Undermining the Wall of Death

Different fields of science often don't talk to each other, even when coming at the same problem from different angles. A stark example of this can be found in the literature on aging. I'm in the field of evolutionary demography, and aging is one of our central focuses. We ask why and how it happens by studying the demographic patterns of different species under different circumstances. The evolutionary demographic theory of aging is built around the idea that there are alleles that have effects at different ages and natural selection acts on these genes to sculpt the age-specific mortality at different ages. Because dying young (before you've had a chance to reproduce) is more disadvantageous than dying old (after you've already passed on some genes) natural selection acts more strongly to minimize mortality in early adulthood than later adulthood, resulting in a chance of dying that increases in age. There are decades of theory built up around this idea, and the idea is not without merit, but it does assume these age-specific gene effects, generally without bothering to say what the actual genes are or how they influence mortality.

Another field within biology that focuses heavily on understanding aging is biogerontology. Biogerontology focuses on understanding the mechanistic basis of aging at the cellular and molecular level. They describe aging as a process of narrowing of the homeodynamic space, often due to accumulation of damage. Homeodynamic space is a concept related to homeostasis (the tendency of organisms to push their physiological state back to some optimum), but with the recognition that the goal that the individual is pushing towards, and its options for pushing, change over time. For example, as the cells in an organism accumulate mutations, it becomes more dangerous to allow them to continue replicating, because this could spawn a cancer. So the cells are forced to turn down expression of genes that allow for cell replication. But if your cells are replicating less, then you should be more reluctant to allow apoptosis, programmed cell death, because cells that die can't as easily be replaced. But if you've down-regulated the genes involved in apoptosis, this means infected cells will be less likely to kill themselves, so you need to have a stronger inflammation response, so that white blood cells will be brought to areas of infection and kill the infected cells from the outside. But increased inflammation has all sorts of nasty side effects, which themselves need to be compensated for. Note that I am just making this chain up as an example. The point being that the organism, in order to deal with the accumulation of damage, has to adjust various aspects of its physiology, which can cause damage or challenges to the system, which requires further adjustments. The organism gradually loses wiggle room, paints itself into a corner as it were. When this homeodynamic space gets too small, the organism can't respond to whatever insults (internal or external) come along and gets killed.

Reading papers in biogerontology, I am struck by two things. The first is how naive and outdated their evolutionary assumptions tend to be. For example, they still will state that aging is not observed in the wild because no individual lives long enough to grow old in the wild, an opinion that evolutionary biologists began to reject in the 1960s and have now disproved with data from numerous species from plankton to humans and birds to aphids. But I am also struck by how naive they would think our assumptions about age-specific genes are. They state as one of the basic principles of biogerontology that are no genes whose roll it is to cause aging, or which act at a particular age to regulate the chance of death. You will remember I said that such age-specific gene effects, from unspecified genes, are at the center of much of the theory behind evolutionary demography. Yet biogerontologists know such genes not to exist. So our assumptions about the mechanisms are as naive and simplistic as their assumptions regarding the demography.

This lack of communication, with each field basing its thinking on ideas the other has long since rejected, is common in science. There are simply too many journals, papers, conferences, etc., too many fields that may produce important information, for anyone to keep a useful fraction of an eye on most of them. So the lack of communication between fields is to some extent inevitable, but it does have significant consequences.

