A new study has shown that elephants took 24 million generations to get to their current size and that they were once the size of a mouse.

Researchers from Monash University in Melbourne, Australia analyzed 28 groups of mammals, including elephants, primates and whales, as reported in the Telegraph.

''We can show that it took at least 24 million generations to make the proverbial mouse-to-elephant size change - a massive change, but also a very long time,'' said study leader Dr. Alistair Evans, from Monash University in Melbourne, Australia in the study published in the journal Proceedings of the National Academy of Sciences.

The researchers also found that changes in whale size were twice as fast as those of land mammals.

''This is probably because it's easier to be big in water,'' said co-author Dr. Erich Fitzgerald, of Australia's Museum Victoria.

Additionally, they found that shrinking happens more than 10 times faster than growing throughout generations and that living on small islands with little resources can speed up this process.

''When you do get smaller, you need less food and can reproduce faster, which are real advantages on small islands,'' said Dr Evans.