Warning to anyone planning a crime: don’t drink the water.

Scientists are reporting this evening that an analysis of hydrogen and oxygen isotopes in human hair reveals where a person drank water, which will allow investigators to figure out if a suspect was in the vicinity of a crime—and also to track past movements of unidentified murder victims.

The new technique analyzes isotopes of hydrogen and oxygen, forms of the elements that have an extra neutron in its atomic nucleus. The ratio of oxygen-18 to oxygen-16 in air is the same everywhere, and ratios of both hydrogen and oxygen ratios in food are also basically the same across the country because the American food supply is so uniform. But water is still like a microbrew, containing different constituents depending on where it comes from.

As a result, geochemist Thure Cerling and ecologist Jim Ehleringer of the University of Utah report in the journal Proceedings of the National Academy of Sciences, a single hair bears clues to where someone has been over the last few weeks or even years, depending on the length of the hair. “You are what you eat and drink—and that is recorded in your hair,” said Cerling in a statement from the university.

Salt Lake County Sheriff's Detective Todd Park is using the hair-isotope method to try to identify a murdered woman whose remains were found by hunters near Interstate-80 along the south end of the Great Salt Lake on October 8, 2000. Detectives recovered 26 bones, some hair, a T-shirt and a necklace. Despite creating a facial reconstruction and publicizing it nationally, the police have been unable to ID the woman, who stood about 5 feet tall and was 17 to 20 years old when she was killed. But when Park arranged with Ehleringer for an isotope analysis of the victim’s hair, it showed that for the last two years of her life she lived in the Northwest, mostly in the Idaho-Montana-Wyoming area, and maybe into Oregon and Washington. Park hopes that examining missing persons records from those areas will lead to an ID.

Ehleringer and Cerling are co-founders of IsoForensics, Inc., which sells isotopic analysis of forensic substances. A method Ehleringer developed to trace the origins of cocaine or heroin is now used by the a method now used by the U.S. Drug Enforcement Administration: variations in the amount of carbon, nitrogen, oxygen and hydrogen isotopes in soil and water show up in coca and poppy plants.

For the hair analysis, says Ehleringer, “You can tell the difference between Utah and Texas,” but probably not Chicago and Kansas City. In general, the amount of the heavy isotopes oxygen-18 and hydrogen-2 levels in drinking water decreases as you move inland from the West Coast: as rainstorms move off the Pacific Ocean, rain drops containing oxygen-18 and hydrogen-2 tends to fall first because it is heavier. But cloud temperatures and season also affect which isotopes rain drops contain, with the result that heavy isotopes are also relatively more common in water inland from the Gulf and southern Atlantic coasts. The lowest concentrations of hydrogen-2 and oxygen-18 are found in water in northern and western Montana, north-central Idaho and northwest Wyoming (because the heavy isotopes drop out of clouds before they reach these inland areas), while the highest amounts of hydrogen-2 and oxygen-18 in drinking water and hair are in southern Oklahoma, north-central Texas, Florida, south Georgia and southern South Carolina (in warm regions with more evaporation, lighter-isotope water evaporates from surface sources first, leaving heavier-isotope water behind to find its way into drinking water.

If the band of showers stretching from the Midwest to New England dampens voter turnout today, we’ll know what to blame.

Cars. Factories, too.

Meteorologists have long known that particles “seed” rainclouds, a process in which water and ice in the clouds grab hold of the particles, forming additional (and larger) droplets that are more likely to fall as rain. That led to the suggestion that particulate pollution emitted by traffic, businesses and factories, all of which are greater during the workweek than on the weekend (traffic to malls notwithstanding), should make for greater rainfall Monday through Friday. A competing theory, however, held that the increased pollution might instead thwart rainfall, by dispersing the water in clouds over more seeds; that would prevent the droplets from growing large enough to fall as rain.

At least for summertime rainfall in the southeastern United States, the verdict is in: weekday pollution is causing more rainfall midweek than on weekends.

