A key component of classical sexual selection theory is the idea that males maximize their evolutionary fitness—the number of children they ultimately have—by mating with lots of females, while females maximize their fitness by selecting only one or a few high-quality partners. It’s pretty clear that this model works well for some species (like ducks), but also that there are many it doesn’t fit so well. Now it looks like one of the “classic” experimental examples of sexual selection may actually fall into the latter category.
Sexual selection was first proposed by Charles Darwin, in his 1871 follow-up to The Origin of Species, The Descent of Man, and Selection in Relation to Sex; but one of the earliest experimental tests of the model wasn’t published until 1948 [PDF]. The biologist A.J. Bateman allowed small groups of fruit flies—good old Drosophila melanogaster—containing equal numbers of males and females to mate at random, then reared the resulting eggs and reconstructed the parentage of the offspring to determine (1) the number of offspring each of the male and female parent flies had produced and (2) how many parters each parent fly had had.
How did Bateman reconstruct parentage decades before the advent of modern genetic testing? He used mutations with known, visible phenotypic effects as “markers”:
The fertility of individual flies of both sexes was measured by means of dominant marker genes. Several flies of each sex were mated together in one bottle, each fly carrying a different dominant marker gene. In this way, assuming the complete viability of all the marker genes, half the progeny of each fly could be identified.
That’s a pretty clever design given the technological limitations of the time. But it also turns out to be the fatal flaw in Bateman’s experiment.
Performers on a float at the 2011 Twin Cities Pride parade. Photo by jby.
Hi! Have you signed our pledge to vote “no” on the amendment?
The actual Pride festival is, in my opinion, the least appealing part of any Pride weekend.
Imagine a small county fair stripped of its rides and livestock shows, the agricultural implements replaced with booths full of rainbow-flag keychains and questionably tasteful erotic art, and with lip-synching drag queens instead of country musicians in the all-day stage shows, all dropped into a city park without enough drinking fountains. The people-watching is, admittedly, pretty great, but I don’t think I’ve ever spent more time in a Pride festival than it takes to walk the circuit of the booths.
This Pride Saturday, however, I spent seven hours among the tents and food trucks in Loring Park—mostly standing within reach of one of the Minnesotans United for All Families canvassing booths, handing clipboarded sign-up sheets to passers-by, reminding them to vote “no” on a proposed amendment to the state constitution that would define marriage as “only a union between one man and one woman.”
I’ve been putting in an evening a week with MN United for nearly six months, now—first making calls to Minnesota voters, but now mostly helping to train and assist other volunteer phone-callers. Since I started back in January, prospects for voting down the anti-marriage amendment are looking better: a new statewide poll shows “no” votes outnumbering “yes”, MNUnited has raised quite a bit more funding than the pro-amendment campaign in the first half of 2012, and President Obama finally stated his support for marriage equality.
And then this weekend, hundreds of thousands of potential MN United supporters converged on downtown Minneapolis. With Pride as an official kickoff, the campaign against the amendment is off to a strong (and fabulous) start.
Public polling has burned us before—in California, prior to the vote on Proposition 8, and in Maine, on Question 1, it looked like things were reasonably secure, until they weren’t. Pro-equality campaigns have outspent anti-equality campaigns in other states—most recently in North Carolina—without success.
All things considered, I’d say I’m optimistic that Minnesota could be the first state to turn down an attempt to restrict the rights of queer people via popular vote—but I still wouldn’t say the odds are in our favor.
So what am I doing spending my Pride Saturday in Loring Park, thrusting clipboards at strangers? Or working the phone bank every Tuesday till November?
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Gerty-Z’s announcement that this year’s Pride edition of the Diversity in Science carnival would focus on advocacy was a good prompt for me to sit back and think about my involvement with the campaign against the amendment, and, yes, advocacy in general.
