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Are These Crime Drama Clues Fact or Fiction?

Steven Avery, featured in the Netflix documentary Making a Murderer, served 18 years in prison for rape, then was exonerated by DNA. He was convicted of murder in 2007, based partly on DNA evidence.
Steven Avery, featured in the Netflix documentary Making a Murderer, served 18 years in prison for rape before being exonerated by DNA in 2003. In 2007, he was convicted of murder, based partly on DNA evidence.

I’m often just as surprised by what forensic scientists can’t do as by what they can. In the Netflix documentary Making a Murderer, for instance, the question of whether police planted the main character’s blood at a crime scene comes down to whether or not the FBI can detect a common laboratory chemical called EDTA in a bloodstain.

On a TV crime show, this would be a snap. The test would take about five minutes and would involve inserting a swab into a magic detector box that beeps and spits out an analysis of every substance known to humankind.

In real life, there’s no common and accepted test in forensic labs for EDTA even today, nine years after the FBI tested blood for the Steven Avery trial featured in Making a Murderer. In that case, the FBI resurrected a test they had last used in the 1995 O.J. Simpson trial, and testified that the blood in question did not contain EDTA and therefore was not planted using EDTA-preserved blood from an evidence vial. (Avery was convicted.)

Questions about the test’s power and reliability have dogged the case ever since. There’s even an in-depth Reddit thread where fans of the Netflix show are trying to sort out the science.

Having worked in chemistry labs, it surprised me at first that this analysis would be difficult or controversial. After all, a quick search of the scientific literature turns up methods for detecting low levels of EDTA in everything from natural waters to beverages.

Steven Averys
Steven Avery’s attorneys Jerome Buting (shown) and Dean Strang struggled to dispute chemical evidence introduced mid-trial that undermined the idea that police had planted blood evidence.

But the key here is that we’re talking about forensic science, not beverage chemistry. Beverage chemistry, in this case, is much more exacting. Was there really no EDTA in the blood swabbed from victim Teresa Halbach’s vehicle, or was the chemical simply too diluted or degraded to be detected with the FBI’s method? Could the test have missed a small amount of EDTA? It would be hard to say without further experiments that replicate crime scene conditions, experiments that essentially put the test to the test.

The reality is that forensic science today is a strange mix of the high-tech and the outdated, so questions about evidence like those in Avery’s case are not uncommon. Methods that we take for granted, like measuring a particular chemical, or lifting a fingerprint off a gun and matching it to a suspect, can be difficult—and far from foolproof. On the other hand, some of the real science happening now sounds like something dreamed up by Hollywood script writers, such as new methods aiming to reconstruct what a person’s face looks like using only their DNA.

Making a Murderer, whether it sways your opinion on Steven Avery or not, has done a service by getting people interested in something as arcane as EDTA tests, and by showing why real-life crimes are not solved nearly so neatly as fictional ones.

I see the messiness of forensic science all the time, because I scan its journals and often come across new studies that make me think either “you mean we couldn’t already do that?” or “I had no idea that was possible.” I’ve gathered a few recent examples for a quiz.

How well can you separate CSI fact from fiction? Here are a few crime-solving scenarios I’ve cooked up; see if you can tell which use real methods based on new forensic research. You’ll find the answers below.

  1. A skeleton is found buried in a shallow grave. The body’s soft tissues have completely decomposed, so only the teeth and bones remain. A forensic anthropologist examines the bones and reports that they come from a female who was five foot six inches tall, and obese. Could she really tell the person was overweight?
  2. The body of a white male in his 50s turns up on a nature trail, scavenged by animals. The victim’s bones show a number of puncture wounds consistent with animal bites, but x-rays reveal fine lines of different density in the bone around some of the punctures. An expert says these lines show that the wounds were made about 10 years before death. Is it possible to tell the approximate age of these wounds from x-rays?
  3. A woman is found dead in her home, bludgeoned to death. A bloody frying pan lies on the floor next to her. Her husband is the main suspect. Fingerprints on the pan’s handle are too smudged to make a definitive ID, but an analyst says she can still rule out the husband: All of the fingerprints on the pan came from a woman, the expert says. Is it possible to tell if the fingerprints were from a male or female?
  4. A woman is sexually assaulted and identifies her male attacker in a lineup. The suspect’s DNA matches DNA found on her body. It looks like an easy case for the prosecutor—until the suspect reveals that he has an identical twin. Neither twin admits to the crime. Is it possible to tell which twin’s DNA was found at the crime scene?
  5. A witness sees a man in a stocking mask rob and shoot a man outside his home. A stocking is found near the house, and a hair-analysis expert testifies that 13 hairs in the mask are all human head hairs from an African-American. A microscopic analysis matches the characteristics of one hair to a particular African-American suspect. The prosecutor tells the jury that the chances are one in ten million that this could be someone else’s hair. Can hairs be matched to an individual this accurately?


