The Most Spectacular Mutation in Recent Human History:
http://www.slate.com/articles/health_and_science/human_evolution/2012/10/evolution_of_lactose_tolerance_why_do_humans_keep_drinking_milk.html
It seems to me that human beings have shared a fairly convoluted relationship with milk. The aforementioned article documents a remarkable evolutionary tale that interlaces lactose intolerance with natural selection.
The author of the article, Benjamin Phelan, begins with a satirically biblical allusion to the “first two Homo sapiens”, Adam and Eve. The introduction sets the tone for the rest of the article; the author’s witty perspective on the subject is woven with scientific evaluations backed up by contemporary research. The purpose of the article is fairly straightforward, Phelan attempts to explain how human beings were predominantly not inclined to drinking milk beyond infancy by developing early-onset lactose intolerant; however, a genetic mutation, that consequently spread like wildfire, resulted in humans gaining tolerance towards lactose and, ergo, somehow may have played a role in shaping the future of human civilization.
What’s remarkable about the mutation for lactose tolerance was the degree with which it spread throughout populations across the world. Except for the Americas, the mutation had made its way from Europe to India along with discrepancies in the mutation cropping up in Africa and the Middle East. Another interesting point put forth by the article is how the cultural development of civilization and agriculture having coincided with the widespread consumption of milk.
Phelan explores a number of theories explaining why and how milk became a preferable source of nutrition. He elaborates on his analysis by stating possible theories by MIT geneticist Pardis Sabeti (whom he hilariously introduces as lactose-intolerant). Sabeti opined that milk had Darwinian implications by being able to boost women’s fertility. She also stated that milk might have provided humans with a healthier, more hygienic alternative to water.
The article concludes in a similar fashion to the way it begins, bringing back the biblical metaphor and creating a sense of syntactic symmetry.
Would you agree with Phelan’s association of the proliferation of civilization with the consumption of milk? Do you think it’s possible for something as trivial as milk to leave that kind of evolutionary footprint on the human race? Or is the author, in the hope of a good read, touting what could have been a natural coincidence as a colossal evolutionary correlation?
Darwin's Legacy 
Very interesting blog post!
This article is very interesting and great blog post heir2hemingway! The author of the article uses the a very satirical form of writing to explain the rapid evolution of this lactose tolerant gene. Using Adam and Eve in an example to show how this mutation occurred over time was really quite witty. It’s clear that while Phelan takes the evolutionary side of the argument he never fully clarifies the true evidence for this lactose tolerance gene. His research doesn’t lead to a clear conclusion. Without a solidified reason for this occurrence, I feel that his argument falls short. The satirical format helps to make the readers understand the argument, but when his lack of conclusive evidence leaves the reader without an answer, the argument loses validity and readers may not trust this as an academic source.
As for whether or not I agree with the author, it’s difficult to say, because, as I previously stated the array of evidence never leads to a solid conclusion as to why this occurred. When you posed your final questions and stated that something as “trivial” as milk could have such an impact on our evolutionary process, I would disagree since milk has such an vital importance in the development of humans. Phelan even goes into the importance milk was during times of poor harvests as the milk provided people with the nutrients that otherwise would have been provided by the harvests. I do believe that because of how beneficial milk is our bodies created such a tolerance that allowed us to survive and procreate effectively. What started as a mutation was passed down through natural selection because these humans we able to take in vital nutrients. This subtopic of evolution can get controversial when there is no solid evidence for any of the proposed reasons for why these mutations occur. Great post, very thought provoking!
in response to your comment, slowdownyourmind–
you say that “[the author’s] lack of conclusive evidence leaves the reader without an answer, the argument loses validity”. However, I think it’s important to note that never in the article did the author really profess to be “arguing” anything. Rather, he was simply relaying data, facts, hypotheses, and theories. I don’t think the article had a persuasive purpose, as the author said himself, on multiple occasions, that a lot of the story is “fuzzy”, and there are only certain parts of it we can be sure of. To me, that gives his piece MORE credibility, if anything. It shows he is not exaggerating or twisting the facts to serve a persuasive purpose. He is honest about not knowing everything– the point of the article is not to prove a point, but to just say, “hey, this is a cool theory– check it out!”
Loved that comment, you get it.
