Thursday, November 27, 2008

The Wisdom Teeth Edition

An adult human typically has 32 teeth. All but 4 of those teeth typically arrive during childhood, before the age of 10. The remaining 4 teeth are the mandibular third molars, more commonly known in English as "Wisdom Teeth". Wisdom teeth typically erupt from the gumline approximately between 18-20 years of age. The etymology of the name revolves around the idea that people get their wisdom teeth after they have gained some wisdom.

Where I grew up, and across much of the 'westernized' world, Wisdom teeth are removed during early adolescence or early adulthood as a purely preventative measure. Wisdom teeth that come in wrong in some way can lead to the crowding of other teeth, infection, impaction, and other problems. However, more recently, several studies have been attempting to determine whether preventative removal of wisdom teeth is appropriate. This summary in the Cochrane Library suggests that there is no reason to remove wisdom teeth until they are causing problems, although the data is apparently very limited.

In my case, the early prognosis from my dentists when I was in high school and college was that my wisdom teeth would come in with no problems. Considering both my parents had wisdom teeth problems, my sister did, and all my relatives on my mom's side did, I should have expected that these teeth would need to be removed eventually. Six years ago I had a wisdom tooth come in Mesioangular impacted, which means it came in facing the front of my mouth (see images on the Wikipedia article for reference). This is apparently the most common orientation of impacted wisdom teeth, and has the potential to crowd or damage the other molars. In my case, since I basically did nothing for 6 years, so I probably have some damage on my 2nd molar. Here's to hoping that's minimal.

I've been unable to find good data on what proportion of individuals have wisdom teeth that are impacted or the proportion that just have them removed (impacted or not). Some recent studies have suggested that even if they aren't causing obvious problems, they may be detrimental. WebMD suggests not removing them at all if you are over 30 and haven't had any problems. Partly this is because not all wisdom teeth pose problems, and partly it is because the older you are, the more the bones around your wisdom teeth have hardened and the longer and more painful the recovery is. Past a certain age, I imagine wisdom teeth are simply not removed.

A huge amount of variation exists among different human populations in the occurance of wisdom teeth (and in the number and arrangement of teeth in general). Citations in this PNAS study (which is really talking about the genetic controls over tooth formation) indicate a range from 0.2 % occurrence for Bantu speakers of Angola to virtually 100% in Mexican Indians.

The whole idea of wisdom teeth is a strong bit of evidence for the continued adaptation of humans to their environment. The exact mechanism for the changes in human jawbones is not clear, but it definitely seems to be related to diet (short discussions here and here). As humans began eating less coarse foods, the jaws began getting smaller, and the teeth (controlled by a different gene) did not have enough room to all fit in the jaw without problems.

I've actually known a number of people who've had their wisdom teeth function perfectly normally. When I was getting a blood test last week in preparation for my wisdom teeth removal, the lady who was taking my blood said that she lost her 2nd molar, and the 3rd molar (wisdom tooth) filled the opening this created and she got good use out of it for 20 years (eventually she had to have it removed...maybe she doesn't brush?). I've heard a few people whose wisdom teeth came in just fine, no problems at all. I'm not really sure how frequently any of these things happen, and I don't have access to very good medical journals.

I was fairly terrified about the prospect of getting my wisdom teeth removed. I've never been under general anesthetic before, and both my sister and dad have had some problems coming out of general anesthetic in surgeries they've had. Plus, there are a number of painful and annoying impacts of the surgery: Swelling, bleeding, and possible nerve or sinus damage. Problems which are more likely the older you are, and I've been feeling very old lately (I just turned 30).

I'm writing this on Tuesday, and I had the surgery on Monday, and I can tell you that my fears were vastly overblown. The surgery itself was brief, painless, and even though I was partially aware during the procedure (turns out it is not a true general anesthetic), I felt no pain or nervousness once sedated. Yesterday I felt great when I got home, and have have very little lingering pain. Today, especially this afternoon and evening, have been a lot more painful, but I think part of that has had to do with me wanting to avoid the pain meds as much as possible. I've also not eaten much, simply because I'm already sick of ice cream, yogurt, smoothies, etc.

Overall, if you're considering this surgery at the advice of a dentist or doctor, I recommend you do it immediately. I've had several painful experiences in my life (ulcer, concussion, foot surgery) and this is no-where near that level of pain and discomfort. Its more like 'persistent headache' than 'injured'. I think that if you need it done, its probably better to get it over with as soon as practical instead of waiting (yes, I'm talking to you!).

