Mass extinctions

The recent rapid decline in vulture population leading gradually to their mass extinction seems to indicate that at some time a species succumbs to some climatic or physiological factors. Some of the well-known mass extinctions that have taken place over millions of years are indicated below:

•Pterodactyls — These were giant flying reptiles with bat-like wings.

•Dinosaurs — These were gigantic four-footed reptiles who ruled the world for 140 million years in the Mesozoic age (180-100 million years ago) and perished 70 million years ago. Some were herbivorous whilst the deadly Tyrano-saurus was carnivorous. A widely held theory is that they couldn’t survive the Ice Age with co-current food shortage.

•Dinotheriums — These were huge herbivorous mammals with curved pointed horns over their heads. They perished during the Tertiary Age (60-3 million years ago).

•Mastodens and mammoths — These were the huge elephants of yesteryears. They became extinct about 20,000 years ago in the Quaternary Age.

•Moas and dodos — These were flightless birds about 13 feet tall. Moa was from New Zealand and Dodo from Mauritius. These species perished about 1,000 years ago.

•Vultures - They are the latest in the list of creatures facing extinction. No one knows the exact cause. They could be victims of virus, pesticides, Diclofenac or heavy build-up of uric acid in their systems.

Just as all species have their own life expectancy at birth, so also they have their own time-span for survival. Human beings have already survived for a few million years and are likely to survive several million years more unless some cataclysmic event causes homo sapiens to disappear completely from this planet.

Dr P. D. SUNAVALA