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Studies show most football coaches make poor decisions on fourth down. Does Bill Belichick have a secret advantage? Photo by flickr user Keith Allison

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This Super Bowl Sunday, as you watch grizzled coaches pace the sideline and bark at players, feel free to play armchair quarterback—or even head coach. Despite the hours they spend scouting players, analyzing game tape and drawing up complex tactical schemes, a pair of recent scientific studies indicates that many football coaches are no better at making some in-game decisions than you or I would be.

A 2006 paper by David Romer (pdf), a University of California at Berkeley economist, started things off by looking at a choice frequently encountered by coaches on fourth down: kick a field goal or try for a touchdown? Using data from more than 700 NFL games, Romer calculated the average chance of winning generated by each choice at different positions on the field. He then compared the data to the actual choices made by NFL coaches.

The conclusion: most avoid risk to an irrational extent, often opting to kick a field goal when going for a touchdown would provide a better chance of winning. Why would coaches—with their salaries and job security determined by on-field success—depart from the best possible choice? Romer speculates:

Perhaps the decision makers are systematically imperfect maximizers. Many skills are more important to running a football team than a command of mathematical and statistical tools…thus the decision makers may want to maximize their teams’ chances of winning, but rely on experience and intuition rather than formal analysis.

Another possible interpretation: for job security, coaches may prefer closer losses, coming after seemingly safe decision-making, to blowouts. A 23-0 loss may get a coach fired faster than a 23-6 score, which gives coaches incentive to kicking meaningless field goals rather than going for touchdowns.

Soon after the Romer study, Indiana University scientist Chuck Bower and partners from the business world went one step further. Using a similar dataset of actual NFL games, they built ZEUS: a powerful computer program that can analyze in-game situations on the fly and provide high-volume data analysis to coaches in real time. Bower said:

ZEUS is a valuable addition to a coaching staff’s tools, and one that can provide that elusive edge over the competition. The ZEUS engine is powerful enough to simulate the equivalent of every game played in the history of the NFL in less than a second. ZEUS can objectively assess crucial play-calling decisions with startling accuracy.

Comparing live data from the game with the historical track record of the NFL, ZEUS can indicate the choice that leads to a better chance of winning for a number of situations: not just what to do on fourth down, but whether to accept or decline penalties, attempt onside kicks, or try for two-point conversions.

In designing ZEUS, Bowers’ team drew upon many of the principles used in building computer models for other games—such as backgammon or chess—and applied them to football. “While the physical nature of the game is very different, the situational nature is strikingly similar. A football coach is constantly making decisions with respect to multiple variables: score, field position, down, yards to a first down, etc.,” said Bowers, an expert backgammon player.

NFL head coaches are a notoriously secretive bunch when it comes to strategy, so if anyone is currently using ZEUS, we’d likely not hear about it. But ZEUS’ own analysis indicates that one coach in particular might be using the cutting-edge program: New England Patriots coach Bill Belichick, set to coach in his 5th Super Bowl on Sunday.

The evidence? Belichick is famous for his unconventional decision-making, often opting to go for an aggressive play on fourth down when most coaches would punt or kick a field goal. The New York Times “Fifth Down” blog has used ZEUS to evaluate real-world decisions on a number of occasions. And when ZEUS was used to analyze a particularly controversial fourth down call made by Belichick—at the end of a crucial 2010 game against the Indianapolis Colts, he opted to go for it on his own 28-yard line, an unusually aggressive choice—ZEUS surprised many by saying he had, statistically, made the right call. The analysis indicated that, overall, it gave him team the best chance of winning.

Of course, statistical projections are not guarantees. In that case, the decision didn’t work out, and the Patriots lost the game. But if Belichick does have ZEUS on his sideline, it might give him that much better odds of being the winning coach on Sunday.

A telomere is like an aglet. Aglets are those plastic or metal tubular thingies at the end of your shoe laces that keep the end of the shoelace from becoming frayed and facilitate inserting the lace into the eyelet. A telomere is a sequence of base pairs at the end of a chromosome. A chromosome zips apart during cell division so that it can be replicated, and a small number of base pairs typically get lost during replication. This is because the molecular machinery that duplicates the chromosome can’t read through to the end of the strand, so it just skips the last bit. Any meaningful genetic information at the end of the chromosome would be lost or garbled. A nice long telomere at the end of the chromosome allows for multiple duplications without the loss of meaningful information, but over time even the telomere may be lost through attrition, and further replication of that chromosome would be a problem.

