Ozzy Osbourne in 2010

Target Health Inc. was at TEDMED  in San Diego, the last week of October, where on the last day of the conference, Ozzy and Sharon Osbourne discussed their decision to have their individual genomes mapped.  After this last section of the conference, one of Ozzy’s songs was sung, while he and Sharon joined the TEDMED audience.  The appearance of these two rock celebrities, caused a stir.  Some attendees thought it made TEDMED less serious.  Target Health Inc: “The more people who understand the importance of individually mapped genomes, the better, because genome mapping leads to personalized medicine………..plus the cost of doing it, goes down.”

Bio-IT-World.com, November 2, 2010, by Kevin DaviesLast year, shortly after completing work on rock music legend Ozzy Osbourne’s memoir, I Am Ozzy, the Sunday Times (London) reporter Chris Ayres was sitting next to Knome CEO Jorge Conde at the TedMed conference in San Diego. (Knome was the first company to offer full-genome sequencing for individuals back in 2007.)

“When Ozzy and I began to do the weekly ‘Dr Ozzy’ column for The Sunday Times — now also in Rolling Stone – I got the idea to ask [Knome] about possibly sequencing Ozzy’s genome as a one-off article. It snowballed from there,” says Ayres.

John Michael “Ozzy” Osbourne, the former lead singer of Black Sabbath, has become the latest member of the celebrity genome club, joining Glenn Close, Archbishop Desmond Tutu, Jim Watson, Craig Venter, Henry ‘Skip’ Gates and others. On October 24, Osbourne penned an absorbing 3,500-word account in the Sunday Times Magazine [subscription required] of his reaction to being presented with his personal genome on a souped-up thumb drive.

Osbourne is a curious character for a genome sequencing project, but his lively musical career, characterized by controversial episodes involving the occasional decapitation of birds and bats onstage and the consumption of copious quantities of drugs and alcohol, makes Ayres and others curious as to whether the secret of his extraordinary longevity lies in the sequence of his DNA.

Osbourne, who described himself as “a rock star, not Brain of Britain,” initially needed some convincing to go along. “The only ‘genome’ I’d ever heard of was the kind you find at the bottom of the garden with a little white beard and a pointy red hat,” he wrote. “The only Gene I know anything about is the one in Kiss.” But he came around. After all, he wrote, “Given the swimming pools of booze I’ve guzzled over the years — not to mention all the [drugs] . . . there’s really no plausible medical reason why I should still be alive. Maybe my DNA could say why.”

Backing Band

Supporting Osbourne was a tight three-piece outfit. The sequencing was conducted at St Louis-based Cofactor Genomics, performed on the Life Technologies SOLiD 4 platform, which also assisted in the early bioinformatic analysis. The final genomic interpretation and presentation was handled by Knome.

Cofactor Genomics was established in 2008 by former members of The Genome Center (TGC) at Washington University, St Louis, who worked in the technology development group under Elaine Mardis. “We’d see people come to The Genome Center with cool projects, but there were reasons why they couldn’t take it on – capacity, funding issues, etc.,” says Jon Armstrong, Cofactor’s chief marketing officer.

Armstrong and colleagues had plenty of experience installing new sequencing platforms, including the very first Solexa machine (serial number #001). “Because of Elaine Mardis and Rick Wilson, we couldn’t have done what we’ve done without being under their tutelage. We had a unique and privileged outlook on the emergence of next-gen sequencing and how that hardware interfaces with genomics. We’ve been involved in the development of those protocols and producing very high quality data under time constraints and doing it right the first time.”

Cofactor offers Life Technologies’ SOLiD 4 and Illumina’s GA IIx instruments, and is contemplating whether to acquire Illumina’s HiSeq 2000, but needs “to understand what that machine means on our operational and fiscal side,” says Armstrong. Other platforms, such as Ion Torrent, might prove a better fit depending on how the sales pipeline evolves. Sometimes, “using a paring knife instead of a cleaver is a better choice,” he says. Armstrong says Cofactor has “a very strong analysis component,” and a good relationship with NGS software company NovoCraft (Malaysia), using NovoAlign for Illumina work and NovoAlign CS for some of the SOLiD data.

Early work focuses mostly on RNA sequencing, with steady business coming from the biofuels and agricultural sector. Cofactor is also preparing a major project with Sigma to sequence the genomes of several strains of rat and build a publicly available database of rat genomic variation.

