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I recently visited the Galapagos (more posts and pictures coming soon).  During that trip I brushed up on some of my Darwin knowledge- in a lecture on board, with some books in the ship’s library, and reading The Voyage of the Beagle on my Kindle. I just got back from a very different trip (visiting family in the UK), but again I managed to brush up on some Darwin, this time by visiting the place where he lived, worked, and died- Down House.

 

Down House, the home of Charles Robert Darwin (1809-1882) for the last 40 years of his life, is in the village of Downe in Kent.  Here Darwin conducted many experiments, and wrote most of his scientific work (On the Origin of Species by Means of Natural Selection (1859) being the most well known).  I am certainly a Darwin enthusiast (some might say a Darwin stalker…), but I expect that even those who have only a mild interest in Darwin, history, evolution, or science would enjoy a tour around this historic site.

 

Down House is located in the village of Downe (the Darwin’s kept the traditional spelling after an “e” was added to the village to distinguish it from the county Down in Ireland), and it has had a number of renovations since it’s initial construction in the early 1700s.  The Darwin’s acquired Down House in 1842, when Darwin and his wife (and first cousin) Emma (nee Wedgewood) wished to escape the hustle and bustle of London with their growing family (at the time they had two children and were expecting a third).  Darwin, in his characteristically frank style wrote, “It is a good, very ugly house, with 18 acres.”, though I think many today would disagree with this assessment!

 

Down House as it is today, with a very excited tourist.

Down House as it is today, with a very excited tourist.

 

Over the course of his 40 years at the house Darwin enlarged it not only for his growing family (he and Emma had ten children, though only 7 survived to adulthood), but also for the comfort of his servants.  Writing to family he said “It seemed so selfish to make the house so luxurious for ourselves and not comfortable for our servants “. One of Darwin’s many interesting (and noteworthy) traits was his humanism.  He was an avid abolitionist (a disagreement with Captain Fitzroy on this subject almost got him kicked off the Beagle), a kind “master” to his house staff, a loving and involved father (an anomaly in Victoria times), and supporter of the humane treatment of animals.

 

Today the name Charles Darwin calls up images of a great scientist, a deep thinker, and a major contributor to human knowledge.  However, this certainly wasn’t the future his family imagined when Charles was a youth.  As a boy he received a classical education at Shrewsbury School.  This was not an education that paired well with young Charles’ interests of beetle collecting (then a national craze), chemistry, and shooting.  His father, a respected physician, is reported to have said “You care for nothing but shooting, dogs, and rat-catching and you will be a disgrace to yourself and all your family.”.

 

After his mediocre performance at Shrewsbury School, Darwin was sent to Edinburgh to follow in his father’s footprints and become a physician.  Alas (or fortunately, for the future of science), Charles could not stomach the brutality of surgery in the era before anesthesia, and he returned home after less than two years.  He was next sent to Cambridge to earn a degree so that he could enter the clergy (entering the clergy was a common career path for men from good families with a penchant for natural history).

 

While Darwin did complete his degree at Cambridge, he never went on to study for the clergy, as he was recommended by a mentor to accompany Captain Robert Fitzroy on the Beagle. Darwin wasn’t the first young naturalist recommended for the job (he actually wasn’t on the boat as the naturalist, though he did later rise to this position, his “job” on the ship was to act as Fitzroy’s companion- a gentleman that a captain could talk to amongst a ship-full of burly sailors).  While his father did not support this decision he did eventually let young Darwin (he was 22 at the time) depart on this adventure at the recommendation of Charles’ uncle Josiah Wedgewood.

 

The expedition aboard the Beagle was meant to last two years, but it stretched into a five-year endeavor.  Darwin’s observations during this travel were instrumental in shaping his thinking and his future.  It is rather fascinating to realize that Darwin’s 5-year, around-the-world journey aboard the Beagle was the only travel he ever undertook.  He returned to England in October of 1836, married in January of 1838, and in September of 1842 took his growing family from the strictures of London to Down House where he would spend the rest of his life.

 

Once at Down House, Darwin preferred to correspond with friends rather than travel back and forth to London.  He was a prolific letter writer- spending the equivalent of thousands of pounds per year on stationary and postage.  While it does seem that Darwin was a bit of an introvert, this insular life was largely a result of ill health.  Once an active and lively young man with a penchant for exploring and shooting, he was plagued with illness after his return from the journey aboard the Beagle.  His symptoms, which were present in varying degrees for the rest of his life, included a number of GI problems, palpitations, and extreme fatigue.  There have been many theories about this illness, ranging from Chagas disease to Chronic Fatigue, including lactose intolerance, Crohn’s disease, and psychosomatic disorders.  Whatever the cause, this illness debilitated Darwin, and at Down House he developed a schedule around his symptoms- working when he could and resting when he must.

 

The Sandwalk at Down House, also sometimes known as the Thinking Path, was where Darwin would walk three times a day (health permitting).  There is a walk down around the property with a loop in the woods, and Darwin would walk laps on the circuit deep in thought.  He would kick rocks from one side to the other to keep track of his laps, as his mind was usually on matters other than his number of "reps".

The Sandwalk at Down House, also sometimes known as the Thinking Path, was where Darwin would walk three times a day (health permitting). There is a walk down around the property with a loop in the woods, and Darwin would walk laps on the circuit deep in thought. He would kick rocks from one side to the other to keep track of his laps, as his mind was usually on matters other than his number of “reps”.

 

Down house wasn’t only Darwin’s home, but also the place where he conducted many experiments – on pigeons, barnacles, orchids, and weeds- work that was instrumental in supporting his theory of natural selection.  Of course Darwin was not the first person to suggest that species were mutable, but he was the first to convincingly propose a cogent mechanistic theory and support it with various lines of evidence.  Both he and Alfred Russel Wallace appreciated the implication of Thomas Malthus’ commentary on populations- that sooner or later populations were checked by famine and disease- and both men independently came to the same theory of natural selection based upon the pressures exerted by nature.  However, it was Darwin who first wrote about the theory (though he did not publish it) and who collected extensive evidence to support the theory.

 

The Hot House at Down House.  A collection of orchids and carnivorous plants are maintained here.  This is where Darwin hypothesized that the orchid Angraecum sesquipeda was pollinated by moth with a long proboscis.  This was discovered to be true, 21 years after Darwin's death.

The Hot House at Down House. A collection of orchids and carnivorous plants are maintained here. This is where Darwin hypothesized that the orchid Angraecum sesquipeda was pollinated by moth with a long proboscis. This was discovered to be true, 21 years after Darwin’s death.

 

The Kitchen Gardens.  Not much going on this time of year, but in summer these beds are full.  This is where Darwin did experiments on pin-eyed and thrum-eyed primroses.

The Kitchen Gardens. Not much going on this time of year, but in summer these beds are full. This is where Darwin did experiments on pin-eyed and thrum-eyed primroses.

 

The remnants of some of Darwin’s experiments can still be seen at Down House.  His hot houses (heated by composting manure!), where he maintained large numbers of orchids and carnivorous plants, are still maintained, as are the large kitchen gardens where he studied primulas.  A reconstruction of “The Worm Stone” that Darwin and his son Horace used to study the action of worms is in the garden, and English Heritage, who maintains the house, continues to dig experimental weed plots similar to those that Darwin constructed to study the succession of plants.