Thanks for the comment slowdownyourmind, I’ve chosen this article because it’s not a heavy read but it’s pertinent and relevant information in the field of evolution. As a blogger, the rubric says we’re supposed to be pick an interesting article with relevant information, ‘academic writing’ was not listed as criteria for picking an article. I tried to provide you’ll with something light and humorous for a change, yet staying relevant to the topic. The article is presented as an overall analysis rather than an in depth case study, and I thought inconclusive ending to the article also leaves us with some interesting points to talk/think about.
And in the medical community, milk, although a valuable source of nutrition, is not considered important to a human’s well-being after infancy- hence, the reference to it as ‘trivial’. Just wanted to clear that up.
I completely agree! I was not trying to say you needed and academic article. I found this particular article interesting because it wasn’t. It was great change to diversify the posts on the blog. The inconclusively does open the floor for use to interpret the data but it’s difficult for students without an advance level of understanding to solve these evolutionary questions.
In my opinion, milk probably became such an important part of adult diets (and evolved into a tolerance) because of times of drought that would prohibit people from harvesting the essential nutrients. While yes, it is unnecessary for fully grown adults to drink another mammal’s milk, it was important in the sense that it helped those survive in times of human vulnerability to their environment.
Great blog post heir2hemingway – this is an aspect of evolution that we really haven’t touched on before! The article that you chose by Phelan was a very fun read, and it made thinking about the evidence in scientific terms a bit more fun. To address some of the questions you pose, I think that Phelan does a great deal to show the relationship of the advancement of civilizations and the direct tie it has to the lactose tolerance. As it is something that I personally have never spent a great deal of time thinking about, I find it very logical and scientifically sound.
Although this is a very interesting topic to consider, I think it is only one, of thousands of things, that has influenced and “left a footprint” in human evolution. So while this mutation is interesting, it is one of millions of mutations that have occurred along the evolutionary path in the human existence.
In short, I think it is one of these natural coincidences that has occurred as we as humans have evolved. So in that light – what would have been the big evolutionary downfall had this mutation not came about? Would humans (as a species, and in their civilizations) be terribly different? What would be the downfalls to not having this mutation (except, of course, not being able to drink milk)?
sm4321, I agree. It is very interesting but I do not see this evolutionary trait as being very significant. Like you said, what would be the downside? I do not think humanity would be much different than it is now just because of a lack of tolerance for milk.
I agree, sm4321, in that the lactose tolerance mutation is only one of many mutations that have impacted human evolution. I think the effect of lactose tolerance in the world affected humans in a somewhat large way. Presently, milk is a huge marketable product that we consume–whether it’s simply to drink or use in other foods/dishes. Dairy farms have grown in size remarkably, and have advanced because of the new technology involved with it. Additionally, as stated in the article, milk could have been a more nutritional form of water for humans to drink.
Glad you enjoyed the article sm4321! And yes, I definitely agree with you on the topic of multiple factors having left a footprint on human evolution. I think another key focus of the article and something Phelan was trying to underline was how quickly the gene passed on and spread through the continents, just wanted to point that out.
As far as your questions go, I’d like to posit that milk has served as an alternative to the ‘elixir of life’, water, as stated in the article and that in itself seems to be an important milestone in the course of evolution. I don’t think evolution, as a whole, would have been thrown off course because of it; but during some rough phases in human history such as perhaps some widespread epidemic or drought, milk may have helped ease the troubles of the population at the time.
Heir2hemingway, I would like to further discuss the advantages to the ability to process lactose. In Phelan’s article, he states that “milk supplemented food supplies. If your crops failed and you couldn’t drink milk, you were dead.’” In certain places, like Europe, milk was a necessary supplement to water. I think that the “high selection differential” was due to primarily to having a widely-available supplement to water. In Africa, milk served as a cleaner alternative to water. I do not think that your description of milk as a “milestone” quite does it justice. Based on the advantages provided to us by Phelan, milk is better described, in my opinion, as the second “elixir of life”.
Out of curiosity, did you happen to see the presentation about milk at the Human Origins Exhibit at the National History Museum?