As for Ozzy, Armstrong was approached by Life Technologies asking if he would be interested in “an amazing opportunity” that had come up. He was told that Life Technologies “needed this done right the first time.” Ozzy was not Cofactor’s first whole genome sequence, but it was Cofactor’s first serious use of the SOLiD 4 machine.

Cofactor generated 39 Gigabases of Osbourne’s sequence (13X coverage) over about three weeks using both long-insert mate pairs and fragment reads. (Human genomes are usually sequenced to 30X coverage, but Osbourne’s sequence was time sensitive.) About 70 percent of the DNA reads were mappable, which he calls “very good.”

Life Line

Houston-based Matt Dyer has a field-based position with Life Technologies, supporting Midwest users of the SOLiD platform on issues including experimental design and data analysis. “Jarret [Glasscock, Cofactor CEO] contacted me, and said they needed some help for an urgent, once-in-a-lifetime project,” says Dyer, who didn’t need to be asked twice. “I’m a big fan of biology and bioinformatics — though not Black Sabbath necessarily!” he says.

Because of the urgency of the project, Dyer used cloud resources offered by Penguin Computing (Penguin On Demand). After Cofactor uploaded the sequence data to the cloud, Dyer logged on and took over, with immediate access to thousands of compute nodes. No read filtering was performed. “We don’t do any filtering — we let the mapping do the filtering,” says Dyer. “If the read is bad, it won’t map to the reference.”

BioScope is Life Technologies’ integrated framework that allows users to perform secondary analysis (mapping sequence back to the reference) and tertiary analysis (e.g. SNP calling, indels, CNVs), all within a single software package. BioScope can run on many different types of hardware, but Dyer says, “for folks who can’t maintain an expensive IT infrastructure, they can use this fee-for-service cloud, buying the CPU hours they need.”

Dyer used BioScope to map Ozzy’s sequence reads to the human reference genome (HG18) – the process took about 8-10 hours. From there, he created BAM files, which were then used for the tertiary analysis. “We gave those pipelines the BAM file and asked to return the SNPs and small indels,” he says. Knome was able to download the SNP and indel data via FTP, while Dyer shipped the full sequence data on a hard drive.

Not gnome, Knome!

“Ozzy is a pretty unique guy with an extraordinary life but he’s still around to talk about it. We thought we could highlight someone, an everyman if you will,” recalls Jorge Conde. He received some external funding (he did not identify the source) while Life Technologies funded the reagent sequencing.

Knome took the assembled sequence and ran it through its internal analysis pipeline, producing a richly annotated genome and a set of interesting DNA variants to select for further analysis. Knome’s director of research, Nathan Pearson, then flew to the UK recently to deliver Osbourne’s results in person, but not before he had conferred with Osbourne’s wife, Sharon, a judge on America’s Got Talent.

“We thought about what it is that makes Ozzy unique,” says Conde. “Given he’s a musician and he’s been diagnosed with a Parkinson’s-like tremor, we looked for things associated with nerve function. We found a couple of interesting things – but as Nathan says, ‘We found smoke but no fire.’ There was no ‘Ozzy variant’ – that goes without saying.” The interesting variants lie in the genes TTN (associated with deafness and Parkinsonism) and CLTCL1 (brain chemistry). They might merit further study, Conde suggests.

Knome also found a novel variant in the ADH4 alcohol metabolizing gene, which might explain Osbourne’s legendary high tolerance for alcohol. Ironically, Osbourne is highly sensitive to caffeine, and has the genetic variant to prove it. Another interesting variant was in the COMT gene – Osbourne carries two versions of the gene that have been associated with “worrier” and “warrior” behavioral tendencies.

Another interesting tidbit was the ability to screen Osbourne’s genome for traces of Neanderthal DNA, following new evidence of ancient inter-breeding between humans and Neanderthals emerging from the Neanderthal genome study. “We were looking for matches for long segments unique to Neanderthals, and found a couple of pretty long segments [in Osbourne’s genome],” says Conde. “But George Church [Knome co-founder] has 3x as much matching segment.”

Overall, Conde says Knome enjoyed working on Ozzy’s genome. “I don’t think doing celebrity genomes is a business model,” he says, “but we’re thrilled to work on interesting projects as they come along. This was a lot of fun!”

