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September 2009 Archives

September 29, 2009

For the Faithful, Eusociality

 by Elizabeth Pennisi

As social as humans are, their cooperative nature pales in comparison to that of ants, bees, wasps, and termites (see hill, left). Colonies of these insects can number in the millions and function seamlessly as “superorganisms.” In their book, The Superorganism: The Beauty, Elegance, and Strangeness of Insect Societies, Burt Hölldobler and E. O. Wilson point out that this way of life makes for very successful living. These insects represent a mere 2% of the insect species yet take up two-thirds of the insect biomass. In tropical rainforests, ants outweigh all the mammals and land vertebrates combined.

Yet the scores of entomologists and evolutionary biologists who have marveled at the efficiency of superorganisms have yet to sort out for sure how superorganisms evolved. True superorganisms are highly eusocial: Typically, one or a few queens lay all the eggs, which are tended to by nonreproductive workers. Their fecundity can be astonishing: In their more than 10-year life span, queens of Atta ants (see right) can produce 150 million daughters, for example. Multiple generations live together; and because workers are sterile, very few conflicts arise, and the colony runs quite efficiently.

Less extreme versions of this lifestyle exist, leading some to suggest that eusociality evolved in stages, starting with a female that set up communal nests with other females, with some forgoing reproduction to help provision and protect the young. A few have suggested that it’s not even that critical that the founding females be all that closely related.

In my Origins essay on cooperation, I  did not touch upon the origin of these truly social insects. But Jacobus Boomsma of the University of Copenhagen, Denmark, has thought extensively about this question and rejects the stepwise progression from cooperative breeding to eusociality, asserting that not just close kinship but also lifetime monogamy is critical to incipient eusociality. Early eusocial species “have a very special form of strict monogamy that has been unappreciated,” he says. This idea has been suggested before, but “Boomsma has performed a valuable service in reviving it and extending it,” says Andrew Bourke of the University of East Anglia, United Kingdom.

Termites mate for life, with a single queen and “king” producing generations of siblings, all equally related to one another. Once in their lifetime, wasps, bees, and ants leave the nest on a mating frenzy, with the queens returning with enough sperm to last the rest of their reproductive years. The consequence of having just one mate for life is that the many generations of offspring are all siblings that on average share half their genes. That number of genes in common is the same as they would have in common with their own offspring should they try to reproduce. Thus, if there is even a small survival advantage to group living, that advantage would be a strong enough selective force to encourage the evolution of sterile castes and true eusociality, Boomsma argues. “When a parent refrains from mating with any additional mates, their offspring are free to stop mating at all,” he explains. However, strict monogamy is rare, particularly over evolutionary time scales, and thus, so is eusociality.

In the late 1950s, Kansas University entomologist Charles Michener suggested that eusociality could arise in one of two ways. By the subsocial route, parents associated with offspring; by the parasocial or semisocial route, females joined forces with their peers in communal settings. Yet even today, that latter scenario lacks any hard evidence, says Boomsma. Such cooperative breeding setups never lead to permanently sterile helper castes; there are too many conflicts of interest. Those conflicts disappear where queens have a brief mating interval and then settle down for a life of reproduction using the sperm acquired during that one fling.

A 2008 phylogenetic analysis of mating systems in ants, bees, wasps, and termites supports Boomsma’s hypothesis. In 2008, William Hughes of the University of Leeds, U.K., and his colleagues looked deep into the past of 267 eusocial bees, wasps, and ants. They found ancestors of these lineages of eusocial insects were monogamous. Only later, once sterile castes had evolved, have some groups begun to mate more than once they reported.

To hear more about Boomsma’s hypothesis, listen to a talk he gave earlier this year at the Evolution of Society meeting sponsored by the Royal Society.


Credits: (termite hill) Summi; Atta ants: Adrian Pingstone

The Hollywood Reporter last week noted that Creation had finally been picked for the U.S. market. Now Americans can decide thumbs-up or thumbs-down.

