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Regal.port Charles Darwin’s theory of evolution certainly transformed the way we view life on Earth. Brian Regal (left) thinks it also had an impact on mythical creatures. Regal, a science historian at Kean University in Union, New Jersey, says that with the publication of On the Origin of Species, canine-man hybrids went out of fashion, making way for new beasts that embodied Darwin’s thinking: ape-men such as Bigfoot (a.k.a. Sasquatch) and the Yeti (a.k.a the Abominable Snowman). I spoke to Regal about how his study of the history of evolutionary theory led him to monsters and eventually to monster hunting.

Q: How did Darwin kill the werewolves?
B.R.: There were already writers in learned circles questioning the concept of the werewolf in the late 1500s. From an evolutionary point of view, the werewolf makes no sense. A half-human half-wolf/dog composite doesn’t work. An ape-man, however, a Bigfoot, makes sense because the ape-man idea is [at] the heart of human evolution. If you look at all the “wild man” stories in various cultures around the world, none of them mentions apes prior to the mid-19th century and the public debate brought on by Darwin's On the Origin of Species (1859) and T. H. Huxley's Man's Place in Nature (1863). This was the key to my idea. The “wild man” and the “ape” did not join forces to become the ape-man until after Darwin.

Q: How do you think Darwin viewed werewolves, centaurs, and other half-man, half-animal creatures?
B.R.: I have checked Darwin’s correspondence and published works, and I have not found him [to] make any direct reference to werewolves. In a letter from Darwin to the naturalist G. R. Waterhouse, dated 3 or 17 December 1843, he does mention that he did not believe there can be half of one thing and half of another. He also called animal monsters "a nasty, curious subject” when addressing a new book he had read by the French naturalist Saint-Hilaire.

Q: We often hear about people who have claimed to have seen Bigfoot, or the Yeti, or Sasquatch. Could they exist today?
B.R.: Peter Byrne, one of the grand old men of Bigfoot hunting, said it well. He said the way we will probably find out these creatures are real is when one of those giant 18-wheel logging trucks from the Pacific Northwest pulls into a roadside diner with a Bigfoot splattered all over the front grill. All my Bigfoot friends will get mad at this, but I think in the end they probably do not exist.

Q: You say that Darwin’s theory has caused us to shift our focus to ape-man hybrids. But recently in pop culture, creatures like Bigfoot seem to be replaced by the werewolf. For example, Harry Potter and Twilight, both blockbuster books and movies, have werewolves as major characters. Why do you think that is? cynocephaly
B.R.: We have to remember that monsters are deeply emotional creations. We tend not to react to them in a rational way, so there are many reasons for believing or not believing in them. While evolutionary theory helped do away with the werewolf [right] as a biological reality, it helped create Bigfoot as one. However, Bigfoot is, in some people's eyes, more real. It has a certain amount of scientific support for its existence where the werewolf does not. It's also less threatening.

Q: Well, it is a very intriguing idea. What sort of feedback have you received so far?
B.R.: It has run the gamut, from "That's an interesting idea" to "How can you say Darwin killed the werewolves? I just saw Twilight, and they show werewolves!” monkey.BostonSo far, no one has called me crazy, though.

Q: How are you going to present your argument?
B.R.: I am using pictures of werewolves, apes, and Bigfoot to trace the visual transformation of the werewolf into Bigfoot. They come mostly from science books and medieval manuscripts. If you look at early drawings of apes, and then cavemen, they look disturbingly like werewolves. I also have an illustration from a Boston almanac from 1785. It’s the first illustration [left] of a primate in North America (based on the work of Edward Tyson), but it is astonishing as to how much it looks like a happy, smiling Sasquatch carrying a walking stick.

Q: If there's someone who believes that the whole Darwin-werewolf-Bigfoot connection has no proof, what would you tell them?
B.R.: I would tell them that as a professional scholar, I looked at the evidence of the written record, saw patterns, made analogies, and came up with a hypothesis that I think is also supported by the visual record. Others might look at the exact same materials I did and come to a different conclusion or find something more interesting in it. That's how the historical method works.

