Science Talk

Tears And Other Traits That Make Us Human; What Color Is Your Placebo Parachute

In this episode, journalist Chip Walter, author of Thumbs, Toes and Tears, takes us on a tour of the physical traits that are unique to humans, with special attention to crying, the subject of his article in the current issue of Scientific American MIND. The University of Cambridge's Gordon Smith discusses the alarming lack of any randomized, controlled trials to determine the efficacy of parachutes. Plus we'll test your knowledge about some recent science in the news. Websites mentioned on this episode include;;

Welcome to the Science Talk, the weekly podcast of <>Scientific American for the seven days starting January 3rd. I am Steve Mirsky. This week on the podcast, Gordon Smith is going to discuss the lack of any randomized controlled trials to see if parachutes are really effective. We will test your knowledge about some recent science in the news. And first up, science journalist, Chip Walter on being human. He is an expert. He is a human. Walter is the author of an article in the current issue of Scientific American Mind magazine called "Why do we cry?" That article was adapted from his book Thumbs, Toes, and Tears: And Other Traits That Make Us Human. To find out more about being human, I called Walter at home in Pittsburgh.

Steve: Hey Chip. How are you?

Chip: Great, great, I am doing well. How are you?

Steve: Pretty good. Good to talk to you. The basic thing in the book is pretty obvious. We want you to talk about that a little bit and also tell us why you decided you wanted to write this book.

Chip: I guess it was really my attempt to try to figure out what makes us tick. I think it got started when I was working at a documentary on the evolution of intelligence for PBS, and I thought well, maybe, how could you get your mind around it? And I began to look at other animals and say, well, there are certain defining traits other animals have. You know, zebras have their stripes or hammerhead sharks have these wide, weird eyes, elephants have trunk[s], you know; and I thought if you look at those specific traits, I'll bet you would learn a lot about how those creatures became the way they are. And so then I thought, What about us are unique traits? And so, I kept trying to push the questions back, and I came up with these six, you know, defining traits that seem to be entirely unique to us, and the physical behavioral traits. The first one is the big toe, second is our opposable thumbs, third is our voices or the pharynx that we have—[it's a] very strange, unique throat with these 100 muscles, and they can make these intricate noises we make; and then kissing, laughing and crying. And so that's what the book kind of takes a close look at that to figure out what makes us tick.

Steve: And let's talk about crying specifically, because part of the book has been adapted into an article for Scientific American Mind in the current issue.

Chip: Right. Yeah, that was a great opportunity to get a chance to talk more about that. Crying is, I guess, when you think about it, really—it is a very powerful, almost primal form of nonverbal communication. And I don't think we necessarily always think about it that way, but it has its roots and[in], kind of, hoots and calls of some of our primate ancestors in the jungle, [and] even, like, has some connections to the barking of dogs and those sorts of things. Yet, we use it and feel it, and[in], you know, highly emotional, personal circumstances, and it's probably one of the most powerful forms of communication of ours.

Steve: And tears are unique to humans.

Chip: Yes, and that's real interesting and a difficult problem to solve—to understand—but yes, we are the only creature that cries tears of emotion. All animals that have eyes, you know, have some form of tears that clean their eyes, you know, or if you get poked in the eyes, you tear up; but we are the only ones that actually have water run out of our eyes when we are feeling intense emotion.

Steve: And one of the interesting things in the article is that the chemical makeup of emotional tears differs from the other kind of tears.

Chip: Yeah! Yeah! That's really interesting. There is a scientist by the name of William Frey who has done a lot of research on that; and yes, if you actually were to, you know, poke someone in the eye or cut onions and then analyze the tears that they cry when that happens—the chemical makeup is quite different from the chemical makeup in tears that you cry whenever you are, you know, proud of your child or, you know, extremely sad.

Steve: So, that would make you think that the tears are carrying those chemical compounds out of the body perhaps for some reason, but there is a lot of disagreement about the role of those specific emotional tears.

Chip: Right, right! Yeah! I mean Frey has a theory that we're actually crying the hormones and the chemicals that make us feel the way we feel—it's kind of get back to normal. But a lot of other scientists aren't sure, that [because] even if you're having a really emotional heaving bout of cry, you're not going to cry out much more than a, you know, teaspoonful of tears. So, there are other theories about why this happens; and another theory is that—which is entirely different—is that it's really the autonomic nervous system's way to try to get us back to normal. We do feel relieved when we cry. We can be very upset when we start to cry; and the way we might all think about it is, I am crying because I am really upset or sad or proud, but in fact it may be the body's way and the brain's way of saying, Okay, wait—you're getting too excited, so let's do this thing that will bring you back to normal and keep you in a kind of Goldie-lock[s] zone; because if you are upset and not focused, and you are an animal living in the wild, that's not a good thing. You want to be able to stay, you know, "normal."