September 24, 2009

Math Tribute to Darwin

by Elizabeth Pennisi

As a year of meetings and celebrations of Darwin anniversaries winds down, mathematicians are planning their own Darwin fest: "The Mathematics of Darwin's Legacy" (23 to 24 November 2009 in Lisbon, Portugal).The legacy begins with Darwin, even though he was no mathematician and took only a qualitative approach to natural history. As Warren Ewens of the University of Pennsylvania will point out at the meeting, Darwin was quite hampered by the lack of knowledge at the time about Mendelian genetics. Offspring were instead thought to be “blends” of the parents’ traits—a process that was problematic because it should lead to the homogenization of traits and the loss of that same variation needed for evolution to occur.

But Darwin’s view that systems could evolve without the guidance or interference of a planner “has the generality and power of a mathematical idea,” says theoretical biologist Peter Jagers of the University of of Gothenburg, Sweden. And within a few decades, mathematics became a boon to the ideas promoted by the father of evolution.

“Once the Mendelian hereditary system [came into] use, mathematics becomes inevitable,” says Ewens. Quantitative methods quickly showed that variation is preserved in offspring.

Throughout the past century, mathematicians have helped promote a better understanding of evolution. In the early 20th century, mathematically minded biologists founded population genetics and put modeling on a firm footing in evolutionary biology. In the 1960s, another set of equations helped explain how cooperation could evolve, the subject of a recent Origins essay.

“There is an increasing community of applied mathematicians working on problems inspired by biology and, in particular, problems related to the theory of evolution,” says meeting organizer Fabio Augusto da Costa Carvalho Chalub of the Universidade Nova de Lisboa, Portugal. And more biologists want to take a mathematical approach to their work. “Our intention is to put these two communities in closer contact.”

September 22, 2009

When Darwin Met a Neandertal


by Michael Balter

GIBRALTAR—The first known Neandertal skull, left, was discovered here in 1848, and some of the last Neandertals may also have taken refuge in Gibraltar’s caves before they finally went extinct about 30,000 years ago. So Clive Finlayson of the Gibraltar Museum organizes a meeting here every few years on the evolution of Neandertals and other ancient humans.

This year, one presentation detailed the links between Charles Darwin himself and that first skull, which was found by workmen at Forbes’ Quarry on the north face of the Rock of Gibraltar. But its significance was not understood until sometime after 1856, when miners working in Germany’s Neander Valley discovered a partial skull and other bones.

Darwin was long interested in the Gibraltar skull, which he recognized as an ancient human, although many years passed before he got to see it. The circumstances of this historic encounter between Darwin and a Neandertal were described at the meeting by Alex Menez, a biologist and science historian at the Gibraltar Museum. Menez mined the 14,500 letters written by and to Darwin available online as part of the Darwin Correspondence Project maintained by Cambridge University and the American Council of Learned Societies. He found that although Darwin never visited Gibraltar, he had a keen interest in discoveries there on Mediterranean plant life and geology, as well as a fascination with the skull.

The Gibraltar skull was first presented in Great Britain in September 1864, to a meeting of the British Association for the Advancement of Science. Darwin had hoped to go, but illness kept him away. So shortly before the meeting his friends Charles Lyell, the famous geologist, and Hugh Falconer, a famed anthropologist, brought the skull to the home of his sister-in-law in London, where Darwin was staying at the time. Darwin’s reaction is recorded simply in a 1 September 1864 letter to his close friend, botanist Joseph Hooker: “F[alconer] brought me the wonderful Gibraltar skull.” As Menez put it: “We can imagine Darwin holding the skull, peering enthusiastically at its well-marked brow ridges, his own eyes beneath brow ridges that were themselves significantly larger than those of most people!”

Exactly what Darwin made of the skull is not known, however. He didn’t mention the Gibraltar or Neander skulls at all in On the Origin of Species and refers to them only fleetingly in the 1871 Descent of Man. Perhaps, as some speakers at the meeting suggested, he deliberately avoided speculating about them out of reluctance to stir up controversy about human evolution.