Whenever MN United comes up in conversation, queer friends have taken to calling me a “good gay”—in a tone that’s simultaneously needling and (usually) admitting they feel a bit guilty about not doing similarly. At the same time, I’ve been pretty firm about keeping my volunteering commitment limited—it’s not exactly cramping my day-to-day schedule. Regardless of how the vote comes out in November, I wouldn’t feel quite right if I hadn’t put in some actual effort to help defeat the amendment, but I don’t particularly want the campaign to dominate my life.
And, really, I’d say that the volunteering doesn’t, of itself, make me a “good gay.” Advocacy of the sort that happens in organized political campaigns, even the rather different kind of advocacy that happens in MN United’s campaign, is important—but I strongly believe that, as with revenge, the best kind of advocacy is a life well lived.
I say that in large part because of the way I came out of the closet. I took a (relatively) long time figuring out my orienation, and by the time I came out I was well aware of, and in agreement with, the political arguments in favor of gay rights. All of that kind of advocacy didn’t, frankly, do me a lot of good.
What did end up making a big difference was when I met my first openly gay friend, a collaborator on my dissertation research, who provided a daily example in matter-of-factness about his orientation. I knew him as a smart scientist and a fun drinking buddy, and the occasional presence of his boyfriend at social events was, really, no more remarkable than the occasional presence of anyone else’s significant other. And he turned out to be entirely the right person to phone up, one night, for one of the most important conversations of my life.
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And but so now, years after that conversation, my sexuality is a mostly unremarkable feature of my life. Day to day, I commute to campus and do the quotidian work of science—check ongoing analyses, start new ones, write up results, read papers, think about the next project. I go to the gym or for a run. Sometimes I go on a date or out for a night with friends; sometimes I stay at home and work in front of the T.V. I cook. I write about deeply metafictional Star Trek parodies.
And yet of course my orientation flavors almost everything I do, just as it would if I were straight. When I go on a date, it’s with another guy, of course; but it also influences which bars I go to when I’m out with friends, what kind of books I read (A Single Man, anyone?) and T.V. I watch (poor Renly), and, yes, even how I think about science (well, how prone I am to take issue with evolutionary psychology, anyway). I don’t immediately identify myself as gay to everyone I meet, but I don’t make any effort to hide it; when I’ve taught, I wore my rainbow wristband and “Legalize Gay” t-shirt to class (ignorant as I was of the biases I was courting—but I have every intention of continuing to do so). I’d like to think my experience of life in the closet and out makes me a little more naturally skeptical about recieved wisdom and existing power structures, and I tend to think that kind of suspicion is a good thing.
If I had to pick a professional model for integrating my sexual identity into my professional identity, I’d lean more towards Douglas Futuyma than Joan Roughgarden; not so much a crusader for equality via science, but someone identifiable as a gay man who does good scientific work. My favorite example of this, I think, is a snippet from a perspective article Futuyma wrote for The American Naturalist back in 1999, lamenting the loss of old-fashioned natural historical specilization in evolutionary ecology:
… I could not begin to estimate the number of students I have met who, in explaining their work on some aspects of the biology of birds, plants, insects, frogs, have hastened to say that they are not interested in birds or insects as such but, instead, as models for studying principles—as if “ornithologist” or “botanist” were a scarlet letter, a badge of shame. I cannot cast the first stone, for I have often done the same. But in parallel with my other experiences of life, I have come to feel that as a closet entomologist, I should come out and stand proud.
I love that final line because Futuyma’s drawing on his sexuality to make a point in pretty much the same way Stephen Jay Gould would quote Gilbert and Sullivan. (But, you know, much less pompously.) It’s simultaneously an identfiable facet of his personality and no big fracking deal.
(See also that previous link on Futuyma for his own statement about a career as a gay biologist, much of it in an era when it wasn’t as easy as it is today.)
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In the end, I think that the point of advocacy is to try and leave the world a little bit better place for the next generation of queer kids, the ones who are just realizing they have to figure out how their orientation fits into the lives they’ve only just begun to build. In the spirit of It Gets Better, if good examples of how to be gay are what helped me come out, how can I not do my best to be a good example of how to be gay now that I’m out?
