So far in this series we have heard from scientists on both sides of the debate over free will. Now, we'll go after a different question: Does free will matter?

Experimental psychologists have been studying what happens when our beliefs about free will are altered. Their results suggest that our opinions about free will may be even more important than free will itself, for if we come to believe that free will is truly an illusion, society might become a less friendly place.

In 2008, Kathleen Vohs, a psychologist and marketing professor at the University of Minnesota, ran an experiment to probe how subjects' beliefs about free will influence their behavior. In each trial, one group of subjects read statements asserting that that our actions are completely predetermined by environmental and genetic factors--that there is no free will. A second group read neutral statements. Then, the participants were given a test of character. In one case, they were asked to complete a computerized math test that was "flawed"--it sometimes "accidentally" showed the correct answer. Subjects were instructed to quickly click away the answer and ignore it, but they had the opportunity to cheat of course.

In a similar experiment, subjects completed another test and were instructed to take a certain amount of money from an unattended source for each correct answer that they scored. Though subjects believed no one was watching--and thus they could take as much money as they wanted--Vohs and her colleagues were actually monitoring the pot.

This is the third part in a four part blog series on the science of free will.

So far in this series, we've focused on scientists who are trying to disprove the existence of free will. But Jeff Miller of the University of Otago in New Zealand thinks these investigators have got it backwards. "We know it's almost impossible to prove that something does not exist (e.g. Loch Ness Monster)," says Miller. "Even after we have looked and looked, it is still possible that it's out there."

So are there any researchers who believe their work provides support for free will? Yes. Björn Brembs, a neurobiologist at the Free University of Berlin, has found evidence of free will in an unlikely place: the mind of a fly. Even when put under strictly controlled stimuli, flies will act in unpredictable ways. Unlike a machine, which will always give one predictable output for one input, even a simple fly brain will react differently to the same input in multiple trials.

Drosophila melanogaster, free thinker. By Mr.checker (Own work) [CC-BY-SA-3.0], via Wikimedia Commons

This kind of variability might be even be an evolutionary adaptation to help animals escape predators. The more unpredictably an animal maneuvers when it is being chased, the more easily it can escape danger. Another use is in exploration. If animals never wandered around without a goal, they would not find new habitats and food sources. Variability is also important in learning. Brembs gives the example of a toddler learning to speak: At first the child is very variable in her language, saying "momoo, mumoo, momma" until she reaches the right word, "mommy."

As Chelsea Ursin's series on the neuroscience of free will continues this week, a morning session at the American Association for the Advancement of Science conference reminded me that the subject of free will is not of purely philosophical and scientific interest. It has deep implications for our legal system and for the way that our society thinks about how and why we punish. For some defendants, the sharp line between life and death may even be drawn by the neuroscientists, philosophers, and legal scholars who ponder the fuzzy question of free will.

If free will is an illusion--if our actions are elaborate reflexes pre-programmed by biology and experience--then an individual is not "responsible" for committing even the most heinous crime. Michael Zigmond, professor of neurology at the University of Pittsburgh, puts it this way: Our behavior is nothing more or less than our brain activity, and brain activity is a function of our genes and our environment. When we punish an individual, then, we're not reprimanding poor choices, we "are punishing electrical and chemical events in the brain."

Nita Farahany, a professor of law and philosophy at Vanderbilt, rejects the notion that our choices can be reduced to such brain static. Brain science cannot absolve individuals of responsibility for their actions, says Farahany. Yet some discoveries from neuroscience are already making their way into the courtroom. Farahany estimates that, between 2005 and 2009, the number of judicial opinions making note of neuroscience doubled, and the rise has been even more dramatic since then. Drug and alcohol addicts argue that their addictions rendered them unable to exercise free choice; defendants claim that they were neurologically incapable of premeditating their crimes; serotonin levels are submitted as evidence of impaired impulse control.

But the biggest changes have come in the sentencing of young offenders, says Farahany. As neuroscience has given us greater insight into the brain's continuing development through adolescence and into adulthood, young people are found to have "less culpability" for their crimes. In the United States, the death penalty was abolished for juvenile offenders in 2005, and in 2010, the Supreme Court ruled that juveniles could no longer be sentenced to life without parole, except in homicide cases.

How far should we take this? If "my brain made me do it" (or, "my brain didn't stop me from doing it") works for some defendants, why not all of them? As Richard Dawkins has written, "Doesn't a truly scientific, mechanistic view of the nervous system make nonsense of the very idea of responsibility, whether diminished or not?"