PHOTO CREDIT: Clive Finlayson, The Gibraltar Museum

by John Travis

Creation, the star-studded biopic of Charles Darwin, opens later this week in the United Kingdom, and scientists and science educators have been bemoaning the fact that the film doesn’t yet have a U.S. distributor. Although the production company behind the movie has hinted that a U.S. deal is imminent, some have suggested that the movie, in which fellow naturalist Thomas Huxley joyfully tells Darwin he has “killed God,” is too controversial to sell in America, where disbelief of the theory of evolution remains strong among religious conservatives. Eugenie Scott, executive director of the National Center for Science Education, even sent out a letter encouraging a lobbying effort on the film’s behalf. Noting that she had seen and liked the movie, she wrote: “But I worry (and can only speculate) that the difficulty the producers have had getting a US distributor might reflect corporate nervousness about getting an audience for a topic that deals with evolution. 'Creation' is definitely honest about Darwin's religious skepticism. The big middle part of America that we are aiming at will see a complex character with a lot of reasons to doubt the Christian pieties spouted by the minister character in the movie.”

From a cinematic standpoint, however, it’s not clear that Creation deserves the fervent support of the scientific community. In a nutshell, the movie, based on the book Annie’s Box, depicts a midlife Darwin at home in an idyllic English village dealing with the grief of his daughter Annie’s recent death and trying to write On the Origin of Species, the book that would make him a household name. The film has many historical inaccuracies, but that’s to be expected when filmmakers condense a life into a few hours. Creation’s larger problem stems from the decision to focus on a narrow slice of Darwin’s life, arguably one of the least interesting.

According to the movie’s press material, the film portrays the “powerful story of Charles Darwin and the single most explosive idea in history. … In Creation, the battleground is a man’s heart. Torn between his love for his deeply religious wife and his own growing belief in a world where God has no place, Darwin finds himself caught in a struggle between faith and reason, love and truth.” What this ultimately means is that the movie centers on why Darwin was so slow to publish On the Origin of Species, attributing the delay to his illness, his grief, and his desire not to offend the world, or at least his wife. In other words, instead of dramatizing how Darwin traveled the world and arrived at the most explosive idea in history, Creation is ultimately about the world’s biggest case of writer’s block.

That’s a flawed choice, especially when one has stars as talented as Paul Bettany and Jennifer Connelly playing the Darwins. Married in real-life, the pair bring a natural, loving chemistry to the well-acted roles (Connelly may need to seek out more ambitious and different roles, however; here she plays the beautiful, supportive wife of a tormented genius who sees things, an almost identical role to the one she had in A Beautiful Mind, the story of Nobel prize-winning mathematician John Nash).  And there’s little question that Creation is beautifully and at times inventively filmed. One scene nicely exploits computer-generated graphics to show how the tragedy of death in nature is necessary for life to continue.

The film periodically tries to suggest the scientific methodology Darwin used, although highlighting his grisly preparation of pigeon skeletons may more likely turn some viewers' stomachs than explain his study of natural variations within species. As Scott notes, the film does reveal a more “complex” picture of Charles Darwin, one that may shock those used to the genius stereotype. The film depicts the celebrated naturalist as a young man so ravaged by depression and illness—whether real or imagined remains a matter of debate; a recent book labels Darwin a hypochondriac—that he avails himself of a quack Victorian water remedy. He’s also seen taking unknown medicinal drugs and hallucinating the ghost of Annie, with whom he discusses his doubts and to whom he relates some of his life’s adventures and scientific undertakings. For example, one interlude shows Darwin studying a captured orangutan, an episode that presumably helped lead to his book The Expression of the Emotions in Man and Animals. But given that he’s telling stories to an apparition, it’s hard for viewers to evaluate how these tales allowed Darwin to form his pioneering ideas. And given that the ghost itself is a creation of the filmmakers’ minds, some viewers may wonder if they can trust the veracity of anything in the movie. As for the topic of science and religion, the movie’s approach would please Richard Dawkins in that it doesn’t offer a middle ground in which one can believe in both evolution and God. Such a compromise would ruin the drama of Darwin’s struggle it seems.