Life Technologies’ Matt Dyer agrees. He says the project was “a great example of how genomics and bioinformatics helps us understand what makes you you and me me.”

As for those front-row Ozzy Osbourne World Tour tickets – the Prince of Darkness descends on St Louis on December 10 and Houston on January 18, 2011 — Dyer says: “Still waiting for those!”

GoogleNews.com, London, Oct 25, 2010  —  Ozzy Osbourne is a descendant of a Neanderthal man, according to researchers who have studied the singer’s DNA.

The researchers discovered that the star shares some DNA with the ancient Romans who were killed in Pompeii when Mount Vesuvius erupted in 79 AD.

He is also a distant relative of outlaw Jesse James, the last Russian tsar Nicholas II and King George I.

Most of us have some Neanderthal genes, study finds.

A Neanderthal-female reconstruction based on both fossil anatomy and DNA (file photo).

Photograph by Joe McNally, National Geographic

Croatia’s Vindija cave, where Neanderthal bones used to assemble genome were found. Image courtesy of Johannes Krause MPI-EVA.

By Ker Than for 2010 National Geographic News

The study uncovered the first solid genetic evidence that “modern” humans—or Homo sapiens—interbred with their Neanderthal neighbors, who mysteriously died out about 30,000 years ago.

What’s more, the Neanderthal-modern human mating apparently took place in the Middle East, shortly after modern humans had left Africa, not in Europe—as has long been suspected.

“We can now say that, in all probability, there was gene flow from Neanderthals to modern humans,” lead study author Ed Green of the University of California, Santa Cruz, said in a prepared statement.

That’s no surprise to anthropologist Erik Trinkhaus, whose skeleton-based claims of Neanderthal-modern human interbreeding—previously contradicted with DNA evidence—appear to have been vindicated by the new gene study, published in the May 2010 journal Science.

“They’ve finally seen the light … because it’s been obvious to many us that this happened,” said Trinkaus, of Washington University in St. Louis, Missouri, who wasn’t part of the new study.

Trinkhaus adds that most living humans probably have much more Neanderthal DNA than the new study suggests.

“One to 4 percent is truly a minimum,” Trinkaus added. “But is it 10 percent? Twenty percent? I have no idea.”

Surprising Spot for Neanderthal-Human Mating

The genetic study team reached their conclusion after comparing the genomes of five living humans—from China, France, Papua New Guinea, southern Africa, and western Africa—against the available “rough draft” of the Neanderthal genome.

The results showed that Neanderthal DNA is 99.7 percent identical to modern human DNA, versus, for example, 98.8 percent for modern humans and chimps, according to the study.)

In addition, all modern ethnic groups, other than Africans, carry traces of Neanderthal DNA in their genomes, the study says—which at first puzzled the scientists. Though no fossil evidence has been found for Neanderthals and modern humans coexisting in Africa, Neanderthals, like modern humans, are thought to have arisen on the continent.

“If you told an archaeologist that you’d found evidence of gene exchange between Neanderthals and modern humans and asked them to guess which [living] population it was found in, most would say Europeans, because there’s well documented archaeological evidence that they lived side by side for several thousand years,” said study team member David Reich.

For another thing, Neanderthals never lived in China or Papua New Guinea, in the Pacific region of Melanesia, according to the archaeological record.)

“But the fact is that Chinese and Melanesians are as closely related to Neanderthals” as Europeans, said Reich, a population geneticist at the Broad Institute of MIT and Harvard University.

Neanderthal-Human One-Night Stand?

So how did modern humans with Neanderthal DNA end up in Asia and Melanesia?

Neanderthals, the study team says, probably mixed with early Homo sapiens just after they’d left Africa but before Homo sapiens split into different ethnic groups and scattered around the globe.

The first opportunity for interbreeding probably occurred about 60,000 years ago in Middle Eastern regions adjacent to Africa, where archaeological evidence shows the two species overlapped for a time, the team says.

And it wouldn’t have taken much mating to make an impact, according to study co-author Reich. The results could stem from a Neanderthal-modern human one-night stand or from thousands of interspecies assignations, he said.

More DNA Evidence for Neanderthal-Human Mating

The new study isn’t alone in finding genetic hints of Homo sapiens-Homo neanderthalensis interbreeding.