This is obvious when we introduce the gerontological observation that gene expression is not highly age specific (at least not late in life) to the evolutionary literature on post-reproductive lifespan (PRLS). Much of the study of PRLS has been motivated by the idea that PRLS shouldn't exist unless post-reproductive individuals do something useful for their younger kin. This idea arises from the evolutionary demographic theory of aging I described above. If an individual has reached the age where it can no longer reproduce, the genes it is expressing at that age should be genes that selection doesn't care about at all, because whether she dies at that age has no effect on how many offspring she has. So mutations that kill post-reproductive individuals should accumulate rapidly, unopposed by natural selection. W.D. Hamilton, a preeminent evolutionary theorist of the mid-20th century, wrote in 1966 that “In the absence of complications due to parental care or other altruistic contributions due to post-reproductives, the [mortality] curve should be roughly asymptotic to the age of the ending of reproduction.” By this he means that as the individual approaches the end of her reproductive period, her chance of dying at each instant should approach 100%. This has been dubbed "Hamilton's Wall of Death." Hamilton's work is influential enough, and his basic logic sound enough, that many of my colleagues still believe we should find the Wall of Death. But in fact we can find PRLS in a huge range of organisms where there is no parental care or anything comparable, and the Wall of Death is nowhere to be found. Hamilton's prediction fails because his model is built around high age-specificity of gene expression, which we now know not to exist. Genes which are being expressed at and after the age of reproductive cessation are the same genes being expressed prior to that age, doing the same things they did prior to that age (except of course reproduction) and so they can't just suddenly cause all sorts of lethal effects. This represents a major constraint on the ways selection can shape the pattern of mortality over age, and we evolutionary demographers are just starting to come to terms with the ramifications of this. When I have time to write another longish post, I'll explain how this leads to a major question in evolutionary demography that I have been thinking about but don't yet have any plausible answer to.

Constraints

The field of life-history evolution, into which the stuff I do roughly fits, spends a lot of time thinking about optimality. What is the optimal age to start reproducing? What is the optimal amount of time to spend foraging each day? What is the optimal body size for a creature in a particular niche? The factor being optimized here is fitness, usually measured by the rate at which a sub-population with a particular trait would increase in size. The trait value that leads to the fastest increase is the optimum. Quite often when we calculate an optimum value and then measure the actual values in the population, most individuals are fairly close to the optimum. But fairly often this does not happen, and then we start talking about "optimality with constraints." By this we mean that there are certain conditions that must be met, and the optimum we are looking for is the best value that is consistent with those conditions. The most commonly considered constraint in my field is the constraint of limited resources. If you have only 100 calories a day of energy to expend, you can't expend it all on growth and maintenance and all on reproduction, your reproduction is constrained by the need for maintenance, and vice versa. So we can calculate, given a set of biologically informed assumptions, what the optimal investment in reproduction is at each age. This kind of constraint makes sense to people, and yields many useful insights. That said, it is often the only type of constraint considered in situations where many other constraints potentially come into play.

One type of constraint that is particularly hard to build theory around is that natural selection can only favor those traits that exist. That is, a trait may be drastically suboptimal, but if all individuals in the population have that trait, and the genes which determine it cannot easily be altered by mutation such that they allow a higher fitness solution, the population will continue being far from optimal.

A classic example of this type of suboptimality is known as the 'obstetric dilemma.' This is the problem that humans have narrow pelvises and big heads, and the head has to pass through the pelvis during birth. In a (now somewhat out of date but still sound for our purposes) summary of one hypothesis of how humans diverged from our chimply relatives, Kristen Hawkes (the anthropologist behind the Grandmother Hypothesis) described (in 2003) the central role this obstetric dilemma played in human evolution thusly:

* Drying environments in the late Tertiary constricted African forests, making capacities to use alternative foods more advantageous among ancestral apes.
* Bipedalism was then favored because it freed hands for tool use, which
increased success at hunting big animals, and this put a premium
on larger brains.
* But the mechanics of bipedal locomotion limited pelvic width, so brain expansion created an ‘‘obstetrical dilemma’’ requiring most brain growth to be postnatal.
Consequently, children with developing brains were immature longer and were more dependent, for a longer time, on maternal care.
* The care requirements interfered with maternal hunting, so mothers relied on
provisioning from hunting mates. This help from fathers allowed mothers to produce more surviving offspring.
* Thus, parents formed lasting bonds and nuclear families became the fundamental
units of cooperation in which a sexual division of labor served familial goals of production and reproduction.

