National Academy of the Extremely Vigorous

People of higher educational attainment live longer. This is widely known. Somewhat less widely known is just how far up the attainment ladder this pattern goes. People with Master's Degrees tend to live longer than those who stop with a Bachelor's. Even more longevous, on the average, are those with doctorate. But people who get a doctorate and then go get some random job don't tend to live as long as those who become tenured professors. And sitting atop this hierarchy of attainment and longevity are the members of the elite scientific academies, such as the National Academies and the Royal Society. Many people's tendency when thinking about this correlation, between attainment and lifespan, is to assume that being better educated helps one live longer. To some extent this is certainly true, and at the level of primary education, and even college education, there is experimental evidence (both true experiments and accidental experiments through policy changes) to prove this. But in thinking about the differences between groups of people with graduate degrees, I rather suspect that the causal relationship is rather different.

I'm thinking about this at present because I have had a very productive evening. Since coming home from a full day at work I've made dinner, done the dishes, played with my daughter, rocked her to sleep, folded the laundry, done more laundry and folded that also, cleaned the cat's box, organized things around the house, rinsed the drop-cloth we put under the highchair while my daughter learns to eat, cleaned the broccoli and potato bits out of the bathtub, written work emails, taken down the garbage and the recycling, climbed the 18 flights of stairs to come back up and written half a blog post. This is extraordinary for me, especially this time of year. I am almost always either coming down with something or trying to recover from it, or coddling an inflamed joint, or just feeling low energy. I lose a disgusting amount of potential productivity to being sickly. The elite academies members I know, and those who are not yet in those academies but seem likely to be in them some day, are all people who are this energetic all the time. If they do get sick, they seem to almost always be back at in after a day or two. It is rare for me to recover from a cold in less than a week, and not rare for me to be out for two or three weeks at a stretch. This is not to say that many of these people are not also smarter than me in important respects, but the trait that most unifies the really successful academics I know is their extraordinary energy and vigor. My boss, nearing his 70th birthday, and a National Academy member, hardly seems to know what it is to feel tired. He'll attend meetings on four continents in the course of a week, say how exhausted he is, and still spring from his chair to scribble equations on his whiteboard. So my belief is that people of the highest academic attainment live longest not because they are of high attainment, but because they are remarkable in their health and energy, which also allows them to produce the torrent of great science necessary to be elected to one of these societies. Alright, enough writing, I'm exhausted.

Halloween, diversity, and the left-leaning scientists

The popular view that scientists tend to be politically liberal has, despite the many counter examples, a pretty good basis in fact, at least as a trend. I don't want to give the impression that I have no conservative colleagues (I have several) or that these people are ostracized (they aren't), but simply that they are in the minority. None of them perhaps would pass a Republican purity test, but they certainly wouldn't pass the Democratic purity test either.

One could easily suggest several possible reasons for left-lean. The liberal might say that scientists are people trained to think carefully about ideas, and liberal ideas stand up to careful thought better than their conservative counterparts. She could add that conservatives, particularly the United States, tend to engage in a great deal of anti-intellectualism, which is not a good way to win the support of scientists and that conservative leaders and movements twist scientific conclusions and ideas more frequently and more disastrously than do liberals. A conservative could argue that as a big-spending liberals tend to support science funding, scientists have a direct interest in supporting liberals. I think all of these things are at least sometimes true.

Another hypothesis occurred to me last night during our Halloween party. Looking around our apartment, I saw not only several Americans (tiger, mime, fisherman, pirate, little girl/trick-or-treater, scarecrow, frog, Dorothy, lumberjack, but no tricorn hats) and Germans (lizard, clown, flapper, schoolgirl, bus stop, Little-Red-Riding-Hood, ninja, and a little boy dressed as a little boy), but also friends from Italy (a mouse and a mummy), Hungary (bank robber), Austria (ghost and witch), Australia (tin man and geisha), Poland (burglar, witches and a ghost), Latvia (witch), Spain (ghost and sorceress) and Finland (clown, penguin, bear and ladybug). We had 34 people from 10 countries, and had invited people from at least a dozen more (Japan, Taiwan, China, Mexico, Brazil, the Netherlands, Denmark, England, Russia, Bulgaria, Turkey and New Zealand). This sort of national diversity is common at gatherings of Institute researchers. I had a similar experience at Berkeley, with colleagues from all over the world.