Brian Regal will present his thesis 5 July at the annual meeting of the British Society for the History of Science in Leicester, U.K.

—Preyanka Makadia

We're halfway through the Origins series of essays in honor of Charles Darwin's 200th birthday, and I'd wager that the other writers who have contributed to it will agree that it's a guaranteed recipe for glorious failure. The origin of life in 2000 words? That's just enough room to give a taste of the wide range of research going on these days but hardly enough to set up a proper banquet. The same goes for my latest essay, on the origin of sex. There, I focused on the intriguing question of why eukaryotes (animals, plants, fungi, and protozoans) have so much sex when it seems to come at a high cost compared with just cloning yourself. But there's an equally intriguing question that I didn't have room to address: Do bacteria have sex, too?

If you define sex as the way we reproduce, then the answer is no. Bacteria (left) aren't born as males and females, and they don't make sperm and eggs. And if you define sex as meiosis—the shuffling of two genomes to produce a new one—-again, the answer is no. But if you define sex as the combining of DNA from two individuals, they've definitely got it.

Viruses can move DNA from one bacterial host to another. Many bacteria carry little extra ringlets of DNA called plasmids that can cause bacteria to join together so that copies of the plasmids can be transferred. Sometimes the plasmids even drag along some of the DNA from the main chromosome. Some species of bacteria will even secrete DNA into their surroundings and slurp up naked DNA they encounter.

This foreign genetic material can be smoothly integrated into a bacterium's own genome. In some cases (known as homologous recombination), the microbe takes up a different version of a gene it already has. It swaps the new version for the old one. In other cases (nonhomologous recombination), it acquires a gene it never had before.

Like eukaryotic sex, bacterial sex has some evolutionary disadvantages. It takes energy to secrete DNA into the environment, for example, and it also takes energy to pump it in and incorporate it into a genome. The energy bacteria put into having sex could be used to grow faster and make more offspring. So, once again, the question arises: Why sex?

In a review in this month's issue of Trends in Microbiology, Michiel Vos of the Netherlands Institute of Ecology takes a look at the potential answers. A lot of them echo the answers that have been offered for the evolution of our own brand of sex. Sex can speed up the evolution of adaptations, for example, by combining beneficial mutations from different bacteria. Sex can bring about entirely new adaptations (such as antibiotic resistance) with the importing of entirely new genes. Sex can add more variation to a population of bacteria, allowing them to adapt to an ever-changing environment, instead of getting stuck in an evolutionary dead end. Sex may help some bacteria do a better job of making us sick by generating new variants that our immune system may not recognize very well.

It's possible, however, that these long-term benefits of sex do not account for their origin through the short-term, generation-by-generation process of evolution. In fact, sex may actually be more of a side effect—what Stephen Jay Gould and Richard Lewontin termed a spandrel. Taking in loose DNA can have an immediate benefit to bacteria that has nothing to do with sex: It's good eating. Some strains of bacteria can live on DNA alone. The fact that sometimes some of the genes they devour end up inserted into their genome does not necessarily mean that the bacteria have evolved a full-blown sexual system. The proteins that swap in new versions of genes during homologous recombination spend most of their time repairing damaged DNA. They may plug new genes in purely by accident.

It's also possible that the adaptation for sex resides not in the bacteria but in their parasites. Plasmids and viruses may evolve increasingly sophisticated ways to move their own DNA from host to host. If they bring genes that benefit their new bacterial host, they benefit as well.