Now according to this story, variations of which are still supported by the scientific evidence,much of the distinctness of human life-history comes through:
1. The need for large brains and small pelvises
2. Which explains why our babies are so undeveloped
3. Which explains we take so long to mature
4. Which is an important part in explaining why we end up with our social system.
5. Which explains why we live so long.

So the optimality of a narrow pelvis, the optimality of a large brain and the need for
that brain to pass through that pelvis ends up being a central fact of human evolution. And why, we may ask, is it optimal for the baby's skull to pass through the mother's pelvis? The apparent answer is that if there is only one possible trait, that trait is the best of all possible traits.

The pattern of vertebrates expelling their young through their pelvis dates back to
before vertebrates actually had pelvises.

Note that this fish has its gonads above and in front of its pelvic fin. That is a common trait among fish, including the lobe-finned fish from which all terrestiral vertebrates are descended. The lobe-finned fishes had bony feet with which they could support themselves on the sea floor, and the bones in their pelvic fins would eventually be modified by evolution into the legs and pelvis.



Now the first terrestrial vertebrates were amphibians, and like most frogs and salamanders, laid small soft eggs, so it was probably no problem for them to continue having the gonads in front and running a tube through the pelvis to the cloaca. This system only became problematic when the eggs got large and hard, as they are in reptiles like turtles. Turtle people like to talk about "pelvic consraint" when they discuss why turtles don't make bigger eggs.

The only non-fish vertebrates to escape the need to run the babies through the pelvis are those that no longer have ana full pelvis, like whales and most snakes. To my knowledge nobody has managed to invent an alternative outlet, so everybody, including us, has to find one way or another to get through the pelvis. In fact, the only alternative is a human invention, the cesarian section.

This obstetric dillema is a very obvious contraint of the 'no alternative' type. Whenever I get a chance to write another longish post, I'll give an example of a constraint where the lack of alternatives is less obvious because it is genetic rather than anatomical.

More fun zoo photos

Rostock Zoo, Oct, 2011

I like zoo photography. Click the caiman to see the slideshow.

Thoughts during a trip to a conference

The Rostock main train station (Hauptbahnhof, Hbf) is an easy walk from our building, even when bedangled with a laptop bag, poster tube and backpack. I was amused to see that three other passengers getting on my same train also had the black plastic tubes which announce that one is going to or from a conference. None of them looked like ecologists, so I figured it wasn't the same conference. I tried to eavesdrop to figure out what topic two of them were discussing, but it was rapid and in French, and so instead I fell asleep as the train pulled out.

It took 34 minutes from the time we arrived at Hamburg Hbf until I was sitting in my gate at the Hamburg airport waiting for my flight to Manchester. This without any running, pushing or hurrying, and the airport is not particularly near the Hbf. A single S-Bahn trip stops directly under the security check, so up two escalators I got on one of the many very short lines, and didn't have to remove my shoes or belt, nor get molested. I like to complain about the fact that you can't get a flight from Rostock's small airport to anywhere, but if door to gate takes only two and half hours, this is still better than many trips to JFK I've made. It is frankly slightly disorienting for an American for a transit system to work this smoothly.

As I sat in the gate, two English gentlemen sitting just behind me recognized each other and began to make small talk. The one is the occasional patient of the other, and has an appointment to see him in late December. They kept up a lively conversation about not much of anything, without a single pause, for about 45 minutes. I have heard the English talent for small talk described before, but I must say this was really impressive. They moved purposefully from one genial topic to the next, always with a smooth transition. Football, Christmas Markets, vacation destinations, and so forth. I felt like congratulating them.

As the bus took us from our gate to the plane, we passed a taxiing airplane from Air Tunis. It wonder if flights to Tunis are cheep these days? I've heard they have trouble filling their hotels since the revolution.

As we pass up then down through layers of clouds, I notice how closely defined their surfaces are. The top of my window can be mostly in the cloud, and the bottom mostly out. I wonder vaguely what sort of fluid dynamics allow for such a sharp transition to be stable.

I hope I have the right ticket for this train.

