Understanding the Trivers Willard Hypothesis
Edited 5-7-18
:owl: Sometimes we get so caught up in the hows of swaying that we forget to think about the whys. But a deeper understanding of WHY swaying works is of vital importance to the success of everyone’s sway. This understanding of the mechanisms that underlie swaying can help you formulate a plan so you can work with your body and with Mother Nature, rather than against them. Plus, it can help you understand why atomic sagebrush advises the things that she does rather than slavishly sticking to traditional sway tactics that other people swear have worked for them and may even have some pseudo-science-y gibberish behind them, and will make it easier for you to let go of things that simply don’t work in favor of concentrating on that which does.
:owl:What is the Trivers Willard Hypothesis? Trivers Nutshell version: the Trivers Willard Hypothesis hinges on the notion that animals have a very good reason, evolutionarily speaking, for being able to skew gender ratio in favor of the gender of offspring with the best odds of survival to adulthood/competing for mates/successfully reproducing, and that both behavioral and biological mechanisms have evolved (editorial note - or, been designed into us by God) to ensure that this happens. For swaying purposes, we’ll set aside the behavioral aspect of Trivers-Willard and focus on the biological – the stuff that is happening inside our bodies totally out of our control that causes us to conceive more of one gender than another – altho I may mention behavior along the way.
Trivers-Willard is all about the genes - if a male offspring has a better chance at handing down their ancestors’ genes to the next generation, then a couple should have more boys (and be willing and able to invest in them more heavily after birth), and if a female offspring has a better chance at handing down her ancestors’ genes, then a couple should have more girls (and be willing and able to invest in them more heavily after birth).
:owl:What’s the difference between boys and girls, anyway? How could the gender of your baby matter to their future survival and their chances of handing down their genes?
Firstly, on average, boys need more calories from the moment of conception, throughout pregnancy, childhood (there ~may~ be a brief period in infancy and toddlerhood where boys do not need more calories, but the data is mixed even during that period) adolescence and into adulthood. Baby boys weigh on average 3.5 oz. more than baby girls do at birth and this difference extends into young adulthood with active older teens and young men requiring in excess of 1000 calories a day more than active females of the same age group. Boys are more demanding even in utero
How Many Calories Do Children Need? | eHow.com
(editorial note – some people like to chalk this up to sexism; as in, boys eat more because parents expect them to be ‘growing boys’ or ‘more active than girls’ or whatever and also claim that moms of boys eat more during pregnancy because they know they’re pregnant with boys. The simple fact is that the average male is larger than the average female and needs more nutrients as a result and research has indicated that male fetuses actually send a signal to their mother’s body that makes them hungrier. So if you see this idea quoted as fact on the Internet, please disregard it because it’s motivated by political correctness and not biological truth.)
Even our breastmilk changes depending on whether or not we’re carrying a boy or a girl. http://genderdreaming.com/forum/scie...s-girls-2.html (there’s a link to a study about halfway down this page that explains this in depth.) Beyond that, as many of us have found, when we don’t ingest enough calories while nursing, our milk supply can suffer as a result and so since boys tend to need more calories, any period of time where we are not producing enough milk for our baby can really have an effect, boys more so than girls.
:owl: So? some may ask. So I don’t make enough milk for a couple days. What difference does it make really? My baby is not going to DIE because I don’t have quite enough milk for a day or two. Well, keep in mind that the modern world in which we live, with a convenience store full on goodies on every corner, clean water, Nestle Good Start, vaccines, penicillin, and indoor heating, is something that has existed only a very short time in the grand scheme of things. Humans and their genetic ancestors have been around in some form or another for 85 million years, starting off as primates diverging from other mammals, and then becoming more and more human as the years progressed until we gradually became what we are today 50-100,000 years ago.
Most of our existence, the time during which all these funny quirky genes were developing, your baby absolutely could die if you didn’t have enough milk for a day or two. Infant mortality before the 20th century ranged from 30-50%...that's not a typo, as many as HALF of all babies born did not survive the first year of life (and it may have been higher still in the environment where our primate ancestors dwelled.)
