Mammals rarely walk on two legs, but they often rear up to fight:
Fighting from a bipedal posture is commonly observed in anteaters, felids including domestic cats, lions and tigers; canids including foxes, wolves and domestic dogs; bears; wolverines; horses; and many species of rodents, lagomorphs and primates, including great apes.
The advantage of standing up to fight is that it allows an animal to use its strong running muscles, which normally push aftward, to strike downward.
David Carrier, of the University of Utah, decided to measure striking power in humans — because they’re cooperative test subjects — from standing and from all fours, and upward, downward, and to the side. It comes as no surprise that humans strike harder from standing, striking downward. I have some questions about this reasoning though:
Experienced fighters were used as subjects to minimize the risk of injury and to reduce biases in performance among the different types of strikes that were studied.
I’m pretty sure the experienced fighters were much more experienced at striking from standing than from all fours.
Anyway, from this superior ability to strike downward from standing, he concludes that the observed female preference for tall men may relate to fighting ability — especially in the time since we lost our ancestors’ impressive canines:
The primary weapons of most primates are their jaws and large canine teeth. Darwin recognized the association of an increased use of the forelimbs in fighting and a reduction in size of their canine teeth in apes. In doing so, he associated habitual bipedal posture with fighting with the forelimbs.
I would think that all these points for height when fighting with forelimbs would hold doubly true for fighting with augmented forelimbs — that is, clubs or rocks.
(Hat tip to io9.)
Science discovers bigger men are better fighters. News at 11.
Bipedalism is even more important for missile attacks. Humans are the only animal that can kill other animals, including other humans, at range.
Archerfish spring to mind. Here is a more complete list, including all sorts of weird things.