Yet most of us cherish the notion of free will and the responsibility that comes with it. We value our sense that we are agents of our own destiny. (In fact, individuals who believe in their own free will are more likely to act ethically--more on that later this week from Chelsea.) So, can neuroscience shape our criminal justice system while keeping free will in the picture?

Peter McKnight thinks so. Neuroscience gives us tools to evaluate whether an individual is capable of reason, and the criminal justice system helps work the levers on that reasoning system by meting out punishments that (in some cases, at least) deter would-be criminals.

Most importantly, we can hope that neuroscience will one day give us the tools to rehabilitate offenders instead of serially imprisoning them. Perhaps we can even imagine a future in which we so deeply understand the interaction of nature and nurture that we can help rehabilitate at-risk individuals before they ever commit a crime.

Search for "parenting" on Amazon and you'll turn up more than 65,000 books peddling dos and don'ts for raising healthy, happy kids. We seem to believe that the right early experiences will turn our children into superstars; the wrong ones will damage them. But is there really a formula for perfect parenting? And how do our early experiences shape who we become?

At the annual meeting of the American Association for the Advancement of Science, running this weekend in Vancouver, researchers came together to share their research on how our earliest experiences--experiences we can't even remember--"wire" our brains and bodies to succeed or struggle in adult life.

In the 1950s and 1960s, psychologist Harry Harlow performed a series of influential but unsettling experiments on baby rhesus monkeys. He separated infant monkeys from their mothers and placed them in isolation with "surrogate" monkey moms--dolls made of terrycloth or wire, equipped to dispense milk but nothing else.

The monkeys grew up disturbed. When they were finally removed from isolation, many went into a "state of emotional shock," Harlow reported. Some refused food; they clutched and rocked. They did not play with other monkeys and could not form relationships with their peers. "Twelve months of isolation almost obliterated the animals socially," wrote Harlow.

Harlow's work has drawn sharp ethical criticism, and of course it is impossible to imagine performing any such experiment on human subjects. But, heartbreakingly, millions of children worldwide who are maltreated or abandoned or who lose their parents to violence or disease are unwitting "subjects" in just such a natural experiment. Many are ultimately raised in poorly staffed institutions where they receive little stimulation, follow fixed routines, and don't get compassionate care. These children typically have sharply lower IQ scores than their peers. Their growth is stunted and they struggle with language, social behavior, and forming attachments.

But how can we untangle nature from nurture in our understanding of these children? Were they "damaged goods" from the start, incapable of benefiting from compassionate care even if it were provided? And if a child should thrive after being adopted, would that be evidence of the reparative power of nurture--or evidence that adoptive parents naturally picked the most gifted and least impaired children?

This was the question the Bucharest Early Intervention Project, led up by Harvard professor Charles Nelson, set out to answer. More than one hundred institutionalized children in Bucharest were randomly assigned to either remain in their institutions or to live with foster families. (Foster homes were available for only half of the children, due to a cultural bias against adoption.) How would the fostered children fare compared to their institutionalized peers? And would they ever catch up with children who had never experienced life in an institution?

Nelson and his colleagues discovered that fostered kids could indeed thrive--their social skills improved, their IQs climbed--but the developmental window of opportunity did not remain open forever. The children saw substantive improvements only if they were placed in foster care before their second birthday, and the younger, the better.

This might seem obvious, but to policymakers in Romania, says Nelson, it was not initially so. The results of the study are informing how public health agencies worldwide will care for the estimated eight million children who are now living in institutional care.

Somehow, the conditions in institutions change the brains and bodies of young children. But how? At the Yerkes National Primate Research Center, Mar Sanchez is studying this question with Harlow's old subjects, rhesus monkeys. But these monkeys are not caged and separated from their mothers. It turns out that between two and five percent of female monkeys are naturally "bad mothers"--they abuse their babies, dragging them screaming across the ground, or they simply ignore them when they seek attention and comfort. These abused and rejected infants spend more time screaming and throwing tantrums than warmly-mothered monkeys; they respond anxiously to new or stressful situations. And, their levels of the stress hormone cortisol are chronically high.

Not all monkeys respond equally--genetic vulnerabilities (or sensitivities, if you like) seem to amplify the damaging effects of abuse and rejection. And, contrary to what you might expect, rejection is actually more destructive than abuse: Rejection was linked to low levels of serotonin in the brain and was the strongest predictor of whether a monkey would perpetuate the cycle of bad mothering in the next generation.