An hour and a half into wandering around Sheffield looking for my accommodation, I'm standing on a corner with three young guys with tattoos on their massive biceps as one of them looks up Edgecliffe Crescent on his iPhone. The guy resting in front of the closed Pakistani restaurant next door says go to the roundabout, take a right, and straight to the top.

Breakfast in the cafeteria is much what you would expect from breakfast in an English University's dormitory cafeteria. The orange juice and eggs are from concentrate, but the sausage is fresh squeezed. I sit across from a young woman who has never been to a conference before. I briefly consider teasing her about the fact that she is nervous despite not having to do anything but listen to other people's presentations. She gives me good directions to the conference hall.

"You can't really understand anything in ecology without thinking about soil biodiversity," says the plenary speaker. I guess what I do isn't ecology.

A couple of people come up to question me further after my talk. One of them is a guy I once emailed for advice on keeping rotifers. I can't remember what the question was, but thank him for how quickly he responded.

There is no way I am going to stay awake through the whole poster session. I get slightly lost on my way back to my room and end up in an OxFam thrift store. I get lost again carrying some used books. I spot an expidition of ecologists and follow them home.

Waking up cold I pass by the Greek place and have peas panner with garlic nann. I happily chew the hard chunks of spices in the sauce. "I'm a womanizer!" announces the old, obese, bald and drunk puddle of English gentleman at the corner table with the off duty waiters. "Yes, Sir, you are!" one of them reassures him.

I consider rehearsing my poster spiel for tomorrow, but instead prepare by sleeping more.

We are joined at breakfast by a conference of dentists (there may be a better term of venery for dentists, but I don't know it). They are easily distinguished by their unecologist-like formalwear.

Lost of people ask questions about my poster, and most of them tell me that while interesting, it has nothing to do with anything they will ever work on. This interesting but not directly relevant feeling is largely mutual.

Typical

In Rostock it is entirely unsurprising that the woman who answers the phone at the Fremdsprachendienst (Foreign Language Services company) proudly speaks nothing but German.

Dan SMASH!

I've just spent six hours trying to convert a file (a poster I'm presenting at a conference next week) from one standard format to another for printing. After six computers and dozens of programs each of which is supposed to be able to do this conversion instantly, it finally converted, although it looks kind of crappy in its converted format. I've sent it to the printer because I don't care anymore. None of the other things I desperately needed to get done today got done.

I am not generally given to violence, but do currently have the urge to break something.

Irene reaches Europe

The National Hurricane Center was remarkably accurate in predicting the track Hurricane Irene would follow up the East Coast of the US. Tropical Storm Irene made her way over New England pretty much as they said she would. They stopped updating that forecast when Tropical Depression Irene passed the northern boundary of Maine into Canada, and even the Canadian press largely stopped covering Irene once it passed out into the Labrador Sea. But now Post-Tropical Cyclone Irene, is forecast to bring gale-force winds to Wales over the next few days. Given that this storm started as a tropical wave over Africa, I wonder if she is just trying to find her way back home. Or maybe she wants to go around again? The only forecast I have seen on the future path of the remnants actually calls for her to come this way (towards the Baltic), as a fairly ordinary low-pressure wave and storm later this week.

Writing while sleep deprived

I am about to submit another big funding application. This one has been a lot more work than the previous applications, as the required research statement, the largest of several sections, is 25 pages. I can't really complain. If I was going to give someone enough money to run a research group for five years, I too would want to know in some detail what they would do with the money. Further, sitting down and trying to put my plans into a single document makes me systematically consider how my various plans fit together, always a useful exercise. My only complaint really is that I should have done much more on this long before my daughter was born. It is hard to care too much about the details of the application while fighting to stay awake and get the baby to sleep.

Busy

I am working on another big funding application. This one is a lot more work than the previous applications, as the required research statement, the largest of several sections, is 25 pages. I can't really complain. If I was going to give someone enough money to run a research group for five years, I too would want to know in some detail what they would do with the money. Further, sitting down and trying to put my plans into a single document makes me systematically consider how my various plans fit together, always a useful exercise. My only complaint really is that I should have done much more on this much earlier. Trying to finish everything up at the same time that my wife is preparing to deliver a baby and my family is visiting is an less than an optimal solution.

