Getting to know "Mitochondrial Eve"

By studying the way it has mutated and changed over time, scientists can trace human mitochondrial DNA — the DNA that is passed from mother to daughter — back to a single woman. Basically, everybody alive is descended from her. But that's not the same thing as saying that Mitochondrial Eve was once the only woman alive. In a very nice piece — with helpful illustrations — the Christian (but evolution-accepting) scientists at BioLogos explain what Mitochondrial Eve really means and why she can't be used as an argument for creationism. Whether or not you've ever found yourself arguing this point with a family member or friend, the piece is really useful for deepening your understanding of a pop-science concept that's often thrown around without a clear explanation behind it. Read the rest

A must-read for anyone who wants to be less stupid

When it comes to discerning truth from myth, our enemy is ourselves — and ourselves really, Really, REALLY like to turn chance events into coherent narratives. (Via Kellan) Read the rest

Did climate change cause Hurricane Sandy? The answer depends on why you're asking

There are two answers here: One for the legitimately curious, and one for people who want a disaster to be a referendum on climate change.

Autism is more than a parasite deficiency

The New York Times Sunday Review had an article this week linking autism with the hygiene hypothesis. Written by Moises Velasquez-Manoff, the piece is part of the Times' opinion coverage, not reported news. It was also one of those sort of stories that comes across as highly persuasive ... until you start looking at the details. About halfway through reading it yesterday, it occurred to me that Velasquez-Manoff was making a lot of big statements—"perhaps 1/3 of autism, and very likely more, looks like a type of inflammatory disease", for example—without citing the sources to back those statements up.

That's easy to do when you're writing a relatively short article summarizing the contents of a much bigger book, as Velasquez-Manoff seems to be doing here. But the problems go deeper than that, according to biologist and science writer Emily Willingham. In a must-read blog post, she goes through the NYT piece and points out many flaws in argument and detail. The main problem, though, is a pretty simple one: Moises Velasquez-Manoff presents what seems to be a largely speculative hypothesis as sure-fire truth. To make that case as persuasive as it is, he leaves out lots of evidence that doesn't match up with his thesis.

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Crackpots, geniuses, and how to tell the difference

Over at Download the Universe, Ars Technica science editor John Timmer reviews a science ebook whose science leaves something to be desired. Written by J. Marvin Herndon, a physicist, Indivisible Earth presents an alternate theory that ostensibly competes with plate tectonics. Instead of Earth having a molten core and a moveable crust, Herndon proposes that this planet began its existence as the core of a gas giant, like Jupiter or Saturn. Somehow, Earth lost its thick layer of gas and the small, dense core expanded, cracking as it grew into the continents we know today. What most people think are continental plate boundaries are, to Herndon, simply seams where bits of planet ripped apart from one another.

The problem is that Herndon doesn't offer a lot of evidence to support this idea.

Once the Earth was at the center of a gas giant, Herndon thinks the intense pressure of the massive atmosphere compressed the gas giant's rocky core so that it shrunk to the point where its surface was completely covered by what we now call continental plates. In other words, the entire surface of our present planet was once much smaller, and all land mass.

I did a back-of-the-envelope calculation of this, figuring out the radius of a sphere that would have the same surface area as our current land mass. It was only half the planet's present size. Using that radius to calculate the sphere's volume, it's possible to figure out the density (assuming a roughly current mass). That produced a figure six times higher than the Earth's current density — and about three times that of pure lead.

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The pros and cons of irradiated food

Irradiating food doesn't make it radioactive, and it does kill dangerous bacteria, like the E.coli that killed many Europeans this summer. But it's also not a panacea against food poisoning and it's definitely not the most popular idea ever thought up. In a column in the New York Times, Mark Bittman examines the evidence behind irradiation, and how that evidence does and doesn't get considered in the choices we make about food.

When it comes to irradiation, you might need a primer. (I did.) Simply put, irradiation — first approved by the FDA in 1963 to control insects in wheat and flour — kills pathogens in food by passing radiation through it. It doesn’t make the food radioactive any more than passing X-rays through your body makes you radioactive; it just causes changes in the food. Proponents say those changes are beneficial: like killing E. coli or salmonella bacteria. Opponents say they’re harmful: like destroying nutrients or creating damaging free radicals.

Many people are virulently for or against. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, says that irradiation “could do for food what pasteurization has done for milk.” (The main difference between irradiation and pasteurization is the source of the energy used to kill microbes.) Wenonah Hauter, the executive director of Food & Water Watch — which calls irradiation “a gross failure” — told me it was “expensive and impractical, a band-aid on the real problems with our food system.”

There are a few people in the middle.

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Breast cancer prevention and evidence

The National Breast Cancer Coalition has come out with new evidence-based position statements regarding several popular preventative and treatment options for breast cancer. Among the findings: There is no link between abortion and breast cancer; there's no evidence that breast self-exams actually do anything useful; and the policy of routine mammograms for every woman doesn't help as much as we think it does. Read the rest