Evolution – Page 11 – artdiamondblog.com

“A Really Nice Story about Adaptability of Our Life Form”

“Felisa Wolfe-Simon takes samples from a sediment core she pulled up from the remote shores of 10 Mile Beach at Mono Lake in California.” Source of caption and photo: online version of the NYT article quoted and cited below.

(p. A1) Scientists said Thursday that they had trained a bacterium to eat and grow on a diet of arsenic, in place of phosphorus — one of six elements considered essential for life — opening up the possibility that organisms could exist elsewhere in the universe or even here on Earth using biochemical powers we have not yet dared to dream about.

The bacterium, scraped from the bottom of Mono Lake in California and grown for months in a lab mixture containing arsenic, gradually swapped out atoms of phosphorus in its little body for atoms of arsenic.
Scientists said the results, if confirmed, would expand the notion of what life could be and where it could be. “There is basic mystery, when you look at life,” said Dimitar Sasselov, an astronomer at the Harvard-Smithsonian Center for Astrophysics and director of an institute on the origins of life there, who was not involved in the work. “Nature only uses a restrictive set of molecules and chemical reactions out of many thousands available. This is our first glimmer that maybe there are other options.”
Felisa Wolfe-Simon, a NASA astrobiology fellow at the United States Geological Survey in Menlo Park, Calif., who led the experiment, said, “This is a microbe that has solved the problem of how to live in a different way.”
This story is not about Mono Lake or arsenic, she said, but about “cracking open the door and finding that what we think are fixed constants of life are not.”
. . .
(p. A4) Caleb Scharf, an astrobiologist at Columbia University who was not part of the research, said he was amazed. “It’s like if you or I morphed into fully functioning cyborgs after being thrown into a room of electronic scrap with nothing to eat,” he said.
Gerald Joyce, a chemist and molecular biologist at the Scripps Research Institute in La Jolla, Calif., said the work “shows in principle that you could have a different form of life,” but noted that even these bacteria are affixed to the same tree of life as the rest of us, like the extremophiles that exist in ocean vents.
“It’s a really nice story about adaptability of our life form,” he said. “It gives food for thought about what might be possible in another world.”

For the full story, see:

DENNIS OVERBYE. “Microbe Finds Arsenic Tasty; Redefines Life.” The New York Times (Fri., December 3, 2010): A1 & A4.
(Note: ellipsis added.)
(Note: the online version of the article is dated December 2, 2010.)

“It Can Be Hard to Tell a Crank from an Unfamiliar Gear”

“Leigh Van Valen.” Source of caption and photo: online version of the NYT article quoted and cited below.

(p. 33) His beard, it was said, was longer than God’s but not as long as Charles Darwin’s. Thousands of books teetered perilously in his office, and a motion-sensitive door startled visitors with cricket chirps. He took notes on his own thoughts while conversing with others.

The evolutionary biologist Leigh Van Valen’s eccentricities were legend far beyond the University of Chicago, where brilliant and idiosyncratic professors rule. He named 20 fossil mammals he had discovered after characters in J. R. R. Tolkien’s fiction, and his most famous hypothesis — among the most cited in the literature of evolution — was named for the Red Queen in Lewis Carroll’s “Through the Looking Glass.”
That hypothesis helped explain why organisms, competing for survival, developed two sexes. It did not explain why Professor Van Valen gave better grades to students who disagreed with him — provoking an instant evolutionary adaptation in the tone of student essays — much less why he wrote songs about the sex lives of dinosaurs and paramecia.
. . .
After his Red Queen paper was initially, and repeatedly, rejected, Dr. Van Valen started his own journal, Evolutionary Theory, to publish it. As its longtime editor, he treated all submissions seriously. “It can be hard to tell a crank from an unfamiliar gear,” he wrote.

For the full obituary, see:

DOUGLAS MARTIN. “Leigh Van Valen, a Revolutionary in the Study of Evolution, Dies at 76.” The New York Times, First Section (Sun., October 31, 2010): 33.
(Note: ellipsIs added.)
(Note: the online version of the article is dated October 30, 2010 and has the title “Leigh Van Valen, Evolution Revolutionary, Dies at 76.”)

