Lots of "likelihood," "probablilities" and "maybes" floating around in that article, and not a lot of certainty. I find the article scant on proof, and speclative at best.
In particular, there's this:
What this meant, says Kindstedt, is that “children
and newborns would be exposed to milk frequently,
which ultimately through random mutations selected
for children who could tolerate lactose later into
adulthood.”
Explain to me how childhood exposure to milk (the period when humans tolerate lactose) selects against lactose intolerance in adulthood?
For example, so let's say you have a mixed population of families, where initially there's a prevaling majority of hereditary lactose intolerance, but with a minority of the new mutants present, who decades later will comfortably continue to consume dairy.
Mutations are typically recessive so you might have households where one parent is lactose tolerant, and none of the children are, due to the lottery of gene expression in sexual reproduction. Maybe some intolerant children are carriers and some aren't, but it's still a roll of the dice.
How does consuming dairy products as a child select for this trait which will not be expressed until years later? What obvious mechanism of selection am I failing to understand here?
Are medieval societies filled with stories of the lactose intolerant humilating themselves with dairrhea on prom night and reducing themselves to social pariahs, doomed to die childless and alone? I mean really.
Explain to me how childhood exposure to milk (the period when humans tolerate lactose) selects against lactose intolerance in adulthood?
People who are lactose tolerant will be able to continue drinking milk well after those in their birth cohort who are lactose intolerant will have to stop. They will thus be likely to be substantially better fed with subsequent better health.
People who are lactose tolerant will be able to survive famines where lactose intolerant people will starve.
Sure, I get the general concept that we assume must exist because it sounds like it's probably reasonable, but there's no concrete smoking gun evidence of that particular mechanism at work anywhere in the world. Not even in folklore.
Where in history is the famine in which plenty of farm animals were thriving and impregnating and lactating amongst one another, but all the humans had to live on was milk?
There wouldn't necessarily be an extreme event like a famine in which only consuming milk would save you. It could well be that consuming milk gave you even just 1% more calories on average (not skipping a meal every so often, when all there is is milk to be eaten right at that moment, because other food spoiled or was unavailable). Even a 1% fitness increase compounds itself over multiple generations into a large effect, even if in each generation it is so small it is hardly noticeable (and so not written into legend).
That's like asking when in history was there some catastrophic era where particles were flying into some organisms' eyes and the only individuals that survived were those who (through genetic mutations) had small hairs around their eyes that managed to catch some of the particles.
Maybe it was more like among a small tribe/civilization there were those who specialized in herding cows and could take them to green pastures when a drought hit the tribe's normal crops. Herders could bring their cows down from the unfarmable hillsides to sustain the other townies with their cow byproducts. They could have milked and produced cheese while holed up along caves etc. during their season "away". (think how trappers live away from their town for most of the year and come in to town, only in the off season.
Producing the lactase enzyme also has a biologic energy cost. If the is no regular milk in your diet, then it is a waste of energy. That's why it is selected against in many situations.
I don't think anyone knows how exactly lactase persistence arose in Europe. Here is a brand new paper describing a DNA analysis of 83 ancient European individuals: http://biorxiv.org/content/early/2015/03/13/016477.article-i...
The relatively late appearance (earliest known example of lactase persistence gene is from 4,300 years ago) and relatively small selective advantage (1.5%) are surprising.
> Mutations are typically recessive so you might have households where one parent is lactose tolerant, and none of the children are, due to the lottery of gene expression in sexual reproduction. Maybe some intolerant children are carriers and some aren't, but it's still a roll of the dice.
Lactase persistence is a dominant mutation. If you only have one copy of the gene you still produce enough lactase to fully digest milk.
The phrasing is wrong, but being lactose tolerant in adulthood would have meant having an extra possible food source compared to those who are not lactose tolerant. That is a pretty major advantage.
I think the idea that natural selection and sexual selection as the only players in gene manipulation is probably wrong. genes are somewhat dynamic and pressures and exposures to a parent will result in offspring more likely to have mutations to deal with them
Those who downvoted me, #1 I dont think comments should be down voted just because you do not 'agree' with them. I am just contributing to the conversation. #2, you probably have a grade school view of the world with regards to genetics. I admit that I have only a laymen / rudimentary understanding of genes.