Taxonomically not what you eat

One should be cautious in naming a taxonomic group for their ecological habits.

I offer you these examples:

1. Most turtles are amphibious; all are reptiles, not amphibians. Turtles have scales, lay hard leathery eggs, have the physiological and genetic makeup of reptiles. I often see phrases such as, "turtles and other Amphibians" in writing about biology by non-scientists. The taxonomic term 'amphibians' is not helpful in getting across to people that turtles are reptiles.

2. Consider the Carnivora. Most Carnivora are carnivores, but some, such as the giant panda, eat largely plants. Further, many carnivorous mammals are not Carnivora in the taxonomic sense. Unnecessarily confusing.

3. Pity the poor Insectivora. It turns out things are worse than just dietary nonconformity (not all the Insectivora ate insects, and not all insectivorous mammals were called Insectivora). The group called Insectivora no longer exists! Biologists had assumed that similarities in diet and morphology among the moles, shrews, tree shrews, golden moles, hedgehogs, moonrats, solenodons, tenrecs, elephant shrews and colugos were the result of common descent (they all had these traits because they were all closely related to each other). It is now clear that Insectivora was an ecological rather than taxonomic grouping. This is because modern molecular genetic and phylogenetic methods make clear that most of these Insectivores are not any more closely related to each other than they are to you, or to an elephant. Specifically, the moles, shrews, solodons, hedgehogs and moonrats form one group, whose closest relatives include the carnivores and hoofed mammals. The tree shrews and culogos (of southeast Asia) are more closely related to the primates. The golden moles, tenrecs and elephant shrews (all African groups) are related to larger mammals found in Africa such as the aardvarks and elephants.

4. The Caprimulgidae (Latin for goat suckers), do not suck goats. They were named for a feeding behavior falsely attributed to them. They are in fact insectivores.

Who's a demographer?

I tend to find religious fundamentalists, whatever the religion, hard to listen to. One of the habits I find objectionable is the tendency for fundamentalists of a religion to argue that others who practice the same religion differently aren't really practitioners of that religion at all. This tendency has recently been popping up in the news as Christian fundamentalists in the US argue that because Mitt Romney is a Mormon, he isn't really a Christian. I have no fondness for Mitt Romney, and frankly suspect he would claim to be a Pastafarian if he thought it would get him elected. That said, the Mormons declare themselves to be Christians (they do talk about Christ a lot), and I can't see as anyone has the authority to tell them they aren't. It is just hubris to go around telling people that you can describe their religious beliefs better than they can.

This is all a roundabout way of getting to the question of who is a demographer. Ask a demographer what is the largest annual scientific meeting for demographers, and she will probably say The Population Association of America (PAA). I consider myself a demographer as well as a biologist, but I think most PAA members would say the stuff I do isn't demography. This is for the simple reason that I mostly study non-human populations, and the PAA defines demography as the study of human population processes. Studying the same processes in non-humans is, by this definition, not demography. Last year they had a session on evolutionary demography, but all the accepted papers were on humans. This year they don't even have such a session. I think that inserting the word 'human' into the definition of demography is roughly akin to saying that anyone who doesn't follow the teachings of a particular Rabii isn't really Jewish, so I call myself a demographer.

I was recently surprised to find myself in a conversation in which the tables were turned. A colleague was arguing that most PAA members are not really demographers, but sociologists. His argument was that many human-focused hard-core demographers feel out of place at the PAA. After their meetings this spring several colleagues complained that most talks at PAA meetings are really quantitative sociology rather than demography. The distinction is a fine one, but basically classical demography has a core set of questions and methods, and these have certainly been supplanted to a considerable degree by questions coming out of sociology, mostly approached with methods that don't require the quantitative machinery of formal demography. My colleague told me, "All the talks are full of regression tables, and most of the regressions aren't even done well."