A reconstruction of "The Wormstone".  I was being optimistic when I took this pic, and hoped that I wasn't actually taking a picture of the septic system...

A reconstruction of “The Wormstone”. I was being optimistic when I took this pic, and hoped that I wasn’t actually taking a picture of the septic system…

 

Throughout my visit to Down House I was overcome with a feeling of awe.  I grew up with a deep respect and affection for Darwin- my father is a huge fan, to the point where my brother’s middle name is Darwin.  Being the second born I received an equally nerdy though significantly less well known middle name- Lyell.

 

Charles Lyell was a geologist (I actually wrote about him briefly in my first blog post!) and a well-respected scientist.  He was a mentor for Darwin, though it took him a while to come around to Darwin’s theory of natural selection.  He eventually did, and it was Charles Lyell and Joseph Hooker who presented Darwin’s and Wallace’s papers On the Tendencies of Species to form Varieties and On the Perpetuation of Varieties and Species by Natural Means of Selection to the Linnean Society in 1858. It was a thrill to see Darwin’s portrait of Lyell in his study, as well as various volumes of Lyell’s books in locations throughout the house.

 

Visiting Down House certainly increased my understanding of this great man, and also increased my respect for him.  He was a humble man, a hard-working man, a loving father, and a great mind.  He was also a troubled man- plagued with illness, profoundly concerned by the implications of his theory, and deeply scarred by the loss of children he loved.

This is a picture of Downe Church (not mine) where Darwin would walk every Sunday.  Darwin lost faith in religion after the death of his first daughter, and while he would walk his family to church on Sunday he would not enter the church.  This is where his wife, Emma, is buried (Darwin is buried in Westminster Abbey).

This is a picture of Downe Church (courtesy of wikicommons) where Darwin would walk every Sunday. Darwin lost faith in religion after the death of his first daughter, and while he would walk his family to church on Sunday he did not enter. This is where his wife, Emma, is buried (Darwin is buried in Westminster Abbey).

 

Darwin’s work on natural selection is a classical example of the scientific method.  As a naturalist, especially during his time aboard the Beagle, he made a number of observations.  These observations led him to a hypothesis (natural selection) that he then researched extensively.  He was not purely a “great thinker”, who came up with a theory, but also a patient and meticulous experimentalist who painstakingly showed that species were mutable through pressures of nature.

 

Sometimes in science, medicine, and certainly in the paleosphere we get stuck on an idea or a theory.  We latch on to something that just “makes sense” or fits in nicely with our current way of thinking, and we start to accept it as fact.  Seeing how hard Darwin worked to build evidence to support a theory, which on an intellectual basis was so obvious, reminds me how important it is to not stand on theory alone, but to work diligently towards better understanding through rigorous science.

 

Though sometimes controversial in the US, Darwin is well loved in the UK.  He had a distinguished funeral at Westminster Abbey and is interred near the monument for Sir Isaac Newton.

Though sometimes controversial in the US, Darwin is well loved in the UK (and is featured on the ten pound note). He had a distinguished funeral at Westminster Abbey and is interred near the monument for Sir Isaac Newton.

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I’ve been fortunate to do some pretty amazing travel in the past, but the journey I just returned from has certainly stolen the show. 

 

As an evolution nerd, a Darwin enthusiast, and a lover of the natural world, a trip to the Galapagos was truly an experience I will never forget.  I’ve wanted to visit the Galapagos for a long time*, and while I had thought about visiting in my 6 months off between med school and residency I only booked the trip about a month ago.  My father (also an evolution nerd, Darwin enthusiast, and naturalist) and I travelled with National Geographic and Lindblad Expeditions on a trip to the Galapagos aboard The National Geographic Endeavour (named in honor of the first vessel that Captain Cook used in his explorations – the one that landed on the eastern coast of Australia; Cook never visited the Galapagos).  I’ll just start by saying the company, the experience, the ship, the crew, the staff, the naturalists, the whole package- were all first rate.  It’s a top of the line option for visiting the Galapagos, and it really shows.

 

In many people’s minds, the Galapagos are inexorably linked with Charles Darwin and his theory of Natural Selection.  Darwin visited the Galapagos, on HMS Beagle, in 1835. Darwin was aboard the Beagle for 5 years, but he only spent 5 weeks in the Galapagos of which only 19 days were on land!  Nonetheless, the observations he made there and the samples he collected were important ingredients for his future theory.

 

Tagus Cove- One evening we stopped in Tagus Cove- an area where Darwin landed.  There is graffiti in this cove, as it was traditional (until recently) to leave the name of your boat on the cliffs (some are amazingly high up).  The earliest inscription we saw was from 1836, the year after Darwin visited.

One evening we stopped in Tagus Cove- an area where Darwin landed. There is graffiti in this cove, as it was traditional (until recently) to leave the name of your boat on the cliffs (some are amazingly high up). The earliest inscription we saw was from 1836, the year after Darwin visited.

 

Most of the walks we took on this cruise were rather relaxed, but this evening’s hike was a change of pace, and we made good speed up a steep trail.  Looking back, we could see the Endeavour and a large pond that Darwin wrote about in The Voyage of the Beagle.  Alas, while he was hoping for a refreshing dip in some fresh water, he was frustrated to find that this pond is brackish.

 

A [disappointingly] brackish pond.

A [disappointingly, at least for Darwin] brackish pond.

I recommend the Galapagos chapter of The Voyage of the Beagle (Chapter 17).  It is a delightful and quick read, and if you have an e-reader you can find it for free online.  The Voyage of the Beagle was a travel journal of sorts, and while Darwin was the naturalist aboard The Beagle (well he was eventually, he didn’t start that way but eventually replaced the original Naturalist) he first became famous as a travel writer (his theory of evolution didn’t make him famous until quite late in life, and strangely his book on Barnacles wasn’t a big seller…).

 

Over the years, the Galapagos became a popular stopping point for ships.  While there is very limited fresh water, it was a good place to replenish food.  Early visitors introduced goats (a species that quickly flourished on the islands, wreaking havoc on endemic creatures) and the Galapagonian tortoises were particularly popular as well.

 

There are a number of species that are uniquely Galapagonian- the tortoise being a prime example.  These giant creatures at one time roamed the islands in great numbers, but their populations were decimated by humans in ~150 years.  The tortoise had two great misfortunes- first, they apparently taste pretty good (Darwin wrote of roasted tortoise breast “Gaucho style” being quite tasty, and was complimentary of tortoise soup (from medium sized animals), though he found nothing remarkable in the rest of the animal).  Perhaps the greater misfortune for these giants is that they can survive for ~2 years without food or water.  In a time before refrigeration, when fresh meat was almost an impossibility on long sea voyages, tortoises could be stashed on boats for ages until they were finally consumed.  I admit to being rather bad about anthropomorphizing animals, but I can only imagine that being kept in the hold of a ship for over a year before being killed and eaten was a rather unpleasant end.

 

A Medium Sized Tortoise- Perhaps this is a good soup-sized tortoise?

A Medium Sized Tortoise- Perhaps this is a good soup-sized tortoise?

 

These giants are believed to live over 200 years, though it is hard to be sure since we haven’t been studying them that long.

These giants are believed to live over 200 years, though it is hard to be sure since we haven’t been studying them that long.