However, if you look up Epigenetics, you will find things are a bit more complicated.
Is lactose tolerance purely genetic, or is there an element of exposure that causes it?
The reason I ask is funnily enough that I've made the same observation as xiaq: I'm Chinese. There's no suggestion of any other ancestry than far eastern, yet I can still drink milk.
My mom is lactose intolerant but my dad seems to be able to process it. Though he doesn't expose himself much; it's just not that big a part of Chinese diets. I grew up in the West, where kids get milk all the time.
I guess another way to say it is if a kid drinks milk and keeps doing it, will he suddenly get the squits from it one day?
I have a friend who's Chinese. Until she was about 10 she grew up in the U.S. and drank milk like every other kid. Then her family moved to Hong Kong and until college she stopped drinking milk and eating dairy products. When she returned to the states she was lactose intolerant. Even a bite of dairy would cause her all kinds of trouble.
A few years ago she married a Caucasian man who loved his milk and cheese, she simultaneously went to cooking school (and you have to taste what you're cooking) and constant relentless exposure to small amounts of dairy seems to have made her tolerant once again as she can now freely drink milk and eat cheese.
My wife is Korean and dairy products are relatively popular in Korea, she drinks milk, eats ice-cream and cheese without trouble and ice-cream, cream in coffee, milk, and cheese (increasingly) are becoming commonplace in her home country. I only know of one Korean off-hand who is lactose intolerant. Here's an example of a fairly common dessert you find all over Korean, mostly in coffee shops. https://www.google.com/search?q=korean+honey+bread&espv=2&bi...
I have likewise managed to adapt myself to eating more dairy by starting with a little yoghurt every day. But I don't know if that means I'm digesting it with lactase. I suspect it only means my gut flora is better at dealing with it, so I just get a bit of gas instead of diarrhoea.
> Multiple studies indicate that the presence of the two phenotypes "lactase persistent" and "lactase non-persistent (hypolactasia)" is genetically programmed, and that lactase persistence is not necessarily conditioned by the consumption of dairy products after the suckling period.
I ate cheese every day for most of my childhood all through my early adult years. It was quite literally my favoriye food. Snack, meals, I had it all day long.
During a 2-year period, I started getting sicker and sicker to the point where I was missing work on a regular basis. Cut dairy out of my diet, and now I have no issues.
Lactose intolerance crept up on me like an assassin.
I'm from India and this is anecdotal, but I've never met a person who's intolerant to dairy. I heard about lactose intolerance only after moving to the US. In most part of India, dairy is an integral part of diet.
I'm from India too, live there presently, and what follows is anecdotal as well.
I first heard of lactose intolerance when my son became lactose intolerant at age 1.5. I also discovered then that the pharmacies were stocked with lactose-free milk substitutes (soy milk was comparatively harder to get hold of). They'd apparently been stocking this stuff for years.
More surprising, the first time I heard of a nut allergy was when a friend (around the same age as yours truly, born sometime in the decade of The Emergency) said he had one.
Also strangely there is no cheese in Indian diet history until a few decades back. Traditionally it has been milk, curd, butter, butter milk & ghee
Milk and its byproducts have been a revered part of Indian religious traditions from ancient times and hence the source of consideration behind the cow as a holy symbol
Interesting. As a Chinese I have always wondered why lactose intolerance is so common in China but not in the west. Turns out I asked the wrong question :)
That is something that I also, as an American of mostly English/French/German descent, have wondered about. It was, quite frankly, a revelation to me when I first encountered people who were lactose intolerant in college.
It seems even more unlikely, given that China has had so much interaction with the nomad peoples from Mongolia, Manchuria, and central Asia, who lived mostly off of their herds and milk-products.
> It seems even more unlikely, given that China has had so much interaction with the nomad peoples from Mongolia, Manchuria, and central Asia, who lived mostly off of their herds and milk-products.