What’s missing in Creation is enough insight into what enabled Darwin to bring together disparate information into a powerful story of how nature works. His daughter is bright and insatiably curious, and presumably a proxy for Darwin the researcher, but the father offers little evidence of being a fountain of brilliant insights. After all, in the movie, his theory is already a fait accompli; he just needs to write it up for publication. While much of the movie is about Darwin trying to get past his grief and illness, in the end it’s only the threat of competition—a letter from Alfred Russell Wallace—that forces him to overcome his writer’s block. And then the filmmakers would have you think that Darwin allowed his wife to decide whether the work should be published. One wishes the script had gone through a few more generations of evolution.

Creation trailer:

by Elizabeth Pennisi

In my essay, On the Origin of Cooperation, I describe experiments in which people are asked to play computer games that help reveal our cooperative tendencies, and I discuss other studies involving the use of microbes to get at the basic principles of working together. But Laurent Keller has gone a step further to work out details of social interactions. An evolutionary biologist at the University of Lausanne, Switzerland, Keller and his colleagues use evolving robots in experiments looking at the evolution of communication, an essential and complex ingredient of cooperation. The robots help him address questions that cannot be addressed through his studies of ants.

image The 15-centimeter-diameter robots (see left) can move in all four directions, like tanks, and are rimmed with LEDs that can emit blue light either randomly or under control of a neural network, depending on the experiment. Each has an omnidirectional camera that sees red and blue light, as well as downward-facing infrared sensors that can distinguish gray from black. The robots are tasked with finding “food,” which emits red light. “Poison” also emits red light and can be distinguished only from up close, when the infrared sensors are able to detect a black paper circle under the poison—the food sits on a gray circle. As the experiments begin, robots flash blue when they find food, a signal others can tap into to locate the food as well

The robots have “brains” and “genomes.” The brains are the software running on onboard computers, with neural networks consisting of 10 “sensory neurons" that convey what the camera and sensors perceive to “activation neurons" that make the motors turn and that light up the LEDs. There are 33 connections in all, with different strengths, each determined by a “gene.”

The researchers tested 100 colonies, each with 10 robots, in a 300-square-centimeter arena with food at one end and poison at the other. (See movie.) The robots got points for detecting and staying by food or lost points for targeting poison. Not everyone could fit by the food, so there was some jostling for position.

Using that system, the researchers scored each robot’s fitness and took the average of the colony's members to assess the colony’s fitness. Depending on the specific test, the researchers selected a subset of the best robots or the best colonies, tweaked their "genes," and ran the experiments again—up to 500 generations' worth. In some cases, they created groups of “related” robots—all with the same “brains”—to assess the affect of kinship on the social dynamics. They wanted to know what behaviors evolved when competition for food was between relatives versus between nonrelatives.

Over time, robots evolved when and where they emitted blue light, and they came to associate high-blue-light areas with food. Foraging efficiency increased, particularly in the highly related robots chosen from the best colonies, Keller and his colleagues reported in 2007. “Reliable communication evolves either when individuals in a group are highly related or when there is increased competition between groups, and so reduced competition between individuals,” explains Keller’s collaborator Sara Mitri.

In a second series of experiments, the researchers focused on “unrelated” robots selected for their individual fitness. Cooperation theory suggests that unrelated individuals have less motivation to share information and thus “one would expect unreliable communication to evolve,” Mitri explains. After 52 generations, the robots were much less likely to emit blue light by food and instead tended to light up around the poison, Keller and colleagues reported 15 September in the Proceedings of the National Academy of Sciences.

But the researchers also discovered that some robots continued to light up at the food source, even after 500 generations. It seems that once the meaning of the blue light became ambiguous, few enough robots were attracted that competition for food diminished to the point that there was little selection against having the blue light on at the food source, they reported. The net result: individual variation in light production and responses, says Keller. That parallels what is seen in animals: variable communication strategies.