 

The tortoises on different islands are considered different sub-species (though where you draw the line at species vs. subspecies or variety was a common quandary during our tour of the Galapagos) and some have gone extinct due to human harvesting, competition (with things such as introduced goats), and decreased hatching (because of damage to nests due to introduced species).  One of the most famous Galapagos Tortoises was “Lonesome George”, the last of his kind- a subspecies of tortoise that inhabited Pinta Island.  While a number of attempts were made to breed George and “save” his kind, none were successful, and he died- the last of his kind- in 2012.

 

Lonesome George had been living at the Charles Darwin Research Station on Santa Cruz Island since his discovery in 1971, and for many years was the center’s most famous denizen.  We visited Santa Cruz, and the Charles Darwin Research Center, during our cruise, and we got to see the conservation efforts there.

 

The National Park manages 97% of the land of the Galapagos (only 3% is habited). The Charles Darwin Research Center does a lot of research, but only the national park can change policy and initiate change in the park.

The National Park manages 97% of the land of the Galapagos (only 3% is habited). The Charles Darwin Research Station does a lot of research, but only the national park can change policy and initiate change in the park.

 

Eggs from different subspecies are hatched and reared in captivity on Santa Cruz (and there are two other tortoise breeding centers elsewhere in the archipelago).  When they are large enough to be released they are tagged and released.  These efforts have generally been very successful and the tortoise population is recovering nicely.  While they claim the number painted on the babies backs are for identification purposes, I secretly hope there is some illicit tortoise racing going on after hours!

Eggs from different subspecies are hatched and reared in captivity on Santa Cruz (there are two other tortoise breeding centers elsewhere in the archipelago). When they are large enough to be released they are tagged and released. These efforts have generally been very successful and the tortoise population is recovering nicely. While they claim the number painted on the babies backs are for identification purposes, I secretly hope there is some illicit tortoise racing going on after hours!

 

After his death, Lonesome George was sent to NYC where he was preserved by experts at the Natural History Museum.  The current celebrity at the Charles Darwin Research Center is a much happier tale.  When conservation efforts were initiated, there were only 14 tortoises of the Española subspecies- 12 females and 2 males.  While conservationists hoped to build the population from these animals, the females were not interested in the males.  In an attempt to save the subspecies, a global search for a male of their kind was initiated- seeking out giant tortoises in zoos and private collections around the world.  Eventually a male was found in the San Diego zoo, and after some negotiating “Diego” made his way back to the Galapagos.  Now, having fathered over 1000 offspring, Diego is known as “Super Diego”, and the subspecies is doing well!

 

The conservation of the Galapagos Tortoises seems to be on the road to success, which is wonderful.  The Charles Darwin Research Station has also had good success breeding and reintroducing some subspecies of Land Iguanas.  In fact, the breeding program at the research center has now been closed because the efforts were so successful.

 

These cuddly guys (land iguanas) have had a hard time on some islands, but with restoration and conservation efforts they are now dong well.

These cuddly guys (land iguanas) have had a hard time on some islands, but with restoration and conservation efforts they are now dong well.

 

There were slim pickings for the Land Iguanas on North Seymour. These guys like to eat prickly pear cactus, but were taking to the trees to find some greenery in this sparse environment.  One of the naturalists we were with said he had never seen Land Iguanas so high in trees before.

There were slim pickings for the Land Iguanas on North Seymour. These guys like to eat prickly pear cactus, but were taking to the trees to find some greenery in this sparse environment. One of the naturalists we were with said he has never seen Land Iguanas so high in trees before.

 

Lusher pastures for this land iguana near Urvina Bay.

Lusher pastures for this land iguana near Urvina Bay.

 

You may not know it, but about 30,000 people live in the Galapagos.  While 97% of the island is National Park (for which you need a permit and a naturalist to visit- no more than 16 tourists per naturalist), there are a number of inhabited areas.  At the end of our cruise we visited Santa Cruz, where the Darwin Center is, and San Cristobal, from where we flew back to the mainland.  In Santa Cruz we took a walk through town, and it was fun to stop at the fish market and see the catch of the day.  Humans weren’t the only interested customers!

 

Pelicans at the self-serve bar

Pelicans at the self-serve bar

 

A bit more anthropomorphizing... I imagined this Sea lion waiting for his number to be called at the deli counter.

A bit more anthropomorphizing… I imagined this Sea lion waiting for his number to be called at the deli counter.

 

The Sea Lion was given a hunk of fish and the fishmonger kept the pelicans back with a fly swatter so he could enjoy it!

The Sea Lion was given a hunk of fish and the fishwife kept the pelicans back with a fly swatter so he could enjoy it!

 

The Galapagos are part of Ecuador, and until fairly recently were not inhabited.  Initially, colonists were “gifted” land, as encouragement to come and live in the Galapagos, but now there are significant efforts to curb immigration.  When we were in Santa Cruz we headed up into the highlands to see tortoise in the wild (they much prefer to be in the highlands with lush vegetation and more water, but the females come out of the highlands to lay eggs- an unfortunate habit, since the smaller females were more desirable fodder for hungry sailors, and were much closer to the ocean than the large males who stayed in the highlands).

The tortoises in the highlands like to relax in ponds such as this one.  They will drink gallons of water when they visit, but can go years without water in hard times.

The tortoises in the highlands like to relax in ponds such as this one. They will drink gallons of water when they visit, but can go years without water in hard times.

 

At first I was confused by the shrubbery this tortoise had acquired, but after seeing them wallowing in the weed-covered pond all became clear.

At first I was confused by the shrubbery this tortoise had acquired, but after seeing them wallowing in the weed-covered pond all became clear.

 

Unfortunately, this method of hiding didn't save tortoise from hungry sailors.  Darwin writes how sailors would flip these hiding beasts over and carry them off to the ships for storage. Darwin also wrote about his attempts to ride these massive creatures!

Unfortunately, this method of hiding didn’t save tortoise from hungry sailors. Darwin writes how sailors would flip these hiding beasts over and carry them off to the ships for storage. 

 

While we were in the highlands we visited a plantation where a family grows coffee and sugar cane.  Both grow well in the Galapagos, and while we visited we learned how people traditionally processed sugar (into molasses and alcohol) and coffee.

 

Sugar Cane processing- This isn’t how the family processes sugar today, but this is the traditional method.  Sugar cane is fed into the press and juice comes out the bottom.  On this plantation half of the sugar cane juice is made into molasses and half is made into alcohol!

Sugar Cane processing- This isn’t how the family processes sugar today, but this is the traditional method. Sugar cane is fed into the press and juice comes out the bottom. On this plantation half of the sugar cane juice is made into molasses and half is made into alcohol!

 

Diabetic Warbler?- This Yellow Warbler really liked to hang out on the sugar cane press!

Diabetic Warbler?- This Yellow Warbler really liked to hang out on the sugar cane press!

 

Hooch- this was the open vat where the sugar cane juice was fermenting.  The final product, after it was passed through a still, was… rough.  There's a reason people age rum!

Hooch- this was the open vat where the sugar cane juice was fermenting. The final product, after it was passed through a still, was… rough. There’s a reason people age rum!

 

Coffee- Having had an introduction to traditional coffee processing methods in Belize, I got a review in The Galapagos.  Here you can see the unroasted cleaned and uncleaned beans.

Having had an introduction to traditional coffee processing methods in Belize, I got a review in The Galapagos. Here you can see the unroasted uncleaned and cleaned beans.