So conclude scientists analyzing data from NASA’s Tropical Rainfall Measuring Mission satellite, known as TRMM. As they report in the Journal of Geophysical Research-Atmospheres, those data show that midweek storms tend to be more intense than those during the weekend, dropping more rain, compared to calmer and drier weekends. Human-caused atmospheric pollution also peaks midweek, as the emissions from tailpipes and smokestacks build up before falling off as Friday approaches.

The scientists find that, on average, it rains more between Tuesday and Thursday than from Saturday through Monday. Tuesday has 1.8 times more rainfall than Saturday, which has the least amount of afternoon rain. Now I understand why, on this Super Tuesday, I am wringing out my drenched socks after venturing out into the storm to vote.

Think of one word that can form a compound word with “sauce,” “pine” and “crab.”

I’ll wait . . . .

Time’s up: did you come up with “apple,” to make “applesauce,” “pineapple” and “crabapple”? OK, let’s consider that a warmup. Try the same exercise—finding a word to make a compound word—with “bump,” “step” and “egg.”

Did “goose” pop into your head?

One more: for “back” “clip” and “wall.” . . . .It’s “paper,” for “paperback,” “paperclip” and “wallpaper.”

If you’re like many people, you tried to solve each problem methodically, first finding a word that would go with, say, “sauce” and then trying it out with “pine” and “crab.” But if you’re like most people in a more important way, if you solved these brain-teasers you did so not through this grind-through-the-possibilities approach, but through insight. That is, you thought a little and then, wham, the answer suddenly hit you.

Scientists have approximately no idea how this happens.

The murder of gorillas in Congo which so shocked the world's conscience is only the tip of the iceberg of the threats facing vanishing primates. This evening, Conservation International is releasing a report documenting the world's 25 most endangered apes, monkeys, lemurs and other primates, which are under unprecedented threat from destruction of tropical forests, illegal wildlife trade and commercial bushmeat hunting.

Today, 29 percent of all species in danger of going extinct, and we may soon witness the first primate extinctions in more than a century. (Overall, 114 of the world’s 394 primate species are classified as threatened with extinction.) One species, Miss Waldron’s red colobus of Ivory Coast and Ghana, already is feared extinct, while the golden-headed langur of Vietnam and China’s Hainan gibbon number only in the dozens. The Horton Plains slender loris of Sri Lanka has been sighted just four times since 1937.

Some images of the possibly doomed:

I'm pretty conservative about attributing weird weather and other climate anomalies to global warming: all you can say is that a record-setting hot October, or a string of 70-degree days in January in New York, is consistent with what a greenhouse world would be like. But when scientists go on record with a specific prediction of how climate change will play out, and when it indeed plays out that way, attention must be paid.

Last year, a study in the journal Science found that "large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons." The greatest increases were in forests of the Northern Rockies, but was seen throughout the west The pattern of western fires matched what would be expected not from changes in land use--mostly logging and ranching--but from climate change.

Specifically, a warmer world caused by the accumulation of heat-trapping greenhouse gases produces alternating deluges and droughts. The extra heat causes greater evaporation, but the water vapor remains in the atmosphere longer, or travels farther, before falling--in buckets. The result is alternating wet and dry years. In wet years, vegetation grows like mad. In drought years, that vegetation becomes tinder, exactly what southern California is now experiencing. As the scientists said, "an increased incidence of large, high-severity fires may be due to a combination of extreme droughts and overabundant fuels."

And no, it's not just a matter of media attention or the ubiquity of fire video on YouTube. The scientists found that the frequency of wildfires beginning in the mid-1980s was nearly four times that of 1970 to 1986, "and the total area burned by these fires was more than six and a half times its previous level." It's real, and it's going to continue.

Hit a wall in your efforts to construct your family tree? Can’t get past the garbled last name that authorities at Ellis Island conferred on great-grandpa Maurizio? It’s DNA to the rescue—or, as critics say, yet another example of questionable “recreational genetics.”