Aside from dehydration (still the number one killer of babies in the developing world, capable of killing within hours) and chronic starvation, even a temporary lack of food can depress the immune system and make a child less likely to withstand a virus or bacterial infection that would otherwise be harmless. As an example, rotavirus is a disease that is generally harmless to healthy children in the US, Europe, and Australia where babies have access to ample breastmilk or clean formula, but kills 450,000 children a year in the developing world Rotavirus - Wikipedia, the free encyclopedia
Beyond sheer survival, a lack of nutrition in infancy can set a child up for a lifetime’s disadvantage. If one doen’t have enough food/nutrients even temporarily in childhood, there can be health effects that last a lifetime. (there are gobs of studies about this that anyone can Google so I won’t share links) Physical development and mental development can be stunted or delayed, the immune system is less able to fight off disease/parasites and so a child is chronically unhealthy. Human development is such a delicate thing, that a major nutritional deficit or life-threatening illness, when a child is 4 days old, 4 months old, or 4 years old can have repercussions that last a lifetime. Developmental delays don’t just go away with a couple of days of good eats. The brain and body can be forever altered by nutritional deficits or serious illness in infancy.
For males, this disadvantage grows huge as maturity approaches. In nature, primates tend to live in harems where one large, strong male is protector and several females live under his protection. Males compete physically for leadership of these harems and a weak male has very little chance of ever becoming the leader of a harem – strong young males band together and bide their time, either by taking the harem over or sneaking opportunities at willing females (sadly, sometimes unwilling females), but a weak male will never get that chance and is usually driven off by the others. If he is even able to survive (single males oftentimes don’t live very long), he’ll never get a chance to mate.
Females, on the other hand, are in high demand as mates. Even smaller, weaker, or more sickly females can typically find someone to mate with them – they don’t have to fight for the right to party (reproductively speaking LOL) Thus, if a mama doesn’t have enough resources to guarantee a big strong son, she’s much better off having a daughter instead because a daughter has much higher chances of surviving to adulthood and successfully reproducing than a son does in that circumstance.
:owl:But atomic, humans aren’t deer, cows, or monkeys. Can this really even APPLY to us? We’ve been living in civilization for thousands of years, surely these factors no longer affect us. Actually, there are some pretty compelling reasons to believe that humans may be the MOST susceptible to the effects of the Trivers Willard Hypothesis. (some are a bit obscure, so PLEASE let me know if this is in any way unclear.)
First of all, animals that have a lot of babies all at once, be it in the millions or even just 5-10 at a time (sponges, sea slugs, most amphibians/most fish/some reptiles, insects, and mammals and birds that have litters or clutches) have a lot less reason to alter the gender ratio. They can take a chance on sending out some boys and some girls and just take the gamble. It's a numbers game. Odds are that someone will survive to reproduce even in less than ideal circumstances. Humans and most of our closest genetic ancestors have babies one or two at a time, Octomom notwithstanding, and so it is in our genes’ self-interest to stack the deck as much as possible in favor of our baby’s survival to adulthood/reproduction.
Secondly, most animals are able to raise a baby in a year’s time or even less. Some animals like rabbits, breed, well, like rabbits, and can have 2-3 litters in a year. If you can have 30 kids in a year, if some are boys and some are girls and some live and some don’t, the odds are still with you that someone will manage to make it to the next generation. Whereas humans take a very long time and a huge investment in resources, to raise ONE fragile little offspring to adulthood, so we have to make sure that one offspring has the best chance we can possibly provide, up to and including skewing the gender ratio to conceive the child with the best odds.
Thirdly, birth is an extremely dangerous proposition for humans. A combination of walking upright on two legs and the increase in head size that enabled us to become rapidly more intelligent than all other animals, has created a situation where human birth is more dangerous for mother and child than it is for all other mammals. A baby human’s ginormous head full of clever brains, may not fit easily through the human pelvis, which altered over time to enable us to walk on two legs. Here’s a thorough explanation. Neandertals Babies Didn't Do the Twist - ScienceNOW
As a result, in order for us to be able give birth at all, our offspring have to come out weak, small, and helpless and require years of constant parental care before becoming independent. This severely limits the amount of offspring we can even have, esp. in the case of women. If you have to exp
end a good 5-8 years raising a child after birth to the point at which leaving them alone for a heartbeat does not lead invariably to their demise, again, you have a lot of motivation to ensure that your effort does not go to waste on anything less than a child with the best chances of survival/reproduction.
Fourthly, humans have a funny quirk called hidden ovulation. We’re the only creatures on the face of the planet who can come into “season” every month and conceive at any point and don’t KNOW we’re capable of conceiving (only very recently have we been able to tell this and even now it’s kinda dicey.) It’s very possible that we might get pregnant at times of year and circumstances that are not ideal, and in less than ideal circumstances, and so it is highly likely that maternal condition is MUCH more important to humans than it is to other animals.