Finding the Neanderthal in Us

“The Vindija cave in Croatia where three small Neanderthal bones were found.” Source of caption and photo: online version of the NYT article cited below.

(p. A3) The burly Ice Age hunters known as Neanderthals, a long-extinct species, survive today in the genes of almost everyone outside Africa, according to an international research team who offer the first molecular evidence that early humans mated and produced children in liaisons with Neanderthals.

In a significant advance, the researchers mapped most of the Neanderthal genome–the first time that the heredity of such an ancient human species has been reliably reconstructed. The researchers, able for the first time to compare the relatively complete genetic coding of modern and prehistoric human species, found the Neanderthal legacy accounts for up to 4% of the human genome among people in much of the world today.
By comparing the Neanderthal genetic information to the modern human genome, the scientists were able to home in on hints of subtle differences between the ancient and modern DNA affecting skin, stature, fertility and brain power that may have given Homo sapiens an edge over their predecessors.
“It is tantalizing to think that the Neanderthal is not totally extinct,” said geneticist Svante Pääbo at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who pioneered the $3.8 million research project. “A bit of them lives on in us today.”
. . .
For their analysis, Dr. Pääbo and his colleagues extracted DNA mostly from the fossil remains of three Neanderthal women who lived and died in Croatia between 38,000 and 45,000 years ago. From thimblefuls of powdered bone, the researchers pieced together about three billion base pairs of DNA, covering about two-thirds of the Neanderthal genome. The researchers checked those samples against fragments of genetic code extracted from three other Neanderthal specimens.
“It is a tour de force to get a genome’s worth,” said genetic database expert Ewan Birney at the European Bioinformatics Institute in Cambridge, England.
In research published Thursday in Science, the researchers compared the Neanderthal DNA to the genomes drawn from five people from around the world: a San tribesman from South Africa; a Yoruba from West Africa; a Han Chinese; a West European; and a Pacific islander from Papua, New Guinea. They also checked it against the recently published genome of bio-entrepreneur Craig Venter. Traces of Neanderthal heredity turned up in all but the two African representatives.

For the full story, see:
ROBERT LEE HOTZ. “Most People Carry Neanderthal Genes; Team Finds up to 4% of Human Genome Comes From Extinct Species, the First Evidence It Mated With Homo Sapiens.” The Wall Street Journal (Fri., MAY 7, 2010): A3.
(Note: ellipsis added.)
(Note: the online version of the review is dated MAY 6, 2010.)

A related article, the online version of which is the source for the caption and photo above, is:
NICHOLAS WADE. “Analysis of Neanderthal Genome Points to Interbreeding with Modern Humans.” The New York Times (Fri., May 7, 2010): A9.
(Note: the online version of the review is dated May 6, 2010 and has the title “Signs of Neanderthals Mating With Humans.”)

“A close-up of the bone Vindija 33.16 from Vindija cave, Croatia.” Source of caption and photo: online version of the WSJ article quoted and cited above.

“Climate Change Was One of the Forces that Led to the Triumph of Homo Sapiens”

“The David H. Koch Hall of Human Origins in Washington includes this 30,000-year-old handprint from France.” Source of caption and photo: online version of the NYT article quoted and cited below.

(p. C32) The exhibition’s theme is “What Does It Mean to Be Human?” And the new image of the human it creates is different from the one from a century ago. It isn’t that nature has suddenly become a pastoral paradise. Some of the most unusual objects here are fossilized human bones bearing scars of animal attacks: a 3-year-old’s skull from about 2.3 million years ago is marked by eagle talons in the eye sockets; an early human’s foot shows the bite marks of a crocodile. In one of the exhibition’s interactive video stations, in which you are cleverly shown how excavated remains are interpreted, you learn that the teeth of a leopard’s lower jaw found in a cave at the Swartkrans site in South Africa match the puncture marks in a nearby early-human skull: evidence of a 1.8 million-year-old killing.

