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Corante Blogs examine, through the eyes of leading observers, analysts, thinkers, and doers, critical themes and memes in technology, business, law, science, and culture.

The Press Will Be Outsourced Before Stopped

Vin Crosbie, on the challenges, financial and otherwise, that newspaper publishers are facing: "The real problem, Mr. Newspaperman, isn't that your content isn't online or isn't online with multimedia. It's your content. Specifically, it's what you report, which stories you publish, and how you publish them to people, who, by the way, have very different individual interests. The problem is the content you're giving them, stupid; not the platform its on."
by Vin Crosbie in Rebuilding Media

Travels In Numerica Deserta

There's a problem in the drug industry that people have recognized for some years, but we're not that much closer to dealing with it than we were then. We keep coming up with these technologies and techniques which seem as if they might be able to help us with some of our nastiest problems - I'm talking about genomics in all its guises, and metabolic profiling, and naturally the various high-throughput screening platforms, and others. But whether these are helping or not (and opinions sure do vary), one thing that they all have in common is that they generate enormous heaps of data.
by Derek Lowe in In the Pipeline

Disrobing the Emperor: The online “user experience” isn't much of one

Now that the Web labor market is saturated and Web design a static profession, it's not surprising that 'user experience' designers and researchers who've spent their careers online are looking for new worlds to conquer. Some are returning to the “old media” as directors and producers. More are now doing offline consulting (service experience design, social policy design, exhibition design, and so on) under the 'user experience' aegis. They argue that the lessons they've learned on the Web can be applied to phenomena in the physical and social worlds. But there are enormous differences...
by Bob Jacobson in Total Experience

Second Life: What are the real numbers?

Clay Shirky, in deconstructing Second Life hype: "Second Life is heading towards two million users. Except it isn’t, really... I suspect Second Life is largely a 'Try Me' virus, where reports of a strange and wonderful new thing draw the masses to log in and try it, but whose ability to retain anything but a fraction of those users is limited. The pattern of a Try Me virus is a rapid spread of first time users, most of whom drop out quickly, with most of the dropouts becoming immune to later use."
by Clay Shirky in Many-to-Many

The democratisation of everything

Over the last few years we've seen old barriers to creativity coming down, one after the other. New technologies and services makes it trivial to publish text, whether by blog or by print-on-demand. Digital photography has democratised a previously expensive hobby. And we're seeing the barriers to movie-making crumble, with affordable high-quality cameras and video hosting provided by YouTube or Google Video and their ilk... Music making has long been easy for anyone to engage in, but technology has made high-quality recording possible without specialised equipment, and the internet has revolutionised distribution, drastically disintermediating the music industry... What's left? Software maybe? Or maybe not."
by Suw Charman in Strange Attractor

RNA Interference: Film at Eleven

Derek Lowe on the news that the Nobel Prize for medicine has gone to Craig Mello and Andrew Fire for their breakthrough work: "RNA interference is probably going to have a long climb before it starts curing many diseases, because many of those problems are even tougher than usual in its case. That doesn't take away from the discovery, though, any more than the complications of off-target effects take away from it when you talk about RNAi's research uses in cell culture. The fact that RNA interference is trickier than it first looked, in vivo or in vitro, is only to be expected. What breakthrough isn't?"
by Derek Lowe in In the Pipeline

PVP and the Honorable Enemy

Andrew Phelps: "Recently my WoW guild has been having a bit of a debate on the merits of Player-vs.-Player (PvP) within Azeroth. My personal opinion on this is that PvP has its merits, and can be incredible fun, but the system within WoW is horridly, horribly broken. It takes into account the concept of the battle, but battle without consequence, without emotive context, and most importantly, without honor..."

From later in the piece: "When I talk about this with people (thus far anyway) I typically get one of two responses, either 'yeah, right on!' or 'hey, it’s war, and war isn’t honorable – grow the hell up'. There is a lot to be said for that argument – but the problem is that war in the real historical world has very different constraints that are utterly absent from fantasized worlds..."
by Andrew Phelps in Got Game

Rats Rule, Right?

