A notorious Alzheimer’s disease villain may also be a germ-busting superhero. Amyloid-beta gums up the brains of people with Alzheimer’s but also takes out dangerous brain invaders, scientists report May 25 in Science Translational Medicine.

As strong as steel, tough strands of A-beta protein imprison pathogens that threaten the body and brain, experiments in mice and worms show. Those results raise the possibility that A-beta plays a role in the immune system and its accumulation in Alzheimer’s might be prompted by an infection.
Earlier studies have shown that A-beta can bust germs in cells in dishes, but the new experiment shows A-beta protection in living mice and worms. Mice engineered to have the human form of A-beta better survived a brain infection of Salmonella bacteria than mice without the human A-beta, Robert Moir and Rudolph Tanzi, both of Harvard Medical School, and colleagues found. And in the bodies of worms, A-beta helped stave off the dangerous yeast Candida.

When researchers injected Salmonella into mice’s hippocampi, a brain area damaged in Alzheimer’s, A-beta quickly sprang into action. It swarmed the bugs and formed aggregates called fibrils and plaques. “Overnight you see the plaques throughout the hippocampus where the bugs were, and then in each single plaque is a single bacterium,” Tanzi says. That rapid response was surprising, he says. “No one expected that.”
And those prisons are probably permanent, Moir says. “In A-beta, those fibrils set like concrete and the bugs have no chance of ever getting out.”

Alzheimer’s has been linked to a host of bacterial, fungal and viral infections, says immunologist Kevan Hartshorn of Boston University School of Medicine. That work, along with the new study, raises the possibility that Alzheimer’s could be spurred by an immune response to a pathogen.

That’s “an extremely provocative and interesting hypothesis,” says neuroscientist Berislav Zlokovic of the University of Southern California in Los Angeles, who says the new data are convincing. But it remains to be seen whether the results are relevant for people with Alzheimer’s. Zlokovic and colleagues recently found that the barrier between brain and blood weakens with age — a situation that could let more microbes into the brain and perhaps spur A-beta accumulation.
A-beta appears to be a general immune system fighter that’s effective against many enemies, says Moir. “This is a classical innate immune response, which means that whatever gets thrown at it, it does the same thing,” he says. “So whether it’s a herpesvirus, a spirochete or chlamydia, it’s going to generate A-beta plaques.”

Moir also raises the possibility that the amyloid’s germ-busting job might play a role in other diseases that come with amyloid accumulation, such as diabetes or heart disease. “I think we may have stumbled across an underlying theme in a lot of major diseases,” he says.

Finding this helpful role for A-beta may complicate a therapeutic approach for Alzheimer’s that attempts to reduce levels of the protein with antibodies, says molecular pharmacologist Marina Ziche of the University of Siena in Italy. “I have always been very skeptical about that approach,” and the new results suggest that people benefit from some A-beta, Ziche says.

The next step is to see whether pathogens are entombed in A-beta plaques in the human brain, Tanzi says. “Now it’s time to start looking for them in patients.” To start, he and colleagues have just begun a project to catalog the collection of microbes in healthy brains and brains with Alzheimer’s.

Finding a strong link between pathogens and Alzheimer’s could suggest new ways to prevent the disease, Tanzi says. Vaccines that fight infections, for instance, might be one way to prevent A-beta pileup.

Two more of the ingredients for life as we know it have turned up in space, this time from a comet orbiting the sun. While hints of both have been seen in comets before, this is the clearest evidence to date.

Glycine, the smallest of the 20 amino acids that build proteins, is floating in the tenuous atmosphere of comet 67P/Churyumov-Gerasimenko, researchers report online May 27 in Science Advances. Comet 67P’s atmosphere also holds phosphorus, which is essential to DNA and RNA. Both detections support the idea that comets are at least partly responsible for seeding early Earth with material needed for life.
The phosphorus, glycine and a handful of other organic molecules were detected by the European Space Agency’s Rosetta spacecraft, which has been in orbit around 67P since August 2014 (SN: 9/6/14, p. 8). Kathrin Altwegg, a planetary scientist at the University of Bern in Switzerland, led the study.

Previous searches for glycine in comets Hale-Bopp and C/1996 B2 (Hyakutake) turned up nothing. Glycine was seen in samples from the Stardust mission, which flew through the tail of comet Wild 2 in 2004 and brought comet dust back to Earth, but those measurements were complicated by lab contamination. Scientists have detected hints of phosphorus in comet Halley.

