Under selection, an endangered species runs low on evolutionary “fuel”

A pale-headed brushfinch, Atlapetes pallidiceps. (Wikimedia Commons:Aves y Conservación/NBII Image Gallery)

The pale-headed brushfinch, Atlapetes pallidiceps, is a conservation success story, or at least the first chapter of one. The birds were thought to be extinct, until a 1998 survey [PDF] of Ecuador’s Yunguilla Valley found four nesting pairs, and observed them foraging for insects and fruit. Following that rediscovery, the Fundacion Jocotoco secured a reserve encompassing the brush finches’ known territory, and took steps to control brood-parasitic cowbirds that were threatening them. Now, the population is five times bigger, with as many as 200 of the birds living in the reserve.

Have the brush finches’ rebounded enough to secure their population for the future? Populations that decline so precipitously can lose genetic variation, and may not regain it even if their numbers increase again. With reduced genetic variation, species that have undergone such a “population bottleneck” event may be unable to respond to natural selection imposed by disease or changing environments.

Bringing back the “king” of American forests

(Flickr: Yuichi Tokutomi)

The American chestnut used to be one of the most common trees in North American hardwood forests, providing enormous crops of nuts that supported birds and other wildlife, and a source of robust, rot-resistant lumber for human use. But American chestnuts were nearly wiped out by the introduction of a virulent chestnut blight from Asia.

But now, after years of selective breeding and some careful genetic engineering, biologists at the State University of New York and the American Chestnut Foundation have produced blight-resistant chestnuts and they’re getting ready to start restoring the population with a crowd-funding campaign. If American chestnuts couldn’t evolve to cope with blight on their own, they may be one of the first species to get an evolutionary helping hand from humans.

Natural selection at the movies: Only the bad guys evolve

You can thank evolution for making Xenomorphs so gosh darn scary. (Flickr: Maggie Osterberg)

It’s almost Halloween, and if you’re anything like me, you celebrate the season by watching scary movies. Although the horror movie marathon is a typical annual tradition of mine, this year I set out with a specific task: to identify as many movies as possible where the villain is somehow associated with evolution by natural selection. As it turns out, there are a lot of them.

Think classic horror films like Alien and Jaws, and also more recent movies like Chronicle, Resident Evil, and Slither. The trend also isn’t restricted to horror movies, with references to natural selection cropping up everywhere from science fiction/adventure films like Edge of Tomorrow to sports dramas like Rocky IV. Nor is it limited to movies alone- television shows like The Walking Dead can give you your fix of “survival of the fittest” references on a weekly basis. Even the urbandictionary.com definition of the word “villains” involves natural selection.

Life, um, finds a way—except when it doesn’t

(Flickr: Armed Forces Pest Management Board)

This week the LA Review of Books has my review of Unnatural Selection, a nifty new book in which ecological toxicologist Emily Monosson describes how living things evolve their way around the things we humans do to try and contain them.

… the introduction of the insecticide DDT rapidly led to the evolution of resistant mosquitoes, houseflies, and, yes, bedbugs. Decades of farming with the herbicide glyphosate, better known under the brand name Roundup, have led to the evolution of resistance in dozens of weed species. One after another, Monosson ticks off cases, dividing them into chapters corresponding roughly to biological classification. She goes beyond these headline examples to describe lesser-known triumphs of “resistance evolution,” such as viruses evading human immune responses and inadequate vaccination, cancer cells overcoming chemotherapy, and fish that survive water polluted by biochemical toxins.

This hits some of the same themes as that recent review about using evolutionary biology to solve major problems in the coming century, though I might have liked it if Unnatural Selection spent a bit more time discussing the cases when life doesn’t find a way—the myriad reasons we’re in the middle of the sixth mass extinction in the history of the planet. But I highly recommend the book for the folks in your life who may not realize how personal evolutionary biology can be.

The evolution of human facial diversity

Signalling individual identity is critical in many aspects of human social interaction (click for video!).

We all rely on our ability to recognize other people’s faces to get along in the world. Most people don’t think too hard about this, it’s so fundamental to our existence. But it turns out that in order to stand out in the crowd, you need to be, well different. A recent study shows that human faces are in fact, much more different from one another than other traits, and suggests that this high facial diversity has evolved specifically to signal individual identity. It’s a pretty interesting story, and I look forward to digging into the details.

Check out this NatGeo piece on the work, and the original publication (paywalled).

Literature Cited:

Sheehan, Michael J., and Michael W. Nachman. “Morphological and population genomic evidence that human faces have evolved to signal individual identity.” Nature Communications 5 (2014).

To thrive in the twenty-first century, can we learn to steer evolution?

Cliff swallow in flight. (Flickr: Don DeBold)

Many of the biggest challenges humanity faces in the next hundred years are biological: dwindling wild lands and disappearing biodiversity, antibiotic-resistant bacteria, and emerging new viruses, but also feeding nine billion people or more a healthy diet in a climate-changed world. As Theodosius Dobzhansky famously remarked—and as this very website’s name proclaims—nothing in biology makes sense except in the light of evolution. So are there evolutionary answers to all these biological challenges? According to a big new review article just released online ahead of print in the journal Science, the answer is emphatically yes.

The long list of authors, led by Scott P. Carroll and including Ford Denison, whose lab is just down the hall from my office at the University of Minnesota, explicitly connect evolutionary principles to global goals for sustainable development. These include the reduction of both “chronic lifestyle” diseases and infectious diseases, establishment of food and water security, clean energy, and maintenance of healthy ecosystems. Carroll and his coauthors divide the applications of evolution to these problems into cases where evolution is the problem, and those where evolution may offer the solution.

Why the whale kept its hips

A bowhead whale’s highly (but not entirely) reduced pelvis. Image via Wikimedia Commons.