Tomorrow, Ancestry.com, the Website where 15 million people have been accessing census and other records to build their family trees since the company’s founding in 1997, is rolling out its latest genealogy resource. Called DNA Ancestry, it starts by having you take a cheek-swab sample and mail it to the company, which will compare it to DNA samples in its database and tell you if it gets a hit—that is, someone to whom you are even distantly related. If it finds someone, you can contact him or her through an anonymous email and piggy-back on their own genealogy research. “If you don’t know your family history, you can match your DNA profile to one in our database and connect to other people who are related to you and might have broken through the wall” of historical records needed to construct a family tree, says Ancestry.com vice-president Brett Folkman.

Both women and men can have a DNA analysis of their mitochondrial DNA for $179. mtDNA, which is inherited by sons and daughters from their mothers, has become a standard way for a number of online sites to trace ancestry, as Family Tree DNA and Ancestry By DNA, among others, do. Men can also have their Y chromosome, which is inherited by sons (but not daughters) from their fathers virtually unchanged, analyzed for $149 or $199, depending on whether you want 33 or 46 genetic markers included. Unlike other DNA-based ancestry sites, which focus on telling you where in the world—sometimes down to the village—your family roots are sunk and even when your “family” migrated out of Africa tens of thousands of years ago, DNA Ancestry aims to link you to specific individuals. It can’t tell you your exact relationship to someone else, only that a relationship exists. For example, a Y-DNA test could verify that you’re related to a co-worker, but not that you both share the same great-grandfather.

This will work as the company says—linking you to someone who has mined federal census data from 1790 to 1930 and the 100 million names in passenger ship records from 1820 to 1960 in Ancestry’s database, among other sources, to piece together a family tree—only if Ancestry.com has lots of DNA profiles in its database. Within six months, that should be about 50,000, says Megan Smolenyak, the company’s chief family historian and co-author of the 2004 book "Trace Your Roots with DNA." “As more people add their results,” she says, “the DNA Ancestry database becomes a powerful asset for users to make connections and discover their family tree.”

The question is whether even 50,000 is enough. The service might tell you that you and another user share a great-great-grandfather—that is, four generations back. Everything more recent than that would diverge, so although genealogical research that this long-lost cousin of yours has done might fill in the distant parts of your family tree, it won’t help much with the branches that include your grandfather’s and father’s generations.

Overselling the value of DNA for ancestry searches is causing more and more scientists to scorn what they are calling “recreational genetics.” Since 2000, a study finds, some 460,000 people have bought DNA tests from some two dozen companies that trace ancestry, and some users are doubtless being misled. One problem is that by testing only a limited number of genetic markers, the services miss many relatives: while they tell you that your family roots are sunk in, say, the Piedmont, they overlook that you have just as many roots in, say, Nova Scotia, or this African village as well as that one. More problematic, in terms of identifying an individual to whom you are related, is that it can make the connection sound more notable than it is. Yes, you and Sam might have the same great-great-great-grandfather but, under standard assumptions about reproduction and survival, so do (on average) 500 other people living today. But hey, you might just get lucky and find that one of them is a demon genealogist who has done all the census-digging and Ellis-Island sleuthing for you.

Something leaped out at me from my colleague David Gates' provocative review of the upcoming Ken Burns World War II documentary, "The War." As he wrote, "some affiliates—which didn't seem to mind the obscenely gruesome Holocaust pictures or the scene where a machine gun blows off a soldier's head—had a problem with the four uses of cusswords, one of which is alluded to in the anagrammatic title of episode five, "FUBAR." (For you youngsters, this was a GI term standing for "F---ed Up Beyond All Recognition." Perhaps it was a snafu to include that.)

This is not news, of course. Films get in trouble with the motion picture ratings board for saying the F in FUBAR and snafu, but not for a high, gruesome body count. You can stop a pleasant dinner cold by uttering that word, but not by describing in gory detail the latest atrocity on the battlefront. For insight into the peculiarities of profanity, I turned to psychologist Steven Pinker's new book, "The Stuff of Thought."