Life’s ingredients keep turning up in cosmic environments. Meteorites carry amino acids and simple sugars have been seen in interstellar clouds(SN: 10/9/04, p. 237). And several of the essential molecules for DNA and RNA, such as ribose, have been created in laboratory experiments that simulate ice grains exposed to ultraviolet radiation from young stars (SN: 4/30/16, p. 18).

Giant squid are the stuff of nightmares. They were even one of the deadly dangers in Jules Verne’s 20,000 Leagues Under the Sea, attacking the Nautilus in a group and carrying off one of the crew:

Just as we were crowding each other to reach the platform, two more arms lashed the air, swooped on the seaman stationed in front of Captain Nemo, and carried the fellow away with irresistible violence…. What a scene! Seized by the tentacle and glued to its suckers, the unfortunate man was swinging in the air at the mercy of this enormous appendage. He gasped, he choked, he yelled: ‘Help! Help!’ … The poor fellow was done for.

What makes Verne’s giant squid all the more frightening is that he didn’t invent the creatures; giant squid strandings had been documented in Europe since at least 1639, and scientists informally described the animals in the late 1850s.

But even if we don’t really have to worry about the huge invertebrates snatching people off boats, giant squid remain mysterious. They weren’t even photographed in the wild until 2004. And many questions remain unanswered about them. The biggest: Just how giant can the giants get? A new study has come up with an estimate — and also highlights the many reasons why it’s so difficult to come up with one.

Charles Paxton of the University of St. Andrews in Scotland starts by laying out five ways that it should be possible to estimate squid length, and why the first four aren’t great measures. Anecdotal accounts — which claim giant squid reaching lengths of 30 meters and 53 meters, not counting the two long tentacles — are often riddled with inaccuracy and exaggeration. Estimating maximum length based on squid growth rate won’t work because squid growth rates just aren’t well known. Some scientists have tried to determine lengths based on the sucker scars found on whales, but since scientists don’t know how whale growth affects the sizes of those scars, those aren’t a good measure either.

Direct measurement of dead squid would seem to be a good option, except that the two long tentacles of a squid — which extend far beyond the animal’s arms and determine its full length — are elastic and can change in length when a squid is preserved, Paxton notes. That leaves the fifth method — estimating length based on the size of the hard beak. Beak size and squid body length are related.

Paxton combined the last two methods to come up with a maximum length for a giant squid of about 20 meters, from the top of its mantle, or body, to the tip of its long tentacles. His estimate appears May 17 in the Journal of Zoology.
The longest squid ever reported was 17.37 meters long, and Paxton questions its veracity, as does another paper published last year in PeerJ. Craig McClain of Duke University and colleagues note that the “longest scientifically verified giant squid” measured a mere 12 meters. “What limits the large size of [giant squid] is unclear,” McClain and colleagues write. But metabolic demands may play a role, keeping squid from getting much bigger than what have washed up onto shore (and also keeping them in the cold depths where they’re so difficult for us to find).

But perhaps the focus on the largest and biggest of species is the wrong approach, McClain and his colleagues argue (in, ironically, a paper all about large marine species). The longest, most giant individuals are, after all, just a tiny fraction of a species — and, these researchers write, “these individuals may reach these extraordinary large sizes through developmental or genetic defects and may not represent the healthiest or, in evolutionary terms, the fittest.”

They are, though, among the most mysterious creatures to inhabit our planet.

From California to China, desert moss (Syntrichia caninervis) braves life in hot deserts and still stays hydrated. What’s its secret? The moss gathers water via a topsy-turvy collection system in its leaves.

Moss leaves have tiny hairlike points at their ends called awns. Previous evidence pointed to a potential role for the awns in water collection and prompted Tadd Truscott of Utah State University and his colleagues to zero in on the structures.

Imaging exposed a system of barbs that line the awns and catch tiny airborne water droplets, the team reports June 6 in Nature Plants. When the air is misty, foggy or the least bit humid, trapped dewdrops move up grooves in the moss leaves by capillary action. The tiny drops form a bigger drop to be absorbed and stored by the plant. When it rains, moss awns reduce splash and capture raindrops by the same mechanism.