. . .
During the brief 200,000-year life of Homo sapiens, at least three other human species also existed. And while this might seem to diminish any remnants of pride left to the human animal in the wake of Darwin’s theory, the exhibition actually does the opposite. It puts the human at the center, tracing how through these varied species, central characteristics developed, and we became the sole survivors. The show humanizes evolution. It is, in part, a story of human triumph.
. . .
. . . at recent excavations in China, at Majuangou, stone tools were found in four layers of rock dating from 1.66 million to 1.32 million years ago; fossil pollen proved that each of these four time periods was also associated with a different habitat. “The toolmaker, Homo erectus,” we read, “was able to survive in all of these habitats.”
That ability was crucial. The hall emphasizes that enormous changes in the planet’s climate accompanied hominin development, suggesting that the ability to adapt to such differing circumstances was the human’s strength. Climate change was one of the forces that led to the triumph of Homo sapiens.

For the full review, see:
EDWARD ROTHSTEIN. “Exhibition Review; Hall of Human Origins; Searching the Bones of Our Shared Past.” The New York Times (Fri., March 19, 2010): C25 & C32.
(Note: italics in original; ellipses added.)
(Note: the online version of the review is dated March 18, 2010.)

“The Evolutionary Concomitant of Incessant Climate Change Was Human Resilience”

“Early Homo sapiens created these symbolic objects between 60,000 and 30,000 years ago. Using natural materials and creativity, they combined animal and human features into fantastical creatures and fashioned instruments for making music. “Source of caption and photo: online version of the WSJ article quoted and cited below.

The sort of artifacts displayed above have been used to argue that homo sapiens had essentially reached their modern capabilities at least by 40,000 years ago.
The handaxes below are fascinating, in that they clearly display progress, and they clearly display how slow that progress was.

(p. D13) The mysterious Ice Age extinction of the Neanderthals, losers in the competition against modern humans, still fires the popular imagination. So it’s startling to learn that as recently as 70,000 years ago, at least four human species coexisted, including tenacious, long-lived Homo erectus and diminutive, hobbit-like Homo floresiensis, found in Indonesia in 2003.

The sensational 1974 discovery in Ethiopia of “Lucy,” resembling an ape but walking upright, located human origins 3.2 million years in the past. Those same fossil deposits have recently yielded even more-ancient ancestors, who stood on their own two feet as far back as six million years ago.
Paleoanthropology is thriving, and human fossil finds–more than 6,000 and counting–regularly force revisions of old timelines and theories. Our species, Homo sapiens, turns out to have had an abundance of long-lost cousins, though scientists are still arguing about the closeness of those relationships. The new David H. Koch Hall of Human Origins at the Smithsonian National Museum of Natural History, whose opening marked the museum’s centennial, provides a formidable overview of this still-developing story.
. . .
It’s long been accepted that different human species were adapted to thrive in specific climatic niches. Neanderthals had short, compact bodies to conserve heat and large nasal passages to warm frigid air, while some of our African forebears had long, skinny frames suited to hotter climes. But this exhibition contends that the evolutionary concomitant of incessant climate change was human resilience–the flexibility to make it almost anywhere, thanks to large, sophisticated brains and social networks.
Versatility apparently characterized even our oldest relatives. The ability to walk upright through the drier, more open grasslands did not immediately divest them of their penchant for climbing trees in the shrinking woodlands. A diorama of Lucy (Australopithecus afarensis) depicts her with one foot on the ground and another on a tree limb, symbolizing her straddling of two environments.

For the full review, see:
JULIA M. KLEIN. “Natural History; Our Species Rediscovers Its Cousins.” The Wall Street Journal (Tues., May 11, 2010): D13.
(Note: ellipsis added.)

