The National Center For Science Education (now at its new ncse.com address) is offering a free pdf of a chapter from my book, The Tangled Bank: An Introduction to Evolution. The chapter, called “Radiations and Extinctions,” is about the two sides of biodiversity. First I look at how biodiversity rises over time (the ascent of the animal kingdom, for example, and the wild exuberance of insects). Then I look at how biodiversity falls, thanks to background extinctions and mass extinctions. And then I take a look forward and see ominous signs for biodiversity’s future, such as corroding oceans.

If you like what you read, you can find out more about The Tangled Bank here. Or you can cut to the chase and get the whole book–as a holiday gift for yourself, or for that special someone who keeps asking you how we can be descended from monkeys if there are still monkeys around.

This spring I blogged about some marvelous videos made by scientists at Brown University in their quest to understand how bats manage to be bats. Turning your hands into membrane-lined wings makes for some awkward trade-offs. Moving around on the ground, for example, gets to be a special challenge. Bats have not simply evolved a single solution to these trade-offs, however. Instead, they’ve explored lots of different compromises. While many bats can only creep awkwardly on the ground, for example,  vampire bats can actually gallop.

Today one of the Brown scientists, Dan Riskin (who has just set up a lab at City College in New York),  published a new study on another extraordinary solution to being a bat. Most bats are well-adapted to roosting by hanging upside-down from long claws. But that is not a universal rule. A few bats have evolved a Spiderman strategy.

These bats have pads on their wrists and ankles that they clamp onto surfaces. The sucker-footed bat of Madagascar (Myzopoda aurita), for example, roosts on  the inner wall of a rolled-up leaf, its head pointed up instead of the usual down.

The Spiderman strategy has evolved many times in animals. Many insects and spiders can cling to walls, as can frogs and gecko lizards. Mammals–not so much. It’s true that many mammals have pads on their hands and feet that add friction to their grip. But sucker-footed bats are among the few mammal species that can really stick to vertical surfaces.

Last year, Riskin and Paul Racey of the University of Aberdeen went to Madagascar to figure out how sucker-footed bats manage this feat. They filmed the bats climbing sheets of glass and brass. As the bats climbed, the scientists tried to drag and pull them around to measure the forces they generated. They came to a surprising conclusion:

The sucker-footed bats of Madagascar, despite their common name, do not actually suck at all.

Suction works in a distinctive way. If you pull a suction cup away from the surface it’s attached to, the cup will strongly resist your efforts. But you can drag the cup along the surface with much less force. When Riskin and Racey tested the bats, they found that the animals could easily be pulled off a surface. Dragging the bats, however, required much more force. In fact, they calculated that a single wrist pad is so strong that it could hold the weight of eight bats.

But there’s one important caveat to the strength of the bat pads. Riskin and Racey measured strong forces when they pulled down on the bats. But when they pushed the bats upwards on a surface, the pads peeled off right away.

These results indicate that a sucker-footed bat sticks to a leaf by gluing its wrists and ankles to it. Riskin and Racey observed that the pads glistened with some kind of fluid. If they tried to dry the pads off, they got wet again before long. It’s possible that this fluid serves as the glue.

While glue (or, more technically, wet adhesion) may be useful for sticking to surfaces, it poses a challenge of its own: once stuck, a bat needs a way to get unstuck. It appears that sucker-footed bats produce a fluid that’s just sticky enough to keep them clamped to the side of a leaf. But they can peel away easily from one end. This technique may explain why sucker-footed bats defy the heads-down rule among roosting bats. If they tried to hold onto a leaf with their heads pointed down, they’d slide off.

The sucker-footed bats were not the only bats to evolve the Spiderman strategy. In Central and South America, there are four species of disk-winged bats (Thyroptera) that can also cling to leaves with pads. Riskin studied disk-winged bats in graduate school and demonstrated that they can form a seal with the disks on the leaves. In other words, they really do suck. Combined with his latest results, the lesson is clear: there’s more than one way to mimic Spiderman when you’re a bat.

Reference: Daniel K. Riskin and Paul A. Racey, “How do sucker-footed bats hold on, and why do they roost head-up?” Biological Journal of the Linnean Society, in press.

Carl Buell, who illustrated many lovely critters for my new book The Tangled Bank, has been adding some new paintings to his Flickr stream. Here’s his holiday ground sloth.

