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Original, non-blogspam article: http://med.stanford.edu/ism/2013/july/ratios.html http://med.stanford.edu/ism/2013/july/ratios.html This PR is ridiculously uns

Original, non-blogspam article: http://med.stanford.edu/ism/2013/july/ratios.html http://med.stanford.edu/ism/2013/july/ratios.html This PR is ridiculously unscientific. This doesn't "prove" their hypothesis. They've found no mechanism of action meaning they found a correlation. Correlation is not causation. Maybe the actual study found something more than the PR says but it doesn't seem like it. Also, they called it the "holy grail". Seriously?

azakai 13y ago
As the Stanford article said, this is "one of the holy grails" in its field because it has been an open question for decades. It was hypothesized but never observed, because collecting the data - multigenerational family histories of animals - is quite hard. The researchers found a clever way by analyzing zoo animals, which do have records. It still took years of work though. Of course they didn't "prove" anything. But you are setting a ridiculously high bar for scientific progress, which is generally very incremental. They took an open question that was undecided for decades and found a way to collect a large amount of data to support the hypothesis. Now that that is - finally! - done, work can proceed to focus on the mechanism.
- DrJosiah 13y ago
  Here's a mechanism that is infinitely times more plausible than the lack of mechanism in any article published so far, which doesn't rely on hand-wavy inter-uterus sperm manipulation: Mothers with multiple sons (as opposed to mixed gender or primarily female) will have a higher likelihood of having a dominant son, thus more grandchildren, due to one or more of the combination of: 1) competition among sons generates sons able to compete against the larger herd/pack, 2) multiple raffle tickets are better than one, 3) cooperative dominance among siblings (they all work to dominate the rest), 4) in some species, only dominant males are allowed to breed (or are allowed to breed more often), which means that a male will father offspring from multiple mothers, of which sons will tend to be dominant based on their father's genetics, which feeds back on #1, #2, and/or #3. I'm not saying that any of these are the cause, but they are reasonably plausible, and have an obvious behavioral mechanism that could easily result in the numbers that the research shows.
  - azakai 13y ago
    Maybe I miss your point, but it seems those are arguments for having more sons? The finding is that the ratio is overall 50-50, so there are not more sons overall. But that the ratio changes over time and individuals, sometimes with more sons and sometimes with less, depending on which would be more effective for the particular time and individual (if the individual has genes that would benefit a female more than a male, then more female offspring, etc.).
    - DrJosiah 13y ago
      I'm going to use human terms, because talking about multi-species offspring is messing with my pronouns. They took a multi-generational history of a collection of mammals. Then they look at how many 2nd generation children are produced when 1st generation tended to be mixed in gender, vs. predominantly males. From this data, they determined that on average, the when the 1st generation of children tended to be male, they had 2.7 times (on average) as many 2nd generation children than if they had been in a mixed-gender 1st generation. From my perspective, it seems as though the study looked at all of the outliers in the population, then used an unsubstantiated hypothesis from 30 years ago to fit the outlier data, despite the fact that if you look at the general population as a whole, those outliers are expected in the sample, and might be explainable when you look at herd/group behaviors. There are potentially many factors that can lead to more children in the 2nd generation for male-dominated 1st generation, of which I listed 4 possible factors that doesn't rely on the mother determining the sex of their offspring. Color me a skeptic, but I'll believe social behavior before uterine gender manipulation any day of the week - especially in animals that are known to be social.
venomsnake 13y ago
Actually I thought of very fun experiment - because the gender of the baby is determined by the father - make two groups live in extreme condition bio-dome style for a month or two - 900 males and 100 females and in the other 100 males and 900 females in the second. Then at the end of the period just examine the ratio of sperm cells with X and Y chromosome in the males' semen. If there is sizable difference means there are mechanisms for regulation and selection. Anecdotal evidence is that even after very bloody wars where the males die off disproportionately the population does not stray off a lot in the gender balance after a few years. Bonus points if you make it with humans as reality TV on Bravo.
- dllthomas 13y ago
  The hypothesis here is that it is not the father that determines the gender of the baby.
  - venomsnake 13y ago
    The father determines the gender in a sense that he provides both X and Y. The woman only provides X. In the facts given in the article I found nothing convincing that the gender selectors are females i.e. they conclude that they are. Now I haven't studied seriously biology but to change the meiosis of sperm cells to skew the odds seems more effective (and simple) than to have the egg cell select the sperm with the X or Y chromosome during the fertilization that is messy as it is. And if X and Y sperm cells were somehow different I think we may have found out.
    - dllthomas 13y ago
      > The father determines the gender in a sense that he provides both X and Y. The woman only provides X. That's not a meaningful sense. Obviously it's a question of whether a sperm cell carrying an X or Y chromosome gets into the egg, but both parties have a lot of biology involved between meiosis and fertilization that might impact that. > Now I haven't studied seriously biology but to change the meiosis of sperm cells to skew the odds seems more effective (and simple) than to have the egg cell select the sperm with the X or Y chromosome during the fertilization that is messy as it is. And if X and Y sperm cells were somehow different I think we may have found out. X and Y sperm cells are different - one is carrying an X and the other is carrying a Y and these will therefore have different masses and probably some other characteristics will differ. As female mammals tend to invest hugely more resources in the individual child, it's more likely to be worthwhile to them to sacrifice some chance of conception to favor a particular gender. Furthermore, if the child is more likely to stay with the female, the female is a better predictor of the environment the child will be raised in. Since meiosis produces an X and Y cell inherently (it splits a cell with an X+Y in half, with one chromosome going each way) and furthermore happens well in advance of mating when the partner may not even be determined, it seems less likely that the cause for any pattern in SR would be manipulation of the ratio of X vs Y cells during meiosis. Of course, biology surprises on occasion, I just think you're making entirely unwarranted assumptions.
nostrademons 13y ago
I thought I've read other papers where a mechanism was both proposed and observed. Selective abortion - female mammalian bodies will abort fetuses in the early months of pregnancy when environmental conditions indicate that offspring don't stand a good chance of survival. IIRC the paper I read showed this happened in mice, but it's known that in humans a large number of women will miscarry in the first 1-2 months of pregnancy, and it may be the same mechanism at work there.
Tloewald 13y ago
There is no proof in empirical science. It's annoying when people claim it, and just as annoying when people demand it.

