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February 2009 Archives

I want to be the rap version of Richard Dawkins.

baba2.jpg—Baba Brinkman lyric

What’s a fan of evolution to do this week when confronted with so many events celebrating Darwin’s 200th birthday? On Monday, for example, one could have been in London for a debate, hosted by our friendly rival Nature, on whether humans are still evolving. What about a London reading of Darwin-related poems by one of his relatives? It would fit with the art theme of this month’s Origins essay, but it wasn’t quite compelling enough, especially when an even more provocative event was taking place here in Cambridge, where Darwin studied. Welcome to the “Devil in Dover and the Rap Guide to Evolution,” a traveling road show sponsored by the British Council and organized by microbiologist Mark Pallen, the author of The Rough Guide to Evolution (and its related blog).

The rain and sleet, and lack of publicity, meant that only a few dozen people filled the cavernous Cambridge University lecture hall. The opening act featured American journalist Lauri Lebo, who covered the 2005 trial in Dover, Pennsylvania, in which parents sued to prevent the school board from forcing the teaching of intelligent design in science classes. Lebo has written a book about the trial, The Devil in Dover, and she and plaintiff Cyndi Sneath discussed how the case ignited a civil war within the small town, with some of the parents even being called atheists by neighbors despite being regular churchgoers. Perhaps Lebo’s most powerful reminiscences concerned how she tried throughout the trial to convince her father, a religious fundamentalist, that the school board was acting dishonorably.

No one had started clapping rhythmically yet, but it was still time to bring on the headline act: Baba Brinkman, a former English literature student and Canadian hip-hop artist whose major claim to fame is his rap take on The Canterbury Tales—hence the boast on his MySpace page that he’s the Geoffrey Chaucer of hip-hop. Lebo herself was anxious to hear the so-called lit-hop artist, noting, “Anyone who can work Australopithecus afarensis into a rap impresses me.”

Down2small.jpgCleaned and dusted, renewed and refurbished, Down House will reopen its doors this Friday (13 February) with a new permanent exhibition on the life and work of its most famous owner: Mr Charles Darwin, Esq.

The exhibition is an interesting mix of old and new, work and leisure. Darwin's study on the ground floor, where he worked for 40 years is full of surprises—Darwin never had a proper desk. He wrote all of his books and correspondence on a board resting on the arms of a chair customized with wheels. Down House's gardens and surrounding fields are restored to their original setting, including the Sandwalk, Darwin's thinking path. The greenhouses where Darwin did his botanical research are once again home to pots and vases of orchids, carnivorous plants and his other botanical favorites.

Down House also opens a window on Darwin’s private life. On the ground floor, next to the study, visitors can see the drawing room where he spent time with his family, the dinning room complete with original Wedgwood china, or the games room where Darwin played billiards with the butler. The top floor of the exhibition has details on his scientific work, including a reconstruction of the Beagle's cabin and a first edition of the On the Origin of Species. Thanks to the Darwin family’s obsession with keeping old things, the exhibition also shows Darwin's medals and awards, his children's toys and drawings, and family photographs. Darwin's personal copy of Karl Marx’s Das Kapital is one of the books on show.

The £1 million investment in the new exhibition and the estate’s restoration should certainly delight visitors but more questionable is whether the improvements will help Down House and its surrounding grounds become a World Heritage site.

February 6, 2009

Extraterrestrial Evolution

Science writer and author of Microcosm: E. coli and the New Science of Life Carl Zimmer wrote the "On the Origin of Life on Earth"  last month. Today he discusses evolution on other worlds.

Imagine you spent your whole life on a tiny island, with only some tortoises and snails to give you a clue to what life was like. You'd be forgiven for failing to imagine a Venus flytrap or an armadillo. Evolutionary biologists are in much the same bind. They are, for the time being, stuck on a planetary island, only able to study life on Earth. While life on Earth takes many forms, every living thing is nevertheless a variation on the common theme of DNA, RNA, and protein. What kind of life, if any—exists on other planetary islands we don't know?

If we do discover life someday on another planet, evolutionary biology would leap to a new level. Biologists would be able to compare how evolution played out on two separate planets. If life began independently on another world and ended up a lot like life on Earth, that might mean that evolution must follow certain rules no matter where on the universe it plays out. Or perhaps evolution has the potential to be a lot weirder than we know, because we're stuck here on our little island of life. The closest place where it makes sense to look for life is Mars. Its surface may have been warm and wet in the past, and puffs of methane discovered in recent years just might be a sign that microbes are still thriving deep under the surface. The best way to see if that's the case is to drill into the Martian soil and find them.