“Handaxes — multipurpose tools used to chop wood, butcher animals, and make other tools — dominated early human technology for more than a million years. Left to right: Africa (1.6 million years old), Asia (1.1 million years old), and Europe (250,000 years old).” Source of caption and photo: online version of the WSJ article quoted and cited above.

Fossil Found of Much Earlier Human Ancestor

Source of graphic: online version of the NYT article quoted and cited below.

(p. A1) Ardi, short for Ardipithecus ramidus, is the newest fossil skeleton out of Africa to take its place in the gallery of human origins. At an age of 4.4 million years, it lived well before and was much more primitive than the famous 3.2-million-year-old Lucy, of the species Australopithecus afarensis.

Since finding fragments of the older hominid in 1992, an international team of scientists has been searching for more specimens and on Thursday presented a fairly complete skeleton and their first full analysis. By replacing Lucy as the earliest known skeleton from the human branch of the primate family tree, the scientists said, Ardi opened a window to “the early evolutionary steps that our ancestors took after we diverged from our common ancestor with chimpanzees.”
. . .
(p. A6) Scientists not involved in the new research hailed its importance, placing the Ardi skeleton on a pedestal alongside notable figures of hominid evolution like Lucy and the 1.6-million-year-old Turkana Boy from Kenya, an almost complete specimen of Homo erectus with anatomy remarkably similar to modern Homo sapiens.
David Pilbeam, a professor of human evolution at Harvard University who had no role in the discovery, said in an e-mail message that the Ardi skeleton represented “a genus plausibly ancestral to Australopithecus” and began “to fill in the temporal and structural ‘space’ between the apelike common ancestor and Australopithecus.”
Andrew Hill, a paleoanthropologist at Yale University who was also not involved in the research, noted that Dr. White had kept “this skeleton in his closet for the last 15 years or so, but I think it has been worth the wait.” In some ways the specimen’s features are surprising, Dr. Hill added, “but it makes a very satisfactory animal for understanding the changes that have taken place along the human lineage.”
The first comprehensive reports describing the skeleton and related findings, the result of 17 years of study, are being published Friday in the journal Science. Eleven papers by 47 authors from 10 countries describe the analysis of more than 110 Ardipithecus specimens from a minimum of 36 different individuals, including Ardi.
The paleoanthropologists wrote in one of the articles that Ardipithecus was “so rife with anatomical surprises that no one could have imagined it without direct fossil evidence.”
A bounty of animal and plant material — “every seed, every piece of fossil wood, every scrap of bone,” Dr. White said — was gathered to set the scene of the cooler, more humid woodland habitat in which these hominids had lived.
This was one of the first surprises, said Giday WoldeGabriel, a geologist at Los Alamos National Laboratory, because it upset the hypothesis that upright walking had evolved as an adaptation to life on grassy savanna.

For the full story, see:
JOHN NOBLE WILFORD. “Fossil Skeleton From Africa Predates Lucy.” The New York Times (Fri., October 1, 2009): A1 & A6.
(Note: ellipsis added.)

“A fairly complete skeleton of Ardipithecus ramidus, which replaced Lucy as the earliest known skeleton from the human branch of the primate family tree.” Source of caption and photo: online version of the NYT article quoted and cited above.

Scientists Believe Life Emerged from a Process of “Creative Destruction” and Global Warming

Source of graphic: online version of the WSJ article quoted and cited below.

(p. A9) In a paradox of creation, new evidence suggests that devastating avalanches of cosmic debris may have fostered life on Earth, not annihilated it. If so, life on our planet may be older than scientists previously thought — and more persistent.