Answers Below


  1. Yes. Biologists have long known that greater body mass changes the weight-bearing bones of the legs and spine, and a new study shows that even bones that aren’t supporting most of the body’s weight, such as arm bones, have greater bone mass and are stronger in obese people. So even in a skeleton missing its legs, our forensic anthropologist might be able to tell that the person was obese.
  2. No. This one is from an actual episode of Bones (The Secret in the Siege, Season 8, Episode 24, reviewed here by real-life bioarchaeologist Kristina Killgrove). In the episode, Dr. Temperance Brennan uses Harris lines to determine the age of bone injuries in two victims. Harris lines are real, but they form only in growing bones, so are useful only in determining childhood injuries or illness.
  3. Yes. A study published in November showed that the level of amino acids in sweat is about twice as high in women’s fingerprints as in men’s. Of course, as with all the new methods, this one could face challenges as evidence in a U.S. court of law, where the Daubert standard allows judges to decide whether scientific evidence is admissible based on factors including its degree of acceptance by the scientific community.
  4. Yes, if you do it right. Standard DNA tests don’t distinguish between twins, who are born with nearly identical DNA, but it’s possible to do a more sophisticated test to catch post-birth mutations and epigenetic differences, which you can think of as genetic “add-ons” that don’t affect the DNA sequence itself. One new test distinguishes between twins by looking for small differences in the melting temperature of their DNA that are caused by such epigenetic modifications.
  5. No. The field of hair analysis has come under heavy scrutiny, especially after a review by the U.S. Justice Department revealed major flaws in 257 out of 268 hair analyses from the FBI. The case described here is the real-life case of Santae Tribble, convicted in 1978 of murder. In 2012, DNA tests showed that none of the hairs matched Tribble—and one was from a dog.

How Undersea Enigmas Reproduced Before the Dawn of Sex

Birds do it. Bees do it. And over 541 million years ago, weird organisms that looked like armored carpets did it. Exactly how they did so, though, was a bit different from the ways we’re familiar with.

University of Cambridge paleontologist Emily Mitchell and colleagues were the ones to reconstruct how these puzzling species reproduced. They focused on a species from the Ediacaran period called Fractofusus. The fossil is a strange, branching frond preserved as flat impressions in the ancient sediment, but it’s so unlike anything alive today that scientists are still unsure whether it was an animal, a plant, or what. Nevertheless, by studying the geographic pattern of how these fossils are preserved across the rocks of Newfoundland, Canada, Mitchell and coauthors have been able to reconstruct how Fractofusus made more Fractofusus.

It wasn’t as simple as catching Fractofusus in The Act. This was still tens of millions before the earliest days of internal fertilization, after all. Rather, Mitchell and colleagues write, the clusters of Fractofusus are patterned in such a way that suggests they’re organized by reproductive factors rather than by currents or other environmental details.

The diagram of Fractofusus spatial arrangements. From Mitchell et al., 2015.
The diagram of Fractofusus spatial arrangements. From Mitchell et al., 2015.

The largest, and therefore oldest, Fractofusus seem to be arranged randomly in respect to each other. This may indicate that these were the first to colonize the habitat, initially carried as tiny “waterborne propagules” that then settled and grew. But from there, Mitchell and coauthors wrote, Fractofusus started doing something different.

The smallest Fractofusus, the researchers found, grouped around the medium-sized ones, which in turn clustered around the largest individuals. With no evidence of little buds or fragments coming off any of the fossils, Mitchell and colleagues suggest that this pattern belies reproduction and connection by a way of a stolon – a wispy “runner” that connects individuals into a kind of communal group. Marine invertebrates, such as some bryozoans, do this today, and, in the prehistoric case, the large Fractofusus would have sent out runners to produce a garden of little Ediacaran clones.


Mitchell, E., Kenchington, C., Liu, A., Matthews, J., Butterfield, N. 2015. Reconstructing the reproductive mode of an Ediacaran macro-organism. Nature. doi: 10.1038/nature14646

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You’ll Find the Biggest Male Appendage in the World—at the Beach

So tell me: Of all the males on our planet—and I’m talking all, scale be damned, from the littlest insects to the biggest of whales—who’s got the most impressive appendage? Who (you should pardon the expression) is our Biggest Daddy?

And I don’t mean just sex organs, impressive as they sometimes are. I’m talking about any outstanding male appendage—whatever guys have that thrills the ladies, the obvious non-penile example being the peacock tail, which as we all know when fully displayed makes peahens dream of George Clooney.

Picture of a peacock with its feathers fanned out
Photograph by Richard I’Anson, Getty
Indian Peafowl, or Peacock, displaying tail feathers.. Photograph by Richard I'Anson

Impressive? Yes. The problem being that between trysts, a superheavy tail must be a drag to lug around. It costs energy to maintain and more energy to get up and unfurled. But the drive to reproduce is a powerful thing, and sexual selection, as Darwin taught us, just keeps pushing the limits of bigness.

Obviously, there is such a thing as too big. I imagine it gets awkward to be a walrus with tusks curling dangerously close to your chest.

Picture of a pacitic walrus with very long tusks lying on rocks
Photograph by Yva Momatiuk & John Eastcott, Minden Pictures / National Geographic
Pacific Walrus (Odobenus rosmarus) bull portrait on coastal rocks in haul-out cove, summer, Round Island, Bering Sea, Bristol Bay, Alaska. Photograph by Yva Momatiuk & John Eastcott / Minden Pictures / National Geographic

And the weight of these things? Not the absolute weight, but the proportional weight—that’s another limitation. How much can a guy carry? According to Douglas Emlen in his wonderful book Animal Weapons: The Evolution of Battle, while the rack of bone that sits atop a male caribou is hugely impressive (those antlers can weigh 20 pounds and stretch five feet across) …

Picture of a caribou with large antlers amid a lush green landscape on a misty day next to an equal sign that says ''8%''
Photograph by Bob Smith, National Geographic Creative
Close up portrait of a male caribou, Rangifer tarandus. Photograph by Bob Smith, National Geographic Creative

… as big as they are, they account for only 8 percent of the male’s total body weight. Moose and elk have even larger antlers, but even the biggest elk antlers equal only 12 percent of its body weight. So that’s doable. Once upon a time, 11,000 years ago, there was a deer (called Megaloceros giganteus, or the Irish elk) that wandered Europe and Asia, and those guys had boney tops so insanely branched, so crazily big, that our prehistoric humans painted them worshipfully onto the cave walls at Lascaux.