Genetic anthropologist Jeffrey Long, who calls the Science study “very exciting,” co-authored a new, not yet published study that found DNA evidence of interbreeding between early modern humans and an “archaic human” species, though it’s not clear which. He presented his team’s findings at a meeting of the American Association of Physical Anthropologists in Albuquerque, New Mexico, last month.

Long’s team reached its conclusions after searching the genomes of hundreds of modern humans for “signatures of different evolutionary processes in DNA variation.”

Like the new Science paper, Long’s study speculates that interbreeding occurred just after our species had left Africa, but Long’s study didn’t include analysis of the Neanderthal genome.

“At the time we started the project, I never imagined I’d ever see an empirical confirmation of it,” said Long, referring to the Science team’s Neanderthal-DNA evidence, “so I’m pretty happy to see it.”

A “first draft” of the Neanderthal genome is adding to evidence that the extinct human species (above, an artist’s reconstruction of a Neanderthal female) was lactose intolerant and could have shared some basic language capabilities with modern humans, researchers announced in February 2009.

The study team hopes the genome may help explain what gave modern humans an evolutionary edge over Neanderthals, which vanished about 30,000 years ago.

Although there are many genes involved in language,” Pääbo said, “there’s no reason to say that they couldn’t articulate the way that we do.”

In addition, the genome offers more proof that Neanderthals couldn’t digest lactose as adults, a condition that today affects close to 50 million U.S. adults, according to the American Gastroenterological Association.

“We can see the Neanderthal was not able to drink milk, [after] they were weaned,” Pääbo said.

Researchers plan to make more comparisons like this, for instance, by looking at genes involved in brain development.

“In humans, we have a lot of recent evolutionary changes,” that could explain our species’ differing intellects, said anthropologist John Hawks at the University of Wisconsin in Madison, who was not involved in the project.

“I’ll be looking at whether there are parallel changes in the ancient Neanderthal lineage.”

Stefan Lovgren
for National Geographic News

A division of labor according to sex and age gave modern humans an advantage over Neandertals, a new study says.

The emergence of “female labor roles” played an important role in human evolutionary history, because it allowed early-human hunter-gatherer societies to draw on more food resources and live in larger communities, researchers say.

It may help explain why the Neandertals (also spelled “Neanderthals”), who occupied Europe until modern humans arrived some 45,000 years ago, went extinct.

“The competitive advantage enjoyed by modern humans came not just from new weapons and devices but from the ways in which their economic lives were organized around … roles for men, women, and children,” said Steven Kuhn, an anthropologist at the University of Arizona in Tucson.

Kuhn co-authored the study with University of Arizona colleague Mary Stiner. It appears in the the journal Current Anthropology.

Out of Africa

Some research has suggested that the practice of dividing labor according to sex dates back as far as two million years.

But the new study suggests the changes didn’t occur until the upper Paleolithic period, which lasted from about 45,000 years ago to 10,000 years ago.

“We argue that the typical patterns of labor division emerged relatively recently in human evolutionary history,” Kuhn said.

At sites dating back to the upper Paleolithic, researchers have found evidence of an emergence of skill-intensive crafts, such as bone awls and needles used to make clothes. They have also found small animal and bird remains.

As in hunter-gatherer societies of the recent past, men likely hunted large animals while women gathered small game and plants, enabling a more efficient use of available food sources.

When small game and plant foods were scarce, women and older children were often involved in other vital activities, such as producing clothing and shelter.

The researchers say this division of labor between sexes is likely to have arisen in a tropical environment.

It was a crucial evolutionary moment for modern humans and may have facilitated the spread of modern humans throughout Eurasia after leaving Africa some 60,000 years ago, the researchers say.

The scientists point out in their study that gender roles were not always the same in early-human cultures, and there’s nothing that predisposes either sex toward certain kinds of work.

“That women sometimes become successful hunters and men become gatherers means that the universal tendency to divide subsistence labor be gender is not solely the result of innate physical or psychological differences between the sexes; much of it has to be learned,” the authors write.

Big Game Hunt

The importance of specialized tasks is something the Neandertals apparently never learned.

Ancient Neandertal sites provide little evidence for any reliance on subsistence foods, such as milling stones to grind nuts and seeds.

Instead, the Neandertals, who lived in Europe from about 250,000 years ago until they disappeared about 30,000 years ago, preyed almost exclusively on large animals like bison, deer, and wild horses.

