Wednesday, 20 August 2014

Evolution of teeth

I don't know if getting most of our energy from eating whole raw carrots would have evolved our teeth to similar shaped to the way they actually are now but if it would have done so, then there should be evolutionary pressure for the following changes during the test:
*evolution of teeth ideally suited for eating whole raw carrots with a blunt end. The test should test the ability to climb up a vertical pole with bare hands and feet at all. After evolution makes it less common for people to be unable to, there should start being high rise apartment building with 2 poles, one for climbing up and the other for climbing down and there should be no elevators. Each person on their test day should be asked by observers whether they climbed up the pole to their apartment the previous day and if not, the partner finding site should do nothing to help them find a partner. Because the assigned day is not known ahead, it will evolve people to climb very high every day. This ensures the human species will always be very full of energy and not easily tireable, something only having to climb really high once won't do. Evolution would eventually evolve us to climb at what ever speed burns the least energy because there's a natural evolutionary disadvantage in climbing at a speed that burns more energy. In addition to that, whole raw carrots with a blunt end should be a huge part of people's diet so that we will evolve teeth ideally suited for eating them, and will even do so quite quickly on an evolutionary time scale because we'll be burning so much energy. Over the generations, the buildings we live in should slowly get taller and taller over the generations until they're 3,000 m tall. For anyone who can't climb the pole to their apartment the day before their assigned test day, it's an absolute no no for any of their descendants who haven't already found a partner to be found one by the site because otherwise, humans would devolve from genetic drift. Each person when buying an apartment to start up their own family should have a room assigned to them instead of getting to choose it themself so that we will evolve to be resistant to the harmful effects of climbing any height per day from 5 m to 3,000 m. That is, almost everybody will both be resistant to gaining so much weight that they can't climb at all from having gotten too little exercise climbing only 5 m a day and resistant to the tiring effects of climbing up 3,000 m a day. Evolution would probably evolve the teeth into a shape that maximizes the ability to get energy from chewing carrots. That's actually a stronger version of evolution of mobility too. People should be marked based entirely on how high they actually climb, not how high they climb for their age. The only reason old people this generation find it so hard is because they previously lacked the evolutionary pressure for mobility. Because a whole carrot is too big to fit into the mouth, incisors would never evolve into another type of tooth so I suspect that the canines would evolve to be in between the shape of an incisor and that of a premolar. Another good thing about this evolutionary pressure is that I suspect that evolutionary pressure for the ability to climb a vertical pole would prevent humans from ever evolving away from human shape.
*evolution against exposed dentin. For anyone who doesn't prove they have no exposed dentin by taking an X-ray, it should be an absolute no no for the site to help them find a partner. People with exposed dentin should not have a partner found for them whether it's from nail biting, physical wear or a dental carry. That way, almost no one in distant future generations will suffer dental pain. In addition to that, that evolutionary pressure would prevent top lateral incisors from not growing all the way in because they would take some of the wear for people with a nail biting habit slowing down the wear of the top central incisors. In addition to that people would evolve a more symmetrical jaw set because that will prevent one tooth from taking so much wear from nail biting because the tooth that's a reflection of it across the sagittal plane is at an awkward angle for nail biting. If in addition to that, we start up a trend where everybody occasionally drinks pure lemon juice but not often enough to corrode all the way through their enamel layer within their life time, some people will dissolve off a microscopic layer of enamel which will cause the plaque to detach from it and make their teeth ultra smooth making it harder for new plaque to stick in the first place. That will prevent dental caries since bacteria live in the plaque and make acid that corrodes the tooth. Some people will happen to be drinking lemon juice at the right frequency that's so on the edge of enough to get the plaque off that some people will natually have smooth enough teeth to have the lemon juice make them smooth enough to detach the plaque and others won't, some of whom will get a dental carry and be refused to be found a partner because of that. That would cause the next generation to on average have smoother teeth and the generation after even smoother teeth until teeth are natually so smooth that practically nothing can stick to them so well, maybe making cavities an impossibility.
*evolution against teeth defects. If someone had any permanent teeth grow in without pushing the decidous teeth out first or has any tilted wisdom teeth or can't prove with an old X-ray that they had all 4 wisdom teeth grow in straight before they got some of them removed, it should be an absolute no no for the site to help them find a partner. If there was enough room for them to grow in straight but not quite enough room for them to finish growing in, then they should be treated normally and be allowed to do the partner finding challenges. After all, the natural evolutionary advantage in having a body more full of energy will probably slowly take care of that problem and the crooked jaw set problem on its own, because people can get more energy from chewing carrots when they have fully grown in wisdom teeth that can do part of the chewing. It should also be an absolute no no for anyone who got any wisdom teeth removed before they had enough time to grow in because it's too late to find out whether they would have grown in untilted. The evolutionary pressure against tilted wisdom teeth would probably also make us evolve a more symmetrical jaw set because that way it's less likely that one side of the jaw will be too crowded for a wisdom to grow in straight.