Picture of an Irish elk painted onto the wall at Lascaux cave next to a ''less than'' sign that says 20% next to it
Photograph by Sisse Brimberg, National Geographic Creative
Prehistoric artists painted a red deer on a cave wall. Photograph by Sisse Brimberg, National Geographic Creative

But even these antlers, 12 feet across and wildly branched, weighed less than 20 percent of the total animal.

Go Small to Get Big

You have to drop down to the insect family, to a group of horned beetles, to find a big appendage that approaches a third of the animal’s body weight. There are several beetles that have fighting, clamping horns almost the size of their bodies, and a thing like that growing out of your skull, writes Emlen, “is a little like having your leg sticking up out of your forehead.” You feel it.

Picture of a rhinocerous beetle on wood
Photograph by altrendo nature, Getty
Rhinoceros Beetle, male, Columbia, South America, Photograph by altrendo nature

But if you’re looking for the male who wears the crown, whose appendage is so big, so startling, so colorful, so attractive, so monstrous, and therefore unequaled in the animal kingdom—if you’re looking for the champ? Well …

He’s not in the African savannah. He doesn’t have a tusk. He’s not especially large. You have to look down to see him, down near your feet when you’re at the beach. This is him:

Picture of a fiddler-type crab standing on sand and waving a claw in the air
Photograph by Michael Nichols, National Geographic Creative
Loango National Park, Gabon. A fiddler-type crab with claw raised standing outside its burrow, Photograph by Michael Nichols, Getty

He’s a fiddler crab. And that appendage is his claw. And while sizes vary from crab to crab, the biggest fiddler crab claws weigh roughly half the body weight of the animal. Half! That’s nature’s biggest appendage, says Emlen. And what is it for? Not for feeding. The claw is useless at mealtime. Males eat with their other, smaller claw only. But, says Cornell biologist John Christy, the claw’s bright colors definitely attract female attention. It can also snap down and inflict real harm, so they’re potential weapons. But mostly, he discovered, males use them—I kid you not—to wave.

“Up and down, up and down, again and again,” writes Emlen, “they raise their claws high and drop them. Dozens of times each minute, thousands of times per hour, hour after hour … ” They look a little silly doing this, like a lonely fan trying to start a stadium wave. Check out this fellow:

Why are they waving? It’s a warning. “Look what I’ve got!” the male is saying to any male who would trespass into his burrow. “This thing is going to pound you if you come near, so stay away!” In effect, Emlen writes, “fiddlers are employing their claws as warnings rather than instruments of battle.” And it works. “An overwhelming majority of contests end before they ever begin, without anything even resembling a fight. A mere glance at a big claw is sufficient to deter smaller males.”

The male has built a tunnel, which leads to a nesting burrow. His claw has attracted a lady, and she’s down below raising his family. His job is to stay on top, waving till she’s done or he drops. It’s a tough life, lifting that gigantic appendage over and over, using up energy, constantly getting bothered by would-be challengers. The male can’t eat. Not while he’s guarding. His food is at the water’s edge, which is down lower on the beach. So he stands there, day after day, getting hungrier, until eventually, Emlen says, “Even the best males run out of steam and are forced to abandon their burrows to go feed and refuel. The instant they leave, others will claim their burrows.” And then they become challengers and have to start all over again.

So while it may be glamorous to top the list of Biggest Appendage Ever, what with the lifting, the waving, the straining, the not eating, the worrying about how long you’ll last, it might be better to have a medium-size claw and not have to be always worrying about the biggest bullies at the beach. Yes, the big claw does dramatically increase your chances of producing babies, which, as Darwin will tell you, is the whole point. But if I were a fiddler crab lucky enough to have the biggest appendage in the world, I think I’d get myself a nail file (claw file?), erase my genetic advantage, and spend lazy afternoons sipping pond scum by the ocean’s edge. I like a gentler life.

Douglas J. Emlen’s book, Animal Weapons: The Evolution of Battle, is a fascinating account of how animal weaponry, both offensive (claws, horns, teeth) and defensive (armor, shelter, thorns, claws again) parallel human weaponry, both offensive (arrows, lances, swords, missiles, A-bombs) and defensive (armor, castles, spying). It’s a compelling, fun, often scary analysis. And David Tuss’ drawings, especially his animals, made me jealous.

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What Do Snails Think About When Having Sex?

It starts with a light, soft touch, one tentacle gently reaching out, hesitant, hopeful, hanging lightly in the air. There’s a pause. Skin touches skin. One softly strokes the other and slides closer, and then, carefully, they wrap themselves together, stroking, probing, entwining. They glisten as they move, and because they are snails, everything happens very slowly. The rubbing, the rapture, the intensity of it all—snail sex is extraordinarily lovely to look at. (If you aren’t at your office desk or on a train where people can see your screen, I’ve got one about a garden snail named Chip who’s trying to lose his virginity, or take a quick peek—30 seconds will do—of this coupling in a garden.)

Lovely but So Dangerous

Garden snails make love in the open—on garden patios, in clearings on the forest floor—and they do it luxuriantly for one, two, three hours at a time, under the sky, where they can be seen by jays, orioles, frogs, snakes, shrews, mice, beetles, and other animals that might want to eat them. Snails can’t make quick getaways, so exposing themselves like this is dangerous, crazily dangerous. What’s going on? What’s making them so impervious, so deeply preoccupied with each other? Here’s one answer: Snail sex is very complicated. Snails have a lot to think about when they make love—because they’re hermaphrodites.

Unlike you, garden snails can produce sperm like males and carry eggs like females at the same time.

