Evolution – Page 6 – artdiamondblog.com

Small Is Beautiful as Life Adapts to Global Warming

“Artist’s reconstruction of Sifrhippus sandrae (right) touching noses with a modern Morgan horse (left) that stands about 5 feet high at the shoulders and weighs approximately 1000 lbs.” Source of caption and photo: online version of the NYT article quoted and cited below.

(p. D3) The horse (siff-RIP-us, if you have to say the name out loud) lived in what is still horse country, in the Bighorn Basin of Wyoming, where wild mustangs roam.
. . .
Its preserved fossils, abundant in the Bighorn Basin, provide an excellent record of its size change over a 175,000-year warm period in the Earth’s history known as the Paleocene-Eocene thermal maximum, when temperatures are estimated to have risen by 9 to 18 degrees Fahrenheit at the start, and dropped again at the end.
Scientists have known that many mammals appear to have shrunk during the warming period, and the phenomenon fits well with what is known as Bergmann’s rule, which says, roughly, that mammals of a given genus or species are smaller in hotter climates.
Although the rule refers to differences in location, it seemed also to apply to changes over time. But fine enough detail was lacking until now.
In Science, Ross Secord, of the University of Nebraska-Lincoln; Jonathan Bloch, of the Florida Museum of Natural History at the University of Florida in Gainesville; and a team of other researchers report on the collection and analysis of Sifrhippus fossils from the Bighorn Basin.
They report that the little horse got 30 percent smaller over the first 130,000 years, and then — as always seems to happen with weight loss — shot back up and got 75 percent bigger over the next 45,000 years.
. . .
“It seems to be natural selection,” said Dr. Secord. He said animals evolved to be smaller during warming because smaller animals did better in that environment, perhaps because the smaller an animal is, the easier it is to shed excess heat.

For the full story, see:
JAMES GORMAN. “As the Planet Heated Up, First Horse Got Tinier .” The New York Times (Tues., February 28, 2012): D3.
(Note: ellipses added.)
(Note: the online version of the story is dated February 23 [sic], 2012 and has the title “A Tiny Horse That Got Even Tinier as the Planet Heated Up.”)

Some Traits (Including Some Diseases) Depend on Many Genes Rather than a Single Gene

(p. D3) A new exploration of how evolution works at the genomic level may have a significant impact on drug development and other areas of medicine.
The report, published in Nature last week, offers new evidence in a longstanding debate about how organisms evolve. One well-known path to change is a heavily favorable mutation in a single gene. But it may be well known only because it is easy to study. Another path is exploitation of mildly favorable differences that already exist in many genes.
. . .
Three biologists at the University of California, Irvine, Molly K. Burke, Michael R. Rose and Anthony D. Long, followed populations of fruit flies through 600 generations and studied the whole genome of some 250 flies in order to see what kinds of genetic change they had undergone.
. . .
The conventional view is that evolutionary change is generally mediated by a favorable mutation in a gene that then washes through the whole population, a process called a hard sweep because all other versions of the gene are brushed away. The alternative, called a soft sweep, is that many genes influence a trait, in this case the rate of maturation, and that the growth-accelerating versions of each of these genes become just a little more common. Each fly has a greater chance of inheriting these growth-promoting versions and so will mature faster.
In sequencing their subjects’ genomes, the researchers found that a soft sweep was indeed responsible for the earlier hatching. No single gene had swept through the population to effect the change; rather, the alternative versions of a large number of genes had become slightly more common.
. . .
Haldane favored the single mutation mechanism, but Fisher and Wright backed multiple gene change.
. . .
The demise of the Haldane view “is very bad news for the pharmaceutical industry in general,” Dr. Rose said. If disease and other traits are controlled by many genes, it will be hard to find effective drugs; a single target would have been much simpler.

For the full story, see:
NICHOLAS WADE. “Natural Selection Cuts Broad Swath Through Fruit Fly Genome.” The New York Times (Tues., September 21, 2010): D3.
(Note: ellipses added.)
(Note: the online version of the article is dated September 20, 2010.)

Crows Use Tools Too

“A captive New Caledonian crow forages for food using a stick tool.” Source of caption and photo: online version of the NYT article quoted and cited below.

(p. D3) New Caledonian crows, found in the South Pacific, are among nature’s most robust nonhuman tool users. They are well known for using twigs to dislodge beetle larvae from tree trunks.

And there’s a good reason. By foraging for just a few larvae, a crow can satisfy its daily nutritional needs, which explains the evolutionary advantage of learning how to use tools, researchers report in the journal Science.

For the full story, see:
SINDYA N. BHANOO. “OBSERVATORY; Crows Put Tools to Use to Access a Nutritious Diet.” The New York Times (Tues., September 21, 2010): D3.
(Note: the online version of the article is dated September 20, 2010.)

After Being “Nasty and Unruly for Decades” Henry Becomes a Father at Age 111

“TUATARA. The tuatara, scientists have learned, is in some ways a so-called living fossil.” Source of caption and photo: online version of the NYT article quoted and cited below.

(p. D1) . . . the animal that may well be New Zealand’s most bizarrely instructive species at first glance looks surprisingly humdrum: the tuatara. A reptile about 16 inches long with bumpy, khaki-colored skin and a lizardly profile, the tuatara could easily be mistaken for an iguana. Appearances in this case are wildly deceptive. The tuatara — whose name comes from the Maori language and means “peaks on the back” — is not an iguana, is not a lizard, is not like any other reptile alive today.

In fact, as a series of recent studies suggest, it is not like any other vertebrate alive today. The tuatara, scientists have learned, is in some ways a so-called living fossil, its basic skeletal layout and skull shape almost identical to that of tuatara fossils dating back hundreds of millions of years, to before the rise of the dinosaurs. Cer-(p. D2)tain tuatara organs and traits also display the hallmarks of being, if not quite primitive, at least closer to evolutionary baseline than comparable structures in other animals.
. . .
Tuataras are living fossils in more than one sense of the term. Through long-term capture, tag and recapture studies that were begun right after World War II, researchers have found that tuataras match and possibly exceed in attainable life span that other Methuselah of the animal kingdom, the giant tortoise. “Tuataras routinely live to 100, and I couldn’t tell you they don’t live to 150, 200 years or even more,” said Dr. Daugherty.
They live, and live it up. “We know there are females that are still reproducing in their 80s,” said Dr. Daugherty. At the Southland Museum and Art Gallery in Invercargill, New Zealand, a captive male tuatara named Henry, a local celebrity that had been nasty and unruly for decades until a malignancy was removed from his genitals, mated with an 80-year-old female named Mildred, and last year became a first-time father — at the age of 111.

For the full story, see:

NATALIE ANGIER. “Basics; Reptile’s Pet-Store Looks Belie Its Triassic Appeal.” The New York Times (Tues., November 23, 2010): D1 & D2.
(Note: ellipses added.)
(Note: the online version of the article is dated November 22, 2010.)

“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.