Fitness Can Improve Even After Age 100

(p. D4) At the age of 105, the French amateur cyclist and world-record holder Robert Marchand is more aerobically fit than most 50-year-olds — and appears to be getting even fitter as he ages, according to a revelatory new study of his physiology.
The study, which appeared in December in The Journal of Applied Physiology, may help to rewrite scientific expectations of how our bodies age and what is possible for any of us athletically, no matter how old we are.
. . .
Conventional wisdom in exercise science suggests that it is very difficult to significantly add to aerobic fitness after middle age. In general, VO2 max, a measure of how well our bodies can use oxygen and the most widely accepted scientific indicator of fitness, begins to decline after about age 50, even if we frequently exercise.
But Dr. Billat had found that if older athletes exercised intensely, they could increase their VO2 max. She had never tested this method on a centenarian, however.
. . .
These data strongly suggest that “we can improve VO2 max and performance at every age,” Dr. Billat says.

For the full story, see:
GRETCHEN REYNOLDS. “Phys Ed; Lessons from a 105-Year-Old.” The New York Times (Tues., FEB. 14, 2017): D4.
(Note: ellipses added.)
(Note: the online version of the article has the date FEB. 8, 2017, and has the title “Phys Ed; Lessons on Aging Well, From a 105-Year-Old Cyclist.”)

The academic article mentioned in the passages quoted above, is:
Billat, Véronique, Gilles Dhonneur, Laurence Mille-Hamard, Laurence Le Moyec, Iman Momken, Thierry Launay, Jean Pierre Koralsztein, and Sophie Besse. “Case Studies in Physiology: Maximal Oxygen Consumption and Performance in a Centenarian Cyclist.” Journal of Applied Physiology 122 (2017): 430-34.

Mice Genome Reprogrammed to Rejuvenate Organs and Extend Life

(p. A22) At the Salk Institute in La Jolla, Calif., scientists are trying to get time to run backward.
Biological time, that is. In the first attempt to reverse aging by reprogramming the genome, they have rejuvenated the organs of mice and lengthened their life spans by 30 percent. The technique, which requires genetic engineering, cannot be applied directly to people, but the achievement points toward better understanding of human aging and the possibility of rejuvenating human tissues by other means.
The Salk team’s discovery, reported in the Thursday issue of the journal Cell, is “novel and exciting,” said Jan Vijg, an expert on aging at the Albert Einstein College of Medicine in New York.
Leonard Guarente, who studies the biology of aging at M.I.T., said, “This is huge,” citing the novelty of the finding and the opportunity it creates to slow down, if not reverse, aging. “It’s a pretty remarkable finding, and if it holds up it could be quite important in the history of aging research,” Dr. Guarente said.
. . .
Ten years ago, the Japanese biologist Shinya Yamanaka amazed researchers by identifying four critical genes that reset the clock of the fertilized egg. The four genes are so powerful that they will reprogram even the genome of skin or intestinal cells back to the embryonic state.
. . .
Dr. Izpisua Belmonte believes these beneficial effects have been obtained by resetting the clock of the aging process. The clock is created by the epigenome, the system of proteins that clads the cell’s DNA and controls which genes are active and which are suppressed.
. . .
Dr. Izpisua Belmonte sees the epigenome as being like a manuscript that is continually edited. “At the end of life there are many marks and it is difficult for the cell to read them,” he said.
What the Yamanaka genes are doing in his mice, he believes, is eliminating the extra marks, thus reverting the cell to a more youthful state.
The Salk biologists “do indeed provide what I believe to be the first evidence that partial reprogramming of the genome ameliorated symptoms of tissue degeneration and improved regenerative capacity,” Dr. Vijg said.

For the full story, see:
NICHOLAS WADE. “Scientists Learn About Human Aging by Lengthening the Life Span of Mice.” The New York Times (Fri., DEC. 16, 2016): A22.
(Note: ellipses added.)
(Note: the online version of the story has the date DEC. 15, 2016, and has the title “Scientists Say the Clock of Aging May Be Reversible.”)