Drawing of a proud snail, with its hands on its shell hips
Drawing by Robert Krulwich
Drawing by Robert Krulwich

Which is both an advantage and a problem. Professor David George Haskell, a Tennessee biologist, once squatted down on a patch of forest floor and watched what you just saw in that video—a snail couple going at it—except with a magnifying glass and only a few feet from the action. What he noticed was their mood. Hot as it was, he writes in his book The Forest Unseen, “Their extended courtship and copulation is choreographed like cautious diplomacy.” Snails don’t pounce, they circle. They “slowly edge into position, always ready to pull back or realign.” Their sex is tense, charged, on, off, then on again, “a prenuptial conference over the terms of the union.” What are they negotiating about?

In most animals, snails included, sperm is plentiful, cheap to produce, and fun to unload. So one presumes that both copulating snails are eager to get that part done.

A drawing of two snails, both looking at each other with thought bubble exclamation points above their heads
Drawing by Robert Krulwich
Drawing by Robert Krulwich

Eggs, on the other hand, are limited and hard to produce—and therefore precious. You don’t let just anybody fertilize your egg sack. So, in Haskell’s imagination, if one of these snails picks up “a whiff of disease” on the other, it may be happy to poke but is not at all interested in being poked. No one wants its precious eggs fertilized by a sick dad, so the receiving snail might lock its partner out of its opening while also trying to penetrate it. This could produce feelings of frustration, confusion, and even unfairness in the other.

A drawing of two snails looking at each other, one with an exclamation mark thought bubble and one with an X through an exclamation mark thought bubble
Drawing by Robert Krulwich
Drawing by Robert Krulwich

“In hermaphrodites,” writes Haskell, “mating becomes fraught, with each individual being cautious about receiving sperm while simultaneously trying to inseminate its partner.” Sexually speaking, two snails with four minds—a foursome in a twosome—makes for complex fornication. That’s why snails are always on tiptoe, Haskell thought as he watched them on the forest floor: They have so much to figure out.

Picture of a brown snail peering its head around to the side
Photograph by © Tetra Images / Alamy
Photograph by © Tetra Images / Alamy

Hermaphrodite Abundance

So why be a hermaphrodite? Are there a lot of them? Well, here’s a surprise: They’re everywhere.

Eighty percent of the plant kingdom produces both seeds (pollen) and eggs (ovules) and can give or receive, making them hermaphroditic. They’ve learned that when the weather gets wet or cold, bees can’t be depended upon to buzz by and pollinate, so they have a we-can-do-this-ourselves backup plan.

Animals, generally speaking, are sexual, divided into male and female. But, writes Stanford biology professor Joan Roughgarden in her book The Genial Gene, if you subtract insects, which make up more than 75 percent of the animal kingdom and are not hermaphrodites, we are left, she calculates, “ … with a figure of 1/3 hermaphrodite species among all animal species.” That’s a hunk of hermaphrodites.

So Who’s a Hermaphrodite?

They’re not animals we pay much attention to (flukes, flatworms, killifish, parrot fish, moray eels, barnacles, slugs, earthworms, and tapeworms, among many others), but they are switch-hitters: They can either give or receive or switch sides during their lifetime. “All in all,” writes Roughgarden, “across all the plants and animals combined, the number of species that are hermaphroditic is more-or-less tied with the number who has separate males and females, and neither arrangement of sexual packaging can be viewed as the ‘norm.’”

Anyone who thinks that male/female is nature’s preference isn’t looking at nature, says Roughgarden. And she goes further.

Adam and Eve or AdamEve?

She wonders, Which came first, the hermaphrodite or the male/female? We have lived so long with the Adam and Eve story—Adam first, Adam alone, Adam seeking a mate, God providing Eve—that the question seems almost silly: Of course complex animals started with males and females.

Painting of Adam and Eve in the Garden of Eden, Eve is offering Adam an apple
Adam and Eve, 1537 (panel), Cranach, Lucas, the Elder (1472-1553) / Kunsthistorisches Museum, Vienna, Austria / Bridgeman Images
Adam and Eve, 1537 (panel), Cranach, Lucas, the Elder (1472-1553) / Kunsthistorisches Museum, Vienna, Austria / Bridgeman Images

But Roughgarden wonders if animals started as hermaphrodites …

Composite of Adam and Eve painting, creating one person
Composite image of Adam and Eve created by Becky Harlan from original paintings by Lucas Cranach © [Royal Museums of Fine Arts of Belgium, Brussels / photo : Guy Cussac, Brussels]
Composite image of Adam and Eve created by Becky Harlan from original paintings by Lucas Cranach © [Royal Museums of Fine Arts of Belgium, Brussels / photo : Guy Cussac, Brussels]

… and then “hermaphrodite bodies disarticulate[d] into separate male and female bodies?” How would that have happened? Roughgarden cites a paper she did with her colleague Priya Iyer.

They propose that maybe the earliest animals started out as both sperm and egg carriers, and a subgroup got especially good at inserting their penises into enclosures, aiming, and directing the sperm to its target (the authors call it “home delivery”). They did this so effectively that they needed fewer and fewer eggs and essentially became sperm sharpshooters or, as we call them now, “males.”

That development gave others a chance to give up sperm altogether to concentrate on chambering their eggs in nurturing nooks, thereby becoming “females,” and so more and more animals found it advantageous to be gendered.

Ayer and Roughgarden aren’t sure this happened. They say that, on available evidence, the story can go “in either direction.”

The alternate view is almost the story you know. It’s Adam and Eve, with a twist: In the beginning, early animals were gendered—except when it was inconvenient.

If, for example, you imagine a group of, well, let’s make them snails …

Drawing of a group of snails standing in front of a volcano erupting
Drawing by Robert Krulwich
Drawing by Robert Krulwich

… and something awful happens—there’s a terrible disease, an ice age, a new ferocious predator, or maybe a volcanic eruption…..