Why is sex, which at first glance (and, if you're lucky, subsequent glances) seems like a nice thing, the source of so many taboo words, including the above? Because "sex has high stakes," Pinker writes, "including exploitation, disease, illegitimacy, incest, jealousy, spousal abuse, cuckoldry, . . . and rape." As a result, "plain speaking about sex"--and what is plainer that using variations on the f-word as noun, adjective and adverb?--"conveys the attitude that sex is a casual matter." Society as a whole does not want that conveyed, and if you think we're beyond that, Pinker counsels, notice that for all our sexual liberation most of us "still don't copulate in public, swap spouses at the end of a dinner party, [or] have sex with their siblings and children." Most people want to keep it that way. Sex-loaded terms starting with f--- threaten to erode the barriers we erect to behaviors like the above, so we treat them as taboo. Indeed, this aversion to casual sex is so embedded in the human psyche that trying to reason your way around it---surely no form of sex, casual or otherwise, is as bad as battlefield atrocities?---just doesn't work.

Any Dallas Mavericks fans who groaned when the execrable Golden State Warriors knocked their team out of the NBA playoffs this spring, or New York Yankees diehards still shaking their heads that their 97-65 (regular season) team watched as the 83-78 St. Louis Cardinals went home with World Series rings last year, take heart: two physicists have devised a way to make 99 percent sure that the “best” team really does win.

Sure, upsets spice up the game. But let’s get real: the 91-71 Florida Marlins as the 2003 world champions and not, say, the 101-61 Atlanta Braves or Yankees? Over the last 100 years, find Eli Ben-Naim and Nicolas Hengartner of Los Alamos National Laboratory, the lower-ranked baseball team “had an astounding 44% chance of defeating” a higher-ranked team. Fans know that this reflects the fact that even a worse team can have a terrific pitcher, and a better team can suddenly find itself putting on the mound someone who just flew in from the minor leagues to fill a gap in the rotation, or that a few bad bounces can determine a game, among other quirks that make the sport exciting. The result, of course, is that “even after a long series of competitions, the best team does not always finish first,” the scientists write in an upcoming paper in the journal Physical Review E.

As I walked from my house to the train station during last week’s torrential downpour in New York, I found myself in need of a 21^st-century Sir Walter Raleigh (you know, he who spread his cloak over a puddle in 1581 so Queen Elizabeth I would not get her feet wet). A cloak wasn’t going to do it for me, though: the intersection I needed to cross to reach the street climbing up to the station had become a 2-foot-deep lake, judging by where the water reached on cars intrepid enough to try to get through. A garbage can bobbed along in the current. I flagged down a passing car, who drove me around the block rather than through the flood.

This comes to mind on yet another morning of torrential rain in the city because of a new study, to be published later this week in the journal Nature (subscription required). Scientists compared global rainfall records from 1925 to 1999 to various models of precipitation: those that include only natural causes (normal variability in the planet’s climate system and changes due to volcano eruptions, for instance), those that include only human effects (release of greenhouse gases into the atmosphere) and those that include both. Their conclusion: human activity “has had a detectable influence on observed changes in average precipitation,” they write, and these changes “cannot be explained by internal climate variability or natural forcing.” (Natural forcing includes things like changes in solar output as well as volcanoes.) In fact, “the estimated contribution of natural forcing to observed zonal precipitation trends is small in relation to the estimated contribution from anthropogenic [that is, manmade] forcing,” the scientists conclude.

Right-wing opponents of immigration and of what they called “amnesty” for illegals weren’t the only ones celebrating last month’s defeat of the White House-backed immigration bill.

In 2002 I was naïve enough to write a column channeling the angst of technology CEOs about the “shortage” of scientists and engineers (a theme that has been sounded since the 1980s, when the National Science Foundation projected a shortfall of about 675,000 over the following two decades, something that never materialized, as discussed in a paper by MIT mathematician Eric Weinstein). Scores of engineers, in particular, wrote to me. In addition to pointing out my basic stupidity (well, credulity), they explained that the career prospects of an engineer these days are so bleak they steer their children away from the field. Most of all, they argued that the shortage is and was a myth.