So is it fair to say that my colleagues and I, who apply classical demographic methods to non-humans are more demographery than the quantitative sociologists at the PAA? I'm afraid not. We can no more revoke their demographer label than they can revoke ours. However, since the social demographers who control the PAA aren't interested in evolutionary demography, and most of their presentations frankly aren't that interesting to us (there really are a ridiculous number of regression tables, mostly demonstrating the relationship between fertility and female education for yet another population), I'm going to let my membership lapse. I'm thinking I'll join the British Ecological Society instead. They have lots of evolutionary demography at their meetings. I don't even feel the need to call myself an ecologist.

Why there are no whale-like birds.

For my birthday, my parents sent DVDs of the Life series with David Attenborough, nature films from the BBC. These are wonderfully made, with amazing photography, and you will likely never hear me say that about any other films. One aspect of the photography that is amazing are the underwater shots. This has got me thinking about marine mammals and seabirds, and the differences between them.

There are five independent lineages of extant (extant is the opposite of extinct) marine mammals:
1. The Cetaceans (whales, porpoises and dolphins), relatives of pigs and hippos.
2. The Sirenians (manatees and dugongs), mildly related to elephants and hyraxes.
3/4. The Pinnepeds (walrus, seals and sea lions), descended from a dog-like carnivore.
3/4. The sea otter, an otter, which is an aquatic weasel.
5. The polar bear, bear.

I have ordered these in the degree to which they have become fully aquatic. The Cetaceans neither need to, nor safely can, leave the water. This is true of Sirenians also, but they tend to feed and birth in shallow water near shorelines, where whales wander the open oceans and dive to amazing depths. The Pinnepeds aren't so good on land, but they do haul up to breed and pup. The sea otter is in some ways more fully marine than the Pinnepeds, mating and usually giving birth at sea. But again, otters are more tied to the land than are Pinnepeds the rest of the year, living and feeding in coastal kelp forests and being capable of fast and efficient movement on land. The polar bear is marine in that it swims long distances, hunts at sea, and has structures that specifically help it do these things. But it still prefers to walk rather than swim, brings its food onto solid ground to feed, breeds and pups out of the water and so forth.

There are more independent groups of sea birds, even if you don't consider each transition from freshwater to saltwater. Penguins are perhaps the most fully marine, flying only in water, feeding entirely on seafood, having special mechanisms for dealing with high levels of salt. The Procellariiformes (albatrosses and petrels) are not far behind, spending about as much time at sea (although over rather than in) as penguins do. The Phaethontiformes (tropicbirds) spend most of their lives at sea, as do many of the Pelicaniformes (pelicans, frigatebirds, boobies, gannets, cormorants and shags). While many gulls live far from the sea, many Charadriiformes (gulls, terns, skuas, plovers, puffins, auks etc.) are extremely marine. Many Anseriformes (ducks, swans and geese), particularly the Merginae (sea ducks) are, well, sea ducks. It was recently discovered that gyrfalcons spend long periods hunting on and around sea-ice, although they probably don't actually swim. I'm sure I've forgotten other examples.

Why so many birds moving out to sea, but so few mammals?

The obvious first hypothesis is that the ability to fly is very useful at sea, while the ability to walk/run/hop etc. is not. The falcons are a pretty terrestrial group, but with few changes beyond the behavioral, gyrfalcons can spend extended periods at sea. Ospreys and eagles, relatives of falcons, use talons that evolved grabbing terrestrial prey to scoop fish. Even hummingbirds and warblers that can't forage or land at sea regularly spend long periods migrating over open ocean. Birds may have an easier entree than do mammals.

Given this, it may be surprising that the most fully marine descendent of terrestrial vertebrates are not birds. All birds lay eggs, and none have figured out how to make that work at sea, so all need to maintain the ability to be land animals. Almost all mammals give live birth, and three groups (Cetaceans, Sirineans and sea otters) can do that without ever leaving the water. The birds may have an easier time getting started down evolutionary paths that lead to a marine life, but they seem to have an inescapable constraint that keeps them from finishing that path: shelled eggs.