Astronomers world-wide have been transfixed by a roiling gash the size of Earth in the atmosphere of Jupiter, caused by an errant comet or asteroid that smashed into the gas giant last month. The lingering turbulence is an echo of a cataclysmic bombardment that shaped the origin of life here 3.9 billion years ago, when millions of asteroids, comets and meteors pummeled our planet.
. . .
But in their super-heated plunge through the atmosphere, these asteroids and meteors may have helped create conditions ideal for emerging life. “Everyone focuses on the meteor that hits the ground,” says geochemist Richard Court at London’s Imperial College. “No one thinks about the products of its journey that get pumped into the atmosphere.”
As they vented, they collectively could have imported billions of tons of life-sustaining water into the air every year, Dr. Court and his colleague Mark Sephton recently determined. They calculated that these showers of volatile rocks delivered 10 times the daily outflow of the Mississippi River every year for 20 million years. By analyzing the fumes emitted under such extreme heat, they discovered these rocks also could have injected billions of tons of carbon dioxide into the air every year.
Combined with so much water vapor, the carbon dioxide could have induced a global greenhouse effect. That could have kept any life emerging on Earth safely in a planetary incubator at a time when the planet might easily have frozen because the Sun radiated 25% less energy than today. “The amount of CO2 that was produced is about the same we produce today through fossil fuel use and we know that is a climate-changing volume,” says Dr. Court.
. . .
“It is literally a revolution in our ideas about how our solar system evolved,” says asteroid expert William Bottke at the Southwest Research Institute. “It could be that our form of life today — every living thing that we see today — is due to this bombardment that happened 3.9 billion years ago.”

For the full commentary, see:
ROBERT LEE HOTZ. “SCIENCE JOURNAL; Some Creative Destruction on a Cosmic Scale; Scientists Say Asteroid Blasts, Once Thought Apocalyptic, Fostered Life on Earth by Carrying Water and Protective Greenhouse Gas.” The Wall Street Journal (Fri., AUGUST 14, 2009): A9.
(Note: ellipses added.)

“A Splendid Birthday Present” for Charles Darwin

Source of the book image: http://images.barnesandnoble.com/images/34510000/34519930.jpg

(p. A13) . . ., on Feb. 12, biologists the world over will celebrate Charles Darwin’s 200th birthday. Throughout the year, at festivals galore marking his bicentennial, “On the Origin of Species,” a mere 150 years old, will be hailed as one of the greatest works in the history of the sciences.
. . .
Mr. Coyne begins with a succinct account of what is at stake. “Life on earth evolved gradually beginning with one primitive species — perhaps a self-replicating molecule — that lived more than 3.5 billion years ago; it then branched out over time, throwing off many and diverse species; and the mechanism for most (but not all) of evolutionary change is natural selection.”
Darwinism is thus a claim with several basic components, and the book is structured by carefully exhibiting the evidence for each. Making that structure explicit allows readers to recognize just where they are in the argument. As they follow Mr. Coyne’s parade of evidence — his discussions of the fossil record, of vestigial traits, of the ways in which living things constantly make novel use of the bits and pieces they have inherited, of the distribution of plants and animals — the components of Darwin’s thesis are sequentially supported. We have a list of things to be shown, they are shown and the truth of evolution is established.
. . .
Yet will any defense of Darwin, however painstaking and lucid, succeed in substantially modifying the public-opinion survey results? Mr. Coyne has seen the opposition first-hand, recounting his experience of talking to a group of businessmen about evolution and eliciting the reaction: “Very convincing — but I don’t believe it.” This sort of skepticism is often rooted in a sense that Darwinism somehow discredits morality — a perception that Mr. Coyne argues against, cogently, in a brief final chapter. But he does not seem to appreciate the depth of popular hostility toward Darwin.
. . .
Whether or not he succeeds in bringing Americans en masse to learn to love evolution, he has offered Darwin a splendid birthday present.

For the full review, see:
PHILIP KITCHER. “Bookshelf; Following the Evidence.” Wall Street Journal (Thurs., JANUARY 29, 2009): A13.
(Note: ellipses added.)

The reviewed book is:
Coyne, Jerry A. Why Evolution Is True. New York: Viking, 2009.

A classic paper on whether the speed of a scientist’s acceptance of evolution was related to the scientist’s age, is:
David L. Hull, Peter D. Tessner and Arthur M. Diamond. “Planck’s Principle: Do Younger Scientists Accept New Scientific Ideas with Greater Alacrity than Older Scientists?” Science 202 (November 17, 1978): 717-723.