More Live to 100, and Those Who Do, Are Living Even Longer

(p. A13) There were 72,197 of them in 2014, up from 50,281 in 2000, according to the report by the Centers for Disease Control and Prevention. In 1980, they numbered about 15,000.
Even demographers seemed impressed. “There is certainly a wow factor here, that there are this many people in the United States over 100 years old,” said William H. Frey, the senior demographer at the Brookings Institution. “Not so long ago in our society, this was somewhat rare.”
Not only are there more centenarians, but they are living even longer. Death rates declined for all demographic groups of centenarians — white, black, Hispanic, female, male — in the six years ending in 2014, the report said.
Women, who typically live longer than men, accounted for the overwhelming majority of centenarians in 2014: more than 80 percent.

For the full story, see:
SABRINA TAVERNISE. “Centenarians Proliferate, and Live Longer.” The New York Times (Thurs., JAN. 21, 2016): A13.

The Octopus, Though Intelligent, Only Lives for Two Years

(p. C5) Around 600 million years ago there lived in the sea a small unprepossessing worm, virtually eyeless and brainless. For some reason this species split into two, thus seeding the vast zoological groupings of the vertebrates and the invertebrates. On one branch sit the mammals; on the other sit the molluscs (and many others). Among these two groups, two notable creatures eye each other warily: the human and the octopus. They have no common ancestor apart from that lowly worm, yet there is a strange affinity, a bond almost. For they are both evolutionary experiments in intelligence–pockets of genius in a vast ocean (sorry!) of biological mediocrity.
In “Other Minds,” Peter Godfrey-Smith, a philosopher at CUNY and an avid scuba diver, has given us a smoothly written and captivating account of the octopus and its brethren, as observed by humans. He celebrates the cephalopods: the octopus, the squid and the cuttlefish. He stresses their dissimilarity to us and other mammals, but he also wants us to appreciate what we have in common. Just as eyes have evolved independently in many lineages, so have intelligent minds. From those mindless worms, via two separate evolutionary paths, to the glories of consciousness and curiosity–we are brothers in big brains.
. . .
(p. C6) Mr. Godfrey-Smith mixes the scientific with the personal, giving us lively descriptions of his dives to “Octopolis,” a site off the east coast of Australia at which octopuses gather. There they make their dens in piles of scallop shells. He also reproduces some excellent photographs of the octopuses and other cephalopods he has observed in his submerged city. It is with a jolt, then, that he announces the average life span of the cephalopod: one to two years. That’s it: That marvelous complex body, the large brain, lively mind and amazing Technicolor skin–all over so quickly. There are boring little fish that live for 200 years, and the closely related nautilus can live for 20 years, but the octopus has only a year or two to enjoy its uniqueness. Mr. Godfrey-Smith speculates that the brevity results from a lifestyle that forces the animal to reach reproductive age as soon as possible, given the problem of predators such as whales or large fish.
Whatever the biological reason for such a brief life, it is a melancholy fact.
. . .
What is it like to be an octopus? It’s not easy to say, but I speculate soft, malleable, brimming with sensation, vivid, expressive, exciting, complicated, tragic and determined. They make good, if brief, use of their portion of consciousness. They must live by the evolutionary laws that have created them, but there is an inner being that makes the best of its lot. Though it’s easy to think of octopuses as alien, a better view is that they are our cousins in biological destiny–spirits in a material world.

For the full review, see:
COLIN MCGINN. “Experiments in Intelligence.” The Wall Street Journal (Sat., December 3, 2016): C5-C6.
(Note: ellipses added.)
(Note: the online version of the review has the date Dec. 4 [sic], 2016, and has the title “Our Noble Cousin: The Octopus.”)

The book under review, is:
Godfrey-Smith, Peter. Other Minds: The Octopus, the Sea, and the Deep Origins of Consciousness. New York: Farrar, Straus and Giroux, 2016.

Superagers Engage in “Strenuous Mental Effort”

(p. 10) Why do some older people remain mentally nimble while others decline? “Superagers” (a term coined by the neurologist Marsel Mesulam) are those whose memory and attention isn’t merely above average for their age, but is actually on par with healthy, active 25-year-olds.
. . .
Of course, the big question is: How do you become a superager? Which activities, if any, will increase your chances of remaining mentally sharp into old age? We’re still studying this question, but our best answer at the moment is: work hard at something. Many labs have observed that these critical brain regions increase in activity when people perform difficult tasks, whether the effort is physical or mental. You can therefore help keep these regions thick and healthy through vigorous exercise and bouts of strenuous mental effort. My father-in-law, for example, swims every day and plays tournament bridge.
The road to superaging is difficult, though, because these brain regions have another intriguing property: When they increase in activity, you tend to feel pretty bad — tired, stymied, frustrated. Think about the last time you grappled with a math problem or pushed yourself to your physical limits. Hard work makes you feel bad in the moment. The Marine Corps has a motto that embodies this principle: “Pain is weakness leaving the body.” That is, the discomfort of exertion means you’re building muscle and discipline. Superagers are like Marines: They excel at pushing past the temporary unpleasantness of intense effort. Studies suggest that the result is a more youthful brain that helps maintain a sharper memory and a greater ability to pay attention.