I think the evolutionary pressure of teeth would result in the following results:
*feet shaped half like hands to be better at climbing
*canines becoming incisors with the top ones having a tiny speck of a second premolar cusp due to a combination of evolutionary pressure for teeth ideally suited for eating carrots and canines being able to be worn down faster than incisors. My top lateral incisors have a really tiny bump at the back very slightly resembling a premolar.
*straighter teeth to make it easier to bite and chew carrots getting more energy from them, even for people who don't wear braces
*dentin extending less far to the tip of the incisors because some people have a bad fingernail chewing habit
*thicker enamel layer because some people frequently drink pop which dissolves it and because of evolutionary pressure against cracks in teeth
*very symmetrical jaw set because that way it's less likely that a tooth will be so heavily worn down because the same type of tooth on the other side can't get a proper grip of the fingernails to do some of the nail biting for it

If this part of the test does not get created, there should at least be a restaurant chain that has a job on the third floor where there are 2 ways to go from the second floor to the third floor, going up a stair case and climbing up a pole. To create evolutionary pressure to be a good climber, the door on the third floor should be locked until the restaurant is open to customers and the people doing the morning shift should be required to enter by climbing the pole with bare hands and feet. The purpose in having the pole go from the second floor to the third floor instead of from the first to the second is that way, the second floor can be kept nice and warm because the cold air on the first floor at the foot of the stairs will sit there not coming up to the second floor because it's denser. Since tools can't be carried very well while climbing, all tools used for the restaurant job should be left on the third floor all the time. The restaurant should also serve a whole raw carrot with a blunt end as part of every main course meal so that people will evolve to have teeth ideally suited for eating carrots because people who can eat carrots can eat pretty much anything.

We should also make the evolutionary change of having a skeleton entirely made of tooth enamel built from the inside out but the only way I see to do that is is to first engineer an asexually reproducing woman with that trait whose clones will slowly outcompete the rest of the population as described in the next post. That would be so good. People will evolve to be unable to get joint pain even when the joint lubrication is accidentally missing because there will be no evolutionary advantage in it because it won't be able to wear out from rubbing anyway. In addition to that, every time somebody falls and breaks a bone, they will have a slight chance of not reproducing or their kids not reproducing because of it, selecting for people who will break a bone less easily because their bones were smoother and hadn't initiated a crack because their bones crack less easily. Also, people will evolve to get physical pain less easily because the evolutionary advantage of pain is smaller because they can't break a bone as easily and there's an evolutionary disadvantage in being so restrictive in what you do to avoid the risk of pain. Maybe that person will have to be engineered to have cartilage ribs so that their ribs won't break when they dive deep underwater because enamel ribs can't bend to reduce the pressure difference between the lungs and the outside of the body.

Monday, 4 August 2014

Evolution of ambidexterity

I not only want to create evolution of ambidexterity but evolution of super high ambidexterity. The ambidexterity part of the test should have you sit in a chair and then there are 2 close together horizontal slits and a ring further away from you both picked at a random spot. One of your hands is randomly picked and you are tested on the ability to throw a golf ball sized ball made of flawless diamond through the horizontal slits and the ring without the ball hitting the edges with that hand and then the test is repeated with the other hand. The inner edge of the ring will slowly get smaller through the generations with the people who miss on either of the 2 attempts being refused to be helped find a partner until it is slightly less than twice as big as the ball.

To further create evolutionary pressure of ambidexterity, there should be some restaurant jobs that for every chiral tool they have, should have an equal number of right-handed and left-handed versions and should only hire people who can do the job in a fast complex way where they take which ever copy of the tool they get regardless of which version of the tool it is if they want to keep the job. Those jobs that tell people which hand to use should warn people ahead in their job ad or interview about that policy so that they won't trick somebody into taking the job who didn't want it and will only take people who knew what it was like and decided to accept it because it's so hard to find a job.