Dairy products never really made it into Chinese diet.
The next question to ask is why diary products didn't make it into Chinese diet despite the interactions with the nomad peoples :)
That is a very interesting question. The most obvious answer is that most of south-central China is just more suited to rice production than cattle/sheep/goats.
I still find it interesting, since many of the more successful Chinese ruling dynasties have central/north asian roots (Tang, Yuan, Qing). Considering that Genghis Khan is probably an ancestor to most of the eastern half of eurasia, once might expect those lactose-tolerant genes to be more prevalent.
Just to make sure the HN record is balanced, I point out for future readers that Wikipedia currently records that some research suggests he is a critical ancestor to approximately 0.5% of the world's population. (http://en.wikipedia.org/wiki/Descent_from_Genghis_Khan#DNA_e...)
I do this not to participate in the argument but to point uninvolved readers to objective sources.
That depends on what you mean by "related". The relations between languages are surely no indication of other forms of relationship (cultural, geographical, historical).
When equating "people" with the language they speak, something that was very popular in the 18th & 19th centuries[0], it is important to remember that the ancestors of many people you know today probably spoke a different language 200 years ago.
That's not what happened. The history of nomadic peoples in China is a continuing series of episodes of nomads conquering, then settling down and becoming a part of the local population. Just as happened with the Vikings in Europe.
Before cows and sheep and goats were domesticated, it made sense for humans to be lactose-intolerant as adults. Otherwise, during a time of scarcity and near-starvation, the strongest members of the group could forcefully take all the available breast milk, or the older siblings would demand it, and the babies and infants would die.
Nature's solution was to make sure that anyone old enough to eat real food would suffer greatly if they refused to wean themselves.
But once people had animal milk available, it was a gigantic natural advantage to be able to drink it as adults -- not just for nutrients and calories, but much more significantly, to avoid dehydration, which was a major killer back then.
You may not know much about lactation, but nutrition is a big part of it. If there is a famine/drought, there is no milk to be had, doesn't matter how strong you may be.
"There is a common misconception that malnutrition greatly reduces the amount of milk a mother produces. Although malnutrition may affect the quality of milk, studies show that the amount of breastmilk produced depends mainly on how often and how effectively the baby sucks on the breast. If a mother temporarily produces less milk than the infant needs, the infant responds by suckling more vigorously, more frequently, or longer at each feeding. This stimulates greater milk production."
No I don't. Perhaps I should do more homework. I was appealing to common sense. If there is a famine or drought, people are starving and thirsty. Making milk is a lot of work and requires at least marginally decent nutrition. If someone is only eating one "meal" a day and drinking 2-4 cups of water a day, there's just not much with which to make milk.
N=1 anecdote, my daughters mother was very easily able to tell how her diet affected breastfeeding. A lot of it had to do with water intake.
Why do you think lactose intolerance came about, if not as evolution's way to ensure that the available milk went to those who needed it because they were not yet old enough to eat normal food?
Producing lactase is costly, those proteins could be doing other things. What's the evolutionary selection pressure to continue digesting a food source that's only present in the infant diet? None.
That's circular reasoning. The only reason it was "only present in the infant diet" is because of the evolution of lactose intolerance. Without that development, children would keep drinking milk for as long as they could get away with it.
But don't take my word for it; here's what Slate has to say: "With Cain weaned, Abel could claim more of his mother's attention and all of her milk. This kept a lid on sibling rivalry [...] while allowing women to bear more young."
> … it made sense for humans to be lactose-intolerant as adults
> Nature's solution was …
What made sense for an individual human is for everyone to be lactose-intolerant except them. This is what gives the best results for the individual in the near-starvation scenario.
Your suggestion sounds very much like “group selection”, an idea with many high-profile detractors (http://en.wikipedia.org/wiki/Group_selection ). The only argument I read against it was in “The Selfish Gene”, but according to the Wikipedia page, I could have picked from other high-profile scientists. Something looking like group selection may work in some cases (“The Selfish Gene” itself describes John Maynard Smith's counter-proposal of Evolutionary Stable Strategies), but offering such an explanation as obvious amounts to ignoring a lot of debunking by many bright people.