Drawing of a snail all alone after the fallout of a volcanic eruption, standing in front of a volcano puffing smoke
Drawing by Robert Krulwich
Drawing by Robert Krulwich

… so that we’re left looking at a lone individual, all by itself, looking around for a reproductive opportunity, crawling across the landscape, hoping to bump into somebody, anybody, to reproduce with, and after a long, long, anxious period, it finally sees what it’s been looking for. It crawls closer, closer, the excitement building.

Drawing of a snail in a vast and sunny landscape seeing another tiny snail in the distance
Drawing by Robert Krulwich
Drawing by Robert Krulwich

But as it gets within wooing range, it suddenly sees that—oh, no—it’s the same gender!

A drawing of two snails with moustaches
Drawing by Robert Krulwich
Drawing by Robert Krulwich

No possibility of babymaking here. And this happens half of the time. (Statistically, that’s the likelihood.) Now instead of being your friend, male/femaleness is your enemy. What wouldn’t you give for a hermaphrodite, a he/she snail that could, in a pinch, be whatever sex you need it to be. With a hermaphrodite, you can (again statistically) always make a baby. What a relief. So maybe that’s what happened. Gender difference disappears when gender no longer helps produce more babies (and when you don’t have to stick around and be a parent).

Which is the true story? We don’t know. Maybe the only story is that nature is flexible. When gender is useful, you get genders. When not, you don’t. What we forget, being humans, is that there are so many ways to flirt, to combine, to make babies—and the world is full of wildly different ways to woo. Tony Hoagland knows this. He’s not a scientist but a poet who lives in New Mexico, and in his poem entitled “Romantic Moment,” he imagines a boy on a date who sits next to his girl imagining … How shall I put this? … how the Other Guys do it.

Romantic Moment by Tony Hoagland

After the nature documentary we walk down,
into the plaza of art galleries and high end clothing stores

where the mock orange is fragrant in the summer night
and the smooth adobe walls glow fleshlike in the dark.

It is just our second date, and we sit down on a rock,
holding hands, not looking at each other,

and if I were a bull penguin right now I would lean over
and vomit softly into the mouth of my beloved

and if I were a peacock I’d flex my gluteal muscles to
erect and spread the quills of my cinemax tail.

If she were a female walkingstick bug she might
insert her hypodermic proboscis delicately into my neck

and inject me with a rich hormonal sedative
before attaching her egg sac to my thoracic undercarriage,

and if I were a young chimpanzee I would break off a nearby tree limb
and smash all the windows in the plaza jewelry stores.

And if she was a Brazilian leopard frog she would wrap her impressive
tongue three times around my right thigh and

pummel me lightly against the surface of our pond
and I would know her feelings were sincere.

Instead we sit awhile in silence, until
she remarks that in the relative context of tortoises and iguanas,

human males seem to be actually rather expressive.
And I say that female crocodiles really don’t receive

enough credit for their gentleness.
Then she suggests that it is time for us to go

to get some ice cream cones and eat them.

Thanks to the poet Thomas Dooley for suggesting Tony Hoagland’s poem, and to Mr. Hoagland for giving us permission to print it here in full. Reading “Romantic Moment” I giggled a little to think of eating ice cream on a sugar cone as a homo sapien mating ritual—but thinking back, I think he’s onto something. The poem can be found in Tony Hoagland’s collection Hard Rain.

New Frog Species Reproduces Like No Other

There’s not really a good time to bring up amphibian mating habits at the dinner table. I figured that I was probably safe given that I was surrounded by scientists, but, all the same, I tried to make sure that no one was raising a fork to their mouths when I blurted out “You guys! There are frogs that have sex!”

The inspiration for my outburst came from a PLOS One paper published just before I headed out the door for New Year’s Eve dinner. In it, biologists Djoko Iskandar, Ben Evans, and Jimmy McGuire describe a frog that reproduces unlike any other known species.

Most frogs and toads look like they’re having sex when they’re mating, but this is a superficial illusion. It’s a behavior called amplexus in which the male amphibian clasps the female around the torso, shoulders, or head and releases his sperm as she lays her eggs.

The new frog species – named Limnonectes larvaepartus – is one of the rare exceptions. Like a handful of other frogs and toads, this newly-described amphibian from Sulawesi Island is capable of internal fertilization. The way the frogs accomplish this is a mystery – the Limnonectes larvaepartus males appear to lack what science has politely called an “intromittent organ” – but what happens next is a sure sign that the fanged frogs don’t spawn like other species.

All other frogs and toad species that have sex deliver their young in one of two ways. The females either lay their internally-fertilized eggs in typical amphibian fashion or the mothers give birth to well-developed froglets. Limnonectes larvaepartus splits the difference. Females of the new species, Iskandar and colleagues report, gives live birth to tadpoles.

The researchers first discovered this unusual ability while prepping collected frogs. When they dissected some of the females, “the abdominal wall was observed to quiver, and incision resulted in living tadpoles emerging from the opening.” Live frogs later gave birth to squiggly tadpoles at the time of collection and while being held for study.

An adult Limnonectes larvaepartus with tadpoles in a pool (yellow circle) and a close-up of the tadpoles. From Iskandar et al., 2014.
An adult Limnonectes larvaepartus with tadpoles in a pool (yellow circle) and a close-up of the tadpoles. From Iskandar et al., 2014.

While there’s a possibility that the fanged frogs may have been capable of retaining those tadpoles until they fully metamorphosed into froglets, Iskandar and coauthors consider this unlikely. All 19 pregnant females collected for the study had tadpoles inside, not froglets, and the researchers also found free-living tadpoles in streamside pools. Once released into the outside world, the developing frogs live off what little yolk they have left before starting to feed for themselves. And given that this news was received positively as dinner concluded, I can heartily recommend that you share the tale of this remarkable frog the next time you meet friends for a meal. I’m sure they’ll find it ribbiting.