The world is easier when everybody is ambidextrous. It really is. Evolution would increase the extent to which a skill automatically transfers from one hand to the other hand making it so that using one hand half the time will slow down the other hand gaining skill by an ever so tiny amount. It allows the same person to sometimes cut celery in one area and sometimes cut celery in another area depending on which of those areas is already getting used by somebody else. Ambidexterity might also be advantageous for cutting a tuna because some parts of it are nonsymmetrical and so favor one hand for cutting off whose reflection across the sagittal plane favors the other hand. It also avoids the need to rearrange people at the dinner table. All new kids should be taught to mirror write when ever they're writing with their left hand which is more natural, and avoids smudging pencil lead and pressing on binder rings and spiral notebook rings. It also creates evolutionary pressure for smartness for people in jobs to suck up learning how to read mirror writing which is not that hard to learn. The cafeteria should have rows of tables with cutlery laid out where people on one side are required to eat with their right hand and those on the other side are required to eat with their left hand. To ensure students don't establish a dominant hand, in early grades, they should be assigned seats at each meal eating with their right hand at some meals and their left hand at other meals. Each person should have a big non-side biased so that the teacher can randomly hand out scissors half of which are left-handed randomly to the class with each student take which ever version of scissors they get and use them with the hand they're designed for, sometimes using right-handed scissors and sometimes using left-handed scissors. All grades should be like the grades starting from grade 7 where the students have different teachers and different binders for different subjects. Each teacher for each class each year should have it randomly decided whether all students in that class are supposed to write normally with their right hand or all of them are supposed to mirror write with their left hand. The reason is because it would create a very disorganized binder having some of the writing in it mirror writing and some of it not with no clear beginning and ending of the binder writing. The teacher should also write on the board the same way as the students are supposed to with the same hand, should mirror print tests and handouts for those classes where the students are supposed to mirror write with their left hand, should give out inverted textbooks for those classes where the students are supposed to mirror write, and should give a zero for a homework assignment that was written normally in a mirror writing class and for a mirror written homework assignment in a normal writing class. If a student continues writing with their dominant hand during a class where they're supposed to write with the other hand, that hand will be restrained with a wire frame glove that goes over that hand and get locked shut during each class where they're not supposed to use that hand. The teacher is not allowed to wrestle the glove on but if the student refuses to put it on themself in a class where they're supposed to, they should get a zero in the rest of the course. All music classes should provide their own instruments with half the copies an inverted version and should randomly hand them out to the class each class so that each student will get one version some classes and the other version other classes. In all music playing tests, each student should be given music they never saw before and have an intrument randomly handed to them by the teacher and may not choose which version to play on. However, the music sheets will either all be mirror written or none be mirror written for the entire year for the entire class because music classes should not be treated differently than other classes. Even for 2 hand tasks such as playing a flute and typing at a keyboard, it's still useful to use 2 versions of the flute or keyboard because it will improve the general skill of to what extent the skill of any task transfers to the skill of its mirror image. For that reason, every school library should have rows of computers where those on one side of each row are uninverted and those on the other side are inverted, and they should have however many computer makes each person who wants to use one to type school work wait as long for a computer as at Steacie Library so that students will be forced to take which ever computer becomes available first and therefore type on an inverted keyboard half the time and an uninverted keyboard the other half of the time. Having half the computers inverted will also force them to normal read and mirror read equally frequently keeping their doors open to being a teacher who has no trouble reading mirror written assignments for those classes where students are supposed to lefty mirror write.