The marine reptiles show an interesting parallel to this. Marine iguanas, saltwater crocs and sea turtles all lay eggs, and all do so on land. Sea snakes, excepting one genus, birth live young, and do so at sea. That one genus lays eggs on land.

If some snakes have evolved the ability to have their eggs hatch internally and their hatchlings ready to swim the moment they emerge from the mother, why can't some bird do the same? Imagine how much better off an emperor penguin would be if instead of spending the Antarctic winter fasting in the cold, it could spend that time feasting in the ocean with it's chick developing internally.

Any answer I could offer would be pure speculation. One class of question that evolutionary biology is very bad at answering is "why didn't X evolve." Why hasn't any bird evolved live birth? Maybe it is something about their egg shells. Maybe they are in a habitat where that just doesn't work. Probably it just never happened.

37 weeks

It is an obvious yet remarkable fact that a fetus, near the end of pregnancy, could as easily be a newborn baby. Whether through natural birth or c-section, removing the full term fetus from the mother is all that is necessary to transform it into a baby. One remarkable thing about this is that a baby is an air-breathing animal much like any other, and a fetus does all its gas exchange through a tube attached to its circulatory system through its belly button. I can’t easily imagine keeping a tortoise alive by sticking a tube into its belly, nor do I imagine one would have much luck doing so with an adult human, or even a child. But somehow it works for the fetus.

Another thing that is striking about the fetus being a nearly complete baby is that it is a nearly complete baby entirely inside the belly of the mother, upside-down, often with its head inside her pelvis. I don’t know about you, but I could not function for very long with a nearly full sized baby inside me and a skull in the middle of my pelvis. I think I wouldn’t last five minutes, but apparently this situation can go for weeks with little danger, and bearable discomfort, to possessor of either pelvis or skull.

A tremendous amount is now known about ontogenesis, the process by which a single egg grows and develops into a whole person. We have studied it on the scale of molecules, cells, tissues, organs and whole individuals and from the perspectives of physiology, genetics and evolution. There are still vast areas we know almost nothing about, but we can largely reject the hypothesis that there is magic involved. Never the less, things can feel like magic even when reason rejects it. This whole process, of self-directed growth of a single cell into a person, makes it easy to understand why spirits, gods and humunculi are so often invoked.

Hyphum

I know a bit about a lot of organisms, but don't really qualify as an expert on any species. It is great fun planning experiments with people who know a lot about a particular organism. I can say, "if a hypha that is only 300 microns breaks in half, do you get two living 150 micron individuals, or two dead hyphae?" and get the immediate response, "The singular of hyphae is hyphum," followed by, "you would get two dead halves, so we don't have to worry about it." This way I can concentrate on designing the experiment and learn good Scrabble words.

EDIT: May 2nd 2017.
 The singular of hyphae is actually hypha. I just stumbled upon my own old blog post and said, "Whoa! That's wrong." I must have misheard that six years ago.

33 weeks LMP

There is a certain irony to being to a researcher who studies mortality risk early in life, and also a soon-to-be father. Sometimes I feel I know way too much about certain topics.

Decreasing population, increasing density

The Institute where I work is built on land that used to be part of huge East German ship building facility. The facility folded shortly after the German Democratic Republic did. The buildings were, for the most part, left derelict. One of the former factory buildings has been converted into an indoor shopping center. Each store is its own single story box built into the bottom of the cavernous factory building, with walkways and cranes still hanging overhead. Most of the other buildings have been torn down, and ~15 waterfront apartment buildings have been built (or are being built) on the land, most just within the two years I have been here. Apartments in these new buildings are on the expensive side for Rostock, but are filling up fast. One or two huge windowless cement monstrosities (one holds a dance club called The Bunker) remain, as well as a couple of older brick warehouses that have been refurbished. One is being used as a temporary home for the Rostock Volkstheater (community theater) while their main hall is closed for fire-code violations. It feels as though a new, fairly fancy, neighborhood is simply sprouting from the root-system of the old shipyards, among the remaining shells, foundations and train tracks to nowhere.