There is a system, using the enzyme “telomerase,” that adds base pairs to the telomeres, but there tends to be an imbalance between adding new base pairs by telomerase and losing the base pairs during replication, so in a given individual, new copies of chromosomes may eventually start to have less information than they are supposed to, which leads to cell death or worse—it is thought that this can be a cause of cancer in some cases. Shorter telomeres may mean a shorter lifespan, and longer telomeres a longer lifespan, for a cell line, or more interestingly, for an individual.

That is all pretty well established science, but the numerical details have been somewhat lacking. There has not been a study of a reasonably large sample of organisms in which telomere length was measured early in life, then lifespan measured in each organism, to verify if there is an association between telomere length and how long an individual lives. Until now.

A Zebra Finch. Photograph by Flickr user pixelblume.

A team of researchers from the University of Glasgow and the University of Exeter at Cornwall have just published an article in PNAS called “Telomere length in early life predicts lifespan.” The paper looks at 99 zebra finches in which telomere length was measured on the 25th day of life, and lifespan was measured by keeping the birds in a controlled captive environment until they died. Lifespan for these birds ranged from less than one year to almost 9 years. One can imagine the researchers waiting around for that last bird to die so they could submit the paper.

Telomere length early in life correlated strongly with lifespan of the birds, though there was enough variation in the outcome to suggest that multiple other factors are involved. The researchers conclude that “[a]lthough reduced telomere length has been associated with a number of degenerative diseases in humans, there has been increasing interest in their role in the aging process in otherwise normal individuals. The results of this study clearly show that telomere length early in life is predictive of longevity.”

At this point you are probably wondering if it is possible to add to our existing telomeres and possibly increase lifespan. It is possible that this could actually work, through gene therapy. This has been done in lab mice and other test animals. It is also possible, however, that long telomeres or telomeres lengthened artificially can cause an increased risk of cancer (for as yet unknown reasons). Also, it is not universally true that telomere length decreases during lifespan; in some organisms is seems to increase. One thing can be said about telomere biology at this point: There are many unknowns. Don’t be surprised to hear more interesting research about them over coming months and years.

Heidinger, B., Blount, J., Boner, W., Griffiths, K., Metcalfe, N., & Monaghan, P. (2012). Telomere length in early life predicts lifespan Proceedings of the National Academy of Sciences, 109 (5), 1743-1748 DOI: 10.1073/pnas.1113306109

A cane toad is highly toxic and should not be eaten or even licked. Photo from Wikicommons.

American cane toads (Rhinella marina), native to Central and South America, are an invasive species in Australia. These toads contain a substance called “bufotoxin” that makes a lot of predators ill, sometimes fatally. (Warning: This is very poisonous stuff. Do not even lick a cane toad!)

Australian animals that eat this toad are typically poisoned by it, but one animal, the bluetongue skink (Tiliqua scincoides), appears to be able to eat the toad with few or no ill effects. Or, more exactly, some bluetongue skinks can eat the cane toads, depending on where they live.

Many animals and plants produce complex molecules (like bufotoxin) that have been shaped by natural selection to be toxic to predators. Some of our favorite spices, such as basil, chili peppers and other aromatic plants, owe their culinary properties to these molecular adaptations to herbivory. Only a few mammals produce molecular toxins, but many frogs and toads do.

The bluetongue skink. Note the blue tongue. Photo from Wikicommons.

If a weapon evolves in nature, there is a certain chance that a counter-weapon will also evolve. Many insects that feed on toxic plants have evolved the ability to sequester the poisonous molecules produced by those plants, rendering them harmless to the insect, and in some cases concentrating the undesirable substance in the insect’s own body to be used as a defense against insect-eating animals (usually other insects). Many mammals have enzymes in their digestive tract that detoxify plants that would otherwise be harmful. The evolution of toxicity and the evolution of anti-toxin strategies is considered an arms race between the eaten and the eaters.