Private Money Supports Quest for Dinosaur DNA

Source of graphic: the online version of the WSJ article quoted and cited below.

(p. A1) JORDAN, Mont. — Prospecting in Montana’s badlands, rock ax in hand, paleontologist Jack Horner picks up a piece of the jawbone of a dinosaur. He examines the splinter, then puts it back and moves on. It isn’t the kind of bone he is looking for.

Prof. Horner is searching for something that many scientists believe no longer exists: dinosaur bones that harbor blood cells, protein and, perhaps, even DNA.

"Most people looking for dinosaurs are looking for beautiful skeletons," he says. "We are looking for information."

. . .

Prof. Horner, a curator at the Museum of the Rockies in Bozeman, is among the world’s most influential and offbeat paleontologists. He pioneered studies of dinosaur parent-(p. A12)ing behavior, species variation and bone cells. He is dyslexic, a former Special Forces operative of the Vietnam War era, a MacArthur Foundation "genius" fellow, and a chaired professor of Montana State University who never finished a formal college degree.

"The lenses that people normally use to look at stuff are broken in Jack," says Mary Schweitzer, an assistant professor of paleontology at North Carolina State University, who has worked with him for years. "That’s what makes Jack such a good scientist. Every now and then, every field should get a renegade weirdo in it who challenges assumptions."

. . .

"The chances of finding any [dinosaur] DNA are pretty low," Prof. Horner acknowledges. "I am still hopeful."

In a field mostly outside the mainstream of federal research funding, Prof. Horner has a knack for attracting private grants. Star Wars producer George Lucas, Qualcomm co-founder Klein Gilhousen and Wade Dokken, a developer of Montana real estate, have contributed toward his research, the university says. Nathan Myhrvold, formerly chief technology officer at Microsoft Corp. and co-founder of Intellectual Ventures LLC, is helping to underwrite this season’s fieldwork.

This summer, in Montana’s Hell Creek Formation, Prof. Horner is searching the last landscape inhabited by dinosaurs. More than 65 million years ago, this plain was a wetland where herds of horned Triceratops watered. Today, it is an arid outwash of boulders, cactus and sage. The red and gray soil is littered with white shards of petrified wood that ring like bone china when tapped together and countless crumbs of dinosaur bone.

. . .

"As long as you are not bound by preconceived ideas of what you can find," Prof. Horner says, "there are an awful lot of things you can discover."

For the full story, see:

ROBERT LEE HOTZ. "Dinosaur Hunter Seeks More Than Just Bare Bones; Prof. Horner Searches For Traces of Blood, DNA; Lucky Break From T. Rex." The Wall Street Journal (Fri., August 24, 2007): A1 & A12.

(Note: ellipses added.)

At top, Prof. Horner; at bottom: "Sarah Keenan, 21, an undergraduate at the University of St. Andrews in Scotland who is working this summer for Prof. Horner, covers the fossilized triceratops frill in a protective jacket of plaster." Source of caption and photos: the online version of the WSJ article quoted and cited above.

Google Evolves

Gary Hamel has recently penned some thoughtful observations about what practices of Google have led to its success. An excerpt from that analysis appears below. (Hamel earlier wrote a popular book in which he makes extensive use of Schumpeter’s process of creative destruction.)

Only time will tell whether Google has succeeded in building an evolutionary advantage. But consider: Since it’s founding, it has repeatedly morphed its business model. Google 1.0 was a search engine that crawled the Web but generated little revenue; which led to Google 2.0, a company that sold its search capacity to AOL/Netscape, Yahoo and other major portals; which gave way to Google 3.0, an Internet contrarian that rejected banner ads and instead sold simple text ads linked to search results; which spawned Google 4.0, an increasingly global entity that found a way to insert relevant ads into any and all Web content, dramatically enlarging the online ad business; which mutated into Google 5.0, an innovation factory that produces a torrent of new Web-based services, including Gmail, Google Desktop, and Google Base. More than likely, 6.0 is around the corner.