Thanks to a remarkably good fossil record, it’s now well established whales and dolphins evolved from land mammals, their forelimbs adapting into flippers, and their hind-limbs almost entirely disappearing. If you’d asked me yesterday what’s going on with that almost—the last vestiges of the hip bones that whales retain, which have no legs to support or direct contact with the rest of their skeletons—I’d have told you they were evolutionary leftovers, and probably going to disappear in another million years or so. I think a lot of other evolutionary biologists (those who aren’t whale specialists, anyway) would’ve agreed with me. But it turns out we’d have been wrong.

As Carl Zimmer describes, a paper recently published in the journal Evolution points out that whales’ hips do have one remaining function, an important one—they anchor muscles that control the penis. And that function is under ongoing sexual selection.

The more promiscuous a [whale] species was, the bigger its pelvis bones tended to be. The scientists also found that as whales evolved to become more promiscuous, their pelvic bones changed shape. These changes weren’t part of some general change to their skeleton, however. The ribs near the hips didn’t show the same patterns of size and shape change.

I strongly recommend Zimmer’s whole article, and you can also read the original research article in Evolution.

Skeptical that PMS is an adaptive response designed to break up your relationship? Me too.

In a pleasantly surprising turn of events, this week a take-down of some dubious evolutionary psychology was published by the popular media!  The original article, a perspective piece published in Evolutionary Applications, claims that moodiness associated with PMS may have historically served an adaptive role by driving infertile couples apart. 

Premenstrual syndrome (PMS) affects up to 80% of women, often leading to significant personal, social and economic costs. When apparently maladaptive states are widespread, they sometimes confer a hidden advantage, or did so in our evolutionary past. We suggest that PMS had a selective advantage because it increased the chance that infertile pair bonds would dissolve, thus improving the reproductive outcomes of women in such partnerships. We confirm predictions arising from the hypothesis: PMS has high heritability; gene variants associated with PMS can be identified; animosity exhibited during PMS is preferentially directed at current partners; and behaviours exhibited during PMS may increase the chance of finding a new partner. Under this view, the prevalence of PMS might result from genes and behaviours that are adaptive in some societies, but are potentially less appropriate in modern cultures. Understanding this evolutionary mismatch might help depathologize PMS, and suggests solutions, including the choice to use cycle-stopping contraception.

Check out the response, published by The Daily Beast, here:

Here’s the scapegoat unhappy spouses have been waiting for: According to a paper out last week by Michael R. Gillings, premenstrual syndrome (PMS) can ruin a marriage. Gillings claims that PMSing women—in infertile couples in particular—may use feelings of “animosity” as well as risk-seeking and competitive behaviors to leave their husbands and find someone new. I’m sorry to say, but the evidence in favor of this hypothesis is thinner than Always Infinity menstrual pads.

Selecting for a butterfly of a different color

Bicyclus anyana in its low-key natural look. Photo by Gilles San Martin, via Wikimedia Commons

Via NPR: a paper published online this week ahead of print at PNAS reports the results of an artificial selection experiment that changed butterflies’ wings from brown to blue.

We used artificial selection on a laboratory model butterfly, [Bicyclus] anynana, to evolve violet scales from UV brown scales and compared the mechanism of violet color production with that of two other Bicyclus species, Bicyclus sambulos and Bicyclus medontias, which have evolved violet/blue scales independently via natural selection.

A guide to the science and pseudoscience of A Troublesome Inheritance, part III: Has natural selection produced significant differences between races?

This is the third in a series of guest posts in which Chris Smith will examine the evolutionary claims made in Nicholas Wade’s book A Troublesome Inheritance. You can read part I here, and part II here. Chris is an Associate Professor of Evolutionary Ecology at Willamette University. He uses population genetic approaches to understand coevolution of plants and insects, and he teaches the interdisciplinary course “Race, Racism, and Human Genetics” with Emily Drew.

A Troublesome Inheritance was published in 2014 by Penguin Books. Cover image via Google Books.

This spring former New York Times science writer, Nicholas Wade, released his latest book on human evolution, A Troublesome Inheritance: Genes, Race, and Human History. In it, Wade argues that genetic studies completed in the eleven years since the Human Genome Project was completed reveal real and important differences between human races. Unsurprisingly, the book’s release has been met with a sharply divided critical reception.Whereas the book has been widely embraced by those on the political right, and by the white identity movement, it has been panned by anthropologists, evolutionary biologists, and population geneticists. For the last two weeks at Nothing in Biology Makes Sense, I’ve been looking in depth at the literature that Wade uses to support his ideas. Last week I considered Wade’s argument that natural selection acting on the MAO-A gene – a neurotransmitter implicated in aggression and impulsivity – has led to behavioral differences between races. This week I will consider Wade’s larger claim that natural selection has produced numerous differences between races.

Throughout the book Wade continually repeats the mantra that natural selection on humans has been “recent, copious, and regional.” It would be hard to find an evolutionary biologist that would disagree with these rather vague pronouncements. Indeed, there are a multitude of studies showing that natural selection has acted on humans, and there is persuasive evidence that selection has caused evolutionary changes in human populations as we have adapted to diverse environments over the course of the last several thousand years (see, for example, Yi et al., 2010).

However, scratching the surface reveals that when he says that natural selection has been “recent, copious, and regional,” what Wade actually means is that natural selection has been “radical, complete, and racial.” By Wade’s account, natural selection has dramatically reshaped the human genome, producing major differences between races. This much more dramatic interpretation is entirely unsupported by the literature, however. In truth, Wade vastly overstates the portion of the human genome that shows evidence for natural selection, and where there has been recent natural selection acting on humans, its effect has primarily been to create genetic differences between members of the same race, and similarities between people of different races.