Some other references and guides to the whole wisdom tooth removal process:

Thursday, November 20, 2008

So I went to a Mexican restaurant yesterday...

...And finally lost my mind with the menu. You probably have seen this menu. The menu is the same at almost every Mexican restaurant I go to. The specific item that has made me realize this is the Vegetarian Combo D: A bean burrito, a chalupa, and a quesadilla.

I know of 5 restaurants in Kansas, 1 in Texas, 1 in Oklahoma, 2 in Indiana, and 1 in Missouri that all have the same, exact, menu. The combinations are all the same, the lunch specials are all the same ("The Speedy Gonzales"), the appetizers are all the same.

Why are all these menus the same? (and yes, I realize this is a different topic for the blog but this is analyze EVERYTHING, not just "Analyze Animals")

My co-worker Eric Johnson and I came up with several hypotheses in our 9+ hours driving the last two days:

1. The restaurants are all owned or financed by the same firm.
2. Random chance (we'll call this the null hypothesis).
3. The food supply firms are selling/promoting this menu.
4. This is the menu all restaurants have in mexico. (which just pushes the question into mexico)
5. There was some 'immigrant worker' promotion years ago which started this and it has just been passed down.

I'm skeptical that this many restaurants all decided to label that particular combination of food items the "Veggie D". Mexican restaurants that don't have this menu (I know of several) generally don't have any Veggie menu at all.

Possibility 4 is one I can't get at, because I haven't spent any real time in Mexico. Anyone got any clues?

I am skeptical that a single entity finances all these restaurants across the country. Maybe something like this is happening, but how would these random guys who start the small town restaurants all over find the investors?

So I really think it comes down to 3 and 5.

The food service industry is the possibility I deem most likely. This thread on Chowhound seems to suggest this possibility, without having any direct evidence. There are only a handful of large-scale food suppliers in the country though: Dot Foods, Sysco, Keith, Hawkeye. I've been unable to find anything online that looks like this kind of menu being sold, but I'm sure they don't have everything online.

Quick Aside Here: The industry group that represents food suppliers (the International Foodservice Distributors Association) has an article on their website that is accompanied by pictures which, for reasons I can't even articulate, I find incredibly humorous ("Look at how serious I am"). Some of the quotes are equally priceless: "We are now insisting that they begin to bring their logistics people to our top to tops that we have with them throughout the year." That quote is repeated twice, so I doubt it is a typo, but seriously, does that mean something?

At any rate, I'm totally stumped. I asked reddit and got back a bunch of irrelevant gibberish. Anyone got any clues?

Thursday, November 13, 2008

Mosasaurs: Ancient Kansas Wildlife

There are few animals in real life that can capture our imagination the way some fossilized animals are able. Take for instance, the Tyrannosaurus rex, which has been fictionalized again and again to represent our more primal understanding of 'monster'. Take also, the beast that once roamed Kansas as the unquestioned top predator: The Mosasaur.

What? You've never heard of a Mosasaur? Imagine a crocodile with flippers and you're superficially there. See, way back around 100 million years ago the North American continent was split by a vast epeiric sea (a shallow, salty, inland sea) called the Western Interior Seaway (really creative science people).

The whole physics and biology of the Western Interior Seaway and other epeiric seas is pretty amazing, and we'll get into that later. For now, let's just focus on what is known: The sea was shallow (for a sea), probably extremely productive, and was fed by mini-continents on either side. In limnology we tend to think of shallow waters as being the most productive, because of the ability of rooted plants to grow. I think the same is true of shallow seas, but I don't think it is for the same reasons (any oceanographers care to enlighten me on this?).

Anyway! The top predator of this inland sea and the ocean at large became the mosasaur (pictured below). Although this is a reptile, this isn't a dinosaur, and it isn't a crocodile. Think lizard. In fact, think monitor lizard (Family Varanidae), which includes the still living and awesome Komodo dragons and the recently extinct Megalania (the feared giant lizard of Australia). Many modern monitor lizards are highly adapted for living in and around water (e.g., water monitors), and so it isn't hard to imagine a scenario wherein these amphibious lizards took the next evolutionary step and became aquatic.