Vos's paper makes the evolution of sex in eukaryotes all the more remarkable. Sex in eukaryotes is a far more complex process, and it's at the core of our biology. Whereas bacteria occasionally swap a gene, eukaryotes blend their genomes every time they reproduce. Biochemist Nick Lane, author of the new book Life Ascending, argues that eukaryotes became different because of a landmark event in their evolution: A microbe took up residence in the eukaryote cell, becoming mitochondria, which we depend on to generate energy. Now the eukaryotic genome was under constant invasion from foreign DNA, coming from close quarters. Worst of all, this foreign DNA included viruslike segments that could make copies of themselves, swamping our own genes. True sex—complete with meiosis—became our best defense. If Lane is right, then it's bacteria we have to thank for not having sex like bacteria.

Carl Zimmer

Credit: Anlace, English Wikipedia Project

Science writer Sharon Begley, who in 2007 returned to her old job at Newsweek after 5 years of writing the “Science Journal” column for The Wall Street Journal, has long reported skeptically about anything smacking of biological determinism. In the 29 June issue of Newsweek, she pens a 4300-word critique of evolutionary psychology, the theory that modern human behavior—including everything from mate choice to child abuse to warfare—is the result of evolutionary adaptations that took place 100,000 or more years ago. Her piece, titled “Why Do We Rape, Kill and Sleep Around?” concludes, as the subtitle puts it, “The fault, dear Darwin, lies not in our ancestors, but in ourselves.”

The heart of Begley’s smack down of evolutionary psychology is a pile of new evidence that, she argues, pulls the Darwinian rug out from under the theory. For example, is rape an adaptation that allows men to spread more of their genes around? Begley writes that this thesis—which was made notorious by biologist Randy Thornhill of the University of New Mexico in Albuquerque in his 2000 book A Natural History of Rape—is undermined by calculations by one of Thornhill’s former colleagues. Those calculations suggest that hunter-gatherers who rape will see their evolutionary fitness go down rather than up because  offspring of such violent encounters have a lower chance of surviving or even being born.

Throughout the article, Begley combines detailed scientific argumentation with rapier-sharp digs at evolutionary psychologists. Here’s her mocking characterization of one of the field’s central hypotheses for what men seek in women:  “Men attracted to young, curvaceous babes were fitter because such women were the most fertile; mating with dumpy, barren hags is not a good way to grow a big family tree.”  

Begley laments that although evolutionary psychology has lost a great deal of ground scientifically in recent years and represents a very simplistic view of human nature, it remains very popular with the mass media.

—Michael Balter

A profile of Begley gives more information on her career.

When I visit researchers in the field, they always bristle when writers compare their search for fossils or antiquities to treasure hunting. Few modern researchers ever profit personally from their discoveries, and in fact they often tell local people that fossils and mummies are worthless in monetary terms. “If you start buying and selling fossils, it will ruin our work,” says paleoanthropologist Elwyn Simons of Duke University in Durham, North Carolina, who has spent decades uncovering early primates in Egypt.

That’s why I was surprised to read this week that the German couple who discovered Ötzi the Iceman—the oldest naturally preserved mummy in Europe—will be paid a finder’s fee of €150,000 (about $250,000). As they were hiking in the Tyrolean Alps of northern Italy in 1991, Helmut Simon and his wife, Erika, spotted the preserved body of a Neolithic hunter protruding from a melting glacier that had encased it for more than 5300 years, according to a report in Radiology. Ötzi has been far more famous in death than in his short, obscure life—he has been the subject of countless scientific papers, books, and documentaries. He is also the star attraction at the South Tyrol Museum of Archaeology, where he earns about €2.5 million a year (about $3.2 million) in admission fees, according to Mummy Tombs.

Not surprisingly, it didn’t take the Simons long to realize that there was money to be made, and they filed a lawsuit asking to be declared the “official discoverers.” Eventually, they sought $300,000 as a finder’s fee, hoping the museum would settle out of court. But local officials appealed. And after a series of court decisions, including a final appeal by local officials to Italy’s highest court, attorneys for the Simons last September announced a six-figure settlement. Last week, the provincial government of Bolzano finally announced that it would pay the Simons $250,000.