Of course, human kids are not rhesus monkeys. But to those perusing Amazon's virtual aisles in search of the formula for perfect parenting--those who fret about too much discipline or too little, about whether baby is getting too much television or too little Mozart--maybe there is some comfort here: As in so many other endeavors, the better part of success may be simply showing up.

This is part two of a four-part blog series on the science of free will.

In the previous entry in this series, I described a classic free will experiment performed by Benjamin Libet in the 1980s. Brain scanning technology has come a long way since then. Can modern scanning shed more light on free will?

In 2007, the neuroscientist John Dylan Haynes of the Bernstein Center for Computational Neuroscience in Berlin, Germany, ran a new experiment. In each trial a subject was given a window of time to make a decision and act on it. The decision was to either press a button in the left hand or a button in the right hand. At the same time, the subject was watching a screen which flashed a series of letters in rapid succession. Subjects were asked to note which letter was being displayed on the screen at the moment that they made the decision to press one button or another.

While Libet used EEG technology, Haynes used more advanced fMRI. Both technologies record brain function in action, but an fMRI reading provides more spatial resolution--it more precisely identifies the specific parts of the brain as they activate. Haynes claimed that, by analyzing the the fMRI data from one specific part of the brain, frontopolar cortex, he could predict which button the subject would choose--left or right--with 60% accuracy seven whole seconds before the participant was consciously aware of his or her decision.

Few scientists are convinced that this is the death knell for free will, though. Marcel Brass, of the University of Ghent, Belgium, points out that the 60% figure is not that much better than chance, but adds, "It shows our decisions are influenced by stuff that happens in our brain before we decide. But it is not showing our decisions are completely pre-determined." Jeff Miller, of the University of Otago in New Zealand, agrees: "Finding that brain activity predicts a decision does not undermine free will." He explained the brain activity used to make the prediction could just be a leaning towards one choice or another, and that the final decision could still have been made consciously.

Haynes himself accepts this possibility. "Maybe this early signal isn't a full decision, it's just like a nudge that you get, it's just biasing you one way, but its not really finally making up your mind." So what is "making up your mind?"

Not free will, says Haynes. "Decisions are caused by unconscious brain processes, then consciousness kicks in later." In Haynes' view, our conscious decisions are predetermined by brain activity even if we cannot yet completely decode that activity. "It is subjective experience that you think that you have free will. It's something that is implausible, its incompatible with the scientific deterministic universe anyway."

So why weren't Haynes' predictions perfect? Haynes lays the blame on technology. FMRI probes regions of the brain but cannot access the activity of single neurons. The next step, Haynes anticipates, may be the experiments currently going on that do monitor single neurons.

At this point, you might wonder whether John Dylan Haynes went into this research with an anti-free will agenda in mind. He would tell you that the answer is no: "People talk to me about determinism and free will a lot, but I actually thought the experiment was about conscious and unconscious processing." And why does he focus on this area? Simply, "I am interested in interesting questions."

To Mark Hallett, chief neurologist at the Human Motor Control Section of the National Institute of Neurological Disorders and Stroke at the National Institutes for Health, the question is of more than philosophical interest. He believes that it could help patients who suffer from a relatively common condition called a psychogenic movement disorder. "The movements look like they are voluntary, but the patients say they are involuntary. It's hard to understand that unless we can understand where the notion of the voluntariness comes from," says Hallett. From studying these patients and performing his own experiments, which explore the human perception of volition, he has concluded, "Free will is not a driving force for movement."

Today we are learning more about how the brain prepares our body to perform actions. At the very least we know as Marcel Brass said, some "stuff" happens in our heads before we are aware of it happening. Some take this as evidence against free will as the cause of our actions, and some do not feel O.K to go that far yet. As technology improves we can predict with more accuracy what that "stuff" might be telling us, but as Haynes noted there is a difference between finding brain patterns that are predictive of our actions and ones that determine our actions. It will be a long time before we have a definite answer as to how exactly real-life decisions, which have greater importance than deciding to press a button, work.

After working in television for 20 years and covering the litany of human experience--from war zones, wildfire tragedies and plane crashes to a moment that delivers the happiest day in someone's life--you don't expect to take on a project that will have the capacity to change your own life.

Yet for me, making Separating Twins and meeting Trishna and Krishna was that fork in the road.