But, you know, I want to get married someday, too. So come tomorrow night, I’ll be back at the phone bank.◼
This week at Nothing in Biology Makes Sense! David Hembry looks back on changes in ecology and evolutionary biology over the course of his dissertation research; and the contributors make plans for Evolution 2012.
Have you submitted somthing for the Pride edition of Diversity in Science? You should do that now.
Competition between scientific tribes? A few choice complaints about the debate over group selection.
The chicken-salad sandwich in your lunch box doesn’t count. Paleontological evidence of mammals that ate dinosaurs.
Philip V. Tobias, 1925-2012. A lifetime of evolutionary anthropology, eulogized.
And finally, Grist reports that the kakapo, New Zealand’s delightfully odd ground-dwelling parrot, is less endangered than it used to be, thanks to considerable effort by some very tolerant conservation biologists. Tolerant of what? Well, let’s go to the video:
Some of the transformations in the field I think I could see coming. For instance, it was clear in 2005 that computational power would keep increasing, phylogenetics would be used more and more to ask interesting questions, more and more genomes would be available for analysis, and evolutionary developmental biology was on the rise. It was unfortunately also predictable that it would be possible to study climate change in real time over PhD-length timescales. And although the 2008 global financial crisis didn’t help, it was clear that funding and jobs were going to be more competitive than they had been for our predecessors.
But there were a number of things I didn’t see coming, and which have made the field look radically different than it was back in 2005.
For a detailed look at the last seven years of advances and shifts in the ways we study descent with modification, go read the whole thing.◼
You’ve already read my fanboy glee in anticipation of John Scalzi’s new novel Redshirts, so it’s only fair to report that I have already finished the book, and I can honestly say it was everything I hoped for.
“Redshirts,” on the original version of Star Trek, were the nameless, red-shirted security officers who’d beam down to strange new worlds alongside the stars of the show—and, if danger should present itself, it usually did so by killing a redshirt. Redshirts, the novel, is about what happens when some redshirts start to realize that their mortality rate is more consistent with a campy TV show than actual military service, even military service in space.
The result is a short novel that might be what you’d get if an episode of Star Trek were exposed to exotic radiation in an ion storm and spontaneously developed self-awareness. Although many of the resulting jokes have been made before (notably in the also-excellent movie Galaxy Quest, which is required viewing for the thoughtful Trek fan), Scalzi draws them out of genuine characters caught in a plot that ventures deep into the weirder end of Trek‘s repertoire without going off the rails.
I can’t go into any meaningful detail about that plot without spoiling it, so I won’t. I can say, however, that Redshirts is hilarious and humane. It’s a story about decent, rational human beings trapped in an indecently irrational universe, which is nevertheless the very kind of universe that human beings routinely imagine in every possible venue for fiction. Scalzi’s ultimate conclusion—that an author has something approaching a moral obligation to tell good and worthy stories with the characters he imagines—gives the story far more depth than mere fanfic.◼
There’s some more new evidence for one of the theories as to how gene variants that make men more likely to be gay could persist in human populations in the face of their obvious selective disadvantages: the same genes could, when carried by women, lead to greater fertility.
The authors interviewed women who were the biological mothers or aunts of gay men, and compared them to women who were mothers or aunts of straight men. They gave each participant a questionaire covering the key question—how many children they’d had. It also covered a sort of focused medical history, covering a slew of conditions that might have affected their fertility—anything from chlamydia infections to ovarian cysts to complicated pregnancies—and asked about their sexual behavior and history. Finally, the team gave the women in their sample a standardized personality test.
Even this relatively small sample showed the previously documented effect of shared genetics with gay men—women who had gay sons or nephews had more children than those who didn’t. Mothers and aunts of gay men also reported lower rates of medical conditions that could reduce their ability to have children. They said they’d had more partners than mothers and aunts of straight men (but this difference wasn’t statistically significant) and were also less concerned about family issues, and more likely to have been divorced. Finally, the personality test revealed that mothers and aunts of gay men were more extraverted.