A better way to approach the Paleo hypothesis is as just that -- a hypothesis. I think all reasonable people agree that humans have changed somewhat since paleolithic times (and grains were possibly part of our early diet) but it still seems quite reasonable to posit that 1) our diet has changed greatly since the longest period of human evolution and 2) it may well be more healthful to return to a diet closer to the paleolithic diet. That's a reasonable hypothesis that can be tested.
Of course that's not the way the popular press and fitness industry approach the Paleo diet, but one shouldn't throw out the baby with the bathwater.
While that is true, it's also good to take into consideration the fact that the rationale/hypothesis behind a diet plan doesn't have to be right in order for the diet itself to be useful.
Personally, the paleo hypothesis has always sounded rather dubious to me, but there's more than enough evidence that the ketogenic effects of paleo-like diets are useful at least: http://ketopedia.com/principia-ketogenica/
Yeah, if your "paleo" diet happens to kick you into ketosis, then you've stumbled across a beneficial thing. If you're eating lots of fruit and starchy vegetables, it's probably not doing much for you.
I can't see how the article justifies its title. Did the (comparatively) lower level of adult lactose intolerance in the West have social, cultural, economic or other effects significant enough to be described as a change in the course of civilisation? If so, what were those changes?
"In a 2004 study, researchers estimated that people with the mutation would have produced up to 19% more fertile offspring than those who lacked it. The researchers called that degree of selection “among the strongest yet seen for any gene in the genome”."
I remember reading about American Indians killing nursing buffalo calves and cutting open the stomachs to feed the curdled milk to their children as a special treat (almost like ice cream). Surely hunters of mammals throughout the ages were familiar with this delicacy. Why isn't this considered the 'discovery' of cheese?
One thing that's missing from this is a more nuanced discussion of lactose intolerance. It's not a simple binary thing like celiac disease or an allergy. It's possible to consume around a cup (250ml) of milk per meal for lactose intolerant people, but doing so without experiencing typical lactose intolerance symptoms requires regular exposure and building up to those levels (possibly due to micro-biome effects). What that means is that a group of people that started introducing animal milk consumption with infants might also begin consuming milk through adulthood in small quantities. That would provide the sort of situation that would make it easy for adult lactose tolerance to have a major evolutionary advantage.
If teens and adults are drinking small amounts of milk regularly as well as some amount of cheese then those who are lactose intolerant (the common case) will only be able to get calories from the fat and proteins. But anyone who has acquired lactose tolerance will be able to consume an unlimited amount of dairy products and will also gain around 40% more calories from the lactose. That's an enormous dietary boost especially for people who are struggling at the margins of livelihood and malnutrition. More calories means less stunted growth, which means stronger bodies, and a greater ability to survive through harsh winters or lean times.
I'm a blue-eyed, blond, cheese eating adult and I like it.
That reminds me of something I read about blond, fair people and milk I didn't see it mentioned in the article about vitamin D which is added to milk these days but I don't know if it has any naturally. People with fair skin, blond hair in northern climates helps in the dim sunlight to get enough vitamin D.
I also recall reading that people living in a northern climate who have access to large amounts of fish allowed generations of that group of people to retain a darker skin colour since the vitamin D from fish meant people didn't need fair skin to get as much vitamin D from the sun.
Cheese is an awesome food. It's high-protein and high-fat and is perfect if you're a farmer or in some other way burning a lot of calories.
Where I live (switzerland) we eat a ton of cheese and it's seasonal, with Spring/Summer cheese being when the cows are in the mountains eating clover, herbs, and grass, versus in the Fall and Winter when the cows are in the valleys eating hay. There are something like 5000 varieties of cheese in Switzerland if you include every village and farmer and their sub-varieties in the list, but for mainstream cheeses there's something like 500 varieties. You can get unusual different cheeses every weekend if you're willing to take a trip to some random village in a tucked-away valley. (sausage too! especially if you're willing to eat sausages made with horse, deer, dog, etc.)