For the full commentary, see:
LISA FELDMAN BARRETT. “Gray Matter; How to Become a ‘Superager’.” The New York Times, SundayReview Section (Sun., January 1, 2017): 10.
(Note: ellipsis added.)
(Note: the online version of the commentary has the date DEC. 31, 2016.)

The passages quoted above are related to Barrett’s academic paper:
Sun, Felicia W., Michael R. Stepanovic, Joseph Andreano, Lisa Feldman Barrett, Alexandra Touroutoglou, and Bradford C. Dickerson. “Youthful Brains in Older Adults: Preserved Neuroanatomy in the Default Mode and Salience Networks Contributes to Youthful Memory in Superaging.” The Journal of Neuroscience 36, no. 37 (Sept. 14, 2016): 9659-9668.

Complex Labor Rules Reduce Work Choices for Older Workers

(p. B4) CALL them boomerang retirees: people who exit gracefully after their career at a company, then return shortly afterward to work there part time.
More and more companies are establishing formal programs to facilitate this, for reasons that benefit both the employer and the retiree. Leaving a satisfying job cold-turkey for a life of leisure can be an abrupt jolt to people accustomed to feeling purposeful, earning money and enjoying their colleagues. From the corporate perspective, it is useful to have experienced hands who can train younger people, pass along institutional wisdom and work with fewer strings attached.
“People in the U.S. define themselves by their work, and they like their co-workers,” said Roselyn Feinsod, senior partner in the retirement practice at the human resources firm Aon Hewitt, the human resources consultancy. Thus, unlike many retirees from past generations, people from both the blue-collar and white-collar sectors are more eager to retain ties to the familiar working world that they enjoyed (and sometimes loathed).
. . .
. . . , Atlantic Health Systems of Morristown, N.J., is among the growing ranks of employers that sponsor a formal program to invite retirees back into the work force, for no more than 1,000 hours a year. The company’s Alumni Club — formerly known as the 1,000 Hour Club — was established in 2006, and about 300 Atlantic Health retirees are currently on the company’s payroll in various capacities. “They’re engaged employees; they’re productive,” said Lesley Meyer, Atlantic Systems’ manager of corporate human resources. “They’re a stable talent pool.”
. . .
Most boomerang retirees return to work after an informal negotiation with a former boss. Programs like the one at Atlantic Systems are still relatively rare — for instance, about 8 percent of the 463 companies surveyed by the Society for Human Resource Management in 2015 had one — but they are on the rise.
They are also tricky to run: Establishing a boomerang retiree program involves a substantial commitment of resources, including systems for navigating complex labor market rules and pension law. Most returning retirees must wait several months before they can come back, and are often limited to that 1,000 hours a year. Companies are increasingly turning to outside staffing firms to manage the nuts and bolts.
. . .
It was a phone call from her former manager that lured Pat Waller, who spent 39 years as an intensive care nurse for Atlantic Health before retiring in 2005 at age 66, back to the work force part time. She joined the Alumni Club in 2007 after the hospital where she had worked, Morristown Medical Center in Morristown, N.J., applied to qualify as a federal center of excellence in knee and hip surgery; her former boss wondered if she would help gather data. Absolutely, she answered.
Since then, Ms. Waller has worked on several projects for Atlantic Health, gigs that easily give her the time to travel with her husband and see her six grandchildren.
Now that she is 77, Ms. Waller works mostly from home, sometimes three to four days a week and other times one to two, depending on the project, “I always said when I was at work I learned something every day,” she said. “Since I’ve come back, I feel the same way.”

