Elephants Took 24 Million Generations to Evolve From Mouse-Size

Evolving bigger bodies takes longer than getting small, mammal study says.

Some mammals need roughly 24 million generations to go from mouse-size to elephant-size, a new study says.

Using both fossil and living specimens, scientists calculated growth rates for 28 different mammalian groups during the past 65 million years—and found that, for mammals, getting big takes longer than shrinking.

It takes a minimum of 1.6 million generations for mammals to achieve a hundredfold increase in body size, about 5 million generations for a thousandfold increase, and about 10 million generations for a 5,000-fold increase, the team discovered.