The robots are allowing us to address questions that cannot be answered with real organisms, says Keller. With respect to the evolution of communication, “there are no fossils allowing us to study how it evolved, and it is not really amenable to experimental evolution.”

Photo credit: Sara Mitri and Walter Karlen

Movie credit: Stéphane Magnenat, Matthieu Bontemps, and Kevin Frugier.

by Michael Balter

In 1984, a team led by Allan Wilson of the University of California, Berkeley, made scientific history: It published the first partial sequences of ancient mitochondrial DNA (mtDNA), from a museum specimen of the quagga, a zebralike animal that had gone extinct almost exactly 100 years before. Thus was born the field of paleogenetics, which celebrates its 25th anniversary this year. Over that quarter of a century, ancient DNA studies have opened new doors to our understanding of human evolution, tracked ancient diseases and the spread of farming, and unraveled the complex phylogenies of woolly mammoths and the bear family. But along with the triumphs have come setbacks and occasional disasters, as paleogeneticists have discovered to their chagrin how easily ancient DNA samples can become degraded and contaminated with modern DNA, giving rise to erroneous and misleading conclusions.

At her opening talk to an ancient DNA meeting this week in Paris,* Eva-Maria Geigl of the Jacques Monod Institute in Paris toured this tumultuous history. Geigl, who organizes an international meeting of ancient DNA experts in Paris every 3 years, pointed out that the field had a “tormented youth.” Just 3 years after extracting mtDNA from the quagga, Wilson’s team discovered that some of its sequences had undergone chemical alteration after the animal died, complicating attempts to figure out how closely related the extinct animal was to living horses and zebras. And in 1994, the claims of a research team to have sequenced dinosaur DNA—later discovered to be human contamination—nearly led to the premature death of paleogenetics. “DNA damage and DNA contamination almost killed the field,” Geigl said.

geiglpicture2 Happily, paleogenetics survived these early setbacks, as ancient DNA leaders began insisting on more rigorous standards. Among them were aseptic methods of excavation, as shown at left, to be sure that researchers did not contaminate samples with their own DNA, as well as laboratory controls to minimize the amplification of modern DNA. As a result, Geigl says, paleogenetics was able to regain its credibility, as shown by the successful extraction of DNA from medieval plague bacteria, extinct cave bears, early samples of domesticated cattle, pigs, maize, and wheat, not to mention Neandertals, one of the field’s greatest triumphs. After the first complete sequencing of mtDNA, from two species of moa (extinct flightless birds) in 2001, it was only a matter of time before ancient DNA researchers would turn to completely sequencing both the mtDNA and nuclear DNA of Neandertals and begin to solve that extinct hominin’s genetic relationship with modern humans once and for all.

Nevertheless, as researchers carry out ever more ambitious and sophisticated ancient DNA projects, the problems that plagued the field in its early days could threaten it again, Geigl said. This is especially true for paleogenetics studies involving poorly preserved DNA samples, such as those of the first domesticated cattle and pigs in the Near East, and where dry conditions result in poor DNA preservation. Geigl pointed out that many reagents used in molecular biology labs are prepared using products such as gelatin and bovine serum albumin, which derive from cattle and pigs and so contain traces of cattle and pig DNA. In a study carried out by her lab, Geigl reported, 13% of 1170 “blank” control samples were contaminated with bovine and porcine DNA. Another source of contamination came to light during forensic investigations into the 15-year career of an alleged serial killer called “The Phantom of Heilbronn,” who supposedly left her DNA at dozens of crime scenes across Europe. It turned out, Geigl reminded the audience, that the DNA actually came from a woman who worked in a cotton swab factory and had contaminated the swabs—used to collect DNA samples—with her own genetic material.

The answer to these problems, Geigl concluded, lies in new and improved techniques to decontaminate DNA samples before they are amplified and sequenced, some of which her own research team is currently working on. If they work out, paleogenetics can be sure of many more birthdays to come.