Most desert plants, especially cacti, get their water from roots, but moss may not be the only plant that uses unique leaf structures to stock up on water, the team argues.

For the second time, scientists have glimpsed elusive ripples that vibrate the fabric of space. A new observation of gravitational waves, announced by scientists with the Advanced Laser Interferometer Gravitational-Wave Observatory, LIGO, follows their first detection, reported earlier this year (SN: 3/5/16, p. 6). The second detection further opens a new window through which to observe the universe.

“The era of gravitational wave astronomy is upon us,” says astronomer Scott Ransom of the National Radio Astronomy Observatory in Charlottesville, Va., who is not involved with LIGO. “Now that there’s two, you can’t get around that anymore.”

Both sets of cosmic quivers were wrought in cataclysmic collisions of black holes. But the latest observation indicates that such merging pairs of black holes are a varied bunch — the newly detected black holes were much smaller than the first pair. And this time, scientists concluded that one in the pair was spinning like a top.
“The most important thing is that it’s a second one,” says LIGO spokesperson Gabriela González of Louisiana State University in Baton Rouge. “But it’s important that it’s different, because it shows that there’s a spectrum of black hole systems out there.”

The two black holes in the most recent detection were about eight and 14 times the mass of the sun and were located roughly 1.4 billion light-years from Earth, the scientists estimate. When the pair fused, they formed one bloated black hole with a mass 21 times that of the sun. One sun’s worth of mass was converted into energy and carried away by the gravitational waves, LIGO scientists announced June 15 in San Diego during a meeting of the American Astronomical Society.
“Gravitational astronomy is real,” LIGO laboratory executive director David Reitze said in a news conference. “The future is going to be full of binary black hole mergers for LIGO.”

A paper describing the finding was published online June 15 in Physical Review Letters.

As the two black holes spiraled around each other and slammed together, they churned up cosmic undulations that stretched and squeezed space — as predicted by Einstein’s general theory of relativity. These waves careened across the universe, reaching LIGO’s twin detectors in Hanford, Wash., and Livingston, La., on December 26, 2015.

Each L-shaped LIGO detector senses the minuscule stretching and squeezing of space across its two 4-kilometer arms. As a gravitational wave passes through, one arm lengthens while the other shortens. Laser light bouncing back and forth in the arms serves as an ultrasensitive measuring stick that can pick up those subtle length changes (SN: 3/5/16, p. 22). As the gravitational waves rumbled past Earth in December, they stretched and squeezed the arms by less than a thousandth the width of a proton. “That’s very, very small,” González said. “That’s like changing the distance between Earth and the sun by a fraction of an atomic diameter.” This tiny deviation, appearing in both detectors nearly simultaneously, was enough to pick out the telltale ripples.

Compared with LIGO’s previously detected black hole merger, this one was a more minor dustup. These black holes were less than half the size of those in the first merger (30 and 35 solar masses according to a recently revised estimate). And the signal of their coalescence was more subtle, hiding under the messy wiggles in the data that result from random fluctuations or unwanted signals from the environment.
The first detection stunned scientists, due to the surprisingly large masses of the black holes and the whopping signals their gravitational waves left in the data. But the new black hole merger is more in line with expectations.
“This is comfort food,” says physicist Emanuele Berti of the University of Mississippi in Oxford, who is not involved with LIGO. “If you had asked me before the first detection, I would have bet that this would have been the first kind of binary black hole to be observed, not the monster we saw.”

There’s little question about whether the signal is real — a false alarm of this magnitude should occur only once in 200,000 years. “It’s very, very exciting,” says physicist Clifford Will of the University of Florida in Gainesville. It “looks like a very solid discovery.”

In a new twist, the scientists found that one of the two merging black holes was spinning. It was rotating at a speed at least 20 percent of its maximum possible speed. Using gravitational waves to study how pairs of black holes twirl could help scientists understand how they form.

The scientists used their data to put general relativity through its paces, looking for deviations from the theory’s predictions. But the black holes’ behavior was as expected.

LIGO also saw hints of a third black hole collision on October 12. The evidence was not strong enough to claim a definitive detection, though.

LIGO is currently offline, undergoing improvements that will allow the detectors to peer even further out into space. Scientists expect it to be back up and running this fall, churning out new detections of gravitational waves. “Now we know for sure that we’ll see more in the future,” González says.