So, it would be reasonable to suspect that the bluetongue skink has evolved a physiological mechanism to combat the bufotoxin produced by the cane toads. But it turns out that the explanation for the ability of some skinks to snack on the toxic toads is a little more complicated.

Another invasive species found in Ausralia is the ornamental “mother-of-millions” plant, a Bryophyllum from Madagascar. This plant produces a toxin that is chemically similar to bufotoxin. Why is it chemically similar to bufotoxin? This is probably a coincidence. If you have a large number of animals and plants producing toxins, sometimes there are going to be accidental similarities.

Mother-of-millions plant. Image from Wikicommons.

The mother-of-millions plant is invasive and found in the wild in certain areas of Australia, but it is not common everywhere. Bluetongue skinks that live where mother-of-millions is common appear to have adapted to eating them, and as such posses the ability to neutralize bufotoxin-like molecules. When these skinks encounter cane toads, they eat them without consequence. In fact, the skinks living in these area regularly eat both the mother-of-millions plants and the cane toads.

This research was was carried out by scientists at the Richard Shine Lab at the University of Sidney.

Price-Rees, Samantha J. Gregory P. Brown, Richard Shine, 2012. Interacting Impacts of Invasive Plants and Invasive Toads on Native Lizards. Natural History Editor: Craig W. Benkman. Published online Jan 25, 2012

One of the most interesting large-scale patterns in evolution is parallelism. For example, flight has evolved many times, in parallel, from numerous non-flying organisms; many species of vertebrates that are not fish have evolved swimming, in parallel. One study discovered parallel evolution in body armor among freshwater stickleback fish from numerous saltwater ancestors.

Another interesting thing about evolution, which has only been appreciated in recent decades, is the fact that there is not a simple correspondence between genes and traits. Rarely does one gene determine one trait, and rarely does one trait vary because of one gene. There are dozens of examples of simple gene-trait relationships, many of which were discovered years ago. Because these relationships were relatively easy to find and describe, our textbooks are full of them and our thinking about genetics was for a long time based on them. But this is a little like basing our conception of how all vehicles work by deeply understanding the workings of a toy wagon. The mechanics and engineering of a little red wagon will not help us understand escalators, submarines, or Apollo lunar launch systems. We now think that most genes affect multiple traits and most traits are affected by multiple genes, and that it is all very complex.

A recent study looking at stickleback behavior seems to be an example one gene affecting multiple traits.

Sticklebacks are members of the Gasterosteidae family of fish, with species that live in salt and fresh water. The freshwater sticklebacks evolved from saltwater ancestors who were landlocked less than about 17,000 years ago at many locations across the Northern Hemisphere. For this reason, differences among freshwater and saltwater sticklebacks represent recent and rapid evolution among a well-known group of species and are thus especially interesting to scientists.

Saltwater sticklebacks have up to 36 bony plates associated with a smaller number of sharp spines. These plates and spines protect the fish from predators, but they are costly to produce and maintain. The bony plates require extra calcium, which is rare in some environments, and they restrict the body movements of the fish.

Freshwater sticklebacks tend to have fewer spines and bony plates. Some have a gap in the row of plates (this is called a “partial morph”) while others have only a few plates at the back end of the fish (“low morph”). Fresh water has less calcium than salt water, so this may be an adaptation to a limiting resource. Also, freshwater environments tend to have fewer predators than saltwater environments, so the protective features of the bony plates may be less important in fresh water; perhaps there was relaxed natural selection on this armor, and over time it was lost in many different populations in parallel.

Top: The ninespine stickleback, Pungitus pungitus, is typical of the saltwater form. Bottom: A freshwater form of stickleback with fewer bony plates and fewer spines. Image based on drawings from the Queensland Government Fisheries

In a 2005 study, scientists looked at a gene (Eda) that determines the growth of the bony plate and found that freshwater sticklebacks had a variant of the gene that caused fewer plates to form in those populations. The gene Eda probably serves a regulatory function, so it could determine one of a range of phenotypes from the fully armored saltwater version to the two lesser armored versions found in fresh water. A combination of genetic and population analysis led the researchers to discover that most freshwater sticklebacks in the Northern Hemisphere which exhibit a loss of bony plates do so because they all inherited a variant of Eda that is rare in the original saltwater populations. So the trait evolved in parallel in many lineages, all of which came from different saltwater populations, but it also evolved from a single pre-existing form of the gene. However, it was also found that one or more of the Northern Hemisphere sticklebacks with reduced bony plates got this trait from an entirely different genetic change.