It’s fine for cows to give birth in March, they’ll have spring and summer and fall for their babies to get big and strong. For humans, thanks to hidden ovulation, our bodies don’t know when we’re going to get pregnant; we can’t necessarily rely on coming into season at a favorable time of year. Our bodies have nothing to go on but our condition (and possibly a few environmental cues such as day length and ambient temperature) so it’s very likely that our condition matters quite a lot in terms of fertility and also our offspring’s gender because that’s all our body has to go off of when judging odds of survival.
Finally, pair bonding. Unlike most other animals, humans tend to live in monogamous relationships that stay mated for some time and childrearing is done together, with both male and female being involved. Behaviorally, we are more similar to many birds than we are to some of our fellow mammals, even primates, and birds with similar behavior patterns to humans have been proven beyond a doubt to alter gender ratio quite significantly. The human male may bring more to the table (both literally and figuratively) than the average mammal/primate male who hangs around more to scare off aggressors and enjoy the favors of his harem, if he hangs around at all, than a human dad who provides a home, food, and care for his offspring. Women who are in committed monogamous relationships, esp. in families headed by a male that is high in the social hierarchy, have more sons than is statistically expected. We don’t know why this is exactly or how it could work, but for a thorough discussion of the possibilities, please read http://genderdreaming.com/forum/gend...pink-blue.html
:owl:atomic, this may be all well and good, maybe it even makes some sense, but doesn’t PROVE that swaying works before conception. Couldn’t people just conceive a gender from luck and then be more likely to miscarry a baby boy? Couldn’t variations in gender ratio boil down to post-conception losses and all this before we conceive is nothing but nonsense?
First of all, the fact is that swaying happens without our doing a single thing. 140-160 boys are conceived for every 100 girls and then so many more boys are lost along the way that the gender ratio falls to 102-106/100 by birth. Even that gender ratio is seriously skewed. Men make 50-50 X and Y sperm and that the gender ratio is any different than that, proves that something is swaying gender blue prior to conception anyway. http://genderdreaming.com/forum/sper...x-y-sperm.html AND http://genderdreaming.com/forum/scie...ying-real.html
Beyond statistics alone, eggs are considered “biologically expensive” to produce. Eggs are scarce and precious and every day that passes, we have fewer of them. Compared to sperm, which men are making constantly in huge numbers and can keep on making into their senescence, we are born with all the eggs we’ll ever have at birth and our eggs actually start dying off in droves before we’re ever even born. Each day that goes by, we have less and less eggs. Additionally, during every month of our fertile window, from puberty through menopause, an average of 15-20 eggs in each ovary start to develop and only the best one or two manage to complete the process and are ovulated. So every month, our limited-and-shrinking-by-the-day egg reserve drops by an additional 30-40 eggs. We only have (assuming puberty at 12 and perimenopause at 45) 396 months in which to even conceive, best case scenario, and of course we lose months and years due to pregnancy, breastfeeding, miscarriage, etc. In the grand scheme of things, that’s not a lot of time.
Due to our narrow fertile window, it would be ludicrous for our bodies to waste time conceiving babies with anything less than optimal odds of survival. A woman whose genes allowed her to repeatedly conceive babies with lower odds of survival only to miscarry, would be needlessly squandering precious eggs and precious months of her limited fertility. Logic dictates that something is most likely swaying before conception simply because the human body doesn’t like waste and is excellent at conservation.
Additionally, miscarriage itself (let alone losses later in pregnancy) can be a risky business and a woman could end up risking her life for a baby with less than ideal chances of survival – genes just don’t favor that kind of scenario. Not only would you risk your own life and that of your unborn child, but you’re your already living children – kids without moms don’t always survive very long, even in human societies.
Your genes WANT to survive and the genes we have, have been the ones that were the level-best at being handed down by our primate ancestors and early humans for nearly 100 million years. It is extremely likely that some mechanism(s) have evolved (or been designed into us by God) to make sure that when we get pg, if one gender vs. another has better odds of survival, we’re going to be at least somewhat more likely to conceive that gender – otherwise our bodies wouldn’t take the chance. It’s not a perfect system and it may very well be that some boys are lost after conception from lack of nutrients, but overall, I believe the data supports the idea that swaying prior to conception is a biological fact even tho we do not yet know how it all works.
:owl:Ok, then, please explain why, if this Trivers-Willard thingamagigger exists, why don’t poor countries have way more girls and rich countries have way more boys?