AUSTIN, TEXAS — Success of an indoor spraying campaign to combat malaria on an African island may have started a worrisome trend in local mosquito evolution.

Since 2004, using pesticides inside homes has eradicated two of four malaria-spreading Anopheles mosquitoes on Bioko Island in Equatorial Guinea, vector biologist Jacob I. Meyers of Texas A&M University in College Station reported June 19 at the Evolution 2016 meeting. Numbers of the remaining two species have dropped. Yet the dregs of these supposedly homebody species are showing a rising tendency to fly outdoors looking for a blood meal, Meyers and colleagues cautioned. The results were also reported April 26 in Malaria Journal.

If the mosquitoes continue to shift toward outside bloodsucking, the campaign could lose some of its bite. Repeated treatments of indoor walls with pesticides that kill mosquitoes clinging to them may not be so effective if the pests venture from home.

What’s changing about these mosquitoes remains to be seen, but this looks like more than simple opportunism, Meyers said. Bed nets are not common, so Meyers doubts that the mosquitoes fly outdoors because no one is available to bite indoors. Nor does their reaction look like escape from repellent pesticides: Outdoor biting didn’t consistently rise after a spraying. The next step is to check for a genetic basis for the shift. Lots of research has explored physiology that lets insects resist pesticides, Meyers said, but the onset of possible resistant behavior has barely been explored.

Bottoms up, from the distant past. Thanks to a new method of analyzing the chemicals in liquids absorbed by clay containers, researchers have uncorked the oldest solid evidence of grape-based wine making in Europe, and possibly the world, at a site in northern Greece.

Chemical markers of red wine were embedded in two pieces of a smashed jar and in an intact jug discovered in 2010 in the ruins of a house destroyed by fire around 6,300 years ago at the ancient farming village of Dikili Tash.
After successfully testing the new technique on replicas of clay vessels filled with wine, then emptied, the scientists identified chemical markers of grape juice and fermentation in clay powder scraped off the inner surfaces of the Dikili Tash finds. None of the vessels contained visible stains or residue, researchers report online May 24 in the Journal of Archaeological Science.

Remains of crushed grapes found near the ancient jar shards and jug had already indicated that Dikili Tash farmers made wine or grape juice, say chemist Nicolas Garnier of École Normale Supérieure in Paris and archaeobotanist Soultana Maria Valamoti of Aristotle University of Thessaloniki in Greece.

Previous reports of ancient wine have largely relied on chemical markers of grapes but not the fermentation necessary to turn them into wine, leaving open the possibility that containers held grape juice. The “juice versus wine” conundrum applies to roughly 7,400-year-old jars from Iran (SN: 12/11/04, p. 371), Garnier says.

Asteroid enthusiasts, rejoice! Thursday, June 30 is your day to remind the world that humankind is just one impact with a space rock away from annihilation (or, at the least, a very bad day).

Asteroid Day, started in 2015, brings together scientists, artists and concerned citizens to raise awareness of the hazards of asteroid impacts and build support for solutions that might avert disaster from the skies. Events are planned at museums, science centers and other locations around the world.

The date coincides with the anniversary of the most powerful impact in recorded history, when a roughly 40-meter-wide asteroid crashed near Tunguska, Siberia, in 1908. The run-in flattened about 2,000 square kilometers of forest and released about 185 times the energy of the atomic bomb detonated over Hiroshima. Estimates vary, but such collisions happen roughly once every several hundred to 1,000 years.

Homo naledi, currently the best-known and most mysterious fossil species in the human genus, may be considerably younger than previously thought, a new investigation suggests.

Evolutionary trees of ancient hominids statistically reconstructed from skull and tooth measurements indicate that H. naledi lived around 912,000 years ago, say paleoanthropologist Mana Dembo of Simon Fraser University in Burnaby, Canada, and her colleagues. That’s a provisional estimate, since researchers have yet to date either H. naledi’s bones or the sediment in which some of its remains were excavated.
The new statistical age estimate, described by Dembo’s group in the August Journal of Human Evolution, challenges proposals that H. naledi’s remains come from early in Homo evolution. Researchers who first studied H. naledi bones retrieved from an underground cave in South Africa noted similarities of the skull and several other body parts to early Homo species dating to between 2.5 million and 1.5 million years ago (SN: 10/3/15, p. 6).

