As weighty reads go, it doesn't get much more serious than the men vying to become the world's leading politician in conversation with the world's leading scientific journal.

And the latest issue of Nature has a front cover of suitable gravitas, evenly split between statesmanlike images of the US presidential contenders.

Pity no one told the advertising department. In an eerie mirror image, the magazine's back cover features two labrador pups, one black, one golden, in uncannily similar poses to Barack Obama, famously the first African American candidate for a major party, and his rival John McCain, looking bronzed by Arizona sun.

The journal swears they were not being deliberately cheeky. "We didn't know until the issue landed on our desks," Nature pleads. "It just goes to show that editorial and advertising aren't working in cahoots."

In which case it must be just the power of suggestion which makes the dog on the left look a little more hopeful, but a little less experienced. And which stirs up a strong desire to tickle John McCain behind the ears.

The journal promises to expore "how John McCain and Barack Obama developed their stances on science; who is advising them on technical issues; and where they might take the country if elected". Plus in-depth insights on the candidates' stances on evolution, stem-cell research and climate change. Nothing about cloning, though. Perhaps that's just as well.

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