I disagree that this evolutionary trait is insignificant. Let me give an example. Let us say that both of us live together on a farm. I can digest milk and dairy products, but you are lactose-intolerant. What if the crops fail and the only sustenance is dairy products? I have a clear advantage to survive over you do I not? While we might not see any significance to a mutation such as the ability to digest dairy products at first glance, it doesn’t mean that the mutation is devoid of any advantage to those who do not have it.
Yes, maybe from person to person. But as a society, would we be worse off without the ability to drink milk?
I find it fascinating that humans were supposed to lose their tolerance of lactose. We’ve been talking about the evolutionary advantages of lactose tolerance. but if we were originally designed (for lack of a better word) to develop intolerance with age, what might be the disadvantages of being able to digest lactose (in other words, why were we like that in the first place)? Could our lactose tolerance be linked in any way to our lengthening childhoods?
Glowcloud, It might not be an issue about the disadvantages of the ability to digest milk. It might have been that the first few people to develop the mutation that allowed the digestion of lactose were killed by bears before they were able to pass on the mutation. This possibility does not seem likely, but I think it helps show the amount of factors that could impact the genetic traits that a population does or does not develop.
That is an interesting point, waterbottle19. But I think it may be too narrow, especially for modern day application. Your example is a way that we can easily see one of the possible outcomes of what would be for those who aren’t lactose intolerant versus those that are. But try considering it in a different light of evolution. For the person who was lactose intolerant – their inability to consume dairy products could work as a force to create new ideas and ways of survival. So if all of the crops failed, but you were still getting milk, then their must be a cow, this would enable other forms of survival, such as the hunter – gatherer techniques from long ago could help to make the individual (and their offspring) to be more resourceful.
I think I’m going to side with you on this part of the debate waterbottle19, I’m sure that around 10,000 B.C., the only two choices in terms of a drink would have been water or milk; and when a certain population only has access to water that is contaminated, milk would have been the only alternative to turn to. Large amounts of lactose-intolerant people would have been wiped out this way leaving the lactose-tolerant population behind. This is my theory for why the mutation spread so quickly in such a relatively short time. All thoughts and opinions on this are welcome!
Waterbottle19- I believe you are narrowing the scope of the issue. Yes, in a case of 1:1 you would have a higher chance or survival. But when refereeing to evolution, mutations act on individuals but evolution acts on a population. So if the farm was to fail could you just not kill the cow and have meat? could you not sell the cow and buy other products? There is always going to be methods to getting around an issue. In this case, I believe that if you were to be lactose intolerant, that specific person would try to find another way for survival thus perhaps obtaining different evolutionary mutations that would lead to different phenotype traits.
Sm4321: My example wasn’t being applied to modern day. We have obviously reached a point in human history where lactose tolerance would make absolutely no difference. We can make and process so many different types of food. However, I do think my example still stands. Maybe i should have said this example happened 100,000 years ago. With a much smaller population, this mutation could have spread easily through the population as my example suggests. Then it is a matter of passing it down generation to generation until we arrive to today.
glowcloud, the reason why we loose our ability to produce lactase is because after infancy, we stop drinking our mother’s milk. It would be a complete waste of energy to produce an enzyme indefinitley that we only need for a short period in our life.
Californiarepublic: That’s thinking short-term. If you kill the cow you can survive off the food for a short while. You still won’t survive a crop failure. However, milking a cow lasts as long as the cow is alive and healthy. It’s a long-term solution.
In addition, I think assuming that you could sell the cow is false as well. Lactose tolerance arose 200,000 years ago according the article. Look at this wikipedia article on the history of currency. http://en.wikipedia.org/wiki/History_of_money
It is hard to sell a cow when the concept of currency doesn’t exist yet. Thank you for your reply. Yours as well as others has really made me think about this article.
Heir2hemingway–you’ve done a great job of concisely highlighting this article and its significance. I think that you point out a really important facet of evolution that sometimes gets overshadowed by all of the hype–that what is in the majority is not what always necessarily is a “dominant” or “normal” trait. I am wondering if for people with very severe lactose intolerance, there would be a way to insert the lactose tolerance mutation into their body. If so, this could maybe even extend to other dietary issues like glucose intolerance. What do you think?
This is a really good point, apluckypremed. It makes one wonder if humans would be able to expand their palate through genetic modification. What is the limit of this idea? I think this is a really great starting point for that kind of discussion because Phelan mentions the autonomy of this mutation as it cropped up independently across the world.