This is a complicated and intriguing question that I’ve spent countless hours thinking about. I don’t claim to have all the answers on every aspect of swaying but I have come up with some explanations that make sense to me and seem to fit the facts. (I ended up writing a full essay on this concept which you can find here: http://genderdreaming.com/forum/sway...fertility.html)
First of all, many countries in Africa DO have more daughters born than is statistically expected, consistently, year in and year out. In fact, most equatorial countries do (with a few exceptions, they tend to be poorer than temperate climates). Also, many countries particularly in Asia and the Middle East, sadly practice female infanticide that skews the gender ratio towards males so much that we really have no way of knowing what the true birth rate is in these countries. (Aside – some of the statistical “data” used to support the French Gender Diet comes from these countries and should be viewed with a skeptical eye. The FGD book quotes very extreme gender ratios from some Asian countries and explains it as due to a high sodium, low calcium diet, but modern research has revealed that the skewed gender ratio in Asian countries is almost certainly because of female infanticide and gender-based abortion.)
Secondly, even in poorer countries and times of famine, there are vast differences in the amount of food resources different individuals have access to. Some people ALWAYS have plenty, some people NEVER have enough, regardless of the overall prosperity of the nation in which they live. Aside from financial resources, some people just don’t eat as much as others, or eat much more, due to personal preference, cultural reasons, health or psychological issues. We’ve all heard the expression, “You can never be too rich or too thin” and many times, obesity and overeating is actually affiliated with poverty, not wealth. Over the course of a country’s entire population, it becomes far too complex to tease out these factors. There is no way to really generalize to the individual level, on the basis of the overall GNP of the country in which a person lives.
Third, it may very well be the case that in times of true famine, some women who were in declining condition and might have been more "set" for girls to begin with, decline further and stop conceiving all together (or choose not to conceive due to lack of resources). Women who might have been neutral with equal odds at a boy or a girl, may decline and have more girls. Women who were in great physical condition, may simply not decline in condition enough to have girls and may continue to have sons even if times are hard for them. (One study in Africa found that women who conceived boys during time of famine, had greater muscle mass than those who conceived girls.)
Or, it may be that due to their individual wealth/health, anyone who is able to conceive (or who is WILLING to, because even poor countries and historically, they had/have their ways of preventing pregnancy) may very well be richer and/or in better health than others and may be preselected towards boys to begin with. The couples who might otherwise have conceived girls, may either be unable or unwilling to conceive, skewing the ratio towards the families who were well off enough to remain fertile in the face of famine, and were willing to continue having children even in less than ideal circumstances.
Basically, all this amounts to the levels of boys and girls staying pretty consistent in times of famine – less babies may be born overall because some people who might otherwise have had babies choose not to or cannot have them due to lack of food; despite this, the gender ratio itself would remain somewhere in the ballpark of 50-50.
Fourth, improving/declining maternal condition may be more effective a sway tactic than nutrient deprivation is. (of course, nutrient deprivation is really just one way of causing declining maternal condition, but there are of course other ways to do the same thing.) Declining condition does not always mean less access to food and more food does not necessarily equal improving condition. People who don't eat much but eat the right foods, can be in great physical condition while another person can be overly nourished and be in poor condition. The reason why we lose weight to sway pink, is because it's unreliable and terrible for health to try and gain weight for swaying. Tons of things outside of food resources have been proven to sway - exposure to chemicals, certain diseases, stress, smoking, increasing parental age; all sway by meeting the prerequisite of declining maternal condition, even in someone who eats 3000 cals a day.
Fifth, humanity has evolved for its entire existence eating very few calories - we can adjust and stay fertile even in a lower calorie environment. The whole idea that women need 2000+ cals a day to survive on, and foods from all four food groups, is new to the human experience. Most of our existence was spent subsisting on a few bites of half-eaten antelope carcass scavenged from some hyenas, a rotten banana, and some termites. We are GOOD at staying fertile and having babies of both genders on not a lot of calories, otherwise there would not be 7 billion of us. Most women around the world eat a lot less than that and always have, and both boys and girls keep right on being conceived. In fact, it may even be that too much food is causing us to decline in condition/fertility due to health issues so for some of us in wealthier countries, we may actually have too much of a good thing going on and gender ratio may be skewed more pink than it would be otherwise, as a result. Please read the following essay for a more thorough explanation. http://genderdreaming.com/forum/gend...irls-boys.html
Finally, gender swaying can never be 100% or even close, because if it were, the human race would have died out a long time ago. Nor can it be easy to figure out - it MUST be multifactorial or those clever old wives would have figured it out long, long ago. It’s very likely that there are dozens, if not hundreds of factors that are swaying, some of which may be utterly out of our control. Food resources are just one of many cues from the environment that our bodies interpret and use to "decide" which gender has the best shot of survival to reproduce. Luck has to play a part as well – obviously my belief is that you can up your odds with swaying (maybe even quite a lot) but Mother Nature/God has a vested interest in ensuring that there are always both boys and girls being born!!