This decision “raises many ethical issues,” writes Heather Pringle in her weekly blog for Archaeology magazine. Not the least is that it creates an incentive for amateurs to search for mummies and fossils at sites worldwide, and it even raises the specter of looting of tombs.

This isn’t far-fetched. Paleontologists have long had problems with locals digging up dinosaurs, such as feathered dinosaurs from Liaoning, China. In one case, local farmers collected legally and then split a dinosaur fossil in half and sold it to two rival museums in China, thereby earning more money but risking damage to the incredibly rare fossil. Researchers add that amateurs who dig also damage the sites, where researchers seek everything from fossilized pollen to animal bones to reconstruct ancient worlds. Antiquities laws in most nations reflect this concern and prohibit the sale of human remains and artifacts, although animal fossils are often fair game.

And yet the Simons won their finder's fee. And that payment comes only weeks after paleontologists were in uproar about the hype over a remarkably complete fossil of a 47-million-year-old primate dubbed Ida, which was bought for an undisclosed six-figure sum. Ida’s discoverers claimed she was a “missing link” between primates and humans, but they were also upset that paleontologist Jørn Hurum of the Natural History Museum of the University of Oslo had bought the fossil, which had been collected illegally. Ida was also split in half, with one part forged and sold to a museum in Wyoming, prompting some paleontologists to wonder if the specimen had been damaged in the process.

They are also worried about the precedent that buying fossils and paying finder's fees establishes. “One thing I’m very upset about is that a huge amount of money was paid for this,” Simons told me when the discovery of Ida was announced. “If collectors are going to divide these fossils and resell them, we can’t study them.”

At the same time, he’s worried that Egyptians who learn about Ida and Ötzi will try to collect and sell the primate fossils he gathers in the Fayum Province. “I’ve told them you can’t sell a jaw for a nickel,” says Simons. “If you start dealing with fossils like this and they’re bought and sold and bring huge amounts of money, this will ruin our chances to work overseas.”

—Ann Gibbons

Farren_Duria Antiquior

(Robert Farren, Duria Antiquior (An earlier Dorset), ca 1843, Calotype photograph, National Media Museum, Dorset. View image)

In March, historian Harriet Ritve reviewed for Science the U.S. opening of a new Darwin-focused art exhibit. This week, the show debuted at the United Kingdom's Fitzwilliam Museum, a place with special significance to Darwin. Origins asked Swedish biology Ph.D. student Anna Ehrlund to share her impressions.

CAMBRIDGE, U.K.—Charles Darwin’s theories of evolution not only changed the ways of science but also raised fundamental philosophical questions about our place in the world, questions approached by artists and thinkers of Darwin’s time and long after. But it was not a one-way street; Darwin was also greatly influenced by the ideas and artistic styles that ruled culture and science in 19th century Britain. During his days as a Cambridge University student, Darwin often visited the Fitzwilliam Museum here to appreciate the Old Masters paintings and other artwork. So it’s fitting that this month the Fitwilliam opened a new exhibition, “Endless Forms: Charles Darwin, Natural Science and the Visual Arts,” that displays some of the interchange of ideas and inspiration between artists and Darwin’s science.

The exhibition, which is part of the bicentenary Darwin celebration in Cambridge, mixes and matches 19th century European art with fossils, books, taxidermy, and scientific drawings. The show is divided into sections following themes or chapters of Darwin’s publications and explores how the conclusions made in them inspired, puzzled, and sometimes terrified artists. The exhibition starts with “Darwin’s eye,” devoted to showing how Darwin learned to see and observe in the scientific sense.

Henslow_Arum maculatum(John Stevens Henslow, Teaching sheet with Arum maculatum (‘Lords and ladies’) (detail), 1836, Collage, pen and ink, and watercolor, Department of Plant Sciences, University of Cambridge. View image.)