Steve: And even the little bit of whatever chemical compounds are involved in emotional tears that they get released could be enough to restore your equilibrium.

Chip: Yeah, could be—that's the way William Frey sees it. Others think that maybe that should decide, you know, that just happens to be something that you can measure. Obviously, the brain is creating certain hormone[s], and your body is creating certain hormones whenever you are crying. And that's coming out in the tears whether or not you're actually emptying all those hormones out of your body, or the brain just kind of gets the signal and says, Okay—let's get back to normal here. It's a complex chemistry all around.

Steve: It's just fascinating that something as basic as crying is still so poorly understood scientifically.

Chip: Yeah, it's really a big mystery. And, actually, I found that to be true with a couple of different things in the book—that these are things that we take for granted as human behavior and therefore, in a strange way, they haven't been looked at as closely as you might look at other things that seem more odd or, you know, extraordinary.

Steve: Let's stay with tears. I just want to make one other point about something in the article—about the study, the side-by-side study of the photographs where the tears were Photoshop-ed out.

Chip: Right, right, yeah—that's a work of a scientist named Randy Cornelius. so vastly has done and It was really fascinating. He spent his whole career studying tears, and what he did was, he and his students got pictures of people that were crying and visibly had tears rolling down their cheeks; and then, he did a test. He would take those images and let people sit in front of them and say, What do you think these people are feeling? And whenever they saw people, you know, feeling these emotions and with tears rolling down their cheeks, they [the subjects] were very clear that they were sad or they were proud or they were, you know, whatever it was that they seemed to be feeling. But when he Photoshop-ed out the tears, then people had a completely different take. Sometimes, they said "rather bored", or "they are awestruck", or, you know, "they are just uncomfortable". Or some people might even think they were laughing because, you know, your expressions can be similar. So, what this tells us is that, you know, tears evolved, and they were extremely useful. They obviously make an extremely powerful statement to others of[about] us—when we see tears rolling down someone's cheeks, we know they're really in trouble, and they need help.

Steve: Right—so visible tears may also be a big signal, a big communication mechanism.

Chip: Yeah, absolutely. And we probably need it, because we are the most social creature on the planet, and communication is extremely important. And it's important for us to know that whenever someone is really upset, that it's genuine, you know, it's, kind of—tears become a kind of a way to say, Hey! I really, really need help, or I am really in trouble; and if they are not, you know—we see this in two-year-olds—I mean, if they are really crying tears, they go, [Aww, they're hurt]all their heart, you know? If they are not, then you know they're alright.

Steve: Right—it's more of a show than actual suffering.

Chip: Right, right, exactly.

Steve: So that's the article in Scientific American Mind. Let's go back to the book for a minute. You briefly mentioned the big toe before, and now, the opposable thumb gets an awful lot of attention, but you don't hear the big toe gets a lot of credit for making us human.

Chip: Right, right. Well I mean, actually, when you think about it, can you imagine any part of the body that’s more homely than a toe, you know, big toe? Maybe that's why it has been kicked to the curb, but the truth is we probably wouldn't have developed or let's put [it] this way—evolution wouldn't have developed and kept [our] opposable thumb if we hadn't had big toes first. And we did, I mean, we stood upright, and big toes made it possible for us to stand upright; and if we hadn't stood upright, it wouldn't have freed up our hands to, you know, to make those opposable thumbs possible. So, we have these big knobby, you know, appendages at the end of our feet and without them, we wouldn't be able to stand upright. And they hold 40 percent of your weight every time you take a step, and so just walking would be quite difficult if we didn't have our big toes—if not impossible—and certainly running and jumping and leaping and all the things you see football players do or ballet dancers do would be out of the question. But the interesting thing about it is, once you have a toe that enable[s] you to get upright, it sets all of these other things in motion. First of all, it changes our sexuality because we are now front facing, you know, not on all fours and that got it—you know, when you read the book, there are all sorts of interesting areas that takes us in. The other thing is that it enabled our throats or caused our throats to elongate and dropped our voice boxes down so that we can make the sounds that we make. But also so we are the only primate that actually can choke, because we have an epiglottis. We have, you know, the passageways between our noses and our mouth meet in one place—that's not true of other primates. So, either all sorts of interesting things get set in motion whenever we got upright, or we never would have gotten upright without those odd toes at the end of our feet.

