More politicians talking science

I wrote about politicians talking science for a blog hosted by Oxford University Press in June 2015. In that posting, I focused on statements by Jeb Bush and Ted Cruz illustrating their misunderstanding of the scientific consensus about climate change. This new posting was inspired by Rand Paul’s answer to a question about climate change in the November 11th debate among Republican presidential candidates and illustrates a valuable aid to critical thinking called argument mapping.

In an interview a year ago, Paul expressed some support for regulating carbon dioxide emissions, but in the recent debate he stated that his first action as president would be to repeal President Obama’s regulations to control emissions that contribute to climate change. Paul argued for an “all of the above” energy policy, including not only sustainable sources like solar power but also traditional fuels like coal that release greenhouse gases contributing to climate change. In making this argument, Paul said: “The planet’s 4.5 billion years old. We’ve been through geologic age after geologic age. We’ve had times when the temperature’s been warmer, we’ve had times when the temperature’s been colder. We’ve had times when the carbon in the atmosphere’s been higher.” Unlike some candidates, Paul accepts the fact that humans influence climate, but, like all climatologists, he believes that “nature also has a role”.

What kind of argument is Paul making here? How does his plan to repeal emissions controls in support of an all of the above energy policy relate to his riff about the climate history of Earth? He doesn’t make an explicit connection between energy policy and climatology, but his main claim seems to be that we can continue to burn fossil fuels without adverse effects because current carbon levels in the atmosphere and current global temperatures are within the range of values that Earth has experienced in the past. Here is a diagram that illustrates his argument:

Rand Paul's argument that humans won't be harmed by continuing to burn fossil fuels.

Rand Paul’s argument that humans won’t be harmed by continuing to burn fossil fuels.

This diagram is called an argument map. The sentence in the top box is Paul’s main contention; the two sentences in the green box below are linked premises that explain his contention by acknowledging that burning fossil fuels causes climate change but suggesting that we can do so safely. The two sentences in the lowest box are the crux of his argument in support of his contention. The premise on the left in this lowest box is what Paul said about carbon in the atmosphere and is a true statement of what climatologists have discovered from various kinds of evidence. The co-premise on the right is an unstated assumption of Paul’s argument that links this climatological record to Paul’s claim about the safety of continuing to burn fossil fuels.

Although the main premise of Paul’s argument is true, the co-premise is irrelevant because humans have never existed with atmospheric carbon dioxide levels as high as they are today. This makes Paul’s contention a non sequitur and refutes Paul’s argument, as illustrated in this expanded argument map:

Refutation of Rand Paul's argument that continued use of fossil fuels won't be harmful.

Refutation of Rand Paul’s argument that continued use of fossil fuels won’t be harmful.

This story of obfuscation by a presidential candidate has several additional dimensions. Besides claiming that humans won’t be harmed by continuing to burn fossil fuels, Paul argues that regulations to control emissions will hurt our economy. Two recent analyses (here and here) by separate groups of researchers independent of the government imply quite the opposite, as illustrated below:

Refutation of Rand Paul's argument that new regulations to control emissions of fossil fuels will harm our economy.

Refutation of Rand Paul’s argument that new regulations to control emissions of fossil fuels will harm our economy.

Another set of researchers estimated that new regulations on emissions would prevent 3500 premature deaths per year, with the greatest benefit in states that rely heavily on coal such as Paul’s home state of Kentucky. How would you extend the argument map to incorporate this information?

Paul discussed only impacts of climate change on humans in his brief comments in the Republican debate. How about impacts on wild plants and animals? Humans have increased atmospheric carbon dioxide from 280 parts per million (ppm) before the Industrial Revolution to 400 ppm now, a level unprecedented in our history as a species. Global temperatures have increased correspondingly, and will continue to increase even if we gradually phase out use of fossil fuels. The rates of change in climatic conditions are also unprecedented, certainly in our history as a species and probably in the entire history of life on Earth. There have been five mass extinctions during Earth’s history, most recently about 66 million years ago when about 75% of all species became extinct, including all of the dinosaurs except their avian descendants. We are now in the midst of a sixth mass extinction, triggered by human activities such as overhunting, destruction of natural habitats, and burning of fossil fuels causing climate change. Many species of plants and animals can adapt to gradually changing climates, but adaptation to the rapidly changing conditions happening now is less likely.