Natural science in Darwin’s time was a highly visual process. Although it was about observing and analyzing, it was also about displaying your findings to others. Many natural scientists were skilled in drawing; they had to be as every observation was documented by hand. During his studies in Cambridge, Darwin benefited from the skills of fellow scientists such as the descriptive drawing by his mentor John S. Henslow, shown above. Even though Darwin could never compete with the artistic skills of Henslow and others, he still had to document what he saw—some of his sketches are displayed at the exhibition.

A huge portrait of Darwin greets visitors as they enter the main halls of "Endless Forms." To the portrait’s left, one sees a small sculpture of a monkey contemplating a skull the way Hamlet contemplated Yorick's. This work by Hugo Rheinhold is arguably the most direct artistic representation of one of Darwin's scientific ideas in the entire exhibition. The sculpture has its own Wikipedia page.

Then starts a section called “The history of the world,” displaying fossils and landscape paintings. Around Darwin’s time, he and other scientists had started to question the biblical dating of Earth, as geological and fossil findings seemed to suggest it to be much older. The show's curators, Jane Munro and Diana Donald, note a shift in the attention of artists of the period from visions of Noah’s flood to the dynamical forces such as erosion and volcanic eruptions shaping and reshaping Earth continuously. Fossil findings also had an impact, seeding imagination in paintings such as Robert Farren’s Duria Antiquior (picture at top of post).

Landseer_Morning(Edwin Landseer, Morning, ca 1853, oil on canvas, Philadelphia Museum of Art, The Henry P. McIlhenny Collection in memoriam of Frances P. McIlhenny, 1986. View image.)

“The struggle for existence” then follows, exploring how only the fittest survive the harshness of nature as well as a Victorian society in which poverty was ever-present. This grimness inspired works such as the dying stags in Edwin Landseer's Morning, seen above.

Redon_The Misshapen Polyp, Les Origines(Odilon Redon, The Misshapen Polyp Floated on the Shores, a Sort of Smiling and Hideous Cyclops, plate 3 from “Les Origines”, 1883, Museum of Fine Arts, Boston, Lee M. Friedman Fund. View image.)

“The Decent of Humankind” and “Animal Kin” tackle the controversial ideas that man is an animal descended from prehistoric apes and that animals may share some characteristics with us. These ideas scared, fascinated, and inspired artists. Odilon Redon, for example, fantasized about human evolution in his nightmarelike series Les Origines depicting misshapen creatures, mixtures of man, animal, and dream (above). Unfortunately, Darwin’s ideas were also misused in “race biology,” which often portrayed Western customs and culture as superior, depicting native tribes as less-evolved “savages.”

Heade_Cattleya Orchid and Three Hummingbirds(Martin Johnson Heade, Cattleya Orchid and Three Hummingbirds, 1871, oil on panel, National Gallery of Art, Washington, D.C., Gift of the Morris and Gwendolyn Cafritz Foundation. View image.)

“Darwin, Beauty and Sexual Selection” shows paintings and pictures of colorful birds and of people dressed to impress, juxtaposing the role of beauty in both the animal kingdom and human society. In the last section, “Darwin and Impressionism,” the curators present links between famous impressionistic painters such as Cézanne and Degas and the scientist’s theories.

Timothy Potts, the director of The Fitzwilliam Museum, calls Endless Forms “the most ambitious exhibition The Fitzwilliam has ever put on.” It was displayed earlier this year at the Yale Center for British Art in New Haven, Connecticut, and got good reviews. (The New York Timesreview features a slide show with selected works from the exhibition, and the BBC also has a slide show narrated by the curators.) I shared the enthusiasm of those art critics. If you are in or around Cambridge, U.K., between now and 4 October 2009, I can thoroughly recommend a visit.

More material, including podcasts and a book club on Darwin in literature, can be found on the exhibition Web page.