The demand for housing that fuels all this building is a story of migration. Rostock is Mecklenberg-Vorpomern, the least densely populated state in Germany, and a state that has steadily lost population since reunification. Many of the outylying villages are dominated by abandoned buildings. Apartment complexes on the outer edges of Rostock, plunked down in the middle of fields by the communist planners, now offer multiple months of free rent to anyone who will move in and still are emptying out. Rostock is full of college students, who don’t want to be on the outskirts in half empty buildings, and an aging population of long-term residents, who don’t either. The more abandoned the outskirts get, the strong the incentive to move toward the city center. So the center of Rostock is becoming denser even as the state loses population.

A name but no face

The first time I saw one? I was out in the rowboat, only a couple of hundred feet from our dock, and had, for whatever reason, dropped an oar over the side. I was probably 11, so there is a good chance I had dropped it on purpose, so as to be able to retrieve it. As I was reaching for the oar, I noticed a little white circle, mostly translucent, maybe the size of a dime, floating just under the oar. My hand retracted as the word 'jellyfish' formed in my brain. But I had swum in this lake many hundreds of times and never been stung, or heard that anyone else had. It wafted back and forth in the wavelets I created as I wiggled down in the boat to get a closer look. I held still and eventually so did it. Definitely a jellyfish, or something very similar to one. I watched it until it sank down into the dark silky water and out of view. I imagined it going back down to its secret world and hidden life. I imagined following it and learning.

The oar by this time was far enough away that I had to jump in and get it. I did this with some reluctance, having been stung too many times before, by jellyfish at summer camp on the Chesapeake Bay, and the previous winter in Florida by a Portuguese Man-o-War. Like every swim in the lake before and since, no stings.

My mother afterwards told me that there were freshwater jellyfish in the lake, but only occasionally, and not as many as my grandfather described from when he was a boy. I’ve seen them occasionally since, usually only on really hot days, one or two at a time. I only recently learned their name, Craspedacusta sowerbyi, when they were suggested to me as a possible study organism. Looking them up, finding that they had been studied down to the molecular, I realized I already knew this organism, but only as scattered phantasms floating by on summer days.

name for a principle?

There is a principle that I want to refer to in an upcoming talk, but I can't find a name for it. Someone must have named it after themselves by now. It is related to Ockham's razor, and to parsimony, but is distinct.

The principle is that an explanation for a pattern should preferably be applicable as broadly as the pattern is observed, but not more broadly. For example, an evolutionary explanation for group living that can be applied to all the group-living insects is preferable to an explanation that works only for one species of ant. The explanation should preferably not explain the pattern more broadly than it occurs. For example, an explanation for the fusion reaction of the sun merely in terms of the presence of hydrogen would also tend to predict fusion in many other contexts where it does not generally occur, making this explanation less desirable than a more complex one which also specifies the need for the physical conditions which encourage the hydrogen to fuse.

This is the sort of logical statement that is so obvious as to rarely need to be said, yet I need to say it for this talk. If you know what I should call it, please let me know.

Reproduction

The ladybugs are successfully reproducing on our mint plant. Oh frabjous day! The larvae are crawling all over the plant scarfing down aphids like mad, and the adults are laying more eggs. It is exciting to see them doing so well.

Two offers out

We have now interviewed two post-doc applicants. Both are extremely well qualified for their respective prospective positions. Both seem very easy to get along with, and both have been offered the positions. Neither, unfortunately, has yet accepted. The first because she is scheduled for a competing interview today, the other because she needs to make sure her partner can also get a job in Rostock. If we hire both of them, I will have a wonderful research team. With either one we could make real progress.

We still have one more candidate coming, next week, and if my bosses like him we could offer a position to him also. If we end up successfully hiring all three, I will be very happy.