For the full story, see:
CHRISTOPHER FARRELL. “Boomerang Boom: Firms Tapping Skills of the Recently Retired.” The New York Times (Sat., December 17, 2016): B4.
(Note: ellipses added.)
(Note: the online version of the story has the date DEC. 16, 2016, and has the title “Retiring; Boomerang Boom: More Firms Tapping the Skills of the Recently Retired.”)

Never Say Die

(p. A7) LONDON — During the last months of her life, a terminally ill 14-year-old British girl made a final wish. Instead of being buried, she asked to be frozen so that she could be “woken up” in the future when a cure was found — even if that was hundreds of years later.
“I want to have this chance,” the teenager wrote in a letter to a judge asking that she be cryogenically preserved. She died on Oct. 17 from a rare form of cancer. “I don’t want to be buried underground,” she wrote.
The girl’s parents, who are divorced, disagreed about the procedure. The teenager had asked the court to designate that her mother, who supported her daughter’s wishes, should decide how to handle her remains.
The judge, Peter Jackson, ruled in her favor. Local news reports said he was impressed by the “valiant way in which she was facing her predicament.” He said she had chosen the most basic preservation option, which costs about £37,000, or nearly $46,000, an amount reportedly raised by her grandparents.
“I want to live and live longer and I think that in the future they might find a cure for my cancer and wake me up,” the teenager wrote in her letter to the judge. Local reports said she had told a relative: “I’m dying, but I’m going to come back again in 200 years.”
. . .
“The scientific theory underlying cryonics is speculative and controversial, and there is considerable debate about its ethical implications,” the judge said in a statement.
“On the other hand, cryopreservation, the preservation of cells and tissues by freezing, is now a well-known process in certain branches of medicine, for example the preservation of sperm and embryos as part of fertility treatment,” the statement said. “Cryonics is cryopreservation taken to its extreme.”
Zoe Fleetwood, the girl’s lawyer, said her client had called Judge Jackson a “hero” after being told of the court’s decision shortly before her death. “By Oct. 6, the girl knew that her wishes were going to be followed,” Ms. Fleetwood told BBC Radio 4. “That gave her great comfort.”

For the full story, see:
KIMIKO DE FREYTAS-TAMURA. “Wish of Girl, 14, to Be Frozen, Is Granted by British Judge.” The New York Times (Sat., NOV. 19, 2016): A7.
(Note: ellipsis added.)
(Note: the online version of the story has the date NOV. 18, 2016, and has the title “Last Wish of Dying Girl, 14, to Be Frozen, Is Granted by Judge.”)

Working Longer May Result in Longer Life

(p. D1) Retiring after age 65 may help people live longer, says a study published online in the Journal of Epidemiology & Community Health. The risk of dying from any cause over the study period was 11% lower among people who delayed retirement for one year–until age 66–and fell further among people who retired between the ages of 66 and 72, the study found.
Even workers who retired for health reasons had a lower risk of dying, compared with those leaving work at 65.
The benefits of remaining in the workforce occurred irrespective of gender, lifestyle, education, income and occupation, the analysis showed.
Postponing retirement may delay the natural age-related decline in physical, cognitive and mental functioning, reducing the risk of chronic illness, the study suggests.

For the full story, see:
ANN LUKITS. “RESEARCH REPORT; Retiring After 65 May Extend Life.” The Wall Street Journal (Tues., May 3, 2016): D1.
(Note: the online version of the story has the date May 2, 2016, and has the title “RESEARCH REPORT; Retiring After 65 May Help People Live Longer.”)

Wu, Chenkai, Michelle C. Odden, Gwenith G. Fisher, and Robert S. Stawski. “Association of Retirement Age with Mortality: A Population-Based Longitudinal Study among Older Adults in the USA.” Journal of Epidemiology and Community Health 70, no. 9 (Sept. 2016): 917-23.

Greenland Shark Likely to Have Lived to at Least 272 Years Old

(p. A11) The mysterious Greenland shark lives at extreme depths in dark, icy waters, which have long protected it from scientists’ prying eyes.
But now, an international group of researchers has estimated the dark brown cartilaginous fish may live as long as 500 years–which would make it the longest-living vertebrate on the planet.
The work, published Thursday [Aug. 11, 2016] in the journal Science, “offers the first hard evidence of how long-lived this poorly understood shark species can be,” said Steve Campana, a shark expert at the University of Iceland in Reykjavik, who wasn’t involved in the study.
. . .
. . . the 11-person team of researchers turned to math models and radiocarbon dating, a technique typically used to date fossils. They focused their work on the eye lens nucleus of each shark, a structure that stops developing at birth and therefore serves as a rough proxy of birth date. They measured the levels of carbon-14 in the tissue, which animals stop accumulating when they die.
The oldest shark in the study, which measured more than 16 feet, lived an estimated 392 years, according to the scientists. Because the study had a margin of error of 120 years for that fish, the researchers concluded the sharks could live up to about 500 years.