No wonder, then, that engineers are cheering the defeat of the immigration bill, which would have increased the number of high-tech employees that companies could bring in on temporary H-1B visas from the current 65,000 per year to 115,000 and eventually to as many as 180,000.

Why isn’t everyone beautiful, smart and healthy? Or, in a less-polite formulation, why haven’t ugly, stupid, unhealthy people been bred out of the population—ugly people because no one will have them as mates, meaning they don’t get the chance to pass their ugliness to the next generation; stupid people because they’re outgunned in the race to financial success (that is, acquiring resources needed to survive and reproduce); unhealthy people because they die before they get a chance to reproduce?

Evolutionary theory predicts that the unfeeling hand of natural selection would lead to a culling of disadvantageous traits—or, as biologists more delicately phrase it, “depletion of genetic variation in natural populations as a result of the effects of selection.”

But look around, and you’ll see that that has not happened—not in people, and not in wild animals where homely and infirm offspring are born all the time.

Evolutionary geneticists try to explain this paradox by positing that mutations for disadvantageous traits keep popping up no matter how hard natural selection attempts to wipe them out, but in their more honest moments the scientists admit that in real life undesirable traits are way more common than this mechanism would account for; “ugly” mutations just don’t occur that often. In a groundbreaking study, biologists at the University of Edinburgh in Scotland have figured out why, at least in one species: genes that are good for males are bad for females and, perhaps, vice versa.

The scientists studied red deer, 3,559 of them from eight generations, living on Scotland’s Isle of Rum. They carefully noted each animal’s fitness, who mated with whom, how many offspring survived, which offspring mated and with what results. Bottom line: “male red deer with relatively high fitness fathered, on average, daughters with relatively low fitness,” Edinburgh’s Katharina Foerster and her colleagues conclude in tomorrow’s issue of the journal Nature. “Male red deer with a relatively high lifetime [fitness, which includes their reproductive success, the only thing evolution cares about] sired, on average, daughters with a relatively low [fitness].” The reverse also holds. Males that were relatively less successful in their reproductive success and fitness had daughters that were extra successful.

The reason is that any particular gene-based trait may have very different effects on males than in females. Extrapolating to humans (and oversimplifying, sorry) you might imagine that a particular shape of the nose or turn of the chin would look drop-dead hunky on a male, but horsey on a woman; dad got to mate because his looks attracted a female, but the result of their togetherness produced daughters whose pulchritude was less than obvious. Traits that evolutionary psychologists tell us make women unfit for mating (having the “wrong” shape) remain abundant in the human race because the DNA for the traits, when inherited by sons, confers a selective advantage; when those sons have daughters, presto—more females with less-than-hourglass shapes. Or as the Edinburgh biologists put it, “optimal genotypes differ between male and female red deer, because a genotype that produces a male phenotype with relatively high fitness will, on average, produce a phenotype with lower fitness when expressed in a female.”

Buzz Aldrin didn't get to be the first man to set foot on the moon--that privilege went to Neil Armstrong--but he did get his own first. After Armstrong took his historic "one small step for a man, one giant leap for mankind" during the 1969 Apollo 11 mission, it was Aldrin's turn to back down the steps of the lunar landing module toward the dusty surface. NASA had told the astronauts to move slowly, Aldrin recalls. So in between steps, he decided he had a moment to, as he delicately puts it, fill the liquid-waste bag inside his space suit. Believe me, you will never again look at the footage of Aldrin slowly descending the steps and pausing almost imperceptibly to stake a claim to his own first the same way again. "Everyone has their own first on the moon, and that one hasn't been disputed," Aldrin says.