If you have never believed in destiny, their story may make you reexamine the possibility that some things are simply meant to be.

Where do I start? The slim chance of the girls being discovered in a Third World orphanage by a foreigner with the will to make a difference, or the almost impossible task of getting the conjoined girls out of their birth country, Bangladesh?

Finding a medical team brave enough to challenge the frightening odds, or finding a stranger with the heart and grace to commit to becoming a full-time mother for these deathly ill girls during their two-year journey toward separate lives?

These twins had "it can't be done" engraved on their birth certificate.

But to see them struggle and survive through one life-or-death surgery after another, unable to comprehend what they were going through or why, plus the in-between times peppered with flashes of lightness and love any infant should enjoy growing up, made me realize how easy it can be to love a child who is not your own.

Yes, a filmmaker must retain some objectivity when saddled with the responsibility of sharing such a remarkable life tale.

But when you stand in an operating theater after spending two years and 32 hours witnessing a miracle unfold and watch as two surgical tables are carefully, incredibly, gently, prised apart to give two tiny souls the same freedom of individual mobility that I had always taken for granted--well, basic human emotions can supersede journalistic integrity.

In the two years since Krishna and Trishna have slept in separate beds much has happened.

The girls still live with Moira Kelly who helps their birth mother make regular trips to Australia to share the joy of her daughters' survival.

Trishna is now a gleeful, energetic five-year-old with a ready, friendly smile who talks non-stop in a strong Australian accent and has taken an undeniable grip on her second chance at life. Her sister's path is more complex. Krishna cannot walk unaided, requires diapers, is yet to eat solid food, and manages only a few words, albeit bellowed with gusto and volume!

Her laughter, however, stops people in the street with its unbridled message "I'm loving life, how 'bout you?"

Amazingly, she navigates her way around an iPad almost blindfolded!

Meanwhile this hardened documentary producer has transformed into "Uncle Wayne." I'm privileged to visit "my girls" twice a week, play with them, bathe them, feed them, change diapers, take Trishna out shopping and on day trips and marvel as they fall asleep in my arms.

I live my life as part of theirs.

They don't know it yet, but their story has touched lives everywhere--those closest to the twins as well as total strangers on the other side of the Earth through the medium of this documentary.

I hope you find your world enriched by traveling this once-in-a-lifetime journey.

Do humans have free will? Philosophers have discussed and debated free will for thousands of years. The question used to be, "Do we get to decide our actions or does God dictate them?" Later it became, "Is our soul a separate entity from our body that tells our body what to do?" Today, science isn't in the business of testing for God or the soul, and we believe that the mind is a product and part of body. Thoughts are patterns of neurons firing in your brain.

Now, scientists are beginning to probe the connection between thought and action. In a series of blog posts over the coming week, I'll discover how far that research has come--and how far it has yet to go.

Part 1: Free Will in the Lab

Part 2: Is Free Will an Illusion?

Part 3: In Defense of Free Will

Part 4: Does Free Will Matter?

As individuals, we believe that our thoughts bring about our actions. First we ask a question to ourselves: "What shall I do now?" Next we make the decision: "I will bake a cake now." Finally, we perform the action; we bake the cake. We believe we baked the cake because of that inner dialogue. But what if the brain "decided" to bake the cake long before the inner dialogue gave voice and awareness to the decision? The brain may have been sending signals to the body to go get the flour before we even thought, "I will bake a cake"! If this is true, you were going to bake that cake all along, and your thoughts arose in order to explain your actions to yourself--the thoughts are, to torture a metaphor, just the icing on a cake that your brain baked before you ever knew it.

With modern science we have the ability to watch brains as they function, something the ancient philosophers could barely have imagined. Does this mean we can now finally figure out how free will works? Can scientists witness our decisions in action? Or will it turn out that free will is just an illusion? The results of experiments in the field and what they mean for free will is hotly debated. In this series, I hope to untangle the science from the semantics and the data from the dogma--without getting stuck in the mire of metaphysics.

This is the first part in a four part series on the science of free will.

First, some history. Though philosophers have debated free will for over 2000 years, scientists only began to take it on experimentally in the 1980s, when Benjamin Libet (1916-2007), a physiologist at the University of California San Francisco, performed a now-classic experiment. Libet instructed participants to flex their wrists whenever they felt the urge to do so, within a window of a few seconds. Subjects watched a rapidly moving clock and were instructed to note to themselves, and later report to the researchers, the time on the clock when they had come to a decision to move. At the same time, their brain activity was monitored by EEG. Libet was looking for a distinct change in brain activity that he called the "readiness potential," which he believed was an indicator of the brain preparing for movement.