Of course Google may ultimately fall victim to hubris and imperial overstretch as it takes on Microsoft, Yahoo, eBay, the occasional telecom giant and pretty much everyone else in cyberspace. Or like Microsoft, it may simply become like every other big company as it grows. But that’s not the way I’d bet. Google seems to have grasped the new century’s most important business lesson: The capacity to evolve is the most important advantage of all.

For the full commentary, see:

Hamel, Gary. "Management à la Google." The Wall Street Journal (Weds., April 26, 2006): A16.

And here is the information on Hamel’s most recent book:

Hamel, Gary. Leading the Revolution: How to Thrive in Turbulent Times by Making Innovation a Way of Life. Revised & Updated ed. Harvard Business School Press, 2002.

Source of image: http://www.amazon.com/gp/product/B000EPFVBE/sr=8-1/qid=1146333251/ref=pd_bbs_1/104-5668094-9083929?%5Fencoding=UTF8

Missing Link Found Between Sea and Land Animals: More Evidence for Evolution

Model recreation of missing link animal. Source of image: Online version of NYT article cited below.

Scientists have discovered fossils of a 375-million-year-old fish, a large scaly creature not seen before, that they say is a long-sought missing link in the evolution of some fishes from water to a life walking on four limbs on land.

In two reports today in the journal Nature, a team of scientists led by Neil H. Shubin of the University of Chicago say they have uncovered several well-preserved skeletons of the fossil fish in sediments of former streambeds in the Canadian Arctic, 600 miles from the North Pole.

The skeletons have the fins, scales and other attributes of a giant fish, four to nine feet long. But on closer examination, the scientists found telling anatomical traits of a transitional creature, a fish that is still a fish but has changes that anticipate the emergence of land animals — and is thus a predecessor of amphibians, reptiles and dinosaurs, mammals and eventually humans.

In the fishes’ forward fins, the scientists found evidence of limbs in the making. There are the beginnings of digits, proto-wrists, elbows and shoulders. The fish also had a flat skull resembling a crocodile’s, a neck, ribs and other parts that were similar to four-legged land animals known as tetrapods.

Other scientists said that in addition to confirming elements of a major transition in evolution, the fossils were a powerful rebuttal to religious creationists, who have long argued that the absence of such transitional creatures are a serious weakness in Darwin’s theory.

The discovery team called the fossils the most compelling examples yet of an animal that was at the cusp of the fish-tetrapod transition. The fish has been named Tiktaalik roseae, at the suggestion of elders of Canada’s Nunavut Territory. Tiktaalik (pronounced tic-TAH-lick) means ”large shallow water fish.”

”The origin of limbs,” Dr. Shubin’s team wrote, ”probably involved the elaboration and proliferation of features already present in the fins of fish such as Tiktaalik.”

In an interview, Dr. Shubin, an evolutionary biologist, let himself go. ”It’s a really amazing, remarkable intermediate fossil,” he said. ”It’s like, holy cow.”

Two other paleontologists, commenting on the find in a separate article in the journal, said that a few other transitional fish had been previously discovered from approximately the same Late Devonian time period, 385 million to 359 million years ago. But Tiktaalik is so clearly an intermediate ”link between fishes and land vertebrates,” they said, that it ”might in time become as much an evolutionary icon as the proto-bird Archaeopteryx,” which bridged the gap between reptiles (probably dinosaurs) and today’s birds.

The writers, Erik Ahlberg of Uppsala University in Sweden and Jennifer A. Clack of the University of Cambridge in England, are often viewed as rivals to Dr. Shubin’s team in the search for intermediate species in the evolution from fish to the first animals to colonize land.

H. Richard Lane, director of paleobiology at the National Science Foundation, said in a statement, ”These exciting discoveries are providing fossil ‘Rosetta Stones’ for a deeper understanding of this evolutionary milestone — fish to land-roaming tetrapods.”