If you want to see and hear astronauts as you've never seen and heard them before, see "In the Shadow of the Moon." At the 2007 Sundance film festival, it won the World Cinema Audience Award, and also picked up prizes for Best Documentary and Outstanding Achievement in Filmmaking at this year's Sedona International Film Festival, the Audience Award for Best Documentary at the Indianapolis International Film Festival, and the Grand Prize at the Boulder International Film Festival. It won't be released in theaters until September, but put it on your calendar now: director David Sington got 10 of the 12 astronauts who walked on the moon to open up as never before. He pairs their reminiscences with space footage that you'd swear is simulated, but it's real: Sington and his crew dug through thousands of hours of NASA archives for scenes in space, at mission control and inside the Apollo spacecraft that have never been shown to the public.

Between 1969 and 1972, from Apollo 11 to Apollo 17, six missions deposited astronauts on the surface of another world. Maybe it's the passage of time, maybe it's the perspective that comes with age, but the astronauts Sington filmed have thrown off the old "right stuff" taciturnity and toe-the-NASA-line reticence. Jim Lovell, best known as the commander of the aborted Apollo 13 mission (Tom Hanks played him; Lovell himself had a cameo at the end as the commander of the naval ship that picked up the crew once they finally landed safely in the Pacific), remembers how he and other astronauts felt at the time President Kennedy declared it the nation's mission to land a man on the moon by the end of the 1960s: "At the time, the Atlas boosters were blowing up every other day at Canaveral. It looked like a good way to have a very short career."

When educators and corporate leaders bemoan America's scientific illiteracy, they're usually referring to how we're losing our competitive edge in science and technology (see, for instance, the 2006 report from the National Academy of Sciences, "Rising Above the Gathering Storn,") or to the fact that fewer than a third of adult Americans know that DNA is the molecule of heredity, that only 10 percent know what radiation is and that 20 percent think the Sun revolves around Earth. But more and more, scientists grappling with the question of what you need to know about science to participate in civic discourse are concluding that the need is more fundamental: you need to know what science is, what it is not, and what it can and cannot answer.

And on that, there is ignorance at the highest levels.

When three Republican presidential hopefuls raised their hands during the recent debate to indicate they "didn't believe in evolution," as moderator Chris Matthews put it, biologist Jerry Coyne was appalled (though not necessarily surprised). As he writes in a scathing--though more in sorrow than in anger--essay, "Because there is just as much evidence for the fact of evolution as there is for the existence of atoms, anyone raising his hand must have been grossly misinformed." But while some of the hand-raising could have been the result of political calculation (more than half of Americans don't believe in Darwinian evolution, and it's always good strategy to be in sync with the majority), when Sen. Sam Brownback expanded on his hand-raising in a New York Times op-ed, the extent of his science ignorance was impossible to ignore.

There is no polite way to say this: people who resist scientific explanations for natural phenomena such as the age of the earth and the fact of evolution are guilty of childish thinking.

So argue two experts in cognitive and developmental psychology, the science of how thinking and other mental functions change as people grow up. “Resistance to certain scientific ideas,” Paul Bloom and Deena Skolnick Weisberg of Yale University argue in the May 18 issue of the journal Science, is largely a result of patterns of thinking that are characteristic of young children but which, in some people, “persist into adulthood.”

Scientists bemoan the huge numbers (42 percent, in a 2005 poll) of Americans—and this does seem to be more an American phenomenon than a European or east Asian one—who believe that humans and all other animals have existed in their current form since their first appearance on Earth, despite fossil and genetic evidence showing that, to the contrary, species change over time in the process of evolution. Tens of millions believe—again, contrary to scientific evidence—that unproved medical therapies work, that out-of-body experiences are real (rather than results of particular brain activity), and that astrology has merit, for instance. But if you look at what children think and how they learn, the resistance to science and the persistence of unscientific thinking doesn’t look so surprising.

We come into the world with preconceived ideas about how that world works; like a computer, we’re pre-loaded with some programs and knowledge. Babies know that objects fall unless held up, for instance (scientists test for this knowledge by noting what surprises babies, and an object defying the law of gravity definitely does). Little kids know that people act according to goals. They believe that actions and situations have purposes.