For the full story, see:
DANIELA HERNANDEZ. “Enigmatic Shark Can Live for Centuries, Study Says.” The Wall Street Journal (Fri., Aug. 12, 2016): A12.
(Note: ellipses, and bracketed date, added.)
(Note: the online version of the story has the date Aug. 11, 2016, and has the title “Mysterious Greenland Shark May Live Hundreds of Years, Scientists Say.” The online version included several additional sentences, interspersed through the article, that were not included in the print version. The sentences quoted above, appeared in both versions, but the formatting of the quotes above, most closely follow the print version.)

The research article reporting findings discussed above, is:
Nielsen, Julius, Rasmus B. Hedeholm, Jan Heinemeier, Peter G. Bushnell, Jørgen S. Christiansen, Jesper Olsen, Christopher Bronk Ramsey, Richard W. Brill, Malene Simon, Kirstine F. Steffensen, and John F. Steffensen. “Eye Lens Radiocarbon Reveals Centuries of Longevity in the Greenland Shark (Somniosus microcephalus).” Science 353, no. 6300 (Aug. 12, 2016): 702-04.

Androgen Lengthens Telomeres

(p. A3) Androgens, a kind of sex hormone, have been used to treat certain genetic blood disorders for decades. But doctors haven’t been able to pinpoint exactly why they seem to help some patients. A small study puts forth a theory behind androgens’ disease-fighting mechanism: They help stabilize and even rebuild telomeres, which increasingly diminish in certain conditions and aging.
. . .
The authors of the study, published Wednesday [May 18, 2016] in the New England Journal of Medicine, treated telomere-disease patients who had a variety of conditions with a high dose of a synthetic androgen called danazol. The goal was to test whether the treatment would help keep telomeres intact longer. Instead, they saw them lengthen.
. . .
Experts, including the study’s authors, . . . warned against concluding danazol is a fountain of youth for the healthy, based on research that suggests that shrinking telomeres may be involved in aging.
“That,” said Dr. Agarwal, “would be purely in the realm of speculation.”

For the full story, see:
DANIELA HERNANDEZ. “How Sex Hormones Might Treat Some Diseases.” The Wall Street Journal (Thurs., May 19, 2016): A3.
(Note: ellipses, and bracketed date, added.)
(Note: the online version of the story has the date May 18, 2016, and has the title “How Sex Hormones Might Treat Certain Diseases.” The print version starts with a one-sentence summary paragraph that is absent in the online version. The second paragraph in the print version differs slightly from the first paragraph in the online version. The version quoted as the first paragraph above, is the first paragraph of the online version.)

The academic article mentioned above (though the date given by the NYT above appears to be a day too early), is:
Townsley, Danielle M., Bogdan Dumitriu, Delong Liu, Angélique Biancotto, Barbara Weinstein, Christina Chen, Nathan Hardy, Andrew D. Mihalek, Shilpa Lingala, Yun Ju Kim, Jianhua Yao, Elizabeth Jones, Bernadette R. Gochuico, Theo Heller, Colin O. Wu, Rodrigo T. Calado, Phillip Scheinberg, and Neal S. Young. “Danazol Treatment for Telomere Diseases.” New England Journal of Medicine 374, no. 20 (May 19, 2016): 1922-31.

If Rapamycin Works in Humans as in Mice, We Gain 20 Years in Good Health

KaeberleinMattWithDogDobby2016-05 -26.jpg“Dr. Matt Kaeberlein, a biology of aging researcher, with his dog Dobby in North Bend, Wash. He helped fund a drug study using his own money.” Source of caption: p. A12 of print version of the NYT article quoted and cited below. Source of photo: online version of the NYT article quoted and cited below.