A comparison of H. naledi skull measurements to those of 10 other hominid species, conducted by paleoanthropologist J. Francis Thackeray of the University of the Witwatersrand in Johannesburg, reached the same conclusion. H. naledi lived roughly 2 million years ago, Thackeray proposed in the November/December 2015 South African Journal of Science.

Dembo disagrees. Her team tested which of 60,000 possible evolutionary trees best fit skull and tooth measurements of H. naledi, 20 other hominid species, gorillas and chimpanzees. The new analysis keeps H. naledi in the genus Homo. But it’s still unclear which of several hominid species — including Homo sapiens, Homo floresiensis (or “hobbits”) and Australopithecus sediba (SN: 8/10/13, p. 26) — is most closely related to the South African species.

Dembo’s team found no signs that bones assigned to H. naledi represent a variant of Homo erectus, as some scientists have argued. H. erectus originated about 1.8 million years ago in Africa and rapidly spread to West Asia. But Dembo’s statistical model assumes that H. erectus skulls and teeth vary in shape throughout Africa and Asia much less than they actually do, says paleoanthropologist Christoph Zollikofer of the University of Zurich. Bones assigned to H. naledi most likely represent a form of H. erectus, he argues.

Further statistical comparisons that include measurements of limb and trunk bones may help to clarify H. naledi’s evolutionary relationships, Dembo says.
Based on geological dates for all hominids except H. naledi, the researchers also calculated the rate at which each species’ skull and tooth features evolved over time. Those results enabled the researchers to estimate H. naledi’s age.

“Homo naledi might be less than a million years old,” Dembo says. She considers that estimate “reasonably robust,” since ages calculated for other hominids in the analysis often fell close to dates gleaned from fossil and sediment studies. In a few cases, though, statistical and geological age estimates differed by 800,000 years or more.

A relatively young age for H. naledi expands the number of Homo species that survived well into the Stone Age, Dembo says. Small-brained H. naledi would have existed at the same time as larger-brained Homo species in Africa, just as small-brained H. floresiensis lived at the same time as larger-brained H. sapiens and H. erectus in Southeast Asia (SN: 7/9/16, p. 6).

If that scenario holds up, H. naledi may have made roughly 1-million-year-old stone tools that have been found in southern Africa, Dembo says.

“A young date for Homo naledi shouldn’t be unexpected,” says paleoanthropologist Matthew Tocheri of Lakehead University in Thunder Bay, Canada. At least some H. naledi bones appear not to have fossilized, he notes, consistent with a more recent age.

While Dembo’s statistical approach to hominid evolution shows promise, “a good geological date for H. naledi will trump the new date,” Tocheri adds.

Paleoanthropologist Bernard Wood of George Washington University in Washington, D.C., doesn’t think Dembo’s approach can accurately date H. naledi. But humanlike hands, feet and teeth of the South African hominid support the possibility that it lived about 1 million years ago, Wood says.

Two H. naledi researchers — John Hawks of the University of Wisconsin–Madison and Witwatersrand’s Lee Berger — still suspect the South African species lived at least 1.8 million years ago, based on its skeletal similarities to H. erectus. But a possible age of about 900,000 years for the cave finds, as proposed by Dembo, would be consistent with H. naledi or closely related species having survived in Africa for a million years or more, Hawks and Berger write in the current Transactions of the Royal Society of South Africa.

The scene was stranger than it looked, even by Las Vegas standards: Two young men pull up in a U-Haul truck to a motel outside the city. They check in and move a cooler into their room. They appear to be handling something of importance, and look to see if the ice needs replenishing. Inside the cooler is not the makings of epic hangovers but instead an experiment in eternal youth.