Derek Lowe: "So, you're developing a drug candidate. You've settled on what looks like a good compound - it has the activity you want in your mouse model of the disease, it's not too hard to make, and it's not toxic. Everything looks fine. Except. . .one slight problem. Although the compound has good blood levels in the mouse and in the dog, in rats it's terrible. For some reason, it just doesn't get up there. Probably some foul metabolic pathway peculiar to rats (whose innards are adapted, after all, for dealing with every kind of garbage that comes along). So, is this a problem?.."
by Derek Lowe in In the Pipeline

Really BAD customer experience at Albertsons Market

Bob Jacobson, on shopping at his local Albertsons supermarket where he had "one of the worst customer experiences" of his life: "Say what you will about the Safeway chain or the Birkenstock billionaires who charge through the roof for Whole Foods' organic fare, they know how to create shopping environments that create a more pleasurable experience, at its best (as at Whole Foods) quite enjoyable. Even the warehouses like Costco and its smaller counterpart, Smart & Final, do just fine: they have no pretentions, but neither do they dump virtual garbage on the consumer merely to create another trivial revenue stream, all for the sake of promotions in the marketing department..."
by Strange Attractor in Total Experience

The Guardian's "Comment is Free"

Kevin Anderson: "First off, I want to say that I really admire the ambition of the Guardian Unlimited’s Comment is Free. It is one of the boldest statements made by any media company that participation needs to be central to a radical revamp of traditional content strategies... It is, therfore, not hugely surprising to find that Comment is Free is having a few teething troubles..."
by Kevin Anderson in strange
In the Pipeline: Don't miss Derek Lowe's excellent commentary on drug discovery and the pharma industry in general at In the Pipeline

The Loom

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June 21, 2004

Taking the Plunge

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Posted by Carl Zimmer

We like to think of boundaries as being clear-cut borders, but at least in the biological world they generally turn out to be fuzzy zones of change. The line between land and sea is my own favorite example. Last summer my wife and I would sometimes take our oldest daughter Charlotte to the beach. At the time she was a year old and refused to put her toe in the water. This summer she heads straight in, but only about up to her knees. She runs back out and goes back in, repeating the circuit a few dozen times. Next year, I still expect to see her chin above the water line. In her own tadpoling way, Charlotte is reenacting an evolutionary journey taken many times by her fellow mammals--the evolutionary transition back to the water.

These treks have something profound to say about biological change--how life can start out exquisitely adapted to one world and then eventually become adapted just as exquisitely to an utterly different one. Before creationists began marketing bacterial flagella and other examples of intelligent-design snake oil, they loved to harp on the transition from land to sea. Who could possibly believe the story those evolutionary biologists tell us, of a cow plunging into the sea and becoming a whale? And it was true, at least until the 1980s, that no one had found a fossil of a whale with legs. Then paleontologists working in Pakistan found the fossil of a 45-million year old whale named Ambulocetus that looked in life like a furry crocodile. Then they found a seal-like whale just a bit younger. Then they found tiny legs on a 50-foot long, 40-million year old whale named Basilosaurus. I wrote about these discoveries and others like them in my first book, At the Water's Edge, in 1998. I'm amazed at how the fossils have continued turning up since then. Paleontologists have found goat-like legs on a dog-sized whale that lived 50 million years ago, known as Pakicetus. They've found other whales that may have been even more terrestrial than Pakicetus, and many others that branch off somewhere between Pakicetus and Basilosaurus. In the latest review of fossil whales, the evolutionary tree of these transitional species sports thirty branches.

All these discoveries have apparently made whales unsuitable for creationist rhetoric. Yes, you can still find some pseudo-attacks on the fossils, but you have to look hard. The more visible creationists, the ones who testify at school board meetings and write op-eds for the Wall Street Journal, don't bring up whales these days. The animals apparently no longer serve the cause. It's hard to distract people from evidence when it can kick them in the face.