I discuss argument mapping more fully in Tools for Critical Thinking in Biology, and illustrate another faulty argument of climate contrarians at a website with many other examples of argument maps. The Australian philosopher Tim van Gelder described the rationale for argument mapping and developed the software used for my argument maps, which can be found at the ReasoningLab website, together with links to tutorials and other resources for learning about argument mapping.

Posted in Argument mapping, Climate change, Science and politics | 1 Comment

Research on medicinal uses of marijuana: Is the cart before the horse?

I describe two studies of medicinal uses of marijuana in Chapter 4 of Tools for Critical Thinking in Biology to illustrate why experiments are considered the gold standard for research. In June 2015, two months after the book appeared, the Journal of the American Medical Association (JAMA) published two reviews and an editorial about research on medicinal uses of marijuana. In their editorial, D’Souza and Ranganathan concluded that: “Since medical marijuana is not a life-saving intervention, it may be prudent to wait before widely adopting its use until high-quality evidence is available to guide the development of a rational approval process. Perhaps it is time to place the horse back in front of the cart.” Before explaining why D’Souza and Ranganathan think the cart is before the horse in marijuana research, I want to tell you what the reviews in JAMA have to say about the two studies I discussed in detail in my book.

Marijuana plant.

Marijuana plant growing in Sherburne National Wildlife Refuge, Minnesota
(US Fish and Wildlife Service).

In one of the studies I discussed, a group of researchers in San Francisco studied the effects of smoking marijuana on a type of pain called peripheral neuropathy experienced by HIV/AIDS patients; in the other, a group of researchers in San Diego studied effects of marijuana on experimentally induced pain in healthy volunteers. Both studies were randomized controlled trials: subjects were randomly assigned to treatments and one of the treatments was a placebo, or control, in which THC, one of the main active ingredients of marijuana, had been removed from cigarettes used by the volunteers. In addition, the experiments were double-blind trials: the subjects were ostensibly unaware of the treatment they received in each phase of the experiments, as were the researchers until the experiments were completed and the researchers started analyzing the data.


Chemical structure of THC, one active ingredient of marijuana, by Yikrazuul.

Neither set of reviewers for JAMA mentioned the San Diego study, presumably because these researchers worked with healthy volunteers rather than testing marijuana for treating a specific disease. I included the San Diego study in my book because it illustrated some important considerations in designing experiments. For example, the researchers asked whether there was a relationship between the dose of THC received by subjects and alleviation of pain. They found that an intermediate dose of THC was more effective than either a lower or higher dose; patients actually felt the most pain with the highest dose. These results are clearly relevant to using marijuana for treating pain caused by a disease such as HIV/AIDS, even though the JAMA reviewers didn’t see fit to mention this study in their papers.

One of the JAMA reviews was couched as a response to a patient who had been treated for chronic back pain for 18 years with only modest success. The patient began using marijuana shortly after it was legalized for medical use in his state. The second review was a quantitative analysis of evidence for the effectiveness of marijuana for treating several medical conditions. Both reviews focused on experimental studies and they reached similar conclusions about strengths and weaknesses of evidence for effectiveness of marijuana for treating various conditions.

Penny Whiting and her colleagues considered 79 randomized controlled experiments in their quantitative analysis. In 28 of these experiments, including the San Francisco study that I described in my book, marijuana was used in an attempt to alleviate chronic pain. Most of these experiments used an oral spray containing purified forms of two active ingredients extracted from marijuana, but the San Francisco volunteers smoked marijuana cigarettes. Subjects in the treated groups felt less pain than subjects in the control groups in most of these experiments, with the greatest reduction in pain for the San Francisco experiment. I used the San Francisco study in my book because it was a good example of how to design a randomized controlled experiment. With Whiting’s review, I can go further and say that the results of this experiment are consistent with those of other recent experiments addressing similar questions; if anything, the results of the California study are even more persuasive than those of similar experiments.