Libet found that the readiness potential appeared, on average, 350 milliseconds before subjects reported that they had made a decision. This meant that the order of the events was: 1) A subject's brain prepared to move the wrist, 2) The subject said to himself, "I have decided to move my wrist," 3) The subject's wrist moved. To Libet, this suggested that the subject's decision was not truly the cause of the movement, since the brain was preparing the movement a fraction of a second before the subject made a conscious decision. Libet came to the conclusion that our conscious control over our actions is limited--or may not exist at all. Wow, sounds like free will just took a pretty hard blow. But did it really?

Jeff Miller of the University of Otago, New Zealand, was set on finding out whether the readiness potential signal was in fact a definite indicator of movement preparation. So, he recreated Libet's experiment, with a twist: This time, subjects did not move on every trial. His team found no evidence of stronger signal before a decision to move than before a decision not to move. They observed the readiness potential both before movements and when no movement happened, meaning it was not a consistent indicator of movement preparation. Since the readiness potential does not cause movement, something else could be the true cause of the movement, "maybe even the person's free will," said Miller.

What exactly does the readiness potential indicate, then? As Miller explained via email, he believes "it reflects some kind of general engagement with this task. I realize that's a very vague answer, but we need to pin down precisely what experimental conditions are necessary to produce this pattern of EEG activity before we can really say what it reflects."

Libet did leave some space in his conclusion for free will to exist, but in a more limited role. He thought there might be conditions in which the conscious mind takes over and "vetoes" spontaneous behavior. He noted that, "subjects have reported some recallable conscious urges were 'aborted.'" In these instances the subject's subconscious presented the urge, or option of how to act, and his conscious mind chose whether or not to act on it.

Critics like neuroscientist John Dylan Haynes, however, argue that the "veto" isn't necessarily a product of free will, either. "Every conscious process, even a veto, will have its brain correlate, its unconscious precursor," says Dylan Haynes. To Dylan Haynes, the very idea of a veto--or, as Mele refers to it, "free-won't"--is an artifact of the discredited philosophy known as "dualism," the notion that mind or consciousness and body or brain/subconscious activity are two separate entities.

Libet's critics also take issue with the design of his experiment, specifically with how subjective the self-reported timing method was. Marcel Brass of the University of Ghent, Belgium has worked on an experiment that proves that a subject's perception of the time of their intention can be manipulated by playing a tone at different intervals after they perform an action. Mark Hallett at the National Institute of Health worked on an experiment that aimed to provide a more objective measure of the time of intention using the subject's real-time decision of whether or not there was a thought to move when a tone occurred.

What did we get out of Libet's studies then? "The work was an excellent stimulus for useful discussions about the challenge of relating neuroscience to philosophical questions about consciousness and free will," says Miller. "Of course these are tough questions and they will not be settled any time soon."

To learn about the more recent work inspired by Libet's experiment, come back to read the next installments in this series.

This excerpt from Digging Snowmastodon: Discovering an Ice Age World in the Colorado Rockies by Kirk Johnson and Ian Miller describes research featured in NOVA's Ice Age Death Trap, premiering Wednesday, February 1 at 9 p.m. ET on most PBS stations.

The digging team celebrates project completion. Courtesy Kirk Johnson

On September 20, the day after my birthday, a Gould Construction Inc. crew began to push dirt at the Ziegler Reservoir construction site near Snowmass Village in the Colorado Rockies. They had two months to dig the footing that would change a small lake into deep reservoir. They were using D6 Cats and big track hoes, loading huge dump trucks to haul away the dirt. Work progressed smoothly, with the trucks making dozens of trips each day and creating an ever-deepening hole.

Kent Olson, Gould's on-site foreman, found a brown bone while walking across the site and had that odd feeling that contractors get when they find bones. He talked about the bone with his boss, Mark Gould, and they showed it to Bob Mutaw, an archaeologist who worked for URS, the engineering firm that was overseeing the site. Mutaw looked over the bone and pronounced it bovine, probably an old milk cow. Kent wasn't so sure. The work continued, but the workers started making nervous jokes about old bones. Kent even played a practical joke by wrapping a big log in black plastic and sticking it on the tailgate of his project manager's truck. Then he casually mentioned that he had found a dinosaur bone. Not funny.