“This would have been a fragile system,” the authors write. “In flush times, Neandertals would have lived high on the hog (or the red deer), but they may have lacked the kind of diversified resource base and labor network … needed to buffer them from major population losses in lean times.”

Female skeletons found at Neandertal sites, like those of their male counterparts, have been shown to be robustly built, sometimes featuring healed fractures.

This suggests that the women didn’t stay at home but joined the men in the often dangerous practice of hunting large game.

Wesley Niewoehner, an anthropologist at California State University in San Bernardino, has studied Neandertal hand mechanics.

“I’ve always been impressed by the observation that female Neandertal hand bones indicate that their hands were just as powerful as those of male Neandertals,” he said.

“This indicates to me that female Neandertals were doing things with their hands that required significant physical force.”

“Whether this fact means that female Neandertals were performing the same tasks as their male counterparts, or they were simply performing different tasks that required the same amount of force, is up for debate,” he said.

“Nevertheless, this line of evidence does support an interpretation that the Neandertal sexual division of labor, or lack thereof, may have been fundamentally different from the division of labor in modern-human groups.”

No Silver Bullet

John Shea, an anthropologist at Stony Brook University in New York State, says there is no single factor that explains the demise of the Neandertals.

“The risk we face when we have one very good study, like this one, is that people who don’t appreciate the problem of variability in [Neandertal] environments over time will take this pattern and say … this is why they went extinct: They didn’t divide labor by sex,” he said.

“Everyone wants to have one explanation, but it’s not the way evolution works,” he added. “It’s never one simple cause.”

Kuhn says his study expands the conversation beyond climate, stone tools, and animals bones to include social factors to explain the Neandertal demise.

“Anthropologists have known for a long time that the ways different human groups cooperate and manage their labor are as important to their success as the kinds of implements they use,” he said.

The findings, he added, should not be taken as a justification for the separation of roles for men and women in contemporary society.

“We shouldn’t look to the remote past for clues about how we ought to behave today,” Kuhn said.

A new study shows Neandertals and humans share the same version of a gene, FOXP2, which contributes to advanced language.The finding suggests that Neandertals might have talked like modern humans.      Illustration courtesy U.S. Department of Energy Genome Programs

John Roach
for National Geographic News

A new cave discovery suggests that Neandertals survived until at least 28,000 years ago—2,000 years longer than previously thought.

The Iberian Peninsula—now home to Spain, Portugal, and Gibraltar—was a final holdout for Neandertals (often spelled “Neanderthals”) as modern humans spread across the rest of Europe and an ice age descended, a new study says (map of the Iberian Peninsula).

Clive Finlayson, an anthropologist at the Gibraltar Museum, and his colleagues studied Neandertal artifacts in Gibraltar’s Gorham Cave. Gibraltar, located at the southern tip of Spain, is an overseas territory of the United Kingdom.

The oldest deposits in the cave date back to 120,000 years ago.

“In that context Neandertals were occupying the cave on and off for the better part of a hundred thousand years,” Finlayson said. “It must have been a pretty special place.”

Finlayson’s team reports its findings on the Web site of the journal Nature.

Radiocarbon Dates

The researchers used radiocarbon dating on 22 pieces of microscopic charcoal found among Neandertal tools in fire pits in Gorham Cave.

According to the dating results, Neandertals repeatedly visited the cave until at least 28,000 years ago and perhaps as recently as 24,000 years ago.

While some of the youngest pieces date to 24,000 years ago, the team is cautious in their interpretation of that material because it is found lower down in the site than older material.

Mixing from the repeated use of the fire pit may or may not explain the messy order.

Nevertheless, Finlayson said, the date of 28,000 years ago “is younger than anything else available today” as evidence of Neandertals.

In an accompanying commentary in Nature, Eric Delson of the American Museum of Natural History in New York City and Katerina Harvati of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, put the early dates in context.

“Such a late survival would reinforce the importance of southern Iberia as a refuge area at a time when modern humans were expanding and diversifying culturally across mid-latitude Europe,” they write.

Last Stand

Scientists believe Neandertals and modern humans are two different species that shared a common ancestor and overlapped for several thousand years in Europe.

Modern humans arrived in western Europe at least 32,000 years ago. Competition between the species in a period of climate change is believed to have doomed the Neandertals by around 30,000 years ago.