But Chris McKay of NASA warns in this week's Science that in our search for a second biosphere, we may contaminate it with our own. As McKay points out, space scientists were already concerned about contaminating other planets in the 1960s. NASA completely sterilized the Viking Probe that landed on Mars in 1976, but the results of that mission suggested that the Red Planet was so harsh that no life could survive and so fewer protections were necessary. The Mars rovers that we've all watched wandering across the Martian landscape probably brought hundreds of thousands of bacteria with them.

Yet, over the years, scientists have grown more concerned again. The surface of Mars is clearly an awful place for even the hardiest microbe. But if we start drilling down into the ground, we might well be injecting microbes from Earth down into a Martian ecosystem. We unfortunately know all too well what happens when we accidentally introduce species to new places. At worst, the new species becomes invasive and drives native animals and plants extinct. At best, native ecosytems are dramatically altered. Do we have an ethical obligation to protect what McKay called "indigenous biospheres"?

Later this year, a meeting will be held to consider just this question. We do need to take responsibility for our actions, but we also should not forget another lesson of evolution here on Earth: Invasive species don't always need people to deliver them to a new home. Darwin himself first recognized that seeds and eggs can been carried to distant islands on the feet of birds. In space, meteorites may act as interplanetary birds, bringing microbes from Earth to Mars—or perhaps the other way as well. Even if we take every possible precaution, the life we find on Mars may turn out to be invasive after all. It just invaded Mars a billion years ago.

Carl Zimmer

Arizona State University joins in the global celebration of Darwin‘s 200th birthday, and commemorates the 150th anniversary of the publication of On the Origin of Species, with Darwinfest—a celebration of how the expression of radical thinking and scientific and technological enterprise can and has changed the world.

Why does Darwin matter? Arizona State University takes that question to students and the public in Arizona 4 to 13 February with core events that capture how Darwin’s bold thinking has evolved into new understanding about some of the most fundamental questions about humanity and the human spirit, including our origins and life beyond Planet Earth.

See the full calendar of events and information for details.

Events include:

· Origins Symposium (3-6 April)

· The Darwin Distinguished Lecture Series (through November 2009)

· The Future of Evolution Lecture Series (4-25 February)

· Looking for Life: Adventures and Misadventures in Species Exploration (11 February)

· Darwin Days (4-13 February) with a Tea Party and Darwin Look-alike Contest


Margaret Coulombe

Coordinator, ASU Darwinfest.


Arizona State University, Tempe

The origin of art ignites strong passion among the people who study it. Michael Balter, who wrote an essay on the origin of art and symbolic behavior for this week’s issue of Science, offers additional insight into one controversial figure of the paleoart world.


How old is the oldest art? As discussed in my essay, many researchers have given up on chasing after ever-earlier objets d’art in the archaeological record, preferring instead to look for early signs of symbolic behavior—of which art is simply one manifestation.

But one archaeologist who has not given up is Australia-based independent researcher Robert Bednarik.

Credit: F. D'Errico and A. Nowell

In this week's Times Higher Education, Tim Birkhead, a behavioral ecologist at the University of Sheffield in the United Kingdom, ponders why Darwin failed to recognize the importance of female promiscuity among animals and the related phenomenon of sperm competition. In his essay called "Sex and Sensibility," Birkhead writes: 

If Darwin had put two and two together, the study of sperm competition - now a major area of research - might have been launched in 1870 rather than 1970. Why did Darwin ignore the evidence and why did it take a century for others to make the connection?

Birkhead wonders if Darwin was just a Victorian prude or whether having a daughter editing his writing led to some censorship. Birkhead never provides a satisfying answer, but he does offer some thoughts on the impact of Darwin's missed opportunity:

The upshot of all this was that Darwin steered clear of female promiscuity and plumped for female monogamy, an idea that then remained firmly fixed, in biologists' minds at least, for a full century. The significance of female promiscuity only really became apparent in the early 1970s with the realisation that natural selection operated on individuals rather than groups or populations. ...