azakai 13y ago

As the Stanford article said, this is "one of the holy grails" in its field because it has been an open question for decades. It was hypothesized but never observed, because collecting the data - multigenerational family histories of animals - is quite hard. The researchers found a clever way by analyzing zoo animals, which do have records. It still took years of work though. Of course they didn't "prove" anything. But you are setting a ridiculously high bar for scientific progress, which is generally very incremental. They took an open question that was undecided for decades and found a way to collect a large amount of data to support the hypothesis. Now that that is - finally! - done, work can proceed to focus on the mechanism.

DrJosiah 13y ago
Here's a mechanism that is infinitely times more plausible than the lack of mechanism in any article published so far, which doesn't rely on hand-wavy inter-uterus sperm manipulation: Mothers with multiple sons (as opposed to mixed gender or primarily female) will have a higher likelihood of having a dominant son, thus more grandchildren, due to one or more of the combination of: 1) competition among sons generates sons able to compete against the larger herd/pack, 2) multiple raffle tickets are better than one, 3) cooperative dominance among siblings (they all work to dominate the rest), 4) in some species, only dominant males are allowed to breed (or are allowed to breed more often), which means that a male will father offspring from multiple mothers, of which sons will tend to be dominant based on their father's genetics, which feeds back on #1, #2, and/or #3. I'm not saying that any of these are the cause, but they are reasonably plausible, and have an obvious behavioral mechanism that could easily result in the numbers that the research shows.
- azakai 13y ago
  Maybe I miss your point, but it seems those are arguments for having more sons? The finding is that the ratio is overall 50-50, so there are not more sons overall. But that the ratio changes over time and individuals, sometimes with more sons and sometimes with less, depending on which would be more effective for the particular time and individual (if the individual has genes that would benefit a female more than a male, then more female offspring, etc.).
  - DrJosiah 13y ago
    I'm going to use human terms, because talking about multi-species offspring is messing with my pronouns. They took a multi-generational history of a collection of mammals. Then they look at how many 2nd generation children are produced when 1st generation tended to be mixed in gender, vs. predominantly males. From this data, they determined that on average, the when the 1st generation of children tended to be male, they had 2.7 times (on average) as many 2nd generation children than if they had been in a mixed-gender 1st generation. From my perspective, it seems as though the study looked at all of the outliers in the population, then used an unsubstantiated hypothesis from 30 years ago to fit the outlier data, despite the fact that if you look at the general population as a whole, those outliers are expected in the sample, and might be explainable when you look at herd/group behaviors. There are potentially many factors that can lead to more children in the 2nd generation for male-dominated 1st generation, of which I listed 4 possible factors that doesn't rely on the mother determining the sex of their offspring. Color me a skeptic, but I'll believe social behavior before uterine gender manipulation any day of the week - especially in animals that are known to be social.