Iskandar, D., Evans, B., McGuire, J. 2014. A novel reproductive mode in frogs: A new species of fanged frog with internal fertilization and birth of tadpoles. PLOS One. 9 (12): e115884. doi:10.1371/journal.pone.0115884

Sex, the Early Years

Sex is an ancient tradition. It’s older than today’s continents, older than dinosaurs, older than trees, dating back to a time when vertebrate life thrived in the seas but had not yet ventured onto land. Back then, over 435 million years ago, armored fish were among the first to try this new mode of perpetuating life.

Finding prehistoric creatures caught in the act is an exceptionally rare occurrence. For vertebrates, copulating turtles and courting sharks were among the very few ancient animals that died at a most inopportune moment. Fortunately, we don’t need such intimate associations to track the beginnings of sex. Ancient anatomy tells the tale.

The story starts with procreating placoderms. These archaic fish flourished between 435 and 360 million years ago, and are easily-recognized by having bony armor on the outside, flexible skeletons of cartilage on the inside, and some of the earliest jaws. And, as reviewed in a new paper by Western Australian Museum paleontologist Kate Trinajstic and colleagues, some placoderm fossils preserve both essential mating equipment and the end result of their underwater unions.

The idea that placoderms relied on internal fertilization isn’t new. In 1938, paleontologist D.M.S. Watson published a report on a placoderm called Rhamphodopsis that seemed to preserve claspers – the tubular, paired “intromittent organs” seen in male sharks and rays. If placoderms had claspers, Watson reasoned, then they probably mated the same way as sharks.

But, as Trinajstic and coauthors note, placoderms were thought to be too primitive to have done as the sharks do. Other experts reasoned that placoderms were egg-layers, relying on the same “spray and pray” method employed by many of today’s bony fish. It wasn’t until 2008, when paleontologist John Long and colleagues described a female placoderm with embryos inside, that Watson was shown to be correct. Carrying embryos inside required internal fertilization, marking the placoderm – named Materpiscis in honor of her developing little ones – as one of the earliest vertebrates to have sex.

Rhamphodopsis and Materpiscis weren’t the only placoderms to reproduce this way. Trinajstic and coauthors point out signs of prehistoric sex among a variety of placoderms with names such as Holonema, Campbellodus, and Coccosteus. And given that placoderms are so close to the root of where jawed vertebrates originated, they likely represent the ancestral mode of reproduction for the greater group of biting fish – the gnathostomes – that included our own fishy forebears. For our early ancestors with jaws, at least, sex was likely the norm.

The anatomy of a male Coccosteus, showing the separation of the pelvic girdle and the claspers. From Trinajstic et al., 2014.
The anatomy of a male Coccosteus, showing the separation of the pelvic girdle and the claspers. From Trinajstic et al., 2014.

Our ancestors probably didn’t retain the ability permanently. Various descendants of the early jawed fish retained internal fertilization, switched back to egg-laying, and even re-evolved internal fertilization. Among fish alone, internal fertilization has evolved at least 29 times! On an evolutionary  timescale, sex doesn’t always stick around.

And there’s another prehistoric point worth keeping in mind. Placoderms were not just like the sharks, ratfish, and rays that rely on the same mode of reproduction today. In these cartilaginous fish, the male’s claspers are formed from part of the pelvic fins. Not so for male placoderms. Their bony pelvic girdles and claspers were actually separate structures, each supported by struts of cartilage.

Such a separation between fin and clasper might not seem like much, but the disjunction questions one hypothesis about how fish fins – including the precursors of our own limbs – first formed. Pelvic fins are essentially copied pectoral fins, and pelvic fins were thought to mark the back border of where alterations to development could produce new paired structures. But the placoderm claspers were situated behind the pelvic fins, Trinajstic and coauthors explain, and another early fish belonging to a different line – named Euphanerops – had paired anal fins. Either evolutionary tweaks to development could produce paired structures further down along the body than scientists previously thought, or something else was going on during the Age of Fishes. Solving the mystery will help resolve what Long has called the “dawn of the deed“, a milestone preserved in bone.


Trinajstic, K., Boisvert, C., Long, J., Maksimenko, A., Johanson, Z. 2014. Pelvic and reproductive structures in placoderms (stem gnathostomes). Biological Reviews. doi: 10.1111/brv.12118

Jurassic Sex Set in Stone

Prehistoric animals had sex. They must have. As paleontologist Derek Ager wrote in his classic Pricinples of Paleoecology, “After eating, the most widespread habits among modern animals are those concerned with sex, and there is no reason to suppose that this did not raise its allegedly ugly head millions of years before Freud.”

This truth is easy to forget. Even though reproduction is an essential act of life, mating itself is often a fleeting event. And given that the known fossil record is a fraction of a fraction of a fraction of life that once existed, what hope do we have that such ephemeral moments are preserved? Finding a complete dinosaur, pristine ammonite, or otherwise intact fossil is reason for celebration enough. We’re lucky if long-deceased creatures preserve anything relating to behavior. This is exactly why the few examples of prehistoric sex are so special.

About 320 million years ago, a pair of sharks died in a mating embrace. No one knows if they got a chance to finish their dance before they perished. Much later in time, about 47 million years ago, coupling turtles died as they sank into the toxic depths of an ancient lake. Their efforts were for naught. Then there were insects. So far, invertebrate paleontologists have found at least 33 examples of prehistoric insects caught in the act, many of these preserved in amber. Now researcher Shu Li of China’s Capital Normal University and colleagues have added another delicate example to the list – a pair of froghoppers found in the Jurassic rock of China that have been stuck in their sex position for 165 million years.