I don't think Darwin thought this subject through. I don't think he ever thought carefully enough about the reproductive consequences of individual selection. As far as I can see, there isn't a hint of this kind of thinking in his voluminous correspondence. This is curious because the idea of female choice was such an integral (albeit controversial) component of his concept of sexual selection. For Darwin, mate choice simply stopped at copulation.

—John Travis


February 4, 2009

Animal Life's Spongy Origins

Researchers analyzing the chemistry of ancient sedimentary rock in southern Arabia have answered a question that has plagued scientists for more than a century and a half: whether animals appeared on Earth slowly and sporadically or suddenly and spectacularly. A story today on ScienceNOW discusses the rise of Demospongiae, a class that includes modern-day sponges, some 635 million years ago, more than 100 million years before the Cambrian explosion of oxygen-breathing animals. The rocks were chock-full of a protein made only by these sponges.

—Elizabeth Pennisi

In all the celebrations of the 200th anniversary of Charles Darwin’s birth and the 150th anniversary of the publication of On the Origin of Species, it’s easy to forget that when Darwin made his prediction in 1871 that the ancestor of humans arose in Africa, it was an educated guess—he had no evidence from the fossil record. It wasn’t until 1924, in fact, that he was proved correct. That’s when the first skull of a human ancestor was unearthed in Africa: the Taung child, now recognized as a member of Australopithecus africanus, which lived about 3 million to 2 million years ago.

Credit: D. Strait and G. Weber


But even though it was the first hominid recognized from Africa, and many more specimens have since come to light, questions linger about A. africanus, including whether it was our direct ancestor and what it ate. In a study published online this week in the Proceedings of the National Academy of Sciences early edition, researchers take a new look at the familiar face of this species and find that it had the anatomy to be an adept nutcracker.

Paleoanthropologist David Strait of the University at Albany in New York state and his colleagues found that A. africanus evolved jaws, teeth, and a face that would have been particularly good at withstanding large forces on its premolars—precisely the place where humans and other primates crack large objects, such as nuts that are too big to chew with our molars. (Most of us can’t open our mouths wide enough to crack a walnut on our molars comfortably.)

The idea that life arose from RNA got a boost 8 January when researchers reported the creation of RNA molecules that could replicate themselves indefinitely. But the debate over life's beginnings continues. Geochemist George Cody of the Carnegie Institution for Science in Washington, D.C., spoke to Science about a competing view of how life got started called "metabolism first."

In brief, what does the "metabolism first" (MF) argument say?

GC: It's basically that the first living organisms, being autocatalytic, could make entire biochemical assemblages based on carbon dioxide, ammonia, etc. The MF idea is that first you have these chemosynthetic systems, then downstream you have these information-based macromolecules [RNA and DNA], and then, genomic emergence. ...

The problem with the RNA-first world is that whereas RNA chemistry is elegant and functional and now developing critical qualities of self-replication, these experiments are done under very carefully controlled conditions. ... I don't think anyone in the RNA world would propose doing these experiments in seawater.

So what's the evidence for the MF idea?

GC: In the so-called MF camp, one seeks to demonstrate that the natural environment is capable of synthesizing molecular intermediates that lie along the chemical reaction pathways [that break down chemicals and nutrients and produce energy] and that these are superficially similar to extant metabolic pathways.

Basically, you're looking at two different ways of making amino acids. The “RNA firsts” say you have to have purines [nucleotides used in building RNA and DNA] and rely on hydrogen cyanide [HCN] chemistry to make amino acids, and metabolists say you can use reductive animation [a type of redox reaction]. In the lab, we can make amino acids either way; ... for example, we can use transitional metal sulfides to make pyruvate.

When will we know who is right?

GC: The question is what kind of chemistry can you do under the actual geochemistry [conditions on early Earth].

I don't think there's going to be an experiment that resolves things satisfactorily. With continued experimentation at the level of what [Scripps’s Gerald] Joyce did on these systems, things will pile on, and slowly the fog will clear. The veils of time are actually being pulled backward, and we're starting to learn more about the early Earth than we ever dreamed we could have.

The best evidence [for the MF idea] would be to discover that the natural world only has one way of synthesizing [life’s] molecular precursors and that [this] one way looks identical to the real-life system. Then extant metabolism is a primordial pathway, directly connected to the chemistry of the planet.

And if not?

GC: If we find out that the early atmosphere is more like Stanley Miller's idea, with an excess of HCN, then the RNA-first explanation might be more satisfying. We're just not there yet.

—Rachel Zelkowitz