 

I took a new camera with me on this trip and certainly had some fun with shots like this...

I took a new camera with me on this trip and certainly had some fun with shots like this…

 

We got to try coffee beans, sugar, coffee, sugar juice (delicious with a squeeze of lime), and hooch (ditto).  While I certainly took lots of pictures in the Galapagos thing, the only physical product I’m coming home with is some Galapagonian Coffee.

 

Admission time- Label something “Evolutionary” and I am 27% more likely to purchase it.

Admission time- Label something “Evolutionary” and I am 27% more likely to purchase it.

 

I have a lot more to write about, and many more pictures to share, but this seems like a good stopping point for now.  I’ll get the next post up ASAP, but it may be a bit of a wait since I head to the UK tomorrow for a quick visit with family.

 

Me and my old new-friend. Unlike Darwin, I didn't try and catch a ride (though you can see why he tried!)

Me and my old new-friend. Unlike Darwin, I didn’t try and catch a ride (though you can see why he tried!)

 

*While I have always been keen to visit the Galapagos, I have also been somewhat wary.  There is no doubt that humans have done a lot of damage in the Galapagos.  While the bulk of this damage was done by early visitors who purposefully introduced a number of hardy species, tourists certainly have the potential to damage the environment, spread seeds, and introduce species or disease.  That being said, done correctly, tourism can be an incredible force for good in the Galapagos.  A lot of damage has been done in the past 200 yrs by sailors, settlers, and visitors.  Progress is being made to repair these damages, with money coming largely from tourists.  If humans were to now abandon the Galapagos, the endemic species would be pushed out by species that have already been introduced. Well-regulated tourism, appropriate management of the land, and conservation efforts can help preserve the Galapagos. They are certainly a wonder worth saving.

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‘Tis the season for cheesy cards, overpriced restaurant dinners, flowers, chocolates, jewelry, and stuffed animals.  I’ll admit that I’ve never been a huge fan of Valentine’s Day.  We started off on the wrong foot, with those awkward grade-school valentine exchanges, and I’ve never seen eye-to-eye with Valentine’s day over the crass-consumerism that seems part-and-parcel with this holiday.  That, and even in my most desperate days I could never understood the gustatory appeal of candy hearts.

 

This year, instead of doing my best to ignore the day, I thought I’d have a little fun. I’ve said it before and I’ll say it again: evolution is everywhere. This is never more true than in the bedroom!

 

Snuggling, cuddling, spooning… name your term.  

 

Why do humans like to cuddle?  There are a number of arguments that can be made for snuggling.  Physical contact in the form of massage increases levels of the “love” hormone oxytocin [1] and decreases cortisol [2] (though some of the data on massage is fuzzy, perhaps because massage, especially in a research setting, can be a rather impersonal experience in comparison to cuddling).  More frequent hugs increase oxytocin levels and lead to lower blood pressure and heart rate in premenopausal women [3]. An interventional trial that looked at the effects of “warm touch” (including hand-holding, hugs, and “cuddling up”) in married couples showed an increase in salivary oxytocin (in husbands and wives) and a decrease in systolic BP (in husbands only) in the treatment group [4].

 

Increased oxytocin seems to enhance the effects of social support on stress responses [5].  Oxytocin also plays a role in the early stages of romantic attachment, and encourages pair-bonding (and parental attachment) [6]. But oxytocin isn’t the only compound that is altered by cuddling-up or that affects the way we feel about other people. There is also evidence that touch alters the release of endorphins[7], and that neuropeptides may play a role in the beneficial nature of physical touch [8].

 

On a day like Valentine’s Day, which purports to revolve around the concept of love (and chocolate sales), the arguments that physical contact reduces stress and increases the hormone associated with pair-bonding are probably king.  Recently  (and I did warn you I’m a bit cynical about this holiday), I’ve been wondering if there is something a little more… “anatomically practical” about cuddling.

 

Why you (men) shouldn’t “hit it and quit it”.

 

Anyone that has spent anytime thinking about human pair bonding has spent time thinking about short-term vs. long-term interests when it comes to the mating game. Yes, humans are predisposed to long-term bonding, but that doesn’t mean that there isn’t a significant role of short-term mating in human procreation (perhaps not as much now, thanks to social norms and the potential for paternity tests, but sources frequently cite that ~10% of children aren’t actually the offspring of the father that raises them, though a more thorough investigation shows that the rate is probably closer to 3% [9].).  As an aside, while on my EMS elective I was repeatedly subjected to the Maury Povich show and it’s ilk while hanging out at headquarters (the lounge TV was usually blaring in the background). I doubt that Frederick Sanger imagined how his great discovery of DNA sequencing would be used when he developed the method in 1975 (for which he later won a Nobel prize in Chemistry- his second). “You are NOT the father!!!” But I digress…

 

Different species have various ways of decreasing paternity uncertainty.  Some animals- canines for example- have a very… awkward (maybe I’m being anthropomorphic, I apologize) way of increasing the likelihood of paternity. After the completion of mating, the male doesn’t leave the female’s side. He can’t. Seriously. He is physically attached.

 

Dog mating is significantly different from that of humans. When the dog’s penis is first inserted into the vagina it isn’t actually erect and is only able to penetrate thanks to the penis bone, also known as the baculum. After insertion, the penis swells and the bulbus glandis at the base of the penis literally locks the penis in place, preventing the removal of the penis. This is known as “knotting” or “tying”.  This cumbersome position usually lasts 5-20 minutes after ejaculation.

 

At least one book on dog genetics says that this process seems “quite irrational”, but the authors submit that it “must serve a purpose as it has remained despite apparent drawbacks, such as vulnerability to attacks during the act.” [10]. I doubt I’m the first to suggest that the advantage of this prolonged intimacy is an increase in certainty of paternity.  It seems rather obvious that this method of copulation gives the lucky suitor’s sperm time to gain advantage in the race to fertilization, before another competitor’s sperm can enter the race.

 

Fortunately, humans have not evolved this mechanism of assuring paternity. Instead, I’d argue that post-coital snuggling can offer some of the advantages of canine-coupling.

 

Some people might think that humans are above such an animalistic tendency. If a man doesn’t stick around long enough to ensure that his sperm have time to reach their destination, would another man’s actually get the chance?

 

Well maybe…  It has actually been argued that the human penis is evolutionarily shaped (literally) to help a man get his semen where it needs to be, even if it didn’t actually get there first.  In the article “The human penis as a semen displacement device*”, researchers argue that the shape of the human penis is “designed” to remove semen from the vagina during sex, clearing the way for new semen to be deposited in the most advantageous location (increasing the likelihood of paternity) [11].  This strengthens the argument that if you’re a man, and you want to ensure paternity, it’s probably best you hang around to make sure your sperm doesn’t have any competition in reaching it’s goal.

 

So there you have it, the “principle into practice evolutionary argument for snuggling”.  Sure, in the modern world men may not WANT paternity with every sexual encounter, but that doesn’t mean that the evolutionary mechanisms and behavioral predispositions aren’t already in place to improve paternity-certainty.  On a day like Valentine’s day, you might rather focus on how cuddling increases oxytocin, leading to emotional bonding.  Just remember that snuggling also physically bonds you, and that may not be such a bad thing…

 

*This paper wins the award for most giggle-worthy methods. Some of the lines could be right at home at #overlyhonestmethods. E.g.: “… this recipe was judged by three sexually experienced males to best approximate the viscosity and texture of human seminal fluid.”