Tucked within, protected from the desert heat, are more than a hundred tiny pond invertebrates. One of the men, Daniel Martínez, with a Ph.D. in ecology and evolution a month or so old, is rearing these little organisms to test a claim that they somehow stay young all their lives, no more likely to die as years go by as they are early on. They can die, however, from high temperatures or starvation. Leaving the animals on their own for more than a day invites disaster, so if Martínez travels, even stopping for sightseeing with his brother in Las Vegas, all the animals in the aging experiment travel, too.
Their road trip was in 1993, when the “dogma,” as Martínez recalls, was that evolution would not allow any multicelled organism to escape aging. Just as humans age, the thinking was, other organisms also decline in health as time goes by, with death becoming more and more likely. Yet few people at the time were bothering to document aging in any creatures other than a few standard lab residents.
Biologists have long tracked aging in fruit flies and lab mice (SN: 7/23/16, p. 16), but a bloom of recent data from more diverse organisms is stirring up discussion about how aging could have evolved — and if it’s inevitable. The ongoing studies of Martínez’s pampered pond invertebrates and a massive effort to study aging in a roadside weed are good examples of these provocative approaches. They’re shaking up basic assumptions of a long-standing theory and inspiring new thinking to explain why there’s so much crazy variety in how life deteriorates — or maybe doesn’t.
Old ideas
Deciding whether an organism is aging can get tricky. For humans, the slowing and graying, the wrinkling and creaking are all too obvious. But what about plants? Or fungi? For a metric that applies across many species, evolutionary biologists often focus on how the number of deaths in a population changes over a particular period of time. If this death rate increases as time passes, the organism ages. (In this scheme, life span is irrelevant. A hypothetical species that lives for just a few months but keeps its death rate flat until the end would still be considered “biologically immortal.”)

Early evolutionary thinkers proposed that aging followed by death is a good thing, another marvel of the mindless force of natural selection. Built into individuals, this inevitable decline kept feeble parents from sapping resources from the young.

But the idea that aging evolved as a boon for the next generation “is really nonsense,” says Axel Kowald of Newcastle University in England, a biochemist who specializes in the bioinformatics of aging. Among the many objections: It’s hard to see why a lucky few that could live a bit longer and continue to reproduce wouldn’t overtake a population. With more offspring, they’d spread more of their genes. Over time, then, genes for aging should be few, fewer, gone.

One of the modern mainstream explanations of aging rests on the idea that evolutionary forces lose their power to edit as adulthood stretches on. As genes are copied generation after generation, mutations are made. Natural selection can remove from a population the typos that harm the young; disadvantaged carriers don’t pass those mistakes down to the next generation in much abundance.

Mistakes that cause trouble late in life, however, can be almost impossible to purge, argued the late zoologist Sir Peter Medawar, a Nobel laureate who titled his autobiography Memoir of a Thinking Radish. In a 1951 lecture, he explained this approach to aging by whimsically tracing the perilous lives of laboratory test tubes. The mortality rate of these hypothetical test tubes, which for the sake of explanation reproduced more than once in their lives, allowed few tubes to reach old age. Test tubes that don’t reach old age don’t reveal detrimental effects from mutations that act only late in life. Therefore natural selection didn’t have a chance to stop those mutations from being passed down to test tube babies. In a scenario now called mutation accumulation, the late-acting mutations could thus build up and cause the declines of aging, also known as senescence. Natural selection doesn’t weed out these mutations because, Medawar said, wild organisms “simply do not live that long.”

In a perverse twist on this idea, natural selection might not just allow genes that bring late-life decrepitude to accumulate but also might favor those genes. Evolutionary biologist George C. Williams, later eulogized as a quiet and deep thinker with the look of Abraham Lincoln, argued in 1957 that genes with split personalities, like Jekyll and Hyde, could help explain aging. The benefits of these genes appear early in life and the gene is thus passed to the next generation, with its downside revealed as frailty only late in life.
Till death do us part
In the 1990s, as the theories were then understood, a widespread idea was that “nothing can escape aging,” Martínez says. Yet as a graduate student at Stony Brook University in New York, he read about some tiny hydra species that had extraordinary powers. These branching bodies can reproduce by budding off clone babies, and they can rebuild themselves after dismemberment. What’s more, they didn’t appear to deteriorate with passing time. Biological immortality was a grand claim for these distant jellyfish relatives, soft translucent stalks a few millimeters tall with a tuft of tentacles wiggling from the top. But no one had done a rigorous test collecting the hydra and tracking their death rates.
Martínez eventually set up 145 Hydra vulgaris in laboratory luxury, where no predator could reach them and they could enjoy catered food all their lives. “When I started doing the experiment, I thought that I was going to prove that hydra could not escape aging,” he says. “A year and a half later I got my Ph.D. — the hydra were still with me.” The expected rise in death rate that characterizes aging organisms still hadn’t started. “I got a postdoc at University of California, Irvine,” he says, “so I crossed the country in a U-Haul truck with the hydra and all my furniture.”