And become aquatic they did! Unlike turtles, crocodiles, walruses, and quite like whales and dolphins, the Mosasaurs gave birth at sea, to live offspring. The arms and hands of this species developed into flippers and became somewhat detached from the backbone (meaning they could not support their own weight on land). Pull this lizard out of the water and it would asphixiate.

One of the many interesting things about this invasion of the seas by lizards is that they weren't exactly getting themselves into an unoccupied niche. The first real mosasaurs occurred in the Cretaceous, and by 90 million years ago (MYA), we had three big subfamilies with lots of known species. However, way back in the Jurassic reptiles had already colonized the oceans with the famous plesiosaurs (think the mythical Loch Ness Monster) and of course the everpresent sharks had managed to come up with a particularly devastating breed (the Ginsu sharks) and you had other random nastiness lurking out there (just don't go swimming in the Cretaceous). Nevertheless, the Mosasaurs got really big and are generally thought to have been the top predator.

The reason I started getting interested again in Mosasaurs was an interesting paper by Mike Everhart published in the latest issue of the Kansas Academy of Science. The paper explores the occurence of mosasaur on mosasaur violence. And for something that happened 90 MYA, we can actually figure out quite a bit. Everhart was able to, fairly convincingly, estimate the size and mass of the attacker and the way in which it bit down on the victim.

A plate depicting the first Mosasaur discovery. The name is from Latin Mosa meaning the 'Meuse river' in the Netherlands, and Greek sauros meaning 'lizard'. The first specimen was found in a Meuse limestone quarry.

The way Mosasaurs ate is interesting, and has lead to some debate about the origin of snakes. Mosasaurs, unlike sharks or dolphins or most other big predators we're familar with, didn't have teeth that cut, just teeth that crushed. As a result, Mosasaurs either had to bite their prey in half (although this might have been possible, the family lacks the heavy skull that is common in crocodilians, making this somewhat unlikely) or swallow it whole. In order to maximize the food consumption, the Mosasaurs apparently had a somewhat hinged jaw that has lead many people to think: SNAKES!

Indeed, the theory of a shared snake and mosasaur marine ancestory has recently been in vogue, although it was first proposed in the 1890s (it's called Pythonomorpha if you're curious). The idea of snakes evolving from water lizards sounds inherently unlikely to me (why evolve flippers if you are just as good off just getting rid of limbs altogether?). Luckily, I don't need to push my uninformed logic, because apparently more recent fossils have shoved this theory to the wayside (read the link on the Phythonomorpha to get a better understanding). You can rest comfortably, however, knowing that this issue will continue to be fought bitterly by individuals committed to one side or the other until they die, at which point the next generation of paleontologists will find some other issue to argue about. And you thought politics lasted forever.

Mosasaurs have been found with a variety of food items in their stomaches: Mostly fish, but also a plesiosaur, other mosasaurs, turtles, birds, and sharks. I know sharks are fish too, but at least some species of sharks appear to have gone extinct as the mosasaurs became more prominent, suggesting they might have out-competed them (via direct predation?). Some species appeared to specialize on clams, and at least one late evolving species (Leiodon) managed to evolve teeth that cut. All of this evolutionary achievement probably put the Mosasaurs at the top of the oceanic food chain for around 20 million years before the K-T event happened and the entire family was wiped out. According to Everhart:

"Mosasaurs ruled the oceans of the Late Cretaceous and were beginning to invade fresh water environments such as estuaries, swamps and rivers when the Age of Dinosaurs ended. Did they die suddenly due the catastrophic effects of an asteroid impact in the Yucatan, or was their extinction more gradual following the general collapse of the marine ecosystem? We may never know."

Everhart doesn't mention a third possibility, which is that they are still out there and we just don't know it. Seriously, don't go swimming in the ocean.

Thursday, November 6, 2008

Is it (energetically) cheaper to can or freeze?

I know some of you had a garden this summer. And you were probably thinking to yourself “Man, what the hell am I going to do with all these zucchini?” I’m grateful that so many people overplant, because lots of people gave me excess zucchini. However, I was eventually faced with a quandary about the best method of preservation.

I was thinking about the carbon footprint of different foods, and how the processing affects that carbon footprint.