Conservatives in many countries are nationalistic, or at least view the traditional ways of doing things in their part of the world as best and most correct. So perhaps the conservative hoping to build a career in science finds herself in many uncomfortably international situations, where her assumptions are challenged or potententally unpopular. If so, such people may tend to either revise their opinions (or pretend to, which often eventually leads to an actual change) or avoid such situations. Such avoidance would make a successful career in science difficult, at least at the prestigious institutions which tend to have international research staff.

The Ivory Tower's relative lack of political diversity may partly result from its high demographic diversity. It is hard to condemn witches when your living room is full of them.

Concepts in the evolution of senescence about which I am increasingly skeptical:

Intrinsic vs. Extrinsic mortality
Optimality hypothesis
Mutation Accumulation hypothesis
Agonistic Pleiotropy hypothesis
Disposable Soma hypothesis
Caloric Restriction Effects
"Rate of living" hypothesis

This list includes most of the theoretical basis for the field

Studies in current evolution

Research Question:
To what extent is the number of children people choose to have in developed nations heritable (in the genetic sense)?

Importance:
If it is heritable, this is most likely the largest determiner of fitness outcomes, as the great majority of children survive to adulthood, no matter how many siblings they have. This implies potentially rapid Darwinian selection for those who choose larger families. Over the course of a few centuries this selection could have important impacts on human demography and population. Given an estimate of heritability, this effect could be quantified.

Method:
The old twins/siblings separated at birth databases?

Ethical considerations: many

Likelihood I will actually get around to this:
small

Long Term Prediction

Several thousand years from now, if there are still humans around, someone will look back and describe the last few thousand years as a time of extraordinarily rapid biological evolution for humanity.

A conjecture on the link between babies and lack of sex

I am told by those who have children that one of the many sacrifices couples make to raise a baby is opportunity for sexual intimacy. I don't have kids, so don't know from personal experience, but it certainly makes sense. Between exhaustion, vehement interruptions and company in the house, it can be hard for a couple to find the time, privacy and energy to maintain their pre-parental levels of activity. I have had friends say that it seems very much like the baby is plotting to destroy its parents' sex lives. It has just occurred to me that in a sense, this could be very true.

Evolutionarily, there are many ways in which the interests of the parent and the interests of the offspring are aligned. The fitness of both are improved if the baby grows, thrives and go on to produce its own offspring. They share many genes, and anything that is good for the one is at least a little bit good for the other. But some things that are good for the fitness of the parents are a net selective loss for the baby. Such as having another baby come along too soon. The parents of course are equally closely related to all their offspring, and therefore will tend to distribute care and resources between their children in a way that maximizes the number of future grandchildren. But the baby is twice as closely related to herself as she is to her full sibling; she is much better off monopolizing her parents' time and resources for longer than they might desire. The parents' fitness is maximized by having an interbirth interval just long enough to get a good return on their investment in this offspring, without unduly diminishing their opportunity to have more children in the future. The child's fitness is maximized by having the parents wait somewhat longer, until the diminishment of their future reproductive chances for each additional day waited is twice the per day increase in her own fitness gain. The technical term for this disalignment of interest, appropriately, is parent-offspring conflict.
At first glance, the advantage in the conflict over the length of the interbirth interval would seem to be distinctly on the side of the parents, rather than the sessile, pre-sentient, altricail lump of chub, digestive organs and breathing apparatus. But oh, those breathing bits can very easily be used to make sounds. Sounds that communicate desperate dire need to protect and nourish the baby. Sounds that cannot easily be ignored. What harm if one screams just a little bit louder, a little more frequently, screams and cries with slightly less provocation, and makes the parents increase their interbirth interval just a little while longer?

Before you label me a conspiracy theorist, let me be clear. I am not implying that the babies of the world are 'trying,' in any intentional way, to deprive their parents of sex. They don't have to try. It comes naturally to them.

Dying for Sex

One of the projects I am working on currently is an analysis, using data from primates, of what life history factors are correlated with sex-biased longevity. To put that plainly, I want to know why in some species the females live longer, in some the males live longer, and in some they live equally long. One of the dozens of hypotheses out there explaining why females live longer, in species where they do, is the 'risky male behavior' hypothesis' which says that males don't live as long because they take risks while out looking for sexual partners.

There has been limited support for this hypothesis, and most of the others, because so many hypotheses make the same predictions that one can rarely conclude that a particular factor is at play unless one ignores all the other possibilities (which seems to be the standard practice.)