Gould's number-one dozer operator was Jesse Steele from Palisade, Colorado. Jesse is a polite, compact cowboy who wears a black hat and tips it when he greets a lady. He is also a third-generation dozer operator. As a toddler, he dozed in his grandfather's lap, in a dozer. He first drove a dozer at the age of five. When it comes to moving dirt, Jesse is a smooth operator.

At about four in the afternoon of October 14, Jesse was operating his D6, pushing through a thick brown layer of organic soil known as peat, when a pair of giant ribs flicked over the top of the blade. Jesse stopped the machine and hopped out to take a look. The ground in front of his blade was littered with big brown bones. Instead of getting excited, Jesse got scared.

Kent came over and together they began to gather the bones. They found a partial jawbone with an 8-inch-long tooth. They found a tusk. They found big vertebrae. It was clear that this was a big skeleton. Joe Enzer came over to the find, took one look, turned to Kent and said, "This is not a cow, and there is no way we can ever call it a cow." Kent took the bones home that night and got on the Internet. It didn't take him long to realize that Jesse had run over the skeleton of a mammoth.

This book is the story of what happened over the next nine months as Jesse's mammoth turned into the most significant high-elevation ice age fossil site in the world and the biggest fossil dig in Colorado history.

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Thursday, November 4 - Wednesday, November 10, 2010

On November 6, several more geologists and paleontologists arrived on site. With their additional brain power we debated how and when this glacial lake had formed and how long it had lasted. We were still waiting for the results from the radiocarbon samples that we had sent to Florida, and we were all still operating under the assumption that the quality of preservation suggested that the site couldn't be much older than 13,000 years.

We now had a pretty big crew of scientists and volunteers on site and were focusing our efforts on excavating the mammoth under the tent. We had smaller crews digging down in the hole where the mastodon and sloth bones had been found. We were in general agreement that the silt layer between the moraine and the peat was barren of fossils. Mark Gould, who had supervised the excavation of nearly 80,000 yards of sediment over the last month, was convinced that his guys had seen no bones in the silt.

Early in the afternoon, this conviction was changed by a dramatic event. Jesse was slowly pushing his dozer through the silt layer at the bottom of the hole with Dane and Ian running blade. Just below the tent, the dozer unearthed a 3-foot-long bone that initially looked like another tusk. Upon close inspection, we realized that the bone was the core of an absolutely immense bison horn. It had been broken into three pieces and there were fresh breaks, indicating that the horn had been sheared from a skull. The pieces exposed the center of the horn, which was formed of a coarse, butterscotch-colored honeycomb latticework. It looked good enough to eat.

We stopped the dozer and spread out with shovels, trying to find the skull. Eight of us looked for the better part of two hours with absolutely no luck. Finally we gave up, grudgingly deciding that the horn must have been a solitary fragment. With that decision, we asked Jesse to fire up the dozer and take another next pass. Amazingly, this time the dozer pushed up a second immense horn. And this time we were able find the spot in the silt where the horn had come from. After an hour of shoveling, we uncovered an incredibly large skull. Both horns fit back to the skull, and we came face-to-face with a huge bison. Productivity dropped way down as the entire crew gathered around to watch the beast emerge from the silt.

We carefully wrapped the two horns and applied burlap and plaster to the giant skull. It was hard to tell that day, but when measured, the skull was an amazing 6 foot 4 inches from broken horn tip to broken horn tip.

The bison discovery prompted volunteers Bill and Judy Peterson to hand me a $100 bill, the first financial contribution to the project. It had also profoundly affected Cathy Dea, who had helped to encase the skull in plaster, and in the process had coated herself in plaster and mud. She looked like a muddy urchin, but the look on her face was one of rapturous delight. A good fossil can do that to you.

For Russ Graham, an expert in ice age bison, this big beast rang some bells. Based on his knowledge, the big-horned bison went extinct more than 40,000 years ago. Russ suggested that our idea that the site was only 13,000 years old was probably wrong. While waiting for the radiocarbon dates to come back in a few days, people started to make wagers about the age of the site.

This was only the first of several mysteries that would appear as the huge excavation stretched over 70 days. NOVA's Ice Age Death Trap chronicles what happened next.

Ice Age Death Trap premieres Wednesday, February 1 at 9 p.m. ET on most PBS stations. Please check your local listings to confirm when it will air near you.