In the caption, he writes: “I’ve certainly drawn and painted enough of them over the past 15 years. Ground sloths are a favorite subject. Too big to hide from the weather, this big guy just hunkered down and slept through the storm. It’s hard to imagine these guys in snow, but Megalonyx ranged as far north as Alaska. Another Card idea that never got off the ground.”

Card or not, I’m glad he’s sharing his handiwork.

This fall I gave a number of talks about the flu, and how evolutionary biologists are helping to make sense of this vexing virus. The University of British Columbia, where I spoke in November, has posted the lecture I gave there on YouTube. For ease of viewing, I’ve embedded all six segments of the talk below.

A few caveats. A couple labels got lost in the conversion of my Keynote to Powerpoint during the preparation of the video. And the numbers I gave for the 2009 H1N1 flu are now a bit out of date. As of this week, the Centers for Disease Control estimate that about 50 million people in the U.S. have come down with the new flu strain since it first hit the country in April. 2009 H1N1 is responsible for just about all the flu so far this year. For the past few weeks it has been subsiding, but it may come back for another whack at us in a few weeks. Meanwhile, there hasn’t been any seasonal flu yet.  Of the people who contracted 2009 H1N1 in the United States, about 10,000 have died. (As I mention in the talk, 36,000 people a year die of the seasonal flu in the U.S.)

And now, without further ado, I give you the flu! (more…)

Hannah Rosa writes: “I am a Science teacher in Central London. My tattoo is part of the Ext-inked project and my endangered species is the narrow bordered bee hawk moth. I decided to sign up for the project as I have worked closely with endangered species in the field as part of my degree studies and understand the importance of closely monitoring and preventing the extinction of these species. I wanted to become a life long ambassador so that I can educate others about the impacts of climate change and other human activites which are threatening hundreds of species in the UK alone.”

(For more pictures from the Ext-inked project, visit Flickr.)

Click here to go to the full Science Tattoo Emporium.

I will be speaking at the University of Massachusetts at Amherst on Friday. It will be my final lecture on evolution this year–the last of nine (whew). They don’t call it the Year of Darwin for nothing…

Here are the details. It’s free and open to the public, so I hope to see you there.

View Larger Map

Did the new Post op-ed by Sarah Palin on global warming get the same multi-layered fact-checking as George Will? Sigh. Deltoid has the details.

My latest podcast is about the ways viruses jump the species fence and give rise to new diseases. I talk to evolutionary biologist Paul Turner, who runs experiments in which viruses evolve to attack new hosts. Plus, how viruses have sex and why.

For more on Turner’s work, here’s an article I wrote about him a few years back.

This is good. Parasites have made it to the Colbert Report. It’s no secret that Stephen Colbert is a modern sort of Mr. Wizard (see his stuff on electromagnetism, microbes, and naming new species of spiders). Now Colbert introduces the nation, nay, the world, to a fish parasite that plays the part of the fish tongue.

I must, however, correct one thing Colbert said. This parasite has been in the news recently thanks to some awesome photographs of a recently caught infected fish. But that doesn’t mean this is the first time anybody ever saw one of these things. Matthew Gilligan of Savannah State University and Richard Brusca of the Desert Museum described the species (not a fish, by the way, but an isopod–think giant lice from hell) back in 1983. And I think I was the first to bring its special horror to the general audience in my book Parasite Rex. Nevertheless, I’m delighted to see Cymothoa exigua hitting the big time (the Colbert Report, at least) at last.

Here’s the clip:

In 2010 I will be teaching two short courses on science writing, one on land and one at sea.

1. At Yale, I will be teaching my fourth annual workshop for science graduate students next month. It consists of two 2-hour sessions. All the gory details, including how to register, are here.

2. This summer I will be back on Appledore Island to teach a week-long science writing class at the Shoals Marine Lab. The picture shows my classroom from summer 2009.

Here’s the course page.

Here’s a post about last year’s class.

Here are some articles the students wrote.

For those beyond college interested in the class, here are some details about taking the course non-credit. Not quite a senior citizen discount, but close…

Long-time readers of this blog will be aware of my Ahab-like obsession with George Will’s global warming errors in the Washington Post–and the Post’s hollow claims to have carefully fact-checked him. I confess that I’ve let a couple of his more recent columns slip by. But I had to stop to blog about his latest take on global warming, in which he jumps on the recently stolen emails among climate scientists. He does a remarkable job of making no sense at all.

