Bare arms don't get much deadlier than the forelimbs of Chuck Norris. But long before the A-team prowled the earth, weapons were already being routinely used in male-male disputes a bit more important than bar fights. What is it about boys and guns though, you may ask. Darwin did too, when he discussed sexual selection in The Descent of Man. Popular examples of the bizarre body plans arising from sexual selection tend to revolve around ornaments and female mate choice: peacocks' tails and the lovely plumage of Norwegian blues and so on. But a recent review article takes a wide-ranging look at another piece of the sexual selection game: the evolution of animal weapons. The article has some fantastic artwork of weapons in all the major groups of animals, from spiny helmets in trilobites to wasp tusks to hadrosaur headgear - and it's well worth skimming through just to look at the pictures.
The survey points out that the exact mechanisms that lead to bizarre weaponry, like stag antlers or beetle horns, are not very well understood. But some important general rules seem to show up: elaborate weapons evolve for fighting when there are localized, defendable resources (food, burrows) that are attractive to females for feeding or egg-laying. And fights are less likely to break out when each opponent can evaluate the other's fighting ability effectively (or, why Bruce Lee does the nunchak dance). A fascinating article, and it's been great fun matching the figures from its pages with real examples from the galleries. So here are a couple of collages of knives and tusks and other bare arms. Don't forget to check out the giraffe weevil.


While photographing fossil weapons, I made the classic mistake of forgetting the Smilodon at the entrance. The next time, I'll remember to take a picture of that toothy smile on the big kitty cat. These next big cats though might not have been particularly good-humored. While every picture of North American extinct mammals includes sabertooths, lions usually seem to be forgotten. Lions ? Wait, don't they mostly chase wildebeest in the African savannah ? Not quite, as the ice age prairie was evidently just as exciting as today's African grasslands, with packs of giant lions chasing giant deer while giant elephants looked on. More about lions from not so long ago: Paleo leo (really more like Pleisto leo, but I have no willpower). And an older article about the giraffe-hunting lions of Kruger, that managed to find the best use for paved roads yet.
When up against packs of huge lions or deer with automatic weapons, sometimes it might be best to hide instead of running. Check out these images of animal camouflage; and remember that you just might evolve cubicle-colored camouflage if you sit inside for too long. So make sure you get out and enjoy the weather !