A tiny, furry-tailed creature was the earliest ancestor of the placental mammals—a group excluding marsupials and egg-laying mammals—and lived after the extinction of the dinosaurs, according to a study in the 8 February Science.
The origins and early evolution of placental mammals have long been a matter of debate.
Arthropods, which include insects, arachnids and crustaceans, are the most diverse group of terrestrial species on the planet. And that might be why researchers have had such a difficult time estimating their numbers, especially in tropical forests where so many arthropod species are known to thrive.
While widespread vaccination led to eradication of smallpox by 1979, a changed world and changing health priorities make it tougher to totally eliminate other infectious diseases, experts said at a AAAS meeting.
“Eradication of smallpox gave rise to a glow of optimism,” said Joshua Rosenthal, acting deputy director of the Fogarty International Center at the National Institutes of Health. If smallpox was gone, could measles, polio, and other diseases be far behind?