Steve: Right—the toes are the beginning of the book, Thumbs, Toes and Tears, then you got your thumbs, the pharynx, laughter, tears and kissing are the six subsections of the book. Chip Walter! Thanks very much.

Chip: Thank you. I really enjoyed it.

Steve: Chip Walter's Scientific American Mind article is available at our Web site, Also check out his Web site, Lots of his writing is available there for free.

Now it's time to play TOTALL....Y BOGUS. Four science stories—.only three are true. See if you know which story is TOTALL.....Y BOGUS.

Story number 1: A woman in Spain has given birth to twins at the age of 57.

Story number 2: Adults who live with children eat more fat than adults without children.

Story number 3: Competitive surfers suffer fewer injuries than college basketball or soccer players.

Story number 4: More than half the dust supplying minerals to the Brazilian rain forests come from the African country of Chad.

We will be back with the answer. But first—some research articles have become classics and are reprinted and cited often. Such is the case with a 2003 British Medical Journal article by Gordon Smith, head of the Department of Obstetrics and Gynecology at Cambridge University and his co-author Joel Pell. The paper was most recently reprinted in 2006 in the International Journal of Prosthodontics and re-cited in September in another British Medical Journal article. The article is called "Parachute Use to Prevent Death and Major Trauma Related to Gravitational Challenge: A Systematic Review of Randomized Controlled Trials. To find out more, I called Smith at his office home at Cambridge University.

Steve: Professor Smith, great to talk to you today.

Smith: Good to talk to you Steve.

Steve: You and your co-author did a meta-analysis of other studies. You did not do any original research where you actually jumped out of airplanes either with a parachute or without a parachute, correct?

Smith: Yes. First it is wise to review the literature before we commit ourselves to [a] possible dangerous course of action.

Steve: Okay! And you were unable to find—or the real finding of your study was you were unable to find any controlled randomized studies in which you had a test group and a controlled group, where one group jumped out of airplanes with parachutes and one group did not jump out of airplanes or jumped out of airplanes without parachutes.

Smith: So, strictly what we were looking for was a placebo parachute. The person jumping out of the aircraft wore something that looked identical to the parachute.

Steve: I see.

Smith: And they were unaware of whether they have been allocated to the parachute or the placebo.

Steve: I see. There have been some natural experiments where some unfortunate people did have what they thought were parachutes, and it turned out that they weren't, and there had been some survivors of these and some not. Did those come into play in your analysis?

Smith: Well, those were excluded as part of the design of the meta-analysis. So, such criteria however with such standard, computerized registries of trials such as Cochrane database and Medline. The search strategy was limited to investigations where there was a control group. Those were reports of survival following jumping from an aircraft at greater than 50,000 feet, but in the absence of a control group, it was impossible either to assess the safety of the parachute or non-parachute use.

Steve: I see. So, what was the bottom line of your findings?

Smith: Well, the bottom line of our findings was despite the very widespread use of parachute[s], there was no objective evidence to support the fact they were beneficial. And then, in a discussion with a paper, we elaborated a number of possible reasons why one might misleadingly feel the parachutes were beneficial when in fact this was not the case. Well, the classical example of this will be what we call a healthy cohort effect; and when you see people on a non-randomized situation, it might give [the impression] those who were using parachutes are somehow healthier—or how it feel pre-existing co-morbidities—and this might explain the apparent better outcome associated with jumping from an aircraft without a parachute.

Steve: For example, economic status is often …

Smith: Economic status is always one; cigarette smoking would be another. And I suppose given the widespread perception of[that] parachutes are beneficial, it is possible that pre-existing psychiatric morbidity may have been a fact leading to the worst outcomes in non-parachute users.

Steve: Right. I mean, if you just talk about economic status, obviously wealthier people could afford parachutes and can also often afford to engage in healthier lifestyles.

Smith: Yes, certainly the apparent better outcome could simply be a reflection of the use of the non-random variation between the two groups. And that has been the substance of issue which underline[s] the importance of randomized controlled trials.

Steve: Okay, now [a] lot of our listeners would have probably thought that we have both lost our minds. So, let's talk about what the actual point of your publication was. There is evidence-based data and there is observational data, and let's talk about the real point of the article.