But the two species did not overlap at Gorham Cave, allowing Neadertals there to survive for much longer, according to the Gibraltar Museum’s Finlayson.

Modern humans are believed to have spread north from Africa into Europe, then west, reaching the Iberian Peninsula last.

The first evidence of modern humans in Iberia is dated to about 18,500 years ago. Before that, human populations in neighboring areas were small, according to Finlayson.

And the mountainous, rugged landscape of the peninsula “probably contributed a lot to keeping the populations isolated from each other,” he said.

Without modern humans as competition, the Neandertals likely feasted freely on plants and animals that inhabited the region’s woodlands, sandy plains, wetlands, and shoreline.

As the climate cooled in more northern latitudes and modern humans moved farther south and west, “these last pockets [of Iberian Neandertals] kept doing what they had always done,” Finlayson said.

But about 24,000 years ago, according to analysis of sediment, a period of prolonged drought struck the region and likely doomed the last Neandertals, he says.

Dates Questioned

Paul Mellars is an archaeologist at the University of Cambridge in England and co-author of a review paper on radiocarbon dating techniques published in Nature. That paper revised the timeline for the spread of modern humans across Europe.

According to Mellars, the idea that the Iberian Peninsula was the last place modern humans reached and that it served as a Neandertal refuge is “perfectly plausible.”

“The question is whether these dates provide evidence of it. And frankly, I don’t think they do,” he said.

Mellars said of the late Neandertal dates presented by Finlayson and colleagues, “The majority are around 30,000 to 32,000 years ago.

“If you’ve got a spread of dates, you should look at the majority of the dates you find, not just the ones that happen to be younger,” he said.

“Second,” he continued, “radiocarbon dates—whether on charcoal or anything else—can be very prone to contamination by more recent carbon that is intrusive from the top [layers of material.”

Contamination of even one percent of the sample, Mellars says, can skew dates 3,000 to 4,000 years younger.

“That makes me think at least some of those dates—the younger dates, 24,000, 28,000—are almost certainly contaminated,” he said.

Finlayson counters that his analysis ruled out contamination of the sample from the higher levels.

Delson and Harvati, the Nature commentators, say Finlayson and colleagues were correct to cite 28,000 years ago as the youngest date.

“There are just too many instances of dates younger than 28,000 years that are out of order, implying that these dates might not be reliable,” they write.

“More extensive sampling of the in situ [unremoved] hearth and surroundings might resolve this issue.”

A map shows the previously known range of Neandertals (dark gray) and an extended range suggested by a new study (light gray).The research looked at a type of genetic material known as mitochondrial DNA (mtDNA). Sites where Neandertal mtDNA was previously found are shown with open circles, while two new sites found to contain such mtDNA are depicted with black circles.

Anthropologists work at the Ortvale Klde Rockshelter, a significant Neanderthal-modern human site in the republic of Georgia.  Drawing on evidence from animal remains found there–largely the bones of a mountain goat species called the Caucasian tur–the scientists have determined that Neandertals at the site were as capable hunters as the modern humans who later lived in the area.

The New York Times, November 2, 2010, by Jane E. Brody  —  Many changes take place in physical abilities as we age. Try as I may, I simply can’t swim as fast at 69 as I did at 39, 49 or even 59. Nor am I as steady on my feet. I can only assume my strength has waned as well — I’m finding bottles and jars harder to open and heavy packages harder to lift and carry.

But in August, I hiked in the Grand Canyon, prompting my 10-year-old grandson Stefan to ask, “Grandma, how many 69-year-olds do you think could do this?”

The answer, of course, is “a lot.” And the reason is that we work at it. For my part, I exercise daily, walking three miles or biking 10, then swimming three-quarters of a mile. In spring and summer, heavy-duty gardening strengthens my entire body.

But now that my physically stronger spouse is gone, I see that I need to make some improvements. With no one handy to open those jars or lift those heavy objects, I’ve begun strength training so I can remain as independent as possible as long as possible.

In a newly published book, “Treat Me, Not My Age”(Viking), Dr. Mark Lachs, director of geriatrics at the NewYork-Presbyterian Healthcare System, discusses two major influences (among others) on how well older people are able to function.

Delaying Bodily Decline

The first, called physiologic reserve, refers to excess capacity in organs and biological systems; we’re given this reserve at birth, and it tends to decrease over time. In an interview, Dr. Lachs said that as cells deteriorate or die with advancing age, that excess is lost at different rates in different systems.