I'm not Swiss but my wife and I still eat a ton of cheese. It's so good here and such a part of the culture that you can't help but take to it. We burn off the calories like the Swiss do with hiking and skiing every weekend.
That's one of the things Europeans (anecdotally Germans and French) who work or study in North America complain about. Cheese quality and selection (and price!) here is crap. In fact, food quality here seems to be a notch lower.
1. US milk does not taste good. Actually, it does not taste at all. I always thought this is just in my mind until a Swiss guy said the same.
2. All milk products are do not taste so well and often have poor quality. Cheese, Yogurt etc.
3. You can get excellent cheese and yogurt but this comes with a hefty price tag. E.g. Whole foods etc.
I have the impression that supermarket foods in the US have a much lower quality compared to Europe. You can get the same or better quality, if you can effort to pay for it.
> 1. US milk does not taste good. Actually, it does not taste at all. I always thought this is just in my mind until a Swiss guy said the same.
I don't believe this. Milk sold at a super market comes from cows and cows need to be semi local to bring milk to any store. I'd love to know how milk from other places is somehow superior. My suspicion is that it isn't and just confirmation bias (that or someone is comparing different types of milk (e.g. 2% versus homogenized) which is a poor comparison).
On the face of it, it is easy to say "it's just milk, it all tastes the same", but there are significant differences in how milk is produced in the US compared to the EU.
Most US-made milk is produced using genetically engineered growth hormones (rBGH) which are banned in the EU as they are believed to increase the risk of cancer. It would not be legal to sell US milk in the EU (or Canada) for health reasons. That, and other differences in production methods, could go some way towards explaining the perceived superiority.
I'm skeptical. Less than 20% of milk produced in the US uses rBGH, and most health organizations, including in Canada and Europe, agree that milk from rBGH/rBST cows is safe for humans. The reason it's banned in the EU and Canada is because it's a health risk for cows, not people. And the reason you're not likely to get US fresh milk in those countries has more to do with transportation costs than production standards.
If I had to guess, I'd say the most likely reasons for flavor differences are 1) different pasteurization techniques 2) fat content 3) consumption temperature (you can't taste sugars as well when they're cold).
I could understand bread factoring in but a growth hormone used in a very low number of cattle in the United States? That doesn't really make sense. It doesn't scale to fit the answer previously provided that I am skeptical of.
I do believe this. I live in the UK where there is regional variance in the taste of milk. I believe this is due to factors such as the breed of cattle, the type of cattle feed (which is sometimes season dependent) and processing techniques. Supermarket milk is commonly from Friesian cows, but sometimes from Ayrshire cows (especially in Scotland) or from Jersey cows (especially in South West England). My personal favourite is non-homogenised milk from Ayrshire cows.
Its different to point to specialist shops, or have enormous choice of best cheeses in every large supermarket. In most supermarkets of continental EU you will have a large cheese and ham stand with qualified person that will cut it for you, give you samples and advice on the one to pick.
Most Whole Foods seems to have a huge cheese section with specialists as well and at least in California, both north and south, they are practically ubiquitous.
In North America -- excellent but expensive selection @ luxury grocery stores for upper class or upper middle class individuals in gentrified areas
Europe - reasonable selection at reasonable prices at large and small grocery stores for ordinary people, fresh, and of good quality and with regional local specialties.
Same goes for wine. Cider. Beer. When I visit family in Europe it's a totally different experience -- here in North America quality is a luxury option, and "local" and "regional" is a branding exercise, and imitative of Europe with little indigenous invention; in Europe generally just sheer weight of history and the influence of 2000 years of farming .. it's entirely different.
A parent post was criticized for being too general, so I'll be extremely specific: cheese from the Whole Foods located at Park Place, San Mateo, California is crap compared to cheese from the cheese shop located on Rue Saint-Hélier, Rennes, France, and is also crap compared to cheese from the weekly farmer's market in Noyal-Châtillon, France.