If forcing ambidexterity on people at a young age is too much bother for them, that's fine, we don't need to do it. The eugenics test will eventually select for people who are naturally ambidexrous anyway. Those people who fail to establish a dominant hand and naturally use each hand half the amount of time will be more likely to pass the throwing eugenics test and less likely for the partner finding site to refuse to find them a partner. Once almost everybody is ambidextrous, the world will be easier if everybody on each side of a linear table is told to eat with the same hand because there will be no bumping elbows. It might as well be that for all linear tables, one side is laid out for right hand use and the other for left hand use becuase then after that change, the throwing eugenics test will further select for people who don't form a tendency to always pick the side that favors the same hand for eating to sit at. Even people who naturally would be fully ambidextrous might form a weak handedness due to the current chiral environment of there being more right-handed tools than left-handed ones. Since ambidexterity is currently so rare, we won't be able to make the fraction of people who are ambidextrous increase as rapidly as those who are left-handed. There is an advantage in selecting for left-handed people over right-handed people. That's that once left-handedness is as common as right-handedness, the world will feel free to start producing both versions of each tool in equal proportions, which will keep up the full ambidexteiry of naturally ambidextrous people. That can be done by having those people who throw the ball really accurately when they do it with their left hand in the test more likely to pass the test. We should also be removing the natural selection against left-handedness by making a law that the proportion of copies of a tool that a factory proces in the left-handed version is not allowed to be lower than the fraction of people who are left-handed so that left-handers won't be stuck with having to get a right-handed copy.

The world is even easier when everybody is a fast skill learner with both hands for so many high motor skills because that enables restaurants to hire somebody who will be given many different cutting jobs in different areas of the restaurant each of which they must do with which ever hand the environment is set up to favor if they want to keep the job. For example, when somebody is first given a mushroom slicing job, they will gain skill really fast and be able to do the job with a different hand at different times depending on which area they do the job in. There should be some restaurants doing the huge bother of tracking down those very few such people now so that they can create evolutionary pressure for that fast skill gaining ability saving employers in future generations the trouble of having people not very good at the job. Once somebody has previous experience with such a job, they will be faster at gaining skill for for which ever of those jobs is set up to favor the opposite hand with the opposite hand in another restaurant. In fact, transfer of skill from a task to its mirror image with the other hand is a special case of the brain's ability to build up skill gaining shortcuts for new skills from practice with old ones. One of the partner finding challenges should be being randomly given a high skilled task that you only get 4(1/2) hours to practice from such a large number of tasks that you couldn't have possibly gotten any practice with all of them and then the tester should use a random generator do decide whether you have to do the task one way or the other mirror image way. For example, flipping a pancake on a frying pan only by jerking the handle with which ever hand you're asked to, freemounting a unicycle where you can't decide which foot starts off on top, going up a slight slope forwards on a rips-tic where you can't decide which foot is over the front wheel, and doing a golf drive on the first attempt at least 250 yards with which ever version of golf driver is randomly handed to you where each version has a 50% chance of being the version handed to you.

It's better to create evolutionary pressure for ambidexterity but if we're not going to do that, we should at least create evolutionary pressure for 50% of people to be left-handed. It's easier for right-handed people to be able to train their left hand to be skilled for the convenience of ambidexterity when evolution makes 50% of us left-handed than when evolution makes 12% of us left-handed because it removes the evolutionary pressure for a predetermined handedness making it easier for a right-handed person to choose to train their left hand to become ambidextrous. It allows restaurants restaurants to hire left-handers for a cutting board job in an area that favors the left hand and right-handers for a cutting board job in an area that favors the right hand because half of all cutting boards in any restaurant job will be in an area that favors the left hand. For example, if there's a wall on the left and a garbage can on the right, it's more favorable to cut the celery with your left hand so that you can throw away the bad end with your right hand not wasting job time putting the knife down to pick up the bad end. When the job has a celery cutting area like that, they should only require somebody to be able to do the job with their left hand, not require them to be left-handed. Having only 50% of people right-handed also solves the problem of people bumping elbows at the dinner table if we use linear tables with people on one side eating with their right hand and those on the other side eating with their left hand and having the cutlery laid out as such. Also making it easier for people on one side to reach a salt shaker with their right hand automatically makes it easier for those on the other side to reach one with their left hand. It also enables schools to save desk space and fit more people into the classroom by having 2-person desks that are so small that the person in the seat on the left side does not have room to write with their right hand without bumping the other person with their elbow even if the other person is also using their right hand.