Whales, moreover, were not the only mammals that moved into the water. Seals, sea lions, manatees, and other lineages evolved into swimmers as well, and paleontologists are also filling in their fossil record. It's fascinating to compare their invasions, to see how they converged on some of the same strategies for living in the water, and how they wound up with unique adaptations. The June issue of The Journal of Vertebrate Paleontology has two papers that shed light on one of the weirdest of these transitions--a transition, moreover, we know only from fossils. The animals in question were sloths.

That's right--I'm talking about the sort of animals that hang from trees by their three toes. Sloths may seem an unlikely choice for a sea-going creature; if you threw one of these creatures in the water, I'd imagine it would sleepily sink away without a trace. I've never hurled a three-toed sloth myself, so I can't say for sure. But the sloths alive today are actually just a vestige of a once-grand menagerie that lived in North and South America. Many species prowled on the ground, growing as tall as ten feet. And one lineage of these giant sloths that lived on the coast of Peru moved into the ocean.

In 1995 Christian de Muizon of the National Museum of Natural History in Paris and his colleagues announced the discovery of sloth fossils in Peru dating back somewhere between three and seven million years. The rocks in which they found the bones had formed in the sea; the same rocks have yielded other ocean-going creatures including fish, sea lions, and weird dolphins with walrus-like tusks. The sloths, de Muizon concluded, were aquatic as well. Terrestrial sloths have much longer lower leg bones than upper ones, but the Peruvian sloths had reversed proportions. Manatees and otters also have reversed legs, which suggests that the sloths' limbs were adapted for powerful swimming strokes. The front of their skull was manatee-like as well: its jaws extended out well beyond its front teeth, with a rich supply of blood vessels. Like manatees, de Muizon argued, the sloths had powerful muscular snouts they used to root out sea grass.

In their initial report, the paleontologists dubbed the fossils Thalassocnus natans. But it was already clear that they might have more than one species on their hands. In the years since, they've dug into the Peruvian rocks and found hundreds of sloth fossils, which they have been carefully studying and comparing. The new papers are not the last word on Thalassocnus, but the sloths are already shaping up as a great illustration of a transition to the water.

Instead of a single species, de Muizon's team has now identified at least five. They lived, respectively, seven to eight million years ago, six million years ago, five million years ago, three to four million years ago, and, finally, 1.5 to three million years ago. The earliest species look more like ground sloths on land, while later species show more adaptations to the water. For example, the radius, one of the lower bones of the foreleg, became much broader. The change--which can also be seen on sea lions--allowed the forelegs deliver a better swimming stroke. The teeth become less like those of ground sloths, adapted for browsing on leaves and assorted vegetation. Instead, they became adapted for full-time grazing. The coast of Peru is a bone-dry desert with nothing to graze on, and so the only thing to graze on would be sea grass.

The sloth skull changes as well. Both the upper and lower jaws stretch out further and further. From the oldest species to the youngest, the distance from the front teeth to the tip of the jaw nearly doubles. At the same time, the entire skull became stronger, to withstand the forces involved in tearing sea grasses from the sea floor. And finally, bones in the palate evolved to support muscles that could keep the digestive tract separate from the sloth's airway--something important when you're feeding underwater.

The changes documented in these fossils suggest that the earliest Thallassocnus sloths eked out an existence on land along the Peruvian shore. In a bleak desert, the sea grass that washed up on the beach would have been like manna. De Muizon and his colleagues have found another clue in the early sloths that supports this beach-comber hypothesis: their teeth bear scrape marks that suggest they were getting a lot of sand in their mouths; later sloths show no such marks. Over five million years or so, the sloths evolved adaptations that allowed them to move further and further out into the water, to feed on sea grass beds. Natural selection would have put a strong premium on these adaptations, since they would let sloths graze in lush underwater forests rather than pick through sandy flotsam and jetsam on the beach.

De Muizon's group have yet to sort out all the differences throughout the entire skeletons of all five species. We'll have to wait for those papers. But there's enough in print now to raise some interesting questions. In whales, seals, and manatees alike, their arms and hands became flippers--stubby, webbed, fin-like limbs. Thalassocnus still had big, long-clawed fingers on its hands. De Muizon proposes that they would have enabled the sloths to hold onto rocks to stay submerged as they fed on sea grass. Manatees don't need to do this because their bones are especially dense; the sloths had not yet acquired this adaptation. It seems that Thalassocnus only traveled part of the way down the road to a marine life before they became extinct.