The truck was supposed to be air-conditioned but wasn’t, and with a hot engine right under the cab, driving a southern route pulling a trailer, Martínez had to keep careful track of ice for the hydra cooler. Plus, there was all the changing of water, the feeding, the raising brine shrimp so the hydra had live prey. This was when the whole party visited Las Vegas.

The hydra made it. (Martínez, however, no longer even considers a hydra project without a technician to manage their care.) In 1998 he published results of four years of hydra watching. His title was cautious: “Mortality patterns suggest lack of senescence in hydra.”

“I published the paper and forgot about it,” says Martínez, now at Pomona College in Claremont, Calif.

Opinions about the inevitability of aging continued to run strong — as demographer James Vaupel of the Max Planck Institute for Demographic Research in Rostock, Germany, discovered in 2002. At a workshop on aging in nonhuman species, Vaupel stood up to say that the paper he had found most interesting was one describing mortality rates in a roadside weed. The rates appeared to drop as time passed, leading Vaupel to propose it as a possible case of what he called “negative senescence.”

“My remark was met with ululations of horror, cries of derision, hisses and boos,” Vaupel says. Eminent biogerontologists said that theorist William Hamilton had proved decades earlier that mortality, at least in repeatedly reproductive adults, universally rises with age and “there was no need for the audience to listen to a demographer who didn’t understand biology.”

Further data on the weed showed a more complex story, but the meeting outcry had a meaningful effect. As soon as Vaupel got back to his Rostock lab, he asked Annette Baudisch, then a new Ph.D. student, to “figure out why Hamilton’s proof was wrong.”

Baudisch published her critique of Hamilton in the Proceedings of the National Academy of Sciences in 2005. Hamilton’s proof could not explain the full diversity of aging, she argued. Some species that keep growing throughout adulthood, tortoises and many plants, for example, might not be included.

Though some researchers believe there’s still much truth to Hamilton’s approach, Vaupel took this conclusion as a cue to go questing for examples of prolonged youth. He talked Martínez into redoing the hydra experiment — but bigger. Instead of four years, the test ran for eight. Instead of 145 animals, the team had multiyear data from 2,256.

The resulting paper came out last year in the Proceedings of the National Academy of Sciences. Two species of hydra, with their many representatives divided between Claremont and Rostock for raising, had continued their usual low-drama lives, feeding and budding off babies but not showing any upsweep in their mortality rates. In 10 of the 12 groups, the annual probability of death stayed around 0.6 percent, and two groups held steady with an even lower annual rate of 0.09 percent.

Continuing the tests until the whole study population died, which would be ideal for tracking the hydra’s entire life history, would take more than 1,000 years, researchers calculate. But eight years of data gave Martínez and Vaupel confidence. The old view that aging is inevitable, the paper declared, “is no longer tenable.”

The hydra results so far are “solid evidence” that not all species age, Kowald says. And there are other, less-studied candidates for what’s called negligible senescence, too: three-toed box turtles and bristlecone pines, for instance.

Into the wild
The lab, of course, isn’t where evolution shapes life. Biologists seeking to understand how aging evolved need to know if and how organisms age in the wild, research that is likewise challenging Medawar’s pronouncements.

The plant study that caused a ruckus for Vaupel was an early version of a test by Deborah Roach, a plant evolutionary biologist now at the University of Virginia in Charlottesville. Her results from 4,476 ribwort plantains (Plantago lanceolata), set out at a long-term research site in Durham, N.C., had suggested that this common roadside weed was escaping the supposedly inevitable decline of aging. But construction of a new art museum wiped out those plots after less than five years.

After moving to Virginia and summoning the resolve to start the experiment again, Roach selected meadows at Thomas Jefferson’s birthplace, close to Charlottesville and under the protection of local historical preservationists. During the years 2000 through 2002, an army of undergraduates set out 30,000 plantains, all of known genetic heritage and marked for individual monitoring.