—Anna Ehrlund

Life for human evolution researchers was so much simpler 50 years ago. There seemed to be a clear distinction between the cognitive capacities of humans and that of all other animals. The proof: Humans made tools, other species did not. The concept was perhaps best expressed in the title of a 1949 book by British anthropologist Kenneth Oakley, Man the Tool-Maker. As late as the early 1960s, most researchers agreed with famed fossil hunter Louis Leakey that toolmaking was a uniquely human activity.

But with more and more scientific observations of primates, identifying “uniquely human” behavior has been getting harder and harder. A paper in the June Journal of Human Evolution now extends animals’ reach even further toward human abilities, reporting that wild chimpanzees can sequentially craft a set of tools for a single task. Primatologist Christophe Boesch and his colleagues at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, conclude that researchers might have to rethink their whole approach to the cognitive divide between humans and their primate cousins.

It’s not often you see a paper that announces “I was wrong,” especially if you’re reading journals like Science and Nature. But that’s what paleoanthropologist Russell Ciochon of the University of Iowa, Iowa City, says in an essay in this week’s issue of Nature. In a 1995 paper, he and colleagues had trumpeted a two-tooth jaw from the Chinese site of Longgupo as the oldest hominin remains outside of Africa, dated to 1.8 million to 2 million years ago. But no longer. “In light of new evidence from across southeast Asia and after a decade of my own field research in Java, I have changed my mind,” Ciochon writes.


He now thinks the Longgupo specimen, as well as others—chiefly, isolated teeth—from similar Chinese sites belong to a “mystery ape” not on the hominin line. “I’ll probably get some grief from people about this,” Ciochon told me. “But it isn’t a hominid, and so I might as well say so.”

In part, the essay codifies current understanding. In his current papers, Ciochon had stopped referring to the Longgupo discovery, and in recent years few others had accepted the specimens as hominins. The Longgupo teeth are worn, making their identification “equivocal,” explains Ciochon. With additional, less-worn specimens from other localities, he is now convinced that this is a “mystery ape”—or apes—too fragmentary to be named.

“It’s great,” says paleoanthropologist Richard Potts of the Smithsonian Institution in Washington, D.C., after seeing the essay. “He’s backing off from Longgupo as a hominin, which a lot of us have been waiting for him to do.”

Ciochon’s real interest is not in the identity of the Longgupo teeth, however, but in the implications of the absence of hominids from that and other localities. He notes that the “mystery ape” sites are all located in what was once a subtropical forest, which also harbored a giant panda species, gibbons, orangutans, and the giant extinct ape Gigantopithecus. But the first hominin indisputably known in Asia, Homo erectus, is never found in such a subtropical forest environment. Instead, it turns up in more open, savanna-like habitat, like that of East Africa where early Homo evolved, says Ciochon. Longgupo and the other “mystery ape” sites sit in what was once a “vast and ecologically unattractive forest,” for hominins, Ciochon wrote in a recent commentary. He predicts hominid hunters didn't have much success in that environment. As he says in the essay:

H. erectus, it seems from this perspective, hunted grazing mammals on open grasslands, and did not or could not penetrate the dense subtropical forest. In fact, there is no record of early hominins living in tropical or subtropical forested environments in Africa or Asia.

But if the field welcomes the change in status of the Longgupo jaw, researchers such as Potts are not so sure about Ciochon’s paleoenvironmental scenario. Potts contends that East African hominids lived in a mosaic of open areas around swamps and lakes, with some shrubs, bushes, and distant forest. “The idea that Africa was a savanna and Homo erectus followed grasslands into Asia—that’s oversimplified from where we stand.”

Potts emphasizes that early hominids were adaptable. For him, the interesting question is not what was their favorite environment but how did they manage to survive in variable environments. Potts admits that there is “no compelling evidence” of hominids in the Asian subtropical forests in the Pleistocene, “but I wouldn’t rule it out.”