Why they became extinct (as opposed to manatees, for example), is also intriguing. Did something happen 1.5 million to 3 years ago that ruined their home? Perhaps the coastal waters off Peru became too cold. If the sloths had spread further along the coast, they might not have been so vulnerable. Other mammals moved into the water at very restricted sites as well. For their first few million years or so, whales could only be found off the coast of Pakistan. If some Indian volcano had blanketed the neighborhood in ash, we might never have known what a whale looks like.

UPDATE Monday June 21, 7 pm: PZ Meyers has put photos of one of the skulls on Panda's Thumb

Comments (11) + TrackBacks (0) | Category: Evolution


1. John Wilkins on June 21, 2004 07:37 PM writes...


Modern sloths can and do swim, hurled or not. The Amazon Basin floods each year and sloths have to swim to get from tree to tree. They aren't fast, but they can do it. Unfortunately for them, so too do jaguars...

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2. Rob Feightner on June 21, 2004 08:50 PM writes...


I have followed the science press on the wolf- or dog-like predecesors of whales and aquatic mammals to the extent that time permits.

I am often amazed, but should not be, of the arguments creationists and so-called intelligent design propogandists use to promote their positions. The more their mythology is eviserated, the more they fractionate their arguments. (I used this argument in a legal case about 15 years ago. The more our arguments defeated those of opposing counsel, the more they split the legal flagella).

So I offer this mostly unrelated anectdote to give a little back to this informative and intellectually invigorating site.

Rob Feightner, JD, LLM, AAMS
Stock Broker

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3. tjeerd plantinga on June 22, 2004 04:27 AM writes...

Dear Mr. Zimmer,

A sophisticated and good article.
I"ll read more about this topic.

Thank you for doing this meaningfull work. Your support helps Dutch evolutionism. By the way our evolutionism is not different from yours.

Yours sincerely,

Tjeerd Plantinga

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4. ~DS~ on June 22, 2004 02:33 PM writes...

Ok ... I'll bite. What is Dutch Evolutionism?

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5. Brian on June 22, 2004 02:52 PM writes...

Aquatic mammals are an interesting example of evolution reversing a previous "decision" - fish evolved to live on land, and aquatic mammals reversed that ecological "choice". Does anyone know of a double-reversal, where an animal (or plant) went aquatic-terrestria-aqautic-terrestrial?

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6. Carl Zimmer on June 22, 2004 03:03 PM writes...

In response to Brian's question--the one example I can think of is snakes (maybe)--they descend from fish that came on land, which evolved into reptiles that some paleontologists believe readapted to the water. There they lost their legs and came back on land legless. This is a controversial hypothesis, but some fossils seem to back it up.

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7. John Wilkins on June 22, 2004 08:31 PM writes...

Dutch evolutionism must be where both parties have to pay the costs of adaptation...

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8. Charith Pelpola on June 23, 2004 04:03 AM writes...

An eye-opening article. Would be interesting to hypothesise on the species' abrupt extinction. To add to Mr. Zimmer's comments about snakes adapting from an aquatic environment to terrestrial; there is a genus of aquatic/semi-aquatic snakes, Homalopsines, in S. E. Asia that have made the transition back to an aquatic existence. The theory again is that they found more favourable food sources in water, and used their aquatic adaption to 'island-hop' in the fragmented archipelagos of the region.

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9. ~DS~ on June 23, 2004 11:53 AM writes...

heh, Wilkins maybe you should stick to chocolate commentary ...

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10. Brian on June 23, 2004 12:02 PM writes...

Thanks Carl. And then some snakes moved back into the ocean (except for laying eggs, I guess). A triple reversal? Nature never fails to astound.

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11. Ed Snack on August 18, 2004 11:45 PM writes...

Humans, Aquatic Apes ? Any considered comments ?

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