 

 

1.            Morhenn, V., L.E. Beavin, and P.J. Zak, Massage increases oxytocin and reduces adrenocorticotropin hormone in humans. Altern Ther Health Med, 2012. 18(6): p. 11-8.

2.            Rapaport, M.H., P. Schettler, and C. Bresee, A preliminary study of the effects of repeated massage on hypothalamic-pituitary-adrenal and immune function in healthy individuals: a study of mechanisms of action and dosage. J Altern Complement Med, 2012. 18(8): p. 789-97.

3.            Light, K.C., K.M. Grewen, and J.A. Amico, More frequent partner hugs and higher oxytocin levels are linked to lower blood pressure and heart rate in premenopausal women. Biol Psychol, 2005. 69(1): p. 5-21.

4.            Holt-Lunstad, J., W.A. Birmingham, and K.C. Light, Influence of a “warm touch” support enhancement intervention among married couples on ambulatory blood pressure, oxytocin, alpha amylase, and cortisol. Psychosom Med, 2008. 70(9): p. 976-85.

5.            Heinrichs, M., T. Baumgartner, C. Kirschbaum, and U. Ehlert, Social support and oxytocin interact to suppress cortisol and subjective responses to psychosocial stress. Biol Psychiatry, 2003. 54(12): p. 1389-98.

6.            Schneiderman, I., O. Zagoory-Sharon, J.F. Leckman, and R. Feldman, Oxytocin during the initial stages of romantic attachment: relations to couples’ interactive reciprocity. Psychoneuroendocrinology, 2012. 37(8): p. 1277-85.

7.            Keverne, E.B., N.D. Martensz, and B. Tuite, Beta-endorphin concentrations in cerebrospinal fluid of monkeys are influenced by grooming relationships. Psychoneuroendocrinology, 1989. 14(1-2): p. 155-61.

8.            Dunbar, R.I., The social role of touch in humans and primates: behavioural function and neurobiological mechanisms. Neurosci Biobehav Rev, 2010. 34(2): p. 260-8.

9.            Anderson, K.G., How Well Does Paternity Confidence Match Actual Paternity. Current Anthropology, 2006. 47(3): p. 513-520.

10.            Ruvinsky, A. and J. Sampson, The Genetics of the Dog. http://www.google.com/books?id=bgZwjdB4xgEC&source=gbs_navlinks_s ed. 2001: Google Books.

11.            Gallup, G.G., R.L. Burch, M.L. Zappieri, R.A. Parvez, M.L. Stockwell, and J.A. Davis, The human penis as a semen displacement device. Evolution and Human Behavior, 2003. 24: p. 277-289.

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Happy New Year!

2012 was a whirlwind year for me. I defended my PhD at the beginning of 2012 and am now almost finished with all the required clerkships of third-year medical school. Phew!

I spent my winter holiday visiting my brother in Dubai, exploring many sites of the United Arab Emirates (UAE). I got to see a lot during my stay, and I’ve been writing a post on some of the interesting things I saw there.  As I was writing about the traditional dietary staples of the Middle East, I took a foray through a lot of literature that is available on camel milk.  It’s interesting stuff, and I found myself heading off on a tangent that I thought I should post as a stand-alone article.

So here we go…

Ship of the desert
Camels were (and still are, but for different reasons) an important part of life in the Middle East. The Arabian camel (the dromedary Camelus dromedarius) is a one-humped beast, and should not be confused with the 2-humped Bactrian camel (Camelus bactrianus) of central Asia.  Dromedaries were the only mode of transportation in the desert before motorized vehicles (walking any substantial distance on foot is out of the question and horses need too much water), and they also were an important form of wealth and source of food. Camel meat was a rare delicacy, while camel milk was a staple of the Bedouin diet. Camel hair was also used to make household necessities and camel dung was often used as fuel (a nice argument against the calories in calories out argument- if biological creatures were bomb calorimeters there wouldn’t be anything worth burning coming out the other end…).

Camel meat was not a staple of the Bedouin diet.  In fact, most nomadic people are reluctant to kill their subsistence animals for meat. Female camels were used for dairy and some males were kept for breeding purposes, but extra young male camels would be slaughtered and eaten for special occasions.

Though definitely not a traditional dish- this seems to be the #1 way to eat camel meat today

Though definitely not a traditional dish, this seems to be the most popular way to eat camel meat today

Camels are uniquely able to provide sustenance for humans in an environment that is generally rather inhospitable. Camels are able to not only survive, but thrive, on the limited and harsh forages that are available in the desert. She-camels can produce enough milk to nurse their offspring and provide liters of milk per day for their owner.

Camel in its native environment. These beasts thrive on the course and sparse forage of the desert.

Camel in its native environment. These beasts thrive on the coarse and sparse forage of the desert.

Camels’ milk is interesting stuff. Unlike the milk of cows, goats, and sheep, it cannot be easily made into cheese.  It doesn’t coagulate with bovine rennet, however recombinant camel rennet is incredibly efficient at coagulating cow milk and can also coagulate camel milk (there is a difference in the camel kappa-casein that makes it more resistant to cleavage) [1, 2].  With the right enzyme the job can be done, and there is at least one company that makes a camel cheese (nicknamed Camelbert!).

Camel milk isn’t much good for making yoghurt either, being much more resistant to lactic acid fermentation than cow milk. The result of camel milk lactic fermentation is very runny, with little microbial growth [3]. Gariss, a traditional Sudanese fermented camel’s milk product, is made with a mixed culture including Lactobacillus, Streptococcus, and yeast [4]. Here’s how it was traditionally made:

fermentation is carried out in two leather bags of tanned goat skin embedded in green or wet grass carried on the bag of camels and subjected to continuous shaking by the jerky walk inherent to camels. Whenever part of the product is withdrawn for consumption, a portion of fresh camel’s milk is added to make up volume and this continues for months [4].

According to one paper I spotted, food scientists can thicken fermented camel milk with gelatin or alginate (a thickener made from seaweed) in order to make a yoghurt-like product that consumers might find acceptable, but I didn’t spot any on the shelves in the stores of Dubai [5].

It seems to me that when it comes to camel milk it might be best to just keep it simple. Plain old milk.

CamelMilk

But camel milk may not be such simple stuff.  There is growing research that explores the use of camel milk for medicinal purposes.

I haven’t gone into the research in depth, but there are a number of small studies looking at the benefits of camel milk for people with diabetes (type 1 and type 2), with rather remarkable results. The addition of 500mL of camel milk on top of usual care for patients with type 1 diabetes resulted in significant improvements in a number of parameters in comparison to people who just received standard care. The camel milk group had a decrease in mean blood glucose levels and hemoglobin A1c.  The study was small, but 3 of the 12 participants in the camel milk group were able to completely stop using insulin (an almost unheard of occurrence for those with type 1 DM).  While the mean amount of insulin used in the control group remained constant, the amount used in the camel milk group dropped rapidly [4].