Smith: Yes, the real point of the article is that when assessing the very basis—whether a medical intervention is beneficial or non-beneficial, the current views of evidence-based medicine give a very strict hierarchy. And I suppose when you get into the most the purist amongst evidence-based medicine, [they believe] the uncertainty of any intervention which is[requires that any determination about it be] based on randomized controlled trial And the points that we are trying to make, the kind of—first of all, the obvious point is that there are going to be some situations that you simply can't address by randomized controlled trial. The second maybe is a slightly subtler point was in relation to the detailed discussion—you could conjure all sorts of possible explanations why the parachute seems to be effective, issues like socio-economic status, issues like pre-existing morbidities. There would be arguments that couldn't be current in the absence of direct evidence. We were suggesting that there was no substitute for having an element of common sense—and in the absence of randomized controlled trial data, you should reduce your scientific sense of the observational data. I guess, this of[is often] an overriding aspect that this is often [of] deciding whether the medical intervention is effective or ineffective; i[t']s a very, very complex question, and addressing very, very complex questions in a simplistic way can lead to a sub[par] results; and I guess that was really a fundamental message of our analysis.

Steve: I was thinking about the case of aspirin because there were levels of evidence-based data as well. You could have the kind of controlled trials that you are talking about with aspirin use, and you would see that it lowered inflammation and decreased pain, but the actual mechanism by which it did that was unknown for about the first century of the use of aspirin, I believe. Is that right?

Smith: Yes, I do agree. Aspirin cross-reacts to, actually, inhibition of an enzyme called cyclooxygenase, and it is a combined COX-1 and COX-2 inhibitor. But that information has really only been available in the last few decades, and for many years aspirin was used without knowledge of its mechanism. I mean, that's a straight question in a way; and that the question of [whether] further something can be shown in the trial to be effective and then, having shown that something is effective, understanding the mechanism by which they[it] act[s].

Steve: Right! And the studies with aspirin that showed it was effective could be done even if you didn't know how it worked.

Smith: Yeah, and in fact it was probably true that those[for a]reasonable number of drugs which are known to be effective, remain to be uncertain[ty remains about] without the precise mechanism of action.

Steve: Alright, so basically your paper was call to common sense, which is really what science is at large, I think.

Smith: A call to common sense and a call not to [address]make a complex question in a very simplistic way. I think that to me is maybe the key thing: Rather than intervention, where there is much more obviously genuine uncertainty, [it] does not [necessarily] result in the case of a parachute, but if some[one] becomes [to]today of a complex question in[with] a very simplistic way of addressing it, then the consequence of that can be really quite misleading; and that's what I mean is the message of the paper for me.

Steve: Right! We should put that you really did this search in literature to try to find any trials [that] were performed without airplanes, right?

Smith: Yeah! (Laughs) Researching without expectation, no.

Steve: Right, right. That's academic integrity, though.

Smith: Yeah, right.

Steve: Professor Smith, thank you very much. I appreciate your time.

Smith: Thank you, Steve.

Steve: The full text of Dr. Smith's parachute article is available free at the Web site of the British Medical Journal. Just go to and search for articles by Gordon Smith.

Now, it's time to see which story was TOTALL....Y BOGUS. Let’s review the four stories.

Story number 1: A 57-year-old has twins.

Story number 2: Adults living with kids eat more fat.

Story number 3: Surfing is safer than soccer and basketball.

Story number 4: Chad dusts Brazil.

Time's up.

Story number 4 is true. Some 56 percent of the nutrient-rich dust feeding the Brazilian rain forest is blown over from a single valley in the country of Chad. For more, check out the January 3rd episode of the daily Scientific American podcast, 60-Second Science.

Story number 3 is true. Competitive surfers have fewer injuries than college soccer or hoops players. That's according to a study in the January issue of the American Journal of Sports Medicine. Not surprisingly, injury rate was correlated with wave heights. That's for surfing. Remember, these data are for competitive surfing when conditions are much more controlled than the usual free-for-all at the beach. Drowning is still deemed highly unlikely in soccer and basketball.

Story number 2 is true. Adults with kids at home eat the equivalent of a pepperoni pizza's extra fat each week. That's according to research just published in the online edition of the Journal of the American Board of Family Medicine. Now that they know, will adults cut down? By definition, there is a fat chance.

All of which means that story number 1 about a 57-year-old woman having twins is TOTALL......Y BOGUS, because it was in fact a 67-year-old woman in Barcelona, who gave birth to twins this week after getting IVF treatments. She is the oldest new mother on record and she is resting comfortably, perhaps in the hospital's new combination maternity and geriatric ward.

Well that's it for this edition of the weekly Scientific American podcast. You can write to us at; check out news articles at our Web site,, and the daily Scientific American podcast 60-Second Science is at the Web site and at iTunes. For Science Talk, the weekly podcast of Scientific American, I am Steve Mirsky. Happy New Year! Wear your parachute, and thanks for clicking on us.

Web sites mentioned on this episode include;;

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