CALGARY - The extinction of dinosaurs 65 million years ago could
have been a classic case of one door closing and another opening
— with mammals being the beneficiaries. A study published in the
prestigious journal "Science" says researchers have demonstrated
that after dinosaurs died out, mammals were able to grow in a
way they had never been able to grow before. Dr. Jessica
Theodor, an associate professor in biological sciences at the
University of Calgary, is a co-author of the study. "We looked
at how maximum body mass changed from the extinction of the
dinosaurs to today," she said in an interview with The Canadian
Press. When mammals shared the land with dinosaurs, the largest
mammal weighed about 10 kilograms, says Theodor. Over the next
25 million years, she says, the largest mammals grew to a
maximum of 17 tonnes. "We tend to think of evolutionary rates
within species or within closely related species over shorter
periods of time, but for an entire massive group like mammals to
increase a thousandfol