venomsnake 13y ago

Actually I thought of very fun experiment - because the gender of the baby is determined by the father - make two groups live in extreme condition bio-dome style for a month or two - 900 males and 100 females and in the other 100 males and 900 females in the second. Then at the end of the period just examine the ratio of sperm cells with X and Y chromosome in the males' semen. If there is sizable difference means there are mechanisms for regulation and selection. Anecdotal evidence is that even after very bloody wars where the males die off disproportionately the population does not stray off a lot in the gender balance after a few years. Bonus points if you make it with humans as reality TV on Bravo.

dllthomas 13y ago
The hypothesis here is that it is not the father that determines the gender of the baby.
- venomsnake 13y ago
  The father determines the gender in a sense that he provides both X and Y. The woman only provides X. In the facts given in the article I found nothing convincing that the gender selectors are females i.e. they conclude that they are. Now I haven't studied seriously biology but to change the meiosis of sperm cells to skew the odds seems more effective (and simple) than to have the egg cell select the sperm with the X or Y chromosome during the fertilization that is messy as it is. And if X and Y sperm cells were somehow different I think we may have found out.
  - dllthomas 13y ago
    > The father determines the gender in a sense that he provides both X and Y. The woman only provides X. That's not a meaningful sense. Obviously it's a question of whether a sperm cell carrying an X or Y chromosome gets into the egg, but both parties have a lot of biology involved between meiosis and fertilization that might impact that. > Now I haven't studied seriously biology but to change the meiosis of sperm cells to skew the odds seems more effective (and simple) than to have the egg cell select the sperm with the X or Y chromosome during the fertilization that is messy as it is. And if X and Y sperm cells were somehow different I think we may have found out. X and Y sperm cells are different - one is carrying an X and the other is carrying a Y and these will therefore have different masses and probably some other characteristics will differ. As female mammals tend to invest hugely more resources in the individual child, it's more likely to be worthwhile to them to sacrifice some chance of conception to favor a particular gender. Furthermore, if the child is more likely to stay with the female, the female is a better predictor of the environment the child will be raised in. Since meiosis produces an X and Y cell inherently (it splits a cell with an X+Y in half, with one chromosome going each way) and furthermore happens well in advance of mating when the partner may not even be determined, it seems less likely that the cause for any pattern in SR would be manipulation of the ratio of X vs Y cells during meiosis. Of course, biology surprises on occasion, I just think you're making entirely unwarranted assumptions.

nostrademons 13y ago

I thought I've read other papers where a mechanism was both proposed and observed. Selective abortion - female mammalian bodies will abort fetuses in the early months of pregnancy when environmental conditions indicate that offspring don't stand a good chance of survival. IIRC the paper I read showed this happened in mice, but it's known that in humans a large number of women will miscarry in the first 1-2 months of pregnancy, and it may be the same mechanism at work there.

Tloewald 13y ago

There is no proof in empirical science. It's annoying when people claim it, and just as annoying when people demand it.