I like how you’ve made the link between this article and the one on genetic engineering, good job apluckypremed!
apluckypremed, gene therapy is a hypothetical proposal to treat diseases that are caused by genetic predisposition. It essentially involves injecting a patient with a “good” virus that replaces the host’s DNA with DNA that contains a revised gene. However, this treatment has seen limited success, and faces many obstacles as described by this article: http://learn.genetics.utah.edu/content/genetherapy/gtchallenges/
Lactose intolerance would by no means qualify for gene therapy, as it is so intrusive, and has even caused cancer in some patients (http://www.mayoclinic.org/tests-procedures/gene-therapy/basics/risks/prc-20014778). People that suffer from lactose intolerance can easily take over-the-counter lactase pills that breaks up the sugar for them.
heirtohemmingway,
First of all great post. I appreciate you choosing an easy read! Makes it must more enjoyable for all of us and it is probably even easier to talk about. Personally, I believe that the ability to consume milk after infancy had to be a very beneficial trait because of the fact that it survived as a mutation. From my personal experience, milk is great to drink just for the amount of calories and protein that it can offer. In this modern world full of multiple food options milk is still what a lot of people turn to when trying to add weight on or simply grow and be stronger. In a world where the other options were very slim I can only imagine that milk was incredibly beneficial. When people simply had nothing else to eat or use to nourish themselves, milk would of been instrumental. So I in fact do believe that lactose tolerance very well could be one of the most impactful and important human mutations of all time.
Thanks vikingsfootball33, I thought the more fun or quirky an article is, the more likely someone would be to remember it even after today.
Coming back to your comment, you’ve touched upon an important aspect of the article, in a world where the options are so very limited, milk would have probably been the ONLY alternative to water and hence, it could very well have played a very large role in shaping human evolution. It’s all very theoretical, but the article makes an interesting correlation and you’ve made a very good, specific observation in that regard.
Although only 33% of the world is lactose tolerant, and it means that it is a less common mutation, it is still a big percentage of people and it’s odd to think about how many things we eat that contain milk. I agree with vikingsfootball33 in the fact that drinking milk must have been imperative for people (probably in Turkey, where it originated from) after infancy in order to stay healthy like we drink milk for today.
I think that the reason lactose tolerance is so low today has to do with 1) increasingly sanitary living conditions and 2) innovations allowing for milk consumption by intolerant individuals. By creating sanitary living conditions we are able to eat all sorts of food and drink water without risking ingesting some form of pathogenic substance, thus nulling this particular benefit of milk. There have also been certain innovations that allow for lactose consumption by intolerant individuals, including obtainable lactase enzymes to assist with digestion and the proliferation of dairy substitutes that are nutritionally similar, like soy, almond, and rice milk (etc.).
I actually learned in my high school biology class that the enzyme responsible for lactose tolerance (lactase) can turn on and off over one’s lifetime. I wonder if this also is affected geographically.
Interesting point gwuw2014. Could you possibly find a brief article explaining this process?I would like to learn more, as I am sure the rest of us would.
Something that is somewhat similar in nature is the intolerance to gluten – which is a fairly recent topic and it seems to be spreading like wild fire in the United States. There are two main types of sensitivity: gluten intolerance, and those with Celiac Disease. Many doctors debate whether the former (gluten intolerance) even really exists, though they are sure of the validity of Celiac’s. Is this fairly new disease perhaps a reaction to this shift that was mentioned in switching to an agriculture based diet? Could this be a something that, like the lactose tolerance, rapidly spreads and eventually is inevitable for the evolution of humans?
http://www.news.wisc.edu/22157
In this article by John Hawks, it is outlined that scientists still really aren’t sure exactly what started this disease or why its occurring. This could be because we are at the beginning of a widespread gluten intolerance. What would the effects of this be? How does it relate similarly or differently to the effects of lactose tolerance?
That’s an excellent find, sm4321. Glad you brought up another interesting side to the article, the shift to an agriculture based diet and it’s effect on how we’ve evolved since. I do see a bit of correlation between both the articles.
sm4321, I’m glad that you pointed out the difference between Celiac Disease and gluten intolerance. Celiac Disease is a very serious problem in people who have it. However, many people jumped on the “gluten intolerance” bandwagon because they “felt better” after they cut wheat out of their diet.