This paper from Proc.Roy.Soc.B. takes an interesting new tack, looking not at whether males that are shorter lived than their mates are taking more risks, but rather at whether their short-livedness can be explained by increased mortality during the season of risk taking.

Here is the abstract:

Abstract

Male excess mortality is widespread among mammals and frequently interpreted as a cost of sexually selected traits that enhance male reproductive success. Sex differences in the propensity to engage in risky behaviours are often invoked to explain the sex gap in survival. Here, we aim to isolate and quantify the survival consequences of two potentially risky male behavioural strategies in a small sexually monomorphic primate, the grey mouse lemur Microcebus murinus: (i) most females hibernate during a large part of the austral winter, whereas most males remain active and (ii) during the brief annual mating season males roam widely in search of receptive females. Using a 10-year capture–mark–recapture dataset from a population of M. murinus in Kirindy Forest, western Madagascar, we statistically modelled sex-specific seasonal survival probabilities. Surprisingly, we did not find any evidence for direct survival benefits of hibernation—winter survival did not differ between males and females. By contrast, during the breeding season males survived less well than females (sex gap: 16%). Consistent with the ‘risky male behaviour’ hypothesis, the period for lowered male survival was restricted to the short mating season. Thus, sex differences in survival in a promiscuous mammal can be substantial even in the absence of sexual dimorphism.

Gender Biased applicants

In the time I have worked on the rotifers, I have had the following assistants:

Lauren
Myfanwy
Rose
Laurel
Chris
Phoebe
Polina
Christina
Nicole
Deanna
Willard
Vincent
Catherine

That makes 3 males and 10 females. Hardly 50/50.

I was wondering why this was, if I was in some way unconsciously discriminating against male applicants, or practicing affirmative action. So I counted how many male and female applicants I have had in the last two rounds of hiring. The most recent I had 2 male and 8 female applicants. The previous time, I had 3 male and 13 female applicants. So if anything, I'm over-hiring males as compared to their representation in the applicant pool.

What I am wondering about now is why so many more females than males apply. The biology classes in my department have a slight majority of females, but not nearly that big. My guess is that because the project specifically investigates the evolutionary basis of menopause, and women tend to be more interested in (and comfortable with the topic of) menopause, fewer males are interested.

Rotifers, sex and locomotion: fast males, slow females

A while back I saw a male rotifer and for the first time knew that it was a male rotifer I was seeing. Three things immediately struck me:
1. Oh! so that's what I've been seeing all this time.
2. Damn they're so tiny compared to the females
3. Golly-gee-willackers they move fast.

To give you a sense of this, observe the following Youtube video I came across. The little bizarrely fast ones are the males.



The males are short-lived, have no digestive system or foot (meaning they can't eat or anchor in one place). They hatch from an unfertilized egg, carry their mothers' genes to other females, and die.

I was discussing this with a friend of mine, who asked, "what good are the males anyway?"

"They're just swimming sperm packets." I replied. But then I thought about it more, and realized the question could be viewed another way. There are plenty of invertebrates that are hermaphroditic. A single individual has both ovaries and testes. I fertelize you while you fertilize me. No need to build a whole separate individual to deliver the sperm. So why go to all the expense of pumping out fleets of males?

Maybe, I thought, it was that speed. The smaller a rotifer is, the faster it can swim. This is the result of the fluid dynamics of how they swim. I don't know a thing about fluid dynamics, so I won't try to explain that, but the data show that swimming speed is predicted with great accuracy by size.

Having fast moving sperm deliverers could have two benefits that immediately occur to me. First, one can spread one's genes much further by producing small, fast males and sending them off in all directions, than by having one big slow female swim around. Especially considering that the female's immediate neighbors have a good chance of being clones of herself, to make sexual reproduction worthwhile, she needs to get get her sperm far away. That may require speed.

Second, maybe being fast is useful in the competition for mating. If the females are not just willing to mate with every rotifer that wanders along, perhaps being fast increases the chance of fertilizing her eggs.

These are all just hypotheses, but they are testable ones, and perhaps some day I will get to testing them.

Why no "grandfather effect"?

Much of my time at present is consumed by setting up an experimental test of what is known as the grandmother hypothesis. The grandmother hypothesis, in short, is the best guess we have as to why the females of humans and a few other species can live well past the age of reproductive cessation. In most species, and indeed in human males, there is no significant post-reproductive lifespan. Individuals are physiologically capable of reproducing for as long as they live. But the females of humans, a few other primates, a couple of cetations and maybe elephants go through menopause and then can live a significant portion of their lifespan after that. Our closest relatives, the chimps and bonobos, apparently go through menopause at the same age as our females, but live at most a few years after that.

