Exponential population growth and other unkillable science myths

There's a widespread understanding that the vaccine-autism link and climate denial are bullshit, but there are plenty of widespread science myths that are repeated by people who should know better, from the idea that early screening lowers cancer mortality to the idea that the human population is growing exponentially.

Nature rounds up five of these myths, and shows how some scientists — either out of self-interest or Dunning-Kruger — have perpetuated them.

Take cancer screening: from the CMO of the American Cancer Society to the meta-analyses carried out by the Cochrane Trust, there's every reason to think that blanket cancer screening does more harm than good. But it's hard to get this to stick: patients who've had surgical interventions to remove early cancer believe that they've had their lives saved, despite the fact that when screening and early surgery increase, mortality stays flat. All surgery carries risks, and the specialists who perform the screening and surgery naturally believe that they're doing good, and that screening is a fundamental right.

But that's nothing when compared to the alleged "exponential" human population growth, which persists despite decades and decades of slowing population growth. This one has a more sinister dimension, since the subtext is so often eugenic in nature: "the wrong kind of people are having too many babies."

But the human population has not and is not growing exponentially and is unlikely to do so, says Joel Cohen, a populations researcher at the Rockefeller University in New York City. The world's population is now growing at just half the rate it was before 1965. Today there are an estimated 7.3 billion people, and that is projected to reach 9.7 billion by 2050. Yet beliefs that the rate of population growth will lead to some doomsday scenario have been continually perpetuated. Celebrated physicist Albert Bartlett, for example, gave more than 1,742 lectures on exponential human population growth and the dire consequences starting in 1969.

The world's population also has enough to eat. According to the Food and Agriculture Organization of the United Nations, the rate of global food production outstrips the growth of the population. People grow enough calories in cereals alone to feed between 10 billion and 12 billion people. Yet hunger and malnutrition persist worldwide. This is because about 55% of the food grown is divided between feeding cattle, making fuel and other materials or going to waste, says Cohen. And what remains is not evenly distributed — the rich have plenty, the poor have little. Likewise, water is not scarce on a global scale, even though 1.2 billion people live in areas where it is.

"Overpopulation is really not overpopulation. It's a question about poverty," says Nicholas Eberstadt, a demographer at the American Enterprise Institute, a conservative think tank based in Washington DC. Yet instead of examining why poverty exists and how to sustainably support a growing population, he says, social scientists and biologists talk past each other, debating definitions and causes of overpopulation.

Cohen adds that "even people who know the facts use it as an excuse not to pay attention to the problems we have right now", pointing to the example of economic systems that favour the wealthy.

The science myths that will not die
[Megan Scudellari/Nature]

(via Skepchick)

(Image: Crowd, James Cridland, CC-BY)