For instance, if I walk out to my garden and pluck two tomatoes, and just slice one up and eat it, I’m not really increasing the carbon footprint of the tomato. If I take the other one and fry it, I’m obviously using more energy to cook it, and therefore I’m increasing the carbon footprint of my food just by the way I process it.

Thinking about this is actually pretty huge, and I’m going to focus in on one particular aspect of processing: Preservation.

I’m going to focus on peaches, because I preserved 25 lbs of them this summer using a variety of methods. Peaches can be canned relatively easily (without a pressure boiler), and can be frozen equally easily (adding a little anti-browning agent keeps them from turning dark). Figuring out the carbon footprint between different energy sources can be difficult, so to simplify things, I’m just going to compare electrical usage.

The equation should be pretty simple really. We want to estimate the energy used per day of storage via these different methods: The electricity used divided by the duration of storage. For canning, almost all of the energy use will be up-front, and the longer you store the cans, the better overall energy use rate you get. On the other hand, foods stored in the freezer will continue to cost energy as long as you preserve them, so long storage times will lead to bad energy efficiency.

So here's the data I collected for this little exercise. Basically, I needed to figure out the energy cost to keep a pint of peaches frozen. I used dedicated freezers because A) its a hell of a lot easier and B) I've been thinking about getting one. I've cut some of the significant digits off to make this a little more legible, and I'm not going to give you the brands of the freezers, because I don't think it really matters much.

chest chest upright upright

Energy per year 274 279 442 582
Energy per day 0.731 0.744 1.179 1.552
Capacity in cubic feet 6.8 7.2 14.2 15.8
Peach pints per cubic foot 59 59 59 59
Peach pint capacity 401.2 424.8 837.8 932.2
energy per day per peach pint 0.0018 0.0017 0.0014 0.0016

Ok, so now we've got an estimate of the energy used per day to store peaches in these freezers. Now we've got to figure out what the energy costs of canning the peaches are on a per-pint basis. This becomes a little bit of a problem. The cooking phase has a limited capacity: My boiler only holds 5 pints at a time (for instance). So really, I'm going to assume you're canning in the appropriate increments. I had a hard time actually finding data on my stove, so I just used the data from a 2600 watt replacement burner. Remember, for most canned foods you have to first sterilize the jars and lids (for ten minutes), then heat the food, then process the cans.
So I opted against figuring out the units of energy that would actually be required to do this work, because I've found that I usually just have to crank my burner on high or close to high for the entire time I'm doing the sterilizing, cooking or processing. Therefore, I'm making a worst case scenario here for the canning. Although I'm making a best case scenario in terms of getting 'even' numbers of cans per process. Regardless, here are my estimates of the energy used to can:
Burners 8-inch burner
Energy consumption 2.6
Sterilizing jars 0.166
boiling peaches 0.333
processing jars 0.333
kilowatt hours 2.1632
Peach pints per process 5
kW/h per pint 0.43264
# of Pints 15
Total energy for canning 6.4896

Ok? So what does this mean? Like I said, the critical part here is how long you actually store the food. Let's take a look at a graph demonstrating this:

What we're seeing here is the estimate of energy use through time. Obviously, the canning doesn't change. Once you've done the canning, you're done. On the other hand, the freezer gets progressively worse through time. However, it takes a surprisingly long time for the freezer to get more energetically expensive. Between 8-10 months depending on the brand.

Obviously, there's a lot of wiggle in these numbers. My estimates on the freezer assume that the entire freezer is in use (if not for peaches, then for something) and if this isn't the case, then your energy cost per unit goes up. Let's look, for example, at a scenario where the freezers are operating at 80% capacity:

Now we're talking about a 6-8 month time-period where freezing is more effective. However, we've still got a lot of assumptions built in here. For one, each time you remove a can, but do not turn off the freezer, you've got to replace that can with something, or you'll be incrementally be increasing the cost per unit to keep the other ones cold. The decision to use a freezer is committing you to an unknown proportion of energy going towards keeping empty space very cold, and unless you're willing to turn off the machine and eat the remainder at some point, you could end up with some really bad efficiency. On the other hand canning uses only the resources necessary to preserve the food you've got.

The other set of assumptions revolve around manufacturing costs and cleaning costs being approximately equal.

So now that I've identified all these problems, I'm a little less sure about my result. I think that if you already own the jars and the freezer, this analysis gives you an idea of how best to utilize them, but I think in terms of the original question, I'm going to have to dig deeper.