You raise an interesting question about the effects of widespread gluten intolerance. However, lactose tolerance would have been an evolutionary advantage which could explain why it spread so quickly. Celiac’s, on the other hand, is not advantageous at all so, I do not believe that it would spread as rapidly.
To all those commenting after this, I feel like the argument is pushing forward in the wrong direction (everyone’s just touching upon the triviality of milk in the course of evolution) so please note that there are several key aspects listed in the article that can be discussed:
-how quickly the mutation spread across the continents
-how milk helped overcome turbulent times of disease (especially water borne)
-the correlation between milk and civilisation
-the author’s style of writing
You raise some excellent questions! While I don’t believe this mutation alone caused the proliferation of society, I do believe the new-found food source in dairy products coupled with new farming techniques certainly did. Lets say, for an example, that a nomadic tribe of people has settle down and made a village. They no longer hunt but gain their food primarily from farms. Lets also presuppose the villagers all can digest milk as well. With this new food source, the village will survive even if the crops fail for a year. As the author of the pointed out this is stability that a nomadic people never had. This stability leads to greater population and therefore the birth of society.
As for your second question, I do believe this is a sign of evolution. Having the ability to digest a new food source gives you an advantage at survival over those who do not possess the mutation. What if the farm fails? What if there is nothing left to hunt? Those who can digest milk can sustain themselves while those who cannot die off. As for how the ability to digest milk spread itself so quickly through the population, I cannot say. If top scientists do not have an answer, I have absolutely no hope of providing a reasonable explanation.
To finish my argument off, I am going to offer a quote from the article. “Agriculture-plus-dairying became the backbone of Western civilization.” I think this succinctly illustrates what I am presenting.
Slate is a consistent source of informative yet engaging articles. I enjoyed the subtle humor and informal style. I think that when information is presented this way it becomes much more reader friendly. I mean, we normally wouldn’t have such conversations about the evolutionary importance of milk because these articles would normally be very technical and probably difficult to understand. Very solid pick, heir2hemingway
Glad I could keep you guys engaged, thank you glowcloud!
I would agree, glowcloud, that Slate put a topic that is normally very difficult to understand into humorous term. Creating an article that many college students enjoy is no easy task! The topic of the evolution of the lactose gene is controversial enough that many can have differing opinions with opposing sides attacking each other. Great choice!
The author of this article provided a closer look at a very ordinary part of life and did a good job at connecting it to evolution overall. I think this is a great example of how genetic mutation and natural selection play a role in the evolution of humans because it is such an easy topic to understand. Phelan wove outside sources and experts into this narrative to effectively authorize and elaborate on this idea. Overall, a very interesting article that gives people a very interesting and usually relevant topic to discuss.
I agree with your claim that this article provided a concrete and easily understandable example of the impact of genetic mutation on natural selection. For those of us who aren’t experts in the field of evolutionary biology, it allows us to comprehend and grasp the concept more easily.
Awesome post heir2hermingway! This idea of lactose tolerance being a mutation is new to me and quite interesting; I have been under the impression that the converse was true: lactose intolerance is a mutation. It makes so much more sense now to view lactose tolerance as the mutation. After some further research it appears that we are the only animals to drink milk into adulthood, indicating that this trait of lactose tolerance deviates from our other ancestral species.
(http://www.thenakedscientists.com/HTML/questions/question/2863/)
I happen to agree with the authors case that milk provided a healthy, sanitary alternative to water for us to drink in crowded environments, therefore providing us with a better means to survive. Our body, and the body of other milk producing organisms, is (almost) completely free of harmful bacteria internally, and contains certain substances that act as sanitizers. Being able to drink a fluid produced directly from a complex organism provided us with a means to a clean fluid and nutrient source, keeping us healthy and nourished. Do you guys agree/disagree with me? Which theory do you guys agree with in regard to why lactose tolerance proved so crucial to human success?