Froghoppers are still around today. They got their name, Li and coauthors write, “because the adults hop around on plants and shrubs like tiny frogs.” And the juveniles are often called spittlebugs because of their ability to cover themselves in a kind of foam. And while the fossils described in the new study belong to a new species, Anthoscytina perpetua, they are mating in a way strikingly similar to the way their living relatives do it.

Jurassic froghoppers preserved while mating (left) with a restoration of one possible mating position (right). From Li et al., 2013.
Jurassic froghoppers preserved while mating (left) with a restoration of one possible mating position (right). From Li et al., 2013.

Paleontologists were lucky to find the pair. Besides being a rare find – this is just one of 1,200 specimens Li and colleagues examined from the one locality – the mating froghoppers are special because they’re preserved as flattened fossils rather than being encased in amber. The fact that there was no ancient sap between researchers and the insects allowed the paleontologists to zoom in on the petrified pair to see the exact mechanics of froghopper fornication. These two were not just preserved belly-to-belly, but, in the words of the paleontologists, they’re fossilized with the “male’s aedeagus inserting into the female’s bursa copulatrix.” I think you get the picture.

The question is whether or not the froghoppers are preserved in their true mating position. Living froghoppers mate side-by-side, not belly-to-belly. Without similar fossils of copulating froghoppers, it’s currently impossible to tell whether the fossil represents the true mating position or if the intertwined insects were preserved that way after death. Nevertheless, the genitals of these ancient insects are strikingly similar to those of their modern counterparts, suggesting that froghoppers have been copulating more or less the same way through the ages. Should you ever stumble across a pair of mating froghoppers, stop and consider a scene that has been playing out since the Jurassic.


Li, S., Shih, C., Wang, C., Pang, H., Ren, D. 2013. Forever love: The hitherto earliest record of copulating insects from the Middle Jurassic of China. PLoS ONE 8, 11: e78188. doi:10.1371/journal.pone.0078188

Hacking Sex – The Odd Lives of Sexual Parasites

Female Amazon mollies need to mate with a male to reproduce. On the face of it, that’s not a terribly surprising statement – it’s on par with “Humans breathe air.” But the tricky secret of these strange fish lies in the details.

Amazon mollies, technically known as Poecilia formosa, are a hybrid species composed entirely of females. Sometime around 280,000 years ago, in a river or stream geneticists have pinned rather specifically to the vicinity of Tampico, Mexico, a pairing of a sailfin molly (Poecilia latipinna) and an Atlantic molly (Poecilia mexicana) resulted in a new fish lineage that has since relied on males of both those ancestral species to mate. And here’s where things get weird. The piscine male mates usually don’t contribute any genes to the Amazon molly offspring. Amazon mollies require sperm to kickstart the development of their embryos, which are genetic clones of their mother, but the male’s genetic contribution is totally wiped out. Amazon mollies are sexual parasites.


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Top 3 Reasons to Stop Fretting About Being an Old Dad

You probably heard about last week’s Nature study on older dads and autism; it got a lot of attention. The basic findings were fascinating but, in my opinion, far less sensational than what most of the news articles would have us believe.

The researchers, led by Kári Stefánsson of deCODE Genetics in Iceland, showed that the average 20-year-old man passes on about 25 new single-letter DNA mutations to his child. (These kinds of mutations happen spontaneously in sperm cells, so they don’t affect the DNA in the father’s other cells.) With each passing year of age, the man’s sperm acquires two more mutations. This makes sense, biologically. Sperm Primordial sperm cells divide over and over throughout a man’s life. To use an over-used metaphor: Each time the code gets copied, it creates an opportunity for a spelling mistake. Eggs Primordial eggs, in contrast, go through far fewer divisions. Women, no matter what their age, pass on about 14 mutations to each child, the study found.

The researchers also showed, using demographic data of Icelanders going back to 1650, that the average age of fathers has recently shot up, from 27.9 years in 1980 to 33 in 2011. Based on their calculations, that means the average number of mutations passed on to each kid (from mother and father combined) went from 59.7 to 69.9.

Here’s the sensational part. Stefánsson says, given that these mutations have been linked to autism, the increase in older fathers could partially explain why autism rates have risen over approximately the same time period. This is a plausible idea, sure, in theory. But there’s actually not much data to back it up (more on that later). And yet the assertion — reported in the New York TimesWall Street JournalWashington Post and more than 250 other outlets (Slate’s XXfactor blog even ran a piece titled, “Dude, Bank Your Sperm. It’ll Get You Laid.”) — was enough to scare some potential fathers. As one of my friends Tweeted, “great, my 34yr-old gonads may be ticking neuro-disorder timebombs.”

It’s an unsettling feeling, I’m sure. I’ve felt a similar panic about being an older mother (though for different reasons). But honestly, men, of all the things to spend time worrying about, this study is not one of them. Here’s why.

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Galápagos Monday: The Sad Sex Life of Lonesome George

To walk from the Charles Darwin Research Station to the center of the town of Puerto Ayora, on Santa Cruz Island, simply follow the “T-Shirt Mile,” a sleepy stone road lined with dozens of souvenir shops. Mugs, onesies and shot glasses pay tribute the town’s only famous resident, a century-old giant tortoise named Lonesome George. My favorite shirt had a cartoon George in the center, with eyelash-batting lady tortoises on either side of him and one line at the bottom: Not So Lonesome George.

Before his unexpected death on June 24, George had certainly been with his share of females. But for the first 60-odd years of his life, he was the most awkward of virgins.

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Galápagos Monday: World Within Itself

This is the third installment of a six-week series about my recent trip to the Galápagos. You can read the first post, about tortoises and donkeys, here, and the second, about eerie mounds of black coral, here.