This trait is thus an example of a feature determined by more than one gene, and an example of parallel evolution occurring by more than one means.

A second study just reported at a scientific meeting looks at what seems to be an entirely different question about stickleback evolution. Most sticklebacks form schools, which is a common adaptation among fish, following the principle that there is safety in numbers. But there is one population of freshwater sticklebacks that does not form schools. The sticklebacks of Paxton Lake, in British Columbia, Canada swim around alone most of the time. Rather than forming schools, they hide out in thick vegetation on the bottom of Lake Paxton.

The research team led by Anna Greenwood of the Fred Hutchinson Cancer Research Center in Seattle devised a machine to test for and measure schooling behavior in sticklebacks. This consists of a mobile-like cluster of fake fish which move together as a robotic school in a circle around a large aquarium. When fish from a schooling population of sticklebacks were placed in the water with this machine, they joined the fake fish and swam around with them. When fish from the non-schooling population were placed in the water with this machine, they did not school. These two populations are so closely related that they can interbreed. The researchers tested offspring of the schooling and non-schooling fish to see which behavior each fish would exhibit. As expected, some schooled, and some did not. Once the hybrid fish were sorted out, their genes were examined to see if there was a particular signature that went with schooling versus solitary swimming.

It turns out that the gene that seems to control schooling behavior in these fish is none other than Eda, the same gene that controls the number of bony plates.

So the sticklebacks not only give us a great example of how parallel evolution can arise, but also a great example of a gene affecting more than one trait. But how does that work? The fish that do not develop bony plates also do not develop a fully functioning lateral line. A lateral line is a sense organ many fish have that allows fish to detect movement elsewhere the water. Some predatory fish use the lateral line to find their prey, other fish use the lateral line to detect predators and thus avoid becoming prey, and schooling fish use the lateral line to keep track of the other fish in the school. Apparently, the sticklebacks with the poorly developed lateral lines can’t school because they can’t properly sense the other fish with whom they would need to coordinate their movements.

Sources:

Colosimo, Pamela F., Kim E. Hosemann, Sarita Balabhadra, Guadalupe Villarreal, Jr., Mark Dickson, Jane Grimwood, Jeremy Schmutz, Richard M. Myers, Dolph Schluter, and David M. Kingsley. 2005. Widespread Parallel Evolution in Sticklebacks by Repeated Fixation of Ectodysplasin Alleles Science 25 March 2005: 307 (5717), 1928-1933. [DOI:10.1126/science.1107239]

Pennisi, Elizabeth. 2012. Robotic Fish Point to Schooling Gene. News and Analysis. Science 335(6066):276-277. DOI: 10.1126/science.335.6066.276-b

How do boa constrictors know when to stop constricting? Image courtesy of Flickr user wwarby

Ed. note: We welcome back guest blogger Greg Laden for a two-week blogging tour on Surprising Science.

This is a story of snakes, islands and students. Let’s start with the snakes.

Among the many different kinds of snakes are the constrictors: boas and pythons. They are close relatives that diverged millions of years ago. Pythons are found in the Old World (Africa and Asia) as well as Australia. Boas (family Boidae) are found in the New World (North, Central and South America including some Caribbean islands). All of them kill their prey by wrapping around it and squeezing it to death.

Among the boas there is an island-dwelling form in Belize that is the subject of interest to conservationists, ecologists and, lately, behavioral biologists. This is the miniature boa of Snake Cayes, a group of islands off the coast of southern Belize. When I say “miniature” I mean that they range in length from 30 cm to about 2 meters (1 to 6 feet). This is small compared to the mainland boas of the same species, which can reach 4 meters (13 feet) in length.