That’s a big pile of factors tested, which makes me wonder about multiple testing issues with a small sample size. The study’s authors build a somewhat complicated narrative out of it all: They speculate that the same genes that make men gay make women less likely to have fertility-reducing conditions, but also more extraverted and more “relaxed” about building a family—which apparently also helps them have more children. So, okay, I guess that’s plausible given the results.
Here’s what the study doesn’t do, however: it doesn’t identify any specific genes involved in making gay men gay. It can’t actually test the hypothesis that there’s a genetic basis to same-sex attraction at all, much less the hypothesis that genes promoting same-sex attraction in men are located on the maternally-inherited X-chromosome. For those questions, you really need full pedigree data—or, better yet, lots and lots of genetic data; interviewing only female relatives isn’t remotely enough.
The text of the article doesn’t necessarily make that point as clearly as it could. The authors spend a great deal of time talking about the X-chromosome hypothesis, and though they make the requisite disclaimer in the Conclusions section—
With this type of limited data, we cannot directly derive a causal connection between the hypothetical sexually antagonistic autosomal or X-chromosome-linked genetic factors and health, behavior, and personality.
—that disclaimer elides the point that their data set can’t really test anything to do with genetics indirectly either.
The authors repeatedly describe their sample as a “pilot study,” however, so maybe something bigger, and more rigorous, is in the works.◼
Camperio Ciani, A., Fontanesi, L., Iemmola, F., Giannella, E., Ferron, C., & Lombardi, L. (2012). Factors associated with higher fecundity in female maternal relatives of homosexual men. The Journal of Sexual Medicine DOI: 10.1111/j.1743-6109.2012.02785.x
… that you go over to 3 Quarks Daily and vote for a science blog post to recieve their 2012 Science Prize? And might I futher suggest that you vote for my entry, that long piece on the genetic architecture of complex traits? Voting closes on Sunday, 16 June, at 11:59 Eastern time—so vote early, even though you can only vote once.
The central idea of sexual selection theory is pretty simple: Females, who invest relatively more in making and raising offspring, have an incentive to be choosy about mating. Males, on the other hand, may be able to get away with no more investment that a squirt of semen—so they have an incentive to mate with any female who’ll have them. How widely that model applies in the animal kingdom is very much an open question, but it does make some specific predictions that can be tested in an evolutionary context.
One of those predictions is that, when relatively more resources are at stake in the process of making babies, sexual selection should be stronger. Austin Hughes, a biologist at the University of South Carolina, recently set out to test for that pattern in waterfowl [$a].
Ducks and their relatives already look like a good fit for classic sexual selection. In many duck species mating is coercive, so females have evolved maze-like reproductive tracts to slow down unwelcome penises—and males have, in turn, evolved corkscrewing penises to navigate those mazes. And in many species, the sexes have strikingly different coloration—generally thought to mean that males are vying for female attention with brightly colored plumage, while females are more concerned with staying hidden while sitting on a nest.
However, there are also plenty of waterfowl species where males and females are almost indistinguishable—think of swans or geese, especially. If sexual plumage differences are related to the strength of sexual selection, maybe that reflects differences in the sexual “stakes” at play in each species. Hughes tested this hypothesis by comparing closely related pairs of waterfowl species or subspecies.
As an index of the reproductive effort made by females of each species, he used the mass of the average clutch of eggs laid, as a fraction of the mass of the average female. He then tested whether the species in each pair whose females made the larger “investment” in reproducing was also the species in the pair with more pronounced sexual differences in plumage coloration. And this was, indeed, what he found.
So that looks like a neat confirmation for one predicted effect of sexual selection. A worthwhile follow-up might be to add male parental care—which may be, admittedly, harder to measure—into the mix. If males help feed and protect the brood (which is often the case for waterfowl), that should offset the cost of reproduction from a female’s perspective, which might also reduce the strength of sexual selection.◼
Hughes, A. (2012). Female reproductive effort and sexual selection on males of waterfowl. Evolutionary Biology DOI: 10.1007/s11692-012-9188-1