It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Some features of ATS will be disabled while you continue to use an ad-blocker.
WASHINGTON - Mammals, once tiny creatures scampering on the forest floor, grew larger as the amount of oxygen in the air increased over millions of years, a new study says.
Today mammals, ranging from dogs and cats to elephants, dolphins and people, dominate the planet.
It's a success story Paul G. Falkowski of Rutgers University and colleagues say was helped by the more than doubling of oxygen in the air over the last 205 million years. Their findings are published in Friday's issue of the journal Science.