In addition to finding credible evidence that marijuana can benefit patients with chronic pain, the JAMA reviewers found moderate support from experimental studies that marijuana can reduce spasticity in patients with multiple sclerosis but only weak evidence that it can reduce nausea and vomiting associated with chemotherapy. The reviewers found essentially no evidence that it helps patients with depression, anxiety disorders, sleep disorders, psychoses, Tourette syndrome, Parkinson’s disease, inflammatory bowel syndrome, or glaucoma. Whiting’s group also found evidence for many adverse side effects, at least in the short term.

Why did the editorial accompanying these reviews in Journal of the American Medical Association conclude we should put the horse back in front of the cart in marijuana research? About half of the US states allow residents to use marijuana for medical purposes, but each state lists a specific set of allowable conditions and these lists are very diverse. In most cases, support for including a medical condition on a state list is not based on randomized, controlled experiments – the gold standard for research – but on weak evidence at best: “anecdotal reports, individual testimonials, legislative initiatives, and public opinion.” Marijuana contains at least 400 secondary compounds, including 70 related to THC, the best known active ingredient. There is great variation in the chemical composition of different samples of marijuana, leading to unpredictable effects on the body. Interactions of marijuana with other drugs that may be taken concurrently are uncertain. There are numerous short-term side effects and potential long-term risks, especially for children and young adults whose brains are still developing, since brain development depends on a natural compound in the brain that is similar to THC and binds to the same receptor molecule on the membranes of brain cells. For these and other reasons, D’Souza and Ranganathan argue in JAMA that we need to gather more and better evidence to justify or discredit use of marijuana for specific medical conditions.

Posted in Experimentation, Medicine | 1 Comment

Brownie, you’re doing a heckuva job

I discuss several examples of the complexity of causation in Tools for Critical Thinking in Biology, ranging from interactive effects of genes and environments on humans and other organisms to webs of relationships connecting predators and prey such as killer whales, sea otters, and sea urchins in the Aleutian Islands. Hurricane Katrina has been in the news because it hit New Orleans 10 years ago. In Chapter 8 of my book, I used the damage from Hurricane Katrina to introduce the idea that events happen due to complex webs of causation: mistakes by the Corps of Engineers that built the levees that were supposed to protect New Orleans, inadequate funding to build effective levees, development of wetlands in the Mississippi Delta, ineffectual responses by government agencies such as the Federal Emergency Management Agency (FEMA) due to patronage appointments of leaders for these agencies. I also discussed the potential role of climate change in increasing the average severity of hurricanes in the coming decades.

Hurricane katrina and New orleans

Web of causation for damage in New Orleans attributed to Hurricane Katrina.

President George W. Bush had appointed Michael D. Brown as head of FEMA two years before Katrina, despite Brown’s complete lack of prior experience in emergency management. Bush told Brown he was doing “a heckuva job” a few days after Katrina hit New Orleans; Brown resigned on September 12 when it had become abundantly clear that FEMA’s response was inadequate and ineffective.

I didn’t think much about Michael Brown when I wrote the book, but this tenth anniversary of Katrina inspired Emily Atkin of ThinkProgress to interview Brown about his activities since Katrina. Despite his ignominious departure from FEMA, Brown continued to do consulting work on emergency management, without much success, then became a talk radio host, where he promotes his views that humans have little if any effect on climate change. For example, he doesn’t believe that rising sea levels are much of a problem. According to Atkin, Brown thinks that “this is partially proven . . . by the fact that people are still buying and developing big properties on the more vulnerable areas of the East Coast”.

It probably shouldn’t be surprising that Michael Brown denies the evidence that humans influence global climate, although I would have hoped that his trial by fire during Katrina might have inspired a more thoughtful approach to this critical issue of our time.