—Elizabeth Culotta

Illustration credit: Russell Ciochon/Nature

June 16, 2009

The Wonders of After Sex

When I sit down to read a scientific paper, I usually brace myself for the worst. I prepare to slog through esoteric, murky language—to have to dig deep to find the buried beauty of science.

But every now and then, you sit down and read a paper that starts like this:

"Picture a pile of freshly cut weeds at the sunny edge of a tropical forest. Metallic green flies dart and circle over it, chasing one another in short dashes. Your eye is caught when a chase ends as one fly grasps another in midair and the pair immediately lands on the pile of weeds. Their genitalia are already coupled, and the male immediately turns to face away from the female. After a few seconds, paradoxically (because he is already securely attached), he begins to court, rhythmically waving his colorful hind legs and tapping the female's abdomen. The courtship continues for a few minutes as the pair remains coupled, and then the flies separate. The female walks down into the pile where she lays eggs (her larvae will feed on the rotting vegetation), while the male rejoins the frenetic chases above the pile."

Why would a male fly wait to court a female until after he has already achieved his evolutionary objective of copulating with her?

The paper is titled Postcopulatory sexual selection: Darwin's omission and its consequences. It was written by William G. Eberhard, an evolutionary biologist at the Smithsonian Tropical Research Institute in Panama, and was just posted online at the Proceedings of the National Academy of Sciences Web site. It offers some wonderfully bizarre examples of the extremes to which evolution reached once sex emerged a couple billion years ago.

Earlier this month, I wrote in Science about the origin of sex. Despite the disadvantages of reproducing with both males and females, sex dominates the animal kingdom and is common among our fellow eukaryotes (plants, fungi, and protozoans). Studies point to several possible benefits that outweigh the cost of sex. Sex may speed up the evolution of adaptations, cleanse our genomes of harmful mutations, or let us fight against parasites more effectively. However sex evolved, it created a new arena in which the evolutionary process could take place. Now reproductive success was not just a matter of surviving and finding enough food. Now it also depended on whether organisms could find a mate.

Darwin recognized this distinctive kind of selection, which he dubbed sexual selection. In his 1871 book, Descent of Man, he argued that males competed with each other for the opportunity to mate with females, and as a result, males had evolved claws, horns, and other weaponry. Darwin also argued that females were attracted to certain males over others, and this preference drove the evolution of gorgeous courtship displays such as the extravagant plumage on some birds.

Over the past 138 years, scientists have discovered a wealth of evidence demonstrating that sexual selection is indeed a powerful force. But it drives evolution in ways that Darwin did not anticipate. In many species, females actually mate with lots of males. And those multiple matings open up yet another arena for evolution. Along with the courtship and battling that goes on before mating, there's an opportunity for lots of strategies for boosting reproductive success after mating.

The underlying logic of postcopulatory sexual selection is simple: Once a male has inserted his sperm in a female, he has not sealed the deal. A female may have the sperm from several males inside of her. There are many strategies that appear to have evolved because they boost a male's reproductive success, from fast-swimming sperm to male genitals that explode after mating, to prevent other males from adding their own sperm.

One of the most intriguing strategies biologists have discovered is when a male courts after the copulation has started. In the case of the flies that Eberhard describes at the start of his paper, it appears that males engage in this after-the-fact courtship so that females will lay eggs immediately after their courtship. If scientists prevent the males from courting during copulation, the female flies fly away without laying any eggs.

Scientists are only starting to test hypotheses about postcopulatory sexual selection, but its effects could turn out to be huge. In fact, it may have bearing on our food supply. Some studies indicate that plants can choose between the pollen of other plants that land on them in order to fertilize their seeds. Plants may even abort fruits that don't come from suitable mates. Such are the unexpected directions in which Darwin's initial ideas have traveled.