*Ancient DNA: From mitochondrial to nuclear DNA, from the evolution of populations to the selection of characters—25 years of paleogenetics, Paris, France, 14-16 September.


Photo credit: Courtesy of Eva-Maria Geigl

September 11, 2009

Darwin and Dance

by Virginia Morell

Birds are noteworthy not only for their wit, charm, and sartorial splendor but also for their great dancing. So, for its contribution to this year’s Darwin celebrations, London’s Rambert Dance Company is putting on a bird-inspired show.

The company has the ideal scientific adviser: Nicola Clayton, an expert on the cognitive talents of jays and crows at the University of Cambridge and a lifelong dancer. Clayton helped the company’s artistic director, Mark Baldwin, come up with a program that she calls a “distillation of Darwinian ideas about evolution, particularly sexual selection.” One dance, for instance, is inspired by the elaborate displays of the six-plumed bird of paradise. In the wild, males inflate “a tutu” of feathers, then vigorously shake their heads and necks while sliding across a stage—all while being critically observed by a gallery of females. “The males are so constrained in their movements by female choice that it’s comical,” says Clayton. Other dances in the program evoke blue manakins and bee hummingbirds.

The show, titled The Comedy of Change, runs 16–19 September at the Theatre Royal in
Plymouth and 3–7 November at Sadler’s Wells in London.

University of Cambridge has produced a video about Clayton's research and the dance.


by John Travis


On Monday, London’s Natural History Museum (NHM) will formally open its new Darwin Centre with a launch ceremony that will be attended by official and unofficial English royalty—HRH Prince William of Wales and Sir David Attenborough, the celebrated naturalist and TV host whose name is bestowed on a multimedia studio in the center. The glassed addition to the museum has drawn attention mostly for the massive “Cocoon,” an 8-story-tall oblong interior structure that will house the museum’s famous plant and insect collections—more than 20 million specimens. NHM's original Victorian building is now a landmark piece of architecture, notes Michael Dixon, director of the museum, and with the Darwin Centre, “we wanted to make an equally impressive statement about the future of the museum.” From a scientist’s perspective, the Cocoon is more than eye-catching; it’s central to the museum’s efforts to provide a more modern collection facility with improved environmental controls. The new Darwin Centre also significantly upgrades the lab facilities for NHM’s scientists and the thousands of visiting researchers who come to study the collections. And as with many new science museums, the Darwin Centre provides the public with more opportunities to watch scientists in action. “Our scientists have traditionally worked behind closed doors; … now, for the first time, we’re metaphorically throwing those doors open,” says Dixon.


September 4, 2009

Join Darwin on Facebook

In late January, New York-based internet consultant Phil Terry made a pitch on Facebook for members to post a Happy Birthday Darwin message. By 12 February, more than 200,000 members had signed on, far exceeding his expectations, he said. Since then, he's been shooting to make an even bigger splash. The goal is to have 1 million Facebook members by 24 November celebrating the 150th anniversary of the darwin150publication of Darwin's seminal book, On the Origin of Species.

Within a week of setting up the Facebook campaign, Terry started a Web site, Darwin150, complete with Tweets. Self-described as a "grassroots and scrappy" initiative "with a sense of humor,"  the project is run by volunteers with no funding other than in-kind contributions from organizations such as National Geographic. Yet it has set up a lecture series that will be webcast live. The series begins 16 September and runs through 24 November, with speakers that include Harvard University's E.O. Wilson and other biology luminaries.

"This series is unique in both the medium and the audience," says evolutionary biologist and author Sean Carroll of the University of Wisconsin, Madison, who has been active in Darwin celebrations across the globe and is involved in making a TV documentary on evolution. "It will be interesting to see its reach and the make-up of the audience."

Right now, the Facebook campaign is 750,000 members short. But, says So Young Park, head of the volunteer marketing team, "We are confident that we'll make our goal" and are expecting exponential growth in the days leading up to the anniversary. Go here to join.

—Elizabeth Pennisi

Image: The Darwin 150 Project