Evolutionarily, this makes sense. If one is no longer increasing one's lifetime reproductive success, staying alive offers no obvious selective advantage. No point in investing in physiologies and structures that will last 100 years if one is only going to reproduce for 50 years. Better to put those resources into having more kids now.

But under a certain set of circumstances, reproduction does not end with, or shortly after, childbirth. If your young aren't really able to take care of themselves for a decade or two, you aren't done reproducing until they don't need you any more. In most hunter gatherer societies, the survival rate of five year olds whose mothers die is quite low. So for human women, having a kid in the last several years of life was likely a waste of time.

Worse, the kid who didn't make it took time and resources that could have been put into other kids, and childbirth, particularly late in life, is dangerous. Plus, elder human females are important for helping their daughters raise their own young, and learn how to do so. It has been shown that young mothers in several societies have a higher success rate raising kids if their mothers are around. The women who stopped having kids and focussed on the kids and grandkids they already had, and avoided the risk of late life childbirth, are thought to have ended up getting more of their genes into future generations than women who kept giving birth as long as they lived. If so, and if this variation in life history was heritable, which seems likely, this differential reproductive success would inevitably lead to a population with more and more women stopping early and fewer and fewer giving birth late in life. This is, we think, why we ended up with this "grandmother effect" of women living well past reproductive age.

The benefit of having a grandmother around seems to be restricted to maternal grandmothers. And this observation, that paternal grandmothers don't seem to make as much of a difference (at least in the societies studied) to the survival of their grandkids, points to at least two possible reasons why we don't see a "grandfather effect" to go along with this "grandmother effect."

First, in most societies, at least those studied in this context, males are providing less in the way of vital care. So if a women has a son who has kids, perhaps she is less involved in care, or in teaching how to care, because her son is not as involved as his mate in that care, and the daughter-in-law is not nearly as likely to look for advice and help from her husband's mother than her own mother. And perhaps this same logic applies to grandfathers on both sides. If they are not who the primary caregiver can go to for help and advice, the advantage of having them around to help is smaller.

Second, paternal grandmothers are less certain of which is really their genetic grandchild. If a woman gives birth to a daughter, and watches that daughter give birth to babies, she can be very confident that those are her descendants. If a woman gives birth to a son, and then watches that husband's mate give birth, there is a significant chance (and we have the genetic data to substantiate this) that the baby was fathered by some other man, and those babies aren't her genetic kin. So investing in them heavily may not be doing her any good. This argument is doubly true for grandfathers. The daughter who is giving birth may not even be his. A couple of generations removed, and who can be sure?

A final reason males may not have evolved to have a post reproductive period comes back to that risk in late life childbirth. Men don't give birth, so the risk to late life survival posed by late life reproduction may be greatly reduced, or completely absent. Without that trade-off, why not keep on breeding as long as possible?

DUDES (Diurnal Urban Detritus Eating Sparrows)

There are at least a dozen outdoor housecats on my block. And, as you might expect, not a whole lot of ground dwelling small wildlife. A few salamanders, the very occasional rat (the only times I've seen these there were at least two cats in purrsuit) and some squirells which can outclimb any of the cats. And there is really only one bird species that spends much time on the gound, a big drab brown sparrow called the California Towhee.

Today I saw two of them fighting. A frantic ball of beaks and feathers twisting crazily through the air. They were so intent on mauling each other, they crashed first into the neighbors' fence, then onto the driveway. The instant they touched down, still rolling and pecking, a cat appeared a few yards from them, coming for them at full speed. The cat pounced, and while it was in the air the towhees joined it, but as it began to come down, they accelerated straight upwards. The cat got nothing but the feathers they had torn from each other.

I've seen birds escape preditors before, but nothing quite that close or sudden. These birds clearly had practice. How could they not, given the feline density around here? But somehow, California Towhees seem to thrive, feeding on the ground, in exactly the kinds of neighborhoods that are full of cats.

Like most species able to exploit human created niches, they've got a bright future ahead of them. The cats could even be good for them, keeping out rodents and other birds that would compete with the Towhees for food.

And that is how we get from natural history observation to testable hypothesis.