In case you haven’t followed it, somebody stole thousands of private emails from the University of East Anglia, where the Climate Research Unit gathers and analyzes climate data. Suspicions are turning to Russian hackers, but there’s been no official word about who did it. The emails ended up on the Internet, and have become a big deal. The University of East Anglia, for example, is investigating both the theft itself and the accusations that have been leveled against UAE scientists as a result.

There’s been a huge amount of stuff published in newspapers and on blogs in the two weeks since the theft. I recommend a piece in Popular Mechanics by a geochemist at Columbia named Peter Keleman. Keleman carefully distinguishes between the possible ethical issues raised in the emails and where this controversy leaves the science of climate change.

Unfortunately, pieces like Keleman’s are not stopping the spread of myths that promote the notion that global warming is a fiction generated by a global (and centuries-old!) conspiracy. For example, US congressmen are claiming that the emails reveal a campaign of suppression that included the firing of the editor of a journal called Climate Research after the publication of a “skeptical” paper. Actually, the editor-in-chief resigned in protest over the paper, which he considered flawed, as well as the publisher’s unwillingness to let him write an editorial about that. (Three other editors resigned at the same time.)

George Will gets on the bandwagon, too, in his latest piece. He tries to fold the news about the email theft into his favorite errors, like the one about how global warming actually “stopped” in 1998, because 1998 was warmer than any other year since. He seizes on one email for his opportunity.

A CRU e-mail says: “The fact is that we can’t account for the lack of warming at the moment” — this “moment” is in its second decade — “and it is a travesty that we can’t.”

Will has put himself in a bind. He loves to tell us that it’s been over ten years that there has been no global warming. In an earlier column, he invoked the World Meteorological Organization as his source, linking to this document (pdf). But the climate record they show (on page 4) is the handiwork of none other than the Climate Research Unit at the University of East Anglia, the epicenter of those wretched climate scientists who, Will assures us, “compound their delusions of intellectual adequacy with messiah complexes.” If you look at analyses produced by other groups, 1998 does not appear as the warmest year on record–instead, it is much more recent. In NASA’s analysis, it’s 2006. The difference lies, in part, in the weather stations included in the analyses.

Will cannot have it both ways. He cannot pretend to speak with authority about the history of climate, but rely on people he considers cranks as authorities on that history.

None other than the Secretary General of Will’s beloved World Meteorological Organization himself wrote to the Post in March to explain why Will’s fixation on 1998 was misleading:

It is a misinterpretation of the data and of scientific knowledge to point to one year as the warmest on record — as was done in a recent Post column ["Dark Green Doomsayers," George F. Will, op-ed, Feb. 15] — and then to extrapolate that cooler subsequent years invalidate the reality of global warming and its effects.

The difference between climate variability and climate change is critical, not just for scientists or those engaging in policy debates about warming. Just as one cold snap does not change the global warming trend, one heat wave does not reinforce it. Since the beginning of the 20th century, the global average surface temperature has risen 1.33 degrees Fahrenheit.

Evidence of global warming has been documented in widespread decreases in snow cover, sea ice and glaciers. The 11 warmest years on record occurred in the past 13 years.

The difference between long-term and short-term patterns was actually at the heart of the email Will quotes. Kevin Trenberth of National Center for Atmospheric Research was writing in reference to a paper (pdf) he recently published in which he wrote that, while the long-term trend in global warming is clear, scientists ought to try to monitor short-term variability more closely to understand its sources. In other words, Trenberth was not  part of a conspiracy to hide some embarrassing facts about the climate history. He was writing about it in public, and proposing ways to move the science forward.

I have no idea if Will was even aware that Trenberth wrote the email, let alone bothered to read the paper to get some context. But a fact-checker definitely should have, and should have raised a host of red flags.

Over the course of the year, Science has published a series of essays in honor of Charles Darwin. I’ve had the pleasure of writing several of them (on the origin of life, the origin of eukaryotes, and the origin of sex). And now I’ve had the pleasure of writing the final one in the series, on the origin of the future–in other words, where evolution goes from here. Check it out. (Plus, if you’re interested, you can listen to a conversation I had about the future of life on Science’s podcast.)