Abdelgadir et al [4]

Abdelgadir et al [4]

It hasn’t been determined how camel milk affects those with diabetes, but there are a number of hypotheses. Some sources think that insulin from camel milk is uniquely able to escape digestion when ingested or that camel milk contains a unique insulin-like small peptide that is bioavailable when consumed [6]. This is unlikely to be the whole story, however, as camel milk is able to increase endogenous insulin secretion in type 1 diabetics (individuals in standard of care + camel milk groups have higher levels of C-peptide, showing an increase in insulin production) [7].

Some readers may know that I have a fondness for fatty liver disease, so I was particularly interested to learn that, in a rat study, camel milk reversed alcohol-induced liver injury. This was seen histologically, where there was minimal fatty accumulation in the livers of alcohol-treated animals supplemented with camel milk in comparison to those just treated with alcohol alone, and serologically, where animals that were treated with ethanol alone had significantly increased liver enzymes in comparison to controls and those fed alcohol and camels milk [8]. I would postulate that it might have something to do with the high levels of carnitine found in camel milk [9], but that’s a story for another day.

Nutritionally, camel milk is unique. As I just mentioned, it has a more free carnitine as a percentage of total carnitine than other species and higher total carnitine than cow or human milk (though lower than sheep and goat milk) [9]. Camel milk has three-times the vitamin C of cow milk, but a similar amount of vitamin E and considerably less vitamin A and riboflavin [10]. Camel milk is low in short chain fatty acids in comparison to other milks and it has primarily long chain fatty acids, a significant portion of which is linoleic acid [11].  I tend to avoid this omega-6 FA, but I suspect that as part of a traditional diet the amount found in camel milk does not cause a problem.
Camels can carry a number of zoonotic organisms, including Coxiella burnetii (which causes Q fever) and Brucella sp. (which causes brucellosis), which can be transmitted through the milk. In fact, there was a recent brucellosis outbreak in Israel caused by raw camel milk [12].  If you’re drinking milk from an untested camel, it’s probably best to have it pasteurized. All the milk that’s available in Dubai supermarkets is pasteurized and homogenized. There are a variety of brands, and you can get milk in an array of flavors!

I spied plain, chocolate, strawberry, saffron, rose, cardamom, and date flavor! In this pic there's saffron, chocolate, strawberry, date, and plain.

I spied plain, chocolate, strawberry, saffron, rose, cardamom, and date flavor! In this pic there’s saffron, chocolate, strawberry, date, and plain.

Of course I had to try some… I opted for plain milk, and found it slightly sour in comparison to cow’s milk, with a watery mouthfeel. It’s been at least a decade since I drank skim milk, but as I remember the mouthfeel is similar.

Sculptors of human evolution

Camels have played central roles in the lives of desert dwelling people for millennia. They are the “ship of the desert” and their milk has nourished and sustained generations.  Their milk has also shaped the human genome…

The predominance of lactase persistence in populations is a well-known and well-studied example of human evolution. In populations that had access to animal milk, a mutation that allowed for the production of lactase past the age of weaning gave humans access to a rich food source. This was a huge advantage to those that had such a mutation.  Those that could easily consume milk were able to have more children, and the mutation spread throughout the population.  The advantage of having persistent lactase expression is so advantageous it has occurred independently in multiple populations over time.  While some mutations are linked back to the domestication of the cow, there are novel mutations found in Middle Eastern populations that are linked to the domestication of, and subsequent milk consumption from, Arabian camels [13].

The advantage of camel domestication is still present today.  A paper from 1996 looked at child health in three populations of Rendille pastoralists in Northern Kenya. Two of the groups had abandoned their nomadic roots to become settled, while one group remained nomadic.  In wet years (good years) there was a similar number of malnourished children in the three groups; however in a drought year, the children of the nomadic group faired significantly better.  The differences in malnutrition were attributed to food- specifically camels milk.  In drought years, the children in the nomadic group consumed three times as much milk as those from the sedentary group, where the children got more starches and sugar.  Other studies have found that nomadic groups generally do poorly during drought years (because of decreased production of milk from their herd), but because the Rendille maintain a large number of camels, they faired better during hard times [14].

So there you have it… I went diving into pubmed looking for a few fun facts to incorporate into a blog post on my trip to Dubai and found myself swept up in a mess of Dromedary data… I hope you found it as interesting as I did!

Camel

1.            Kappeler, S.R., H.J. van den Brink, H. Rahbek-Nielsen, Z. Farah, Z. Puhan, E.B. Hansen, and E. Johansen, Characterization of recombinant camel chymosin reveals superior properties for the coagulation of bovine and camel milk. Biochem Biophys Res Commun, 2006. 342(2): p. 647-54.

2.            Sorensen, J., D.S. Palmer, K.B. Qvist, and B. Schiott, Initial stage of cheese production: a molecular modeling study of bovine and camel chymosin complexed with peptides from the chymosin-sensitive region of kappa-casein. J Agric Food Chem, 2011. 59(10): p. 5636-47.

3.            Attia, H., N. Kherouatou, and A. Dhouib, Dromedary milk lactic acid fermentation: microbiological and rheological characteristics. J Ind Microbiol Biotechnol, 2001. 26(5): p. 263-70.

4.            Abdelgadir, W., D.S. Nielsen, S. Hamad, and M. Jakobsen, A traditional Sudanese fermented camel’s milk product, Gariss, as a habitat of Streptococcus infantarius subsp. infantarius. Int J Food Microbiol, 2008. 127(3): p. 215-9.

5.            Hashim, I.B., A.H. Khalil, and H. Habib, Quality and acceptability of a set-type yogurt made from camel milk. J Dairy Sci, 2009. 92(3): p. 857-62.

6.            Malik, A., A. Al-Senaidy, E. Skrzypczak-Jankun, and J. Jankun, A study of the anti-diabetic agents of camel milk. Int J Mol Med, 2012. 30(3): p. 585-92.

7.            Mohamad, R.H., Z.K. Zekry, H.A. Al-Mehdar, O. Salama, S.E. El-Shaieb, A.A. El-Basmy, M.G. Al-said, and S.M. Sharawy, Camel milk as an adjuvant therapy for the treatment of type 1 diabetes: verification of a traditional ethnomedical practice. J Med Food, 2009. 12(2): p. 461-5.

8.            Darwish, H.A., N.R. Abd Raboh, and A. Mahdy, Camel’s milk alleviates alcohol-induced liver injury in rats. Food Chem Toxicol, 2012. 50(5): p. 1377-83.

9.            Alhomida, A.S., Total, free, short-chain and long-chain acyl carnitine levels in Arabian camel milk (Camelus dromedarius). Ann Nutr Metab, 1996. 40(4): p. 221-6.

10.            Farah, Z., R. Rettenmaier, and D. Atkins, Vitamin content of camel milk. Int J Vitam Nutr Res, 1992. 62(1): p. 30-3.

11.            Gorban, A.M. and O.M. Izzeldin, Fatty acids and lipids of camel milk and colostrum. Int J Food Sci Nutr, 2001. 52(3): p. 283-7.

12.            Shimol, S.B., L. Dukhan, I. Belmaker, S. Bardenstein, D. Sibirsky, C. Barrett, and D. Greenberg, Human brucellosis outbreak acquired through camel milk ingestion in southern Israel. Isr Med Assoc J, 2012. 14(8): p. 475-8.

