This journal provides immediate access to some articles. Volume 275(1636); April 7, 2008 Research Articles Recovery from the most profound mass extinction of all time PMCID: PMC2596898 A clear human footprint in the coral reefs of the Caribbean PMCID: PMC2596901 Population dynamics and sex ratio of a parasitoid altered by fungal-infected diet of host butterfly PMCID: PMC2596907 The correlation of learning speed and natural foraging success in bumble-bees PMCID: PMC2596909 The trade-off between number and size of offspring in humans and other primates PMCID: PMC2596903 Observational learning in chimpanzees and children studied through ‘ghost’ conditions PMCID: PMC2596905 Donning your enemy's cloak: ground squirrels exploit rattlesnake scent to reduce predation risk PMCID: PMC2596899 | ||