Elephants took 24 million generations to become land giant

BOSTON — Elephants may be tougher then we thought.

According to new research, it wasn't easy for them to become the largest land mammal on the planet. 

The study, The Evolution of Maximum Body Size of Terrestrial Mammals, suggests it has taken elephants 24 million generations to become so large. 

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“Big animals represent the accumulation of evolutionary change, and change takes time,” evolutionary biologist Alistair Evans of Australia’s Monash University, a co-author of the study told Wired Magazine.

The study suggests before dinosaurs went extinct, larger land animals like elephants were actually the size of present day rodents. 

Says the abstract: 

The extinction of dinosaurs at the Cretaceous/Paleogene (K/Pg) boundary was the seminal event that opened the door for the subsequent diversification of terrestrial mammals. Our compilation of maximum body size at the ordinal level by sub-epoch shows a near-exponential increase after the K/Pg. On each continent, the maximum size of mammals leveled off after 40 million years ago and thereafter remained approximately constant.

What made the size of these mammals level off? Humans.

Once we became the new dominant species, elephants and other large land mammals had less space and less food to continue evolutionary growth. The researchers believe it is highly unlikely any mammal will grow larger so long as humans are on earth. 

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While it may have taken 24 million generations to grow so large, it takes far less time to grow small. The researchers found mammals shrink at a rate 100 times faster then they grow, meaning it took a door mouse a mere 100,000 generations to become so small.

Next time you see an elephant, pat him on his large back for all the hard work it took to become that size. 

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