13.            Enattah, N.S., T.G. Jensen, M. Nielsen, R. Lewinski, M. Kuokkanen, H. Rasinpera, H. El-Shanti, J.K. Seo, M. Alifrangis, I.F. Khalil, A. Natah, A. Ali, S. Natah, D. Comas, S.Q. Mehdi, L. Groop, E.M. Vestergaard, F. Imtiaz, M.S. Rashed, B. Meyer, J. Troelsen, and L. Peltonen, Independent introduction of two lactase-persistence alleles into human populations reflects different history of adaptation to milk culture. Am J Hum Genet, 2008. 82(1): p. 57-72.

14.            Nathan, M.A., E.M. Fratkin, and E.A. Roth, Sedentism and child health among Rendille pastoralists of northern Kenya. Soc Sci Med, 1996. 43(4): p. 503-15.

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As the popularity of an evolutionary approach to wellness grows, the belief that everything can be fixed with an appropriate diet and exercise plan seems to diminish. While eliminating Neolithic components of the diet that humans don’t thrive on and participating in physical activities that challenge and benefit our bodies are vital elements of wellness, it’s becoming increasingly obvious that food and movement alone do not a healthy body make.

One of the big topics du jour in the paleosphere and in scientific research is the role of an appropriate gut microbiome in health and wellness. I’ve written about it a bit in some of my past posts on the appendix and breast-feeding, and it seems like you can’t surf too far on the paleo interwebz without seeing something about how to feed, nurture, or modify your microbiome. Having the right little guys inhabit your gut is important as commensal bacteria are capable of utilizing molecules that we can’t otherwise metabolize (turning them into compounds we can use), are capable of making vitamin K which we need to thrive, and they outcompete nasty bacteria that cause disease. Also, as mentioned in one of my posts on the appendix, a healthy and appropriate gut microbiome is probably essential in keeping the immune system appropriately occupied so that it doesn’t get bored and start attacking our own body.

But there’s more to a healthy human biome than bacteria. If we imagine out large intestines as something akin to the Great Plains, I imagine our bacteria as the diverse species of rodents that run around and occupy their little niches. Mice, voles, prairie dogs and beavers- they all play their part in keeping that ecosystem healthy. There is another creature, however, one much larger that once roamed those grassy prairies. The Bison were a keystone species of the Great Plains: their grazing and migration helped maintain the native prairie and shape the environment. Much as the buffalo were almost eradicated by modern civilization, the keystone species of our intestine- parasites such as helminths- have all but disappeared in the modern world.

In my first year of medical school I attended a seminar by one of the faculty in our immunology department where he discussed the role of intestinal parasites in appropriately priming the immune system. The human body did not evolve in a sterile bubble; it coevolved with bacteria and intestinal parasites. This means that our immune system has been selected to function in (and indeed is optimized for) an environment where we interact with parasites. Similarly, while there are definitely situations where parasites are problematic (when in the wrong host, or when infections occurs on top of other disease or malnutrition, and when the parasite burden is too high), parasites have not evolved to be overly harmful to their host. A parasite that kills its host is an evolutionary dead end.

It turns out that internal parasites significantly modulate our immune system. The gut is especially rich in immune tissue, specifically GALT (gut-associated lymphoid tissue) as mentioned in previous posts. Helminths secrete a multitude of molecules, including protease inhibitors, cytokine homologues, and a number of other compounds that alter T-cell function. These molecules down-regulate the host’s immune system. While the idea of down-regulating our immune system may make some wary, remember that this is a relationship that our immune system (indeed, probably the immune system of all mammals) evolved to handle. In fact, our rather unique modern environment, in which our immune system is no longer occupied with intestinal parasites, might be considered as something of an evolutionary arms race that has suddenly gone unopposed.

This theory is supported by a number of interesting findings, both in people living in pre-industrial cultures who are chronically exposed to parasites, and in those of us living in the hygienic modern world where our immune systems have become a bit out of whack. In Africa, children living in rural communities carrying chronic parasite infection have a shorter course of asthma (a condition caused by inflammation of the respiratory tract) [1]. Similarly, a study in children in Gabon demonstrated that chronic parasite infection decreased the immune response to common allergens such as dust mites [2, 3]. In these situations, carrying parasites appears to mitigate or prevent an abnormal immune response.

In the developed world, where hygiene and pharmaceuticals have all but eliminated human parasites, we are starting to recognize conditions that may occur as a result of an immune system with a well-developed arsenal and no enemy to use it on. One interesting and promising example of this was an experimental trial where individuals with Crohn’s disease were infected with porcine whip worms (used because they are self-limiting and do not leave the intestine) in an attempt to otherwise occupy an immune system that had turned on its host. While the trial was limited in size, the results were resounding. Almost 80% of participants saw a decrease in disease severity, with 72% seeing a remission of disease [4]. In another study, patient with multiple sclerosis who were also infected with intestinal parasites had significantly fewer adverse events and diminished disease progression in comparison to those free of parasites [5]. Furthermore, experiments utilizing animal models of immune-regulated diseases such as colitis, type 1 diabetes, arthritis, and allergies also show promising results that appropriate parasitic infection may prevent these conditions.

Principle into Practice

Reconstituting the human biome in order to control the epidemics of allergic and autoimmune diseases has been suggested. Much like some other things I’ve written about, there’s a certain ‘gross factor’ that some people find uncomfortable when you start to suggest that everyone should have a domestic helminth residing within them. Perhaps the idea of reconstituting the cocktail of secreted compounds that helminths produce to modulate our immune system is a little more appealing, but the problem here, as with so many other aspects of biology, is that we are only just starting to understand the complex interaction between our immune system and the parasites they were ‘designed’ to control. With only a limited understanding, how can we hope to fully and correctly mimic biology? Furthermore, the understanding that normal parasites, which we evolved with over hundreds of thousands of years, actively alter the functioning of our immune system makes us realize that almost all our research on the immune system has thus far focused on the very evolutionary-novel depopulated gut.

There is a fantastic paper that was published last year in ‘Medical Hypotheses’ (it’s probably time for me to admit that “Publish in ‘Medical Hypotheses’” is one of the few items on my bucket list) entitled Reconstitution of the human biome as the most reasonable solution for epidemics of allergic and autoimmune diseases [6]. If you’re interested in this subject, I highly recommend you give this paper a look. I particularly like their statement that:

“Just as we have the option of safely utilizing proper diet and exercise regimens to give our cardiovascular system what it has evolved to require, it is expected that, far more effortlessly, we can safely utilize selected organisms to give our immune system what it is evolved to require”.

Parasites are definitely not something to be ignored or downplayed. While I’ve focused here on the role these interesting creatures can play in health and wellness, parasites can also be the source of illness and disease. For the most part, a low or moderate burden of normal human parasites in an otherwise healthy individual seems to be benign, if not helpful. Problems arise, however, with some non-human parasites and in unwell individuals. Porcine whipworms are a useful model for studying the effects of parasites in humans because they elicit an immune response, are limited to the intestines, and are self-limiting (you have to keep dosing yourself every 2-weeks if you want to sustain an infection). On the other hand, some parasites that did not evolve with humans as their host are not always so well behaved. Perhaps the best-known pathogenic parasite infections are those that occur with non-human parasites that exit the intestines. Parasites evolved with their host, and as such have a bit of a built in road map as to where they should migrate within their normal host. Unfortunately, in the wrong host, this road map can take parasites very seriously off course. Cysticercosis is a condition that occurs when humans are infected with pork tapeworm that encyst in different parts of the body, including the brain in a condition known as neuro cysticercosis. Similarly, if humans pick up the raccoon roundworm Baylisascaris procyonis, the course is frequently fatal because of damage caused during the parasites’ migration throughout the body. A good parasite does not want to kill its host- doing so would be self-destructive- but in the wrong host parasites can go awry. Nonetheless, ‘domestication’ of appropriate human parasites and their prophylactic or therapeutic use may one day be an important and normal part of modern wellness.

