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Like humans, some song sparrows are more effusive than others, at least when it comes to defending their territories. New UW findings show that consistent individual differences exist not only for how aggressive individual song sparrows are but also for how much they use their signals to communicate their aggressive intentions.

The basics of how a muscle generates power remain the same: Filaments of myosin tugging on filaments of actin shorten, or contract, the muscle – but the power doesn’t just come from what’s happening straight up and down the length of the muscle, as has been assumed for 50 years. The rest of the force should be credited to the lattice work of filaments as it expands outward in bulging muscle – whether in a body builder’s buff biceps or the calves of a sinewy marathon runner.

New work in Argentina where scientists had previously thought Earth’s first grasslands emerged 38 million years ago, shows the area at the time covered with tropical forests rich with palms, bamboos and gingers. Grit and volcanic ash in those forests could have caused the evolution of teeth in horse-like animals that scientists mistakenly thought were adaptations in response to emerging grasslands.