To create that evolutionary change, one of the partner finding challenges should be taking a chiral tool and using it, where the number of available copies is the same as the number of people currently doing the challenge, which the fraction of copies that are left-handed a tiny bit more than the fraction of left-handers in the population, leaving a small fraction of right-handers stuck with a left-handed version. That fraction has to be small in order to not lose support for eugenics. Men who can flip a pancake on a frying pan with their left hand only by jerking the handle should have the option of donating a large number of sperm to grow a zygote in vitro. Elementary schools should start having those 2-person desks and purposefully ordering 2 versions of scissors that are mirror images of each other and have half of them be the left-handed version and not order very many more pairs of scissors than the number of students in the school and then it will finally be right-handed people competing for right-handed scissors and for seats on the right side of the desk having to suck up using left-handed scissors and not the other way around. To make sure right handed people don't use left-handed scissors with their right hand, the school should purposely order a type of scissors that will fail to cut if used with the opposite hand than it's designed for. Left-handed kids and those right-handed kids who failed to win a seat on the right side of the desk from competing should be taught to mirror write with their left hand. If they persist in using their right hand to write, the school should restrain their right hand by putting their right hand in a wire frame glove and locking it shut until the school day is over. That way, the kid will start developing skill in their left hand until they eventually become left-handed.

Evolution of smartness

A star puzzle should get invented and we should select for those who can look at it, blind fold themselves and then solve it in the bare minimum possible number of moves all within 4 minutes at any age past reproduction age. That way, people will evolve to build up smartness with time up to a huge extent. It's like a Rubik's cube except that it's a sphere with triangular and pentagonal faces that can slide against each other as shown in Figure 1. People whose ascendants didn't fail the test after they were born can choose when to use that program to help them find a partner but their assigned day for that part of the test can occur any time after they choose to use that program. In that part of the test, the original position of the puzzle should be random among all possible arrangements that can be solved. Unlike the Rubik's cube, the design on the solved state could be something like an abstract picture that totally ignores the lines where all pieces have asymmetry and are not identical to another piece or its mirror image. Half of all star puzzles produced should have one design on them and the other half should have the mirror image of that design. Maybe the orientation of the design compared to the pieces should be random, so that one star puzzle is not necessarily the same as another star puzzle or its mirror image.
XT_Icosa_F1_Sphere_PPT.jpg
Figure 1: Star puzzle Source:http://myweb.tiscali.co.uk/oaktree/butterfly/backpages/icosa_great_circles.htm

We should do what ever we can to research how to gradually get society functioning in such a way that gives selective pressure for smartness in the real world. There should be people keeping track of other people doing certain useful types of tasks that are hard to figure out how to do and those people who do things that are the hardest to figure out how to do, especially those that require a huge amount of past knowledge to figure it out from, should be more likely to be counted as passing the smartness part of the test even though the smartness that was tested was not done in the test. It's not possible for testing only of what's done in the test to create evolutionary pressure for the same type of smartness. Calculators that eliminate the need to do mental computation should also gradually get sold less and less until they don't get sold at all. Also, cash registers should use unvigesimal and should not do the adding for you either and instead there should be shift supervisors seeing if the cashier can add and subtract in their head properly. There should also only be coins whose value is that of a penny × a power of 2 because that reduces the number of coins in change.

The chemistry careers that deal with formulae such as the density of water as a function of temperature should be using exact formulae, not approximate ones. I know the exact formula won't be an elementray function but that doesn't mean nobody is able to be taught how to apply that function to a randomly generated value given up to 5 unvigesimal decimal places because that's all that's needed to make a super accurate calculation. Their task should be to be told how many univigesimal decimal places they are to express the result in then be given a randomly generated number assuming its a tapered number and not a rounded one then then output the ends point of an interval where the lower end point is the greatest lower bound that terminates after that number of decimal places and the upper end point is the least upper bound that terminates after that number of decimal places. Those people should even be required to apply those functions in their mind and not using a computing device. That would create evolutionary pressure for smartness because somebody without a well paid job is less likely to have 3 kids than somebody with one. To create evolutionary pressure for even higher smartness, they should only hire those people who show that they can memorize a randomly generated unvigesimal number tapered to 44 decimal places without forgetting and relearning any digits then compute the continuous tetration of it to the base 2 mentally like in Hyperschooling.

Alternatively, people can also evolve to be really smart through extremely weak selection to be able to win a chess competition at any age past reproduction age that works as follows: you play with another human doing the test on a computer. Given your marks on the other tests, there's 1 chance in 1,000 less that they will not find you a partner if you lose and 1 chance in 2,000 less if you draw. The rules differ from real chess in the following ways. You can't resign or declare a draw. There's no 50 move rule. Each player has 30 seconds to make their first move before they forfeit the match and each time it becomes their turn, 30 seconds gets added to the amount of time they have to make a move in order to not forfeit. If the game doesn't end after 4.5 hours, it's a draw. The advantage in keeping the selection weak is that it will be highly subject to genetic drift creating a defect in the ability to supress connections irrelevant to playing chess so people will evolve to be hyperaware and able to become really smart at anything. With that selection, people are actually better off without strong selection to be able to compute continuous tetration in their mind as doing so will evolve them to supress other connections too much. After all, the ability to almost definitely be trained to do that will come with the trait that's selected for naturally.