1.            Medeiros, M., Jr., J.P. Figueiredo, M.C. Almeida, M.A. Matos, M.I. Araujo, A.A. Cruz, A.M. Atta, M.A. Rego, A.R. de Jesus, E.A. Taketomi, and E.M. Carvalho, Schistosoma mansoni infection is associated with a reduced course of asthma. J Allergy Clin Immunol, 2003. 111(5): p. 947-51.

2.            van den Biggelaar, A.H., C. Lopuhaa, R. van Ree, J.S. van der Zee, J. Jans, A. Hoek, B. Migombet, S. Borrmann, D. Luckner, P.G. Kremsner, and M. Yazdanbakhsh, The prevalence of parasite infestation and house dust mite sensitization in Gabonese schoolchildren. Int Arch Allergy Immunol, 2001. 126(3): p. 231-8.

3.            van den Biggelaar, A.H., R. van Ree, L.C. Rodrigues, B. Lell, A.M. Deelder, P.G. Kremsner, and M. Yazdanbakhsh, Decreased atopy in children infected with Schistosoma haematobium: a role for parasite-induced interleukin-10. Lancet, 2000. 356(9243): p. 1723-7.

4.            Summers, R.W., D.E. Elliott, J.F. Urban, Jr., R. Thompson, and J.V. Weinstock, Trichuris suis therapy in Crohn’s disease. Gut, 2005. 54(1): p. 87-90.

5.            Correale, J. and M. Farez, Association between parasite infection and immune responses in multiple sclerosis. Ann Neurol, 2007. 61(2): p. 97-108.

6.            Bilbo, S.D., G.A. Wray, S.E. Perkins, and W. Parker, Reconstitution of the human biome as the most reasonable solution for epidemics of allergic and autoimmune diseases. Med Hypotheses, 2011. 77(4): p. 494-504.

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As my last post may have suggested, I’ve recently been taking a deeper look at the large intestine – specifically the appendix. The appendix is a small, intestinal, diverticulum (basically a little pouch) that protrudes off the cecum (the first part of the large intestine, itself a little pouch- though much bigger than the appendix). You may have heard (and indeed, at the time of writing, Wikipedia has it written) that the appendix is a vestigial structure- a now useless remnant of something that was useful to our ancestors. Darwin actually helped propagate this belief, theorizing that the appendix was a shrunken remnant of a larger cecum. Furthermore, the relatively common and apparently benign surgical removal of the appendix, the procedure known as appendectomy, seems to support the idea that the appendix is of no particular use to humans today.

But is it?

There is an increasing body of information supporting the idea that the appendix is not a vestigial structure and that it has a specific role in human health. This might get a bit lengthy, so I will approach this topic in stages- probably culminating in a few posts.

First things first- is the appendix really vestigial? As I mentioned above, Darwin believed that the appendix was vestigial. He came to this idea because of the (erroneous) belief that hominids were the only primates to possess an appendix. Other primates that eat vast quantities of leaves and fibrous material that needs to be fermented by gut microflora, have large cecums where fermentation can occur. Humans, who don’t rely on copious vegetation for nutrition, only have a small cecum. It was thus hypothesized that the appendix was the shrunken remains of our forbearers’ large cecum. What Darwin was missing, however, was the fact that a number of species, including many primates, have large cecums and ALSO have an appendix. Hmm…

Another clue that the appendix is not simply the excess baggage of our herbivorous forbearers is that according to phylogenetic analysis, the appendix has actually arisen at least twice, independently, in evolutionary history. Such research also suggests that the appendix has been maintained in mammalian evolution for 80 million years [1]. To have evolved twice, independently, and to have been maintained for 80+ million years, suggests the appendix is not a useless remnant.

If the appendix is not vestigial, what is its function?

The dual evolution of the appendix, and the occurrence of an appendix in species with large cecums suggests that the organ plays an important role in normal physiology. Anatomically, the appendix is found at the end of the cecum, in a rather secluded corner of the intestines (if you can imagine such a thing). While the length of the appendix varies greatly from human to human, the diameter remains relatively constant. Another constant is the appendix’s association with a large amount of immune tissue known as GALT (gut-associated lymphoid tissue). While most people tend to think of immune tissue as ‘bacteria-fighting’ stuff, it turns out that some immune tissue produces substances (such as secretory IgA and mucin) that actually support bacterial growth, specifically the growth of biofilms.

Biofilms have been the focus of quite a bit of research recently, and usually not in a good way. Because people tend to think of biofilms (literally aggregates of bacteria embedded in self-produced slime) as pathogenic and problematic conglomerates, the focus of most research has been how best to disrupt and destroy them. It’s not entirely unwarranted either, Biofilms tend to be associated with unpleasant conditions, such as infections of medical implants and dental plaque. However, biofilms of commenselate bacteria (the ones we evolved with, on our skin and in our gut) are a way of safeguarding good bacteria.

When this is all put together, it appears that the appendix, with its relatively constant diameter and with the secreted products of GALT, is well adapted to facilitate and maintain communities of mutualistic intestinal flora [2]. It has thus been theorized that the appendix can act as a source of normal microbiota that can inoculate the gut when needed.

Why would your gut need to be inoculated with normal microbiota? Isn’t that what’s already in your gut?

It has been suggested [2, 3] that the appendix acts as a ‘safe house’ for resident microbiota when a GI infection occurs. When disease-causing bacteria are flushed from the intestines by diarrhea, the normal bacteria are eliminated as well. The appendix safe-guards a population of the normal bacteria that can then repopulate the large intestine after the diarrhea has passed. This function may not seem too important today in the developed world, where we enjoy relatively good hygiene and relatively low levels of epidemic diarrhea, but in the not too distant past and in populations that still suffer from diseases such as cholera, the appendix likely plays an important role in recovering from diarrheal diseases.

While the appendix offers benefits if you live in a developing country, it is less important (though not entirely so- I’ll get to that later) in developed countries with modern hygiene practices such as water treatment and sewage systems. In fact, in the developed world, the appendix has become a bit of a liability, with a surprisingly large portion of the population developing appendicitis at some point during their life. In my next post I’ll discuss the appendix in disease and health, and probably wax poetic about how we should consider this interesting little organ in our modern environment.

1.            Smith, H.F., R.E. Fisher, M.L. Everett, A.D. Thomas, R.R. Bollinger, and W. Parker, Comparative anatomy and phylogenetic distribution of the mammalian cecal appendix. J Evol Biol, 2009. 22(10): p. 1984-99.

2.            Bollinger, R.R., A.S. Barbas, E.L. Bush, S.S. Lin, and W. Parker, Biofilms in the normal human large bowel: fact rather than fiction. Gut, 2007. 56(10): p. 1481-2.

3.            Laurin, M., M.L. Everett, and W. Parker, The cecal appendix: one more immune component with a function disturbed by post-industrial culture. Anat Rec (Hoboken), 2011. 294(4): p. 567-79.

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