It is interesting that there are still so many lactose intolerant individuals in the world today, but I guess it makes sense with the introduction of lactase pills, pills containing an enzyme that helps in the lactose breakdown process. This allows for lactose intolerant individuals to consume just as much dairy as lactose tolerant individuals. This raises another question, will lactose tolerance become more or less prevalent in the future? Or will it not be effected? What types of things will affect this distribution of genetic makeup?
gatorade15, I agree that it goes against intuition to view lactose tolerance as the mutation. I found this article very relevant because in my Biology class, we had a similar discussion on the evolution of milk drinking. Professor Doebel staged an interesting question, pondering whether lactose persistance is a more accurate term for those who can can digest lactose. In reponse to your question, it is clear there are multiple factors that correlate with increased lactose persistance in a population, and causation cannot clearly be attributed to one single benefit of drinking milk.
Correction to my previous comment: it is lactASE persistence. LactOSE is a disaccharide sugar. LactASE is the enzyme that breaks lactose into its constituent galactose and glucose molecules.
Some people stated earlier that milk did not play a part in contributing to the proliferation of society, I think it did. Getting milk from a cow for example, requires the domestication of the cow and the ability to keep the cow with you. This forces human cultures to start to develop the farm culture that can lead to the development of agricultural practices that become the foundation for modern civilization. Milk itself can be implicated in the transition from hunter gatherer living to the development of the first villages and cities.
You make some interesting points serrobert, and I agree with you in believing that agriculture helped the human race proliferate. I do have a question: do you think that our ability to domesticate animals and harvest milk developed at the same time as agriculture, or did one precede the other? Because the timing of these developments can change the causation that you explain.
It’s always refreshing to remember that discoveries like these are happening all the time. Whether or not this hypothesis carries weight, it is undoubtedly fascinating – specifically, the question of HOW this genetic mutation spread so fast! I appreciated how Phelan noted the professor at University College London and his acknowledgement of the vitality of the mystery. Hopefully, soon, this mystery will be solved.
In regards to the questions posed at the end of this post, I would say it is certainly possible for such a seemingly insignificant aspect of life like lactose tolerance to affect evolutionary change in a major way; it has certainly happened before. The difference in even one gene can change everything. Remember, we are something like 98% genetically identical to chimpanzees – but so very different! I would like to see some additional empirical data to prove the direct causation and correlation in the change in lactose tolerance with the change in human survival rates and body features (since in this article they primarily talk about these changes with the beginning of agricultural utilization), but otherwise, my mind is completely open to the idea of lactose tolerance playing a large role in human evolution.
Great post!
While the search for the precise evolutionary pressures that led to this change in our species is an interesting and worthwhile pursuit, I think this is a good reminder of how wacky and seemingly random the evolutionary process can be. A lesson that Darwinists like Moran and Richard Dawkins are always trying to hammer home is that evolution is not striving towards the creation of a perfect or specific species- it is simply a process that occurs as advantageous mutations spread through populations. Lactose tolerance doesn’t seem like an especially worthwhile trait, and yet it quickly made its way through our species. Evolution can take 100 million years to change the shape of an arm, or 10,000 years to let us drink milk; that’s simply the nature of the process.
You raise an interesting question Gatorade15, I think I am arguing that the ability to digest milk came first, however I could see them perhaps feeding off of each other and appearing around the same time as humans start to develop a stationary lifestyle rather than a migratory one.
I think this article is interesting in the sense that it points out how the lactate tolerance mutation varies throughout our species and shows the sort of gambling trait of mutations in evolution of how they pass on and spread. I think it’s interesting to point out that it shows the randomness of genetic mutation and evolution, going against the planned out ideals that Intelligent Design proposes. Having studied a case based on the controversy of Intelligent Design, I just find it an interesting point to raise towards ID and Creationist advocates on how one man being able to drink milk and another not being able to falls into the grand design of things, when in actuality it only proves that the universe doesn’t work in lines or graphs but rather is random and wild.
First of all, you raise some very fascinating questions. I definitely feel like milk has the ability to leave evolutionary footprints on humans; lactose tolerance itself is an evolutionary trait that humans who lived in close proximity to dairy producing animals developed; for example, Sweden’s population is close to one hundred percent lactose tolerant, while many countries in Africa have a very low tolerance. This shows how evolution is very much a non-geological process; non-goal oriented and completely random, driven by environmental factors.