After collecting seven years of data on when plants died, Roach picked up a subtle signal she hadn’t observed in Durham. At first, plantains of different ages had about the same mortality rates, all relatively low, with six-month mortality rates at less than 10 percent. But during the three years that followed, the plantains clearly struggled. Roach suspects soggy winters plus competition from neighboring foliage were to blame. Death rates rose to around 30 percent and — this was the important bit — the death rates climbed higher for the older plants. A population that had looked as if it weren’t physically declining with age showed signs of senescence when the going got tough.

The results contradict Medawar’s fundamental assumption that life is so short and brutal in the wild that the possibility of seeing frail, aged organisms there would be exceedingly rare. “Now we have a great body of literature showing that in fact there are these old animals out there, these old plants,” Roach says.
A 2013 tally by Dan Nussey of the University of Edinburgh and an international array of colleagues documented more examples of aged organisms in the wild — 175 species, in fact, including Dall sheep, antler flies and great tits, among others. A study of painted turtles published June 7 in the Proceedings of the National Academy of Sciences added that species to the list, showing that human impacts might inadvertently be nudging an Illinois population toward senescence.

Across the tree of life, aging now looks more varied than old ideas predicted. Drawing on data for 46 species, Vaupel, Baudisch (now at the University of Southern Denmark in Odense) and 12 coauthors published a paper in 2014 featuring a full page of mortality curves, which track how the number of deaths in a given group changes over time. Many of the organisms show the expected upsweep with time, but other curves are idiosyncratic. The curve of Soay sheep curls concavely downward during early adulthood before rising again to a rounded hilltop in old age. Alpine swifts’ curve looks like a side view of a lawn chair relaxed way back for a summer snooze.

With mortality data on so few of the species on Earth, it’s too early to pronounce big trends. So far, body size and life span don’t appear to dictate the shape of the curve: The curves of water fleas and lions look remarkably similar. Organisms from different kingdoms can also have similar curves: The curves for desert tortoises and netleaf oaks both tilt downward.

“We’re going to have to figure out what it is about the biology of these species that explains the variety,” Roach says. The new reports, she adds, “are putting a big, bold spotlight on the theories and saying, ‘Hey guys, we need to update.’”

Think again
Last year in Experimental Gerontology, Kowald and Thomas Kirkwood of the Institute for Ageing at Newcastle University proclaimed that Medawar’s idea about natural selection losing its power appears to be “difficult to reconcile” with new research. The discussion on that point isn’t over yet, though.

Baudisch, for her part, would like theoretical frameworks that describe aging (or its lack) as part of the whole topography of change during a life. “Theories that just deal with the end of life don’t speak to all this diversity,” she says. “Physicists don’t make theories that only apply on Sundays.”

One long-standing approach does offer more of a whole-life framework. Kirkwood proposed the approach, called disposable soma theory, back in 1977. Wild organisms have to split their limited resources between reproduction and maintaining the soma, the nonreproducing parts of the body, he noted. In many cases, the best strategy demands such liberal spending on reproduction that there’s not enough left for full upkeep of the rest of the body. Aging is, in this interpretation, the sum of deferred maintenance.
Australian Antechinus marsupials and members of two related genera offer the most dramatic example of mammals that forgo upkeep for extravagant reproduction. The climate where these marsupials live supplies a surge of insect nourishment for nursing moms only once a year. The males, roughly the size of mice or rats, grow disproportionately large testes and devote all their resources to vying for fatherhood, Diana Fisher of the University of Queensland in Australia and her colleagues reported in 2013. After healthy males reach adulthood, they stop producing new sperm , start mating and, a few weeks later, are all dead. Their immune systems collapse. A once-per-lifetime bout of intense competition leads males to what Fisher calls “suicidal reproduction.”
The hydra species in the big lab test pursue a different strategy. Because they can regenerate and reproduce through budding, there is no distinction between reproductive cells and soma. Kirkwood says that the lack of senescence in hydra fits easily with the disposable soma approach. He would bet on their immortality.

He also thinks the ideas proposed by Medawar and Hamilton still have great value, with “central relevance to understanding aging.” To explain all the recently uncovered variety in aging, researchers may simply need more than these theories. They might need to know, for example, the particulars of a species’ home, be it pond, meadow or bug-rich forest.

Understanding these details may or may not allow humankind to do much about the process of aging. But creating better theories might finally reveal how some pale brainless squiggles of pond life may have achieved perpetual youth when humankind, despite all its apparent sophistication, has not.