It is common for animal populations that live on islands to exhibit differences in size from those on the mainland. Medium and larger mammals like deer tend to be smaller on islands, small mammals like rodents tend to be larger. Something like this may happen with snakes as well.

Allison Hall (left) says “It’s a normal thing to be a little afraid of snakes, but you really get into the project and come to love the animals.” Amanda Hayes is on the right. Image provided by Dickinson News and Events.

Scott Boback is an expert on these animals, and from the time he was a graduate student at Auburn University, he’s been trying to answer the question “how and why are these snakes small?”

The most likely explanations for size differences would seem to be either diet or other features of the environment, or genetics. Perhaps there is a limited food supply on the islands, so snakes grow slowly, and thus there are few or no large ones. It would take them so long reach a large size that somewhere along the line they would have met their demise. Alternatively, it could be that snakes that grow slowly or nearly stop growing as they approach a certain size survive longer or reproduce more effectively (probably owing to food supply being limited). If so, the genes involved in growth would be shaped by natural selection and over time the island snakes would be small because they are genetically different. You can easily imagine how the two processes would work together, perhaps with environmental effects working initially but genetic changes accruing over time.

Boback did eventually come to a conclusion about the small size of the island boas. He recently told me, “we determined that there is some genetic component to dwarfism on islands. However, we believe that it is actually a combination of genetic and environmental effects that ultimately determine island boa size. That is, growth rates are different between island and mainland boas and this appears to be determined partly by genetics.” (See below for the reference to his paper on this research.)

More recently, Boback and his students at Dickinson College have been addressing a different question about boas: How do they know when to stop squeezing their prey? This is an interesting question because, as you might imagine, contracting the majority of muscles in one’s body for an extended period of time is energetically costly, but letting go of prey before it is fully dead may cause the loss of a meal. As an informal experiment, I asked five different people this question over the past two days, after reading of Boback’s research, and everyone gave approximately the same answer: The snakes let go when the prey is dead and stops struggling.

Well, it turns out that we do science to prove ourselves wrong, because that is not the answer. Suspecting a particular mechanism, Boback his students, who maintain a colony of these boas in their lab at Dickinson, devised a brilliant experiment. They took a number of dead rats that would normally be fed to the snakes, and installed robotic “hearts” in them. When the snakes constricted the rats, the hearts were allowed to beat for a while, then they were turned off. Soon after, the snakes loosened their grip, then let go.

It turns out that boas have the ability to detect a heartbeat in the prey, and they use this information to determine how much pressure to apply. Snakes that had never killed or eaten live prey acted the same as snakes with experience with live prey, suggesting that this behavior is innate and not learned.

“Many of us think of snakes as audacious killers, incapable of the complex functions we typically reserve for higher vertebrates,” says Boback. “We found otherwise and suggest that this remarkable sensitivity was a key advancement that forged the success of the entire snake group.”

One of the neat things about this project is that it involved the efforts of undergraduate researchers. The undergraduates not only participated in the research, but they helped produce the peer reviewed paper and are listed as authors. Katelyn McCann, who was a student on this project and now works as a clinical-research coordinator at Children’s Hospital in Boston, notes, “I got to experience the true collaborative nature of research as well as the hours of independent work that go into the final product. Now, working in research I feel like I truly understand the scientific method and what goes into any study.” Boback adds, “student-faculty research at Dickinson is an opportunity for students to experience science in action. It is the most fundamental level of learning in science as the student actively participates in the process of discovery.”

Source:
Boback, S., Hall, A., McCann, K., Hayes, A., Forrester, J., & Zwemer, C. (2012). Snake modulates constriction in response to prey’s heartbeat Biology Letters DOI: 10.1098/rsbl.2011.1105

Boback, S. M. and D. M. Carpenter. 2007. Body size and head shape in island boas (Boa constrictor) in Belize: Environmental versus genetic contributions. Pages 102-116 in R. W. Henderson and R. Powell, editors. Biology of the boas, pythons, and related taxa. Eagle Mountain Publishing, Eagle Mountain, UT.

Additional information for this story came from Dr. Scott Boback, and a press release from Dickinson College.