If you go to the Galápagos, and even if you go, as I did, in a herd of clumsy American tourists, you will at some point feel like a field biologist. Regulations dictate that you be accompanied by licensed guides, and ours reminded me of my favorite college professors: authoritative and rhetorical most of the time, with sudden bursts of passion when they get a whiff of their pet topic.

Within an hour of my arrival, one of the guides launched into the difference between the islands’ endemic, native and introduced species. Endemic species arrived naturally but struggled to survive in the strange environment. Over many generations, they gradually adapted and are now found, in their modified form, nowhere else on earth. Native species also came naturally, but didn’t struggle as much and didn’t need to change. So they’re found in the Galápagos as well as other places. Introduced species did not “naturally” arrive, but were brought in by people.

My guides seemed to be obsessed with these definitions, mentioning them dozens of times over the course of my eight-day visit. When discussing endemic species — such as the marine iguana or Galápagos tortoise — they beamed like proud parents. But introduced species were the shameful family secret. “What are those trees?” someone asked guide Jason while hiking in the highland swamps of Isabela. “Those are cedars,” he said with a long sigh and a sad shake of his head. “Introduced.”

I rolled my eyes. I understand the concept, professor, really I do, now can we please move on? But, like most of the other times I’ve been annoyed with a good teacher, I was wrong. Several weeks and a lot of reading later, I’m finally beginning to get it. If you understand endemism, you understand the value of the Galápagos.

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Women’s Work

I write mostly about neuroscience, genetics and biotechnology. That means I spend most of my time talking to and writing about men.

In May of 2011 (chosen arbitrarily just because it was a year ago and I’m pretty sure I wasn’t thinking about this gender gap then), 89 percent of my phone interviews were with men.

I can think of a few reasons for this. One is that journalists typically talk to the senior leaders of labs, rather than the graduate students or postdocs who actually do the work. As you climb higher up the ladder of academic science, the male-to-female bias grows. According to the latest stats from the National Science Foundation, women earn 57 percent of all science and engineering undergraduate degrees and 41.1 percent of doctoral degrees. Yet the number of male PhDs in science jobs outnumbers females by two and a half times.

Another possible reason: Within science, the subfields with the most female-friendly sex ratios are: psychology (which employs twice as many women as men), political science (balanced ratio), and anthropology/sociology (balanced ratio). In contrast, for my pet topic, biology and life science, about twice as many jobs go to male versus female PhDs. Neuroscience, in particular, has a reputation for male domination. As of 2006, only 1 in 5 papers published in Nature Neuroscience — one of the field’s top journals — had a female corresponding author. A 2009 survey of neuroscience departments and programs reported that just 29 percent of tenure-track faculty are women. “So many of our best students and postdocs are women,” says Ben Barres, chair of neurobiology at Stanford. “But you don’t see them represented in our faculty. A lot of them are dropping out.”

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Tick Tock

Ginny and her niece

I’d like to be a mother—someday. Now is not a good time. I’m 28 years old, unmarried, and trying to build a freelance writing business from a small New York apartment.

I grew up in the wake of the feminist movement, and boy am I glad about that. Gender inequalities still exist, of course (ahem). But since grade school, my parents, teachers and favorite after-school-TV-show characters have encouraged me to invest in my education and career, just like any ambitious man. And I have.

Alas, biology still holds a trump card: my closing fertility window. By the time I’m 38, my bank account may be pregnant, but my eggs will be fossils. In last week’s issue of New Scientist, I wrote about a far-out experimental solution: freezing pieces of my ovary. The premise of the story was that if this technology ever gets off the ground, it could fulfill the original promise of the birth control pill, allowing women to make career decisions without the pressure of a ticking clock.

And it’s such a satisfying premise, isn’t it, especially for science-loving feminists like me. But after five months of airing it, triumphantly, to everyone I know, and thinking about their responses, my enthusiasm has waned. The cultural limits on the age of motherhood, I’m afraid, are far stronger than the biological ones.

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Sperm Waves

Some 40 years ago, researchers at the University of Missouri were searching for an alternative to the condom — a cheap, trustworthy and reversible form of male birth control.

For their first study, published in 1975, they strapped anesthetized rats, face-down, to a plexiglass platform with a cut-out cup full of water for their dangling scrota. The scientists then exposed the animals’ testicles to a variety of things.

Heat, for example, can kill sperm (which is thought to explain why the testes hang outside of the body). So some of the animals got a 140-degree Fahrenheit water bath for 15 minutes. Others received a dose of infrared radiation, or short blasts of microwaves or ultrasound. After treatment, the animals had constant access to females until they impregnated them.

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Alcohol, Retinol and a 50-Year Quest for the Male Pill

Last Sunday, the day before the world’s population hit 7 billion, I went to a scientific meeting on the future of contraception.

I had expected to hear, and did hear, about a slew of labs trying to develop a birth control pill for men. What I did not expect: one pill was shown to work in men more than 50 years ago.

In the late 1950s, researchers from the University of Oregon and University of Washington tested drugs called ‘bis(dichloroacetyl) diamines’ on inmates from the Oregon State Penitentiary.* The scientists doled out one of three pills — dubbed Win 13,099, Win 17,416 and Win 18,446 — to 26 volunteers once or twice a day for up to 54 weeks, and measured the men’s sperm counts along the way.

The results were stunning: the compounds reduced the amount of sperm in the men’s semen, and sometimes completely wiped it out. The pills didn’t affect libido, and the only reported side effect was bloating and gas. What’s more, within a few weeks of stopping treatment, sperm counts went back up. It was, perhaps, the horny grail: reversible birth control for men, no rubber required.