The effects can sneak up on a person, he said, because even when most of the excess capacity is gone, we may experience little or no decline in function. A secret of successful aging is to slow down the loss of physiologic reserve.

“You can lose up to 90 percent of the kidney function you had as a child and never experience any symptoms whatsoever related to kidney function failure,” Dr. Lachs said. Likewise, we are born with billions of brain cells we’ll never use, and many if not most of them can be lost or diseased before a person experiences undeniable cognitive deficits.

Muscle strength also declines with age, even in the absence of a muscular disease. Most people (bodybuilders excluded) achieve peak muscle strength between 20 and 30, with variations depending on the muscle group. After that, strength slowly declines, eventually resulting in telling symptoms of muscle weakness, like falling, and difficulty with essential daily tasks, like getting up from a chair or in and out of the tub.

Most otherwise healthy people do not become incapacitated by lost muscle strength until they are 80 or 90. But thanks to advances in medicine and overall living conditions, many more people are reaching those ages, Dr. Lachs writes: “Today millions of people have survived long enough to keep a date with immobility.”

The good news is that the age of immobility can be modified. As life expectancy rises and more people live to celebrate their 100th birthday, postponing the time when physical independence can no longer be maintained is a goal worth striving for.

Gerontologists have shown that the rate of decline “can be tweaked to your advantage by a variety of interventions, and it often doesn’t matter whether you’re 50 or 90 when you start tweaking,” Dr. Lachs said. “You just need to get started. The embers of disability begin smoldering long before you’re handed a walker.”

Lifestyle choices made in midlife can have a major impact on your functional ability late in life, he emphasized. If you begin a daily walking program at age 45, he said, you could delay immobility to 90 and beyond. If you become a couch potato at 45 and remain so, immobility can encroach as early as 60.

“It’s not like we’re prescribing chemotherapy — it’s walking,” Dr. Lachs said. “Even the smallest interventions can produce substantial benefits” and “significantly delay your date with disability.”

“It’s never too late for a course correction,” he said.

In a study published in The Journal of the American Medical Association in 2004, elderly men and women who began strengthening exercises after a hip fracture increased their walking speed, balance and muscle strength and reduced their risk of falls and repeat fractures.

“Minor interventions that may seem trivial — like lifting small weights with multiple repetitions — can lead to dramatic improvements in quality of life,” Dr. Lachs said.

Supportive Environment

As with your body, your environment can be tweaked to enhance life in the upper decades. You can make adjustments at home to anticipate medical problems you are likely to face as you get older — allowing you to keep your independence, remain in familiar surroundings and minimize the risk of injury.

As Dr. Lachs put it, “It’s not just mold and radon that can make homes sick.” His colleague Rosemary Bakker says that most dwellings and equipment today were designed for 21-year-olds, and she has listed a set of issues that can jeopardize older people’s ability to function safely on their own:

¶Windows or doors that are hard to open.

¶Poor lighting, especially in crucial areas like the bathroom and kitchen.

¶ Rugs, irregular floors and other tripping hazards.

¶Tubs and showers that are hard to use if you have arthritis.

¶Stair widths or heights that are difficult to negotiate if you have neurological troubles.

¶Appliances and utensils that are challenging to handle if you have limited manual dexterity.

¶Poor layout of rooms, like a bathroom far from the bedroom, that can be a problem when you walk slowly.

Ms. Bakker, a certified interior designer with a master’s degree in gerontology, is the author of “AARP Guide to Revitalizing Your Home: Beautiful Living for the Second Half of Life” (Lark, 2010). The book shows how homes can be modified to promote lifelong safety and independence and still remain stylish. Many ideas can be found on her Web site, environmentalgeriatrics.com.

“These things are underpublicized, underappreciated and underutilized,” Dr. Lachs writes. Most fixes are simple and unobtrusive and “many are dirt-cheap,” he said, adding that if money is tight, it is best spent on improvements in the bathroom.

Photograph by Joel Sartore, National Geographic.com

November 2, 2010, Photo of the Day: Animal Migration Photos

Millions of monarch butterflies travel to ancestral winter roosts in Mexico’s shrinking mountain fir forests. Surfing winds from southern Canada and the northern U.S., they travel thousands of miles, taking directional cues from the sun.