Friday, 1 August 2014

Evolution of mobility

One of the things each person should be tested on is the unaided ability to walk up a flight of 4 stairs and anyone who can't do that should fail the test. Also if the person doing the test trips during the test then can't get up on their own, they should fail the test. There should be no exception to not being allowed to decide the assigned day is inconvenient and changing the day to take the test. On rare occasion somebody might be space travelling in no gravity when they get called to take the test the next day and will probably fail the test from having adapted to no gravity. However, if space travel becomes very common for everybody, the evolutionary pressure against adaption to no gravity will be stronger than the genetic drift for it and people not using their muscles will no longer make them lose them and they will be really easily able to function in 1 G immediately after a prolonged period in 0 G. That evolutionary change would also make it no longer possible for anyone to make themself really strong by training their muscles which is a good thing because it means they can't fight another person without them defending themself.

Evolution of hearing

One of the things tested in the test for deciding whether someone is allowed 2 or 3 kids should be testing how small an electrical spark they can hear while blindfolded where they show a sign of hearing it by reacting to hearing it. The hearing ability, at least for high hearing, can be further improved  by creating evolutionary pressure for clear Eustachian tubes because a difference in pressure between both sides of the ear drums reduces the amount of high frequency vibration of them in response to sound. Temperature changes of the air are creating a pressure differnce at the eardrum all the time. There's also a disadvantage in having clear Eustachian tubes which is that the clearer somebody's Eustachian tubes are, the more easily water can go into the inner ear when swimming underwater, especially when very deep with high pressure. That problem can be solved by creating evolutionary pressure for people to be able consciously control their nose muscles to hole their breath by closing their nostrils instead of by closing the valve people close to make more air come out of their mouth when playing a wind instrument. The test should test how much of the way people can close their own nostrils without touching them with their hands.

We should also track down those men who are the very best at how much of the way they can close their nose without touching it and allow them to donate sperm to millions of women who want to raise children on their own because once evolution has made some people able to completely close their nostrils, the next evolutionary change of clear Eustachian tubes will follow naturally for people from deep freediving tribes. Somebody should invent a spear gun that people can wear around their neck instead of holding in their hand while freediving for fish because that way, they will be able to swim more efficiently. Also, somebody should invent a type of googles that will turn each set of parallel light rays in the water into parallel light rays going in the same direction in air but spaced further apart just before they enter the eyes so that the evolutionary pressure for underwater vision with those googles won't resist the evolutionary pressure for vision working in the way described in the previous post. Fortunately, the fish to be caught are much bigger than pupil size preventing evolutionary pressure of super sharp underwater vision which would sacrifice super sharp air vision.

That evolutionary change doesn't just improve hearing. It also prevents feeling a pressure change in the ears with height as well as removing the runny nose caused by the common so that people no longer care if they have the common cold and the only symptom of it being having slightly weaker muscles. Another thing that would create evolutionary pressure for clear Eustachian tubes once evolution of the ability to close nostrils has already occurred is that the clearer their Eustachian tubes are, the less their ears will hurt if they dive to the ocean floor which is sometimes 20 m deep where they are, so the more likely they are to dive that deep so the less likely they are to starve to death from not catching enough fish.

It would be even better if we could select for people who any time after reproduction age can freedive through ice cold water to what ever depth will have them evolve to take 4 minutes to dive to and return from that depth and then do it again and again and then come out appearing very dark on an infrared camera for quite a while. That's because people would even evolve the ability to hold their breath for 4 minutes while moving because a certain swimming speed minimizes the amount of oxygen consumed for distance, to thrive in a wide range of temperatures, to not feel pressure changes in their ears or the bends with height at all, and to grow until reproduction age so that people below reproduction age will be shorter than those at and above reproduction age because a certain tall height will be evolutionary stable for people past reproduction age because being bigger consumes less oxygen per body mass per distance but being smaller is better for not having too much weight to support when you're walking. If only there was a way to make that evolutionary change without some people dying in the process.