(p. A12) But scientists who champion the study of aging’s basic biology — they call it “geroscience” — say their field has received short shrift from the biomedical establishment. And it was not lost on the University of Washington researchers that exposing dog lovers to the idea that aging could be delayed might generate popular support in addition to new data.
“Many of us in the biology of aging field feel like it is underfunded relative to the potential impact on human health this could have,” said Dr. Kaeberlein, who helped pay for the study with funds he received from the university for turning down a competing job offer. “If the average pet owner sees there’s a way to significantly delay aging in their pet, maybe it will begin to impact policy decisions.”
The idea that resources might be better spent trying to delay aging rather than to cure diseases flies in the face of most disease-related philanthropy and the Obama administration’s proposal to spend $1 billion on a “cancer moonshot.” And many scientists say it is still too unproven to merit more investment.
The National Institutes of Health has long been organized around particular diseases, including the National Cancer Institute and the National Institute of Diabetes and Digestive and Kidney Diseases. There is the National Institute on Aging, but about a third of its budget last year was directed exclusively to research on Alzheimer’s disease, and its Division of Aging Biology represents a tiny fraction of the N.I.H.’s $30 billion annual budget. That is, in part, because the field is in its infancy, said the N.I.H. director, Dr. Francis Collins.
. . .
“The squirrels in my neighborhood have a 25-year life span, but they look like rats that live two years,” said Gary Ruvkun, a pioneer in aging biology at Harvard Medical School. “If you look at what nature has selected for and allowed, it suggests that you might be able to get your hands on the various levers that change things.”
. . .
Over 1,500 dog owners applied to participate in the trial of rapamycin, which has its roots in a series of studies in mice, the first of which was published in 2009. Made by a type of soil bacterium, rapamycin has extended the life spans of yeast, flies and worms by about 25 percent.
But in what proved a fortuitous accident, the researchers who set out to test it in mice had trouble formulating it for easy consumption. As a result, the mice were 20 months old — the equivalent of about 60 human years — when the trial began. That the longest-lived mice survived about 12 percent longer than the control groups was the first indication that the drug could be given later in life and still be effective.
Dr. Kaeberlein said he had since achieved similar benefits by giving 20-month-old mice the drug for only three months. (The National Institute on Aging rejected his request for funding to further test that treatment.) Younger mice, given higher doses, have lived about 25 percent longer than those not given the drug, and mice of varying ages and genetic backgrounds have been slower to develop some cancers, kidney disease, obesity and symptoms of Alzheimer’s disease. In one study, their hearts functioned better for longer.
“If you do the extrapolation for people, we’re probably talking a couple of decades, with the expectation that those years are going to be spent in relatively good health,” Dr. Kaeberlein said.
. . .
. . . what dog lovers have long considered the sad fact that their pets age about seven times as fast as they do, Dr. Kaeberlein knew, would be a boon for a study of rapamycin that would have implications for both species. An owner of two dogs himself, he was determined to scrounge up the money for the pilot phase of what he and Dr. Promislow called the Dog Aging Project.
Last month, he reported at a scientific meeting that no significant side effects had been observed in the dogs, even at the highest of three doses. And compared with the hearts of dogs in the control group, the hearts of those taking the drug pumped blood more efficiently at the end. The researchers would like to enroll 450 dogs for a more comprehensive five-year study, but do not yet have the money.
Even if the study provided positive results on all fronts, a human trial would carry risks.
Dr. Kaeberlein, for one, said they would be worth it.
“I would argue we should be willing to tolerate some level of risk if the payoff is 20 to 30 percent increase in healthy longevity,” he said. “If we don’t do anything, we know what the outcome is going to be. You’re going to get sick, and you’re going to die.”

For the full story, see:
AMY HARMON. “CHASING IMMORTALITY; Dogs Test Drug Aimed at Humans’ Biggest Killer: Age.” The New York Times (Tues., MAY 17, 2016): A1 & A12.
(Note: ellipses added.)
(Note: the online version of the story has the date MAY 16, 2016, and has the title “CHASING IMMORTALITY; Dogs Test Drug Aimed at Slowing Aging Process.”)

An academic paper that discusses the wide variability in life span of different species in the order Rodentia (which includes short-lived rats and long-lived squirrels), is:
Gorbunova, Vera, Michael J. Bozzella, and Andrei Seluanov. “Rodents for Comparative Aging Studies: From Mice to Beavers.” Age 30, no. 2-3 (June 25, 2008): 111-19.