Carl Zimmer

Photo: Stefano Baldacci, Wikimedia

June 5, 2009

Darwin's Life in Verse

“I found that his questions were mine, everything from ‘Why is life short?’ to ‘Why do monkeys cry?’ ”

On a visit to Cambridge last week to read her latest work, novelist and poet Emily Ballou offered that reflection on her 5 years researching the life of Charles Darwin. The result, her

emily balloubook The Darwin Poems, attempts to uncover the man behind the grand ideas that spawned evolutionary theory. The book follows the naturalist’s life from boyhood to after his death, with poems slicing through layers of Darwin’s character, exploring how his inquiring mind permeated his life’s work, his relationships, and his loss of faith in God.

“Darwin believed that the mind was a function of the body. So I wanted to talk about Darwin’s … emotional and social life, his love for Emma [his wife] and his kids, as well as how his thoughts appeared to him,” Ballou says.

Ballou, born in Milwaukee, Wisconsin, first “picked up the trail” of Darwin when she moved to Australia, to the small village of Wentworth Falls in the Blue Mountains. Darwin passed through the village in 1836 during a stop on his seminal Beagle voyage—his path in the village is now dubbed “The Charles Darwin Walk.” Ballou would go by the path “nearly every day,” she says, and began to wonder about the naturalist on his journey: “What was he doing? How warm was it? What was he wearing?” she muses.

On a mission to find out more, Ballou traveled to Darwin’s home of Down House in Kent in the United Kingdom and to Cambridge University to scour the notes, journals, and papers he left behind. “It made a difference to see the tools he used, his scribble, the way he circled things and would go back to answer them in another hand,” says Ballou. “It gave a tangible essence to the person.” Ballou enlisted the help of Adam Perkins, curator of scientific manuscripts at Cambridge University, to analyze Darwin’s papers. She also contacted the Darwin Correspondence Project, which archives letters between Darwin and his family, and other scientists of the time, such as botanist Asa Gray.

After “immersing herself” in Darwin’s life, Ballou documented the naturalist’s musings leading up to his theories on the struggle for existence in “To be a seed”:

Late at night he imagined the dispersal of seeds
across seas, could imagine the distances
in the instances of finches
strewn by wind and wing
but how did those fragile seeds swim?
Were they carried in the guts of ducks
or trapped like bubbles in an ice floe
floating until slow snow melt released them?
Did they hook like barnacles to the wood of rafts?
And what of plants? And what of snake eggs
wholly floating, bobbing the waves
to new places? And once there, once born,
once cracked open,
how did one live on entirely foreign islands?
By wits? By chance? By sheer
stubborn determination
to be?

In “Darwin’s Noah,” Ballou ponders how a seasick Darwin on the Beagle voyage may have thought about the journey of Noah’s ark.

sexartSex gives nature much of its spice. Fireflies flash through the night to find mates; a flower’s perfume lures insects to carry pollen to distant partners; male bullfrogs croak to impress females. Currently, biologists understand the molecular nuts and bolts of sex fairly well. But the why of sex is still fairly mysterious. Bacteria don’t have to search for mates; they just grow and divide in two. An aspen tree can simply send out shoots that grow into new trees. No muss, no fuss with finding a partner, fertilizing an egg, and joining two genomes.

Darwin felt the whole subject of sex was "hidden in darkness.” In this month's Origins essay, Carl Zimmer sheds light on sex with his examination of progress since Darwin's day in understanding the "why." Today, scientists use genomics and other 21st century tools to search for answers. They are finding hidden signs of sex in the DNA of supposedly asexual organisms and are tracking the evolutionary impact of sex among living populations of animals and plants. Some use sophisticated mathematical models to assess the conditions under which sex can arise. These efforts are providing new hints about how sex first emerged some 2 billion years ago and about the forces that have made it so widespread. The new studies bolster a handful of hypotheses: Sex may speed up evolution, for example, or it may provide a better defense against parasites. In the past, scientists have focused on just one of these hypotheses at a time, but today many argue that several forces may be at work at once.

—Elizabeth Pennisi

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