The only decent cheeses at this Whole Foods are the safe choices like hard aged cheese. The more delicate cheeses to get right, like an Emmenthal de Savoie (you want it yellow, mellow and flavorful; not white, hard and tasteless) or many types of goat cheese, always disappoint.
Note that French supermarkets (Carrefour, Super U, etc) offer much worse cheese than Whole Foods. At least that was the case a decage ago - I haven't visited the cheese section of a French supermarket since, so I might be out of date. If you want good cheese you need to head for a cheese shop ("fromagerie") or a farmer's market (which might also supply good bread to pair with your cheese).
This. The selection of cheese at an expensive chain or a specialist gourmet food in the US is okay and comparable to what you find in European low-price chains (albeit at 2-3x the price). Try going to a gourmet cheese shop in France and get your mind blown. Even the butter is so good you'd eat it by the spoonful!
As an American in Wisconsin with Swiss roots (southwest Wisconsin has a strong Swiss imprint), your comment sounds so cool to me. It's much the same here... more cheese and sausage than the dietitians recommend, and while we don't have the Alps we have plenty of beautiful ways to work it off. Having visited family in Switzerland and seeing the country, I've come to appreciate how similar our regions of the world are.
I don't like the term "lactose intolerant". It implies that having difficulty digesting lactose is differentiating you from some loosely defined norm.
In fact, the opposite is true[1]. As the article states, being able to digest lactose is a recent genetic adaption. What it doesn't state is that still, even in the West, a lot of people experience lower tolerance to lactose as a natural process of aging.
I would therefore say that the correct way of labeling it is that adults in general have different levels of _lactose tolerance_.
Anecdotally, I can add that my level of lactose tolerance was very low for two years after drinking half a liter of milk that was two weeks old (don't ask). I assume that it severely messed up my small intestine. After I cut carbs and gluten from my diet for a month and a half, I could suddenly digest lactose again. As with lactose intolerance, I believe gluten intolerance is a misnomer, as all people are sensitive to excessive amounts of gluten, though here the case is not nearly as clear cut. My intestine finally being able to repair itself might instead be due to the fact that I didn't eat many carbs at all during this period, and so avoided the gastro-intestinal allergens known as FODMAPs[2]. Wheat contains the FODMAP fructan, which might be the reason many people say they feel better on a gluten free diet[3].
Cheese, milk, and other dairy products in general are very common in American and European cuisine. In the English-speaking world, not being able to consume these foods is kind of deviating from the norm. Language reflects the culture it develops in, not the world outside of it.
> I don't like the term "lactose intolerant". It implies that having difficulty digesting lactose is differentiating you from some loosely defined norm.
Nonsense. It's a simple statement of fact, and any value judgement you derive from it is pure projection.
> I don't like the term "lactose intolerant". It implies that having difficulty digesting lactose is differentiating you from some loosely defined norm
It's a scientific term created purely for succinctness and description, it carries no connotations.
Fair enough, I'm surely being overly sensitive here. It's just that, here in Sweden at least, being 'lactose intolerant' suggests there is something wrong with you, when the truth in fact is just that your lactase persistence[1] is more akin to that of the rest of the world.
It carries connotations here. I'd say it does in the US as well, given the jokes about it I've seen on shows like the Big Bang Theory.
In particular, there's this:
Explain to me how childhood exposure to milk (the period when humans tolerate lactose) selects against lactose intolerance in adulthood?For example, so let's say you have a mixed population of families, where initially there's a prevaling majority of hereditary lactose intolerance, but with a minority of the new mutants present, who decades later will comfortably continue to consume dairy.
Mutations are typically recessive so you might have households where one parent is lactose tolerant, and none of the children are, due to the lottery of gene expression in sexual reproduction. Maybe some intolerant children are carriers and some aren't, but it's still a roll of the dice.
How does consuming dairy products as a child select for this trait which will not be expressed until years later? What obvious mechanism of selection am I failing to understand here?
Are medieval societies filled with stories of the lactose intolerant humilating themselves with dairrhea on prom night and reducing themselves to social pariahs, doomed to die childless and alone? I mean really.