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