Posted in Causation, Science and politics | 1 Comment

Vaccination and the Eradication of Human Diseases

Smallpox was a scourge of humanity for centuries, but in 1977 became the first human disease eliminated by a worldwide vaccination campaign. In Chapter 6 of Tools for Critical Thinking in Biology, I explain how the reproductive rates of disease organisms influence the potential success of vaccination campaigns. Smallpox virus has a much lower reproductive rate than measles virus, making it easier to protect an entire population against the spread of smallpox than measles. This is important because no campaign, no matter how intense, can vaccinate everyone – even if it would be logistically possible to do so, some people can’t be vaccinated because they are too young, too old, or have compromised immune systems.

After the success with smallpox, public health agencies began a campaign to eradicate polio. This has reduced cases of paralysis caused by the polio virus from about 350,000 in 1988 to fewer than 2000 per year since 2001, and only 359 in 2014. These few cases occurred in Nigeria, Afghanistan, and Pakistan; polio has persisted in these countries in part because extremist groups such as Boko Haram in Nigeria have blocked vaccination efforts, sometimes by killing vaccinators.

Public health groups working in Africa have stepped up their efforts and adjusted some of their tactics to gain more support for vaccination from local populations. On August 11, 2015, the Global Polio Eradication Initiative reported that for the first time ever, Africa had gone a full year without a case of polio. The last reported case was in August 2014 in Somalia; if there are no more cases in the next two years, the World Health Organization will declare Africa free of polio, putting us even closer to eliminating a second human disease from the world.

I discuss smallpox and polio briefly in Chapter 6 of Tools for Critical Thinking in Biology, but the main purpose of this chapter is to explain how biologists use models to help answer important practical questions. I describe a simple model that we use to estimate the fraction of a population that must be vaccinated to prevent a disease from spreading and apply this model to measles and whooping cough, two diseases with much higher reproductive rates than smallpox and polio. It will be extremely difficult if not impossible to eradicate these diseases. In fact, there are still large numbers of cases in less developed countries as well as outbreaks in more developed countries with good health care systems. In addition to describing this model in the book, I discuss its ethical implications. Do parents have a social obligation to have their children vaccinated, in order to protect not only their own children but the community as a whole, including those who can’t be vaccinated because of age or compromised immune systems? This bears on a movement to reject routine vaccination that has many adherents in some parts of the US and other countries. For whooping cough, those who reject vaccination make a logical error in thinking about causation. Anti-vaccinators want to attribute recent outbreaks of whooping cough to use of a less effective (but safer) vaccine rather than a decline in the rate of vaccination associated with their campaign against vaccination. In making this claim, anti-vaccinators fail to appreciate that events can have multiple, interacting causes. Decreased rate of vaccination probably acted synergistically with use of a less effective vaccine to cause recent outbreaks of whooping cough. See “Complexities of causation” for further explanation and Tools for Critical Thinking in Biology for other complexities of causation.

Posted in Modeling, Vaccination | Comments Off on Vaccination and the Eradication of Human Diseases

Why blog about critical thinking in biology?

Tagged monarch butterfly

Monarch butterfly wearing an ID (photo by Jim Gagnon)

Oxford University Press published my book, Tools for Critical Thinking in Biology, in April 2015. I wrote this book because 37 years of teaching biology at the University of Nevada, Reno taught me that the most important thing for students to learn is how to think critically about ideas and evidence. To become thoughtful and well-informed citizens, students need to learn how to evaluate evidence from observations, comparisons and correlations, experiments, and even models. They need to learn how to make decisions based on the weight of disparate forms of evidence. I use engaging, contemporary examples to illustrate these and other tools of critical thinking. For several of these examples, researchers have already published new findings that extend the discussion in my book. New work in the months and years to come will undoubtedly overturn some of my conclusions. I’ll use this blog to call attention to these developments so readers can use my book as a foundation for understanding new research and for continuing to hone their critical thinking skills.

Posted in General material | 2 Comments