hypothesis:
In evolutionary biology, the Trivers-Willard hypothesis proposes that, if parents have information on their offspring, it is more beneficial to invest in the sex that gives them the greatest reproductive payoff (‘grand-offspring’) with increasing or “marginal” investment, and that the “optimal” avenue of investment may differ according to the parent’s condition. It was formally put forth by Robert Trivers and Dan Willard.
For example, in species where some males may mate with multiple females and other males achieve few or no matings (polygynous species), parents in good condition can have many more grand-offspring if they produce and invest in sons rather than daughters, because their good-condition sons have an increased chance of mating with multiple females—a huge reproductive benefit—whereas daughters will experience smaller benefits from being in good condition.
On the other hand, the offspring of parents in poor condition are also likely to be in poor condition (all else being equal), so (among polygynous species) parents in poor condition will have more grand-offspring if they produce and invest in daughters rather than sons, because those daughters are likely to achieve at least some mating success (i.e. from the good-conditions males of other parents), whereas sons in poor condition may be outcompeted by other males and end up with zero mates (i.e. those sons will be a reproductive dead-end).
Thus, the Trivers-Willard hypothesis predicts greater investment in males by parents in good condition and greater investment in females by parents in poor condition (relative to parents in good condition). The hypothesis was used to explain why, for example, Red Deer mothers would produce more sons when they are in good condition, and more daughters when in poor condition. In polyandrous species where some females mate with multiple males (and others get no matings) and males mate with one/few females (i.e. “sex-role reversed” species), these predictions from the Trivers-Willard hypothesis are all reversed: parents in good condition will invest in daughters in order to have a daughter that can outcompete other females to attract multiple males, whereas parents in poor condition will avoid investing in daughters who are likely to get outcompeted and will instead invest in sons in order to gain at least some grandchildren.
One can define “good condition” in multiple ways, such as body size, low parasite loads, or dominance, which has also been shown to affect the sex of offspring, with dominant females birthing more sons and non-dominant females birthing more daughters. This effect has been found in macaques (Macaca sylvanus) where males born to high-ranking females have greater reproductive success than those of low-ranking females. Consequently high-ranking females give birth to a higher proportion of males than those who are low-ranking (Kuesterl & Arnemann 1992).
The Trivers-Willard hypothesis rests on certain assumptions:
1. Parental condition influences offspring condition;
2. Differences in offspring condition will persist into adulthood;
3. Being in good condition increases the mating success of one sex more than it does the other sex.
Evolutionary biologists predict a Trivers-Willard effect where these conditions hold, and no effect when these conditions do not hold. In polygynous species where some males have multiple mates and others have none (i.e. greater variance in mating success among males than females), being in good condition affects males more than females. This is reversed in polyandrous species, and possibly in species where condition is based on social status and males disperse.
No direct biochemical explanation of how the effect occurs has yet been given.
This reflects the core of the argument for why a woman should want to raise her son by an Alpha to adopt the reproductive strategy of his father. Since Alpha traits are largely genetically endowed, she stands to squander a major boost to her reproductive fitness if she successfully raises him to relate to women as a Beta “nice guy” instead. On the other hand if his father was a Beta this may represent his best opportunity at reproductive success. For non-Alpha fathers, daughters may present the best reproductive opportunity as they are likely to reproduce with either an Alpha or a Beta father but may be better endowed by a Beta father who passes on genes for less masculine characteristics and lower testosterone levels. The lesson here is that certain traits in offspring are more desirable than others and the choice hinges on parental reproductive fitness.
If this hypothesis holds in humans, we should see sexual biases in the offspring of parents with identifiable traits that would confer a reproductive advantage on their offspring, and indeed this is precisely what we find:
The generalized Trivers–Willard hypothesis (gTWH) [Kanazawa, S., 2005. Big and tall parents have more sons: further generalizations of the Trivers–Willard hypothesis. J. Theor. Biol. 235, 583–590) proposes that parents who possess any heritable trait which increases the male reproductive success at a greater rate than female reproductive success in a given environment will have a higher-than-expected offspring sex ratio, and parents who possess any heritable trait which increases the female reproductive success at a greater rate than male reproductive success in a given environment will have a lower-than-expected offspring sex ratio. One heritable trait which increases the reproductive success of daughters much more than that of sons is physical attractiveness. I therefore predict that physically attractive parents have a lower-than-expected offspring sex ratio (more daughters). Further, if beautiful parents have more daughters and physical attractiveness is heritable, then, over evolutionary history, women should gradually become more attractive than men. The analysis of the National Longitudinal Study of Adolescent Health (Add Health) confirm both of these hypotheses. Very attractive individuals are 26% less likely to have a son, and women are significantly more physically attractive than men in the representative American sample.
So there you have it gents. The most desirable gender of offspring hinges on the traits of the parents. If both are large and masculine female offspring will suffer reduced reproductive fitness, but males will benefit. If both are attractive with more effiminate features, or diminuitive, daughters will be the better bet. Like most areas of biology niche specialization confers benefits.
