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There and Back Again

A new study estimates the number of generations necessary to evolve from mouse-sized to elephantine, and shows that it’s quicker to get small.

By | February 1, 2012

image: There and Back Again Pygmy hippos. Wikimedia Commons, Chuckupd

Pygmy hipposWIKIMEDIA COMMONS, CHUCKUPD

A new study, published this week in the Proceedings for the National Academy of Sciences, estimates the time necessary for mammals to evolve from the size of mice to the size of elephants—about 24 million generations. Led by scientists at Australia’s Monash University, the researchers looked at how long it took large scale changes in body size to evolve, rather than small changes within species, and found that land mammals changed size more slowly than whales. While it took about 5 million generations for land mammals to increase in size 1000-fold, cetaceans increased by a similar factor in just 3 million generations. Researchers also saw that decreasing in size occurred about 30 times faster than increasing.

“This tells us how much slower so-called macroevolution is compared to microevolution,” lead author Alistair Evans of Monash University told Nature. “The kinds of short-term rates of evolution we can measure in the lab, or even in short-term ecological observations, are not likely to be sustained for thousands of generations,” agreed Mike Benton, a palaeontologist at the University of Bristol, UK.

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Comments

Avatar of: Ken Pimple

Ken Pimple

Posts: 10

February 1, 2012

"While it took about 5 million generations for land mammals to increase
in size 1000-fold, cetaceans increased by a similar factor in just 3
million years."

Is the comparison between 5 million generations and 3 million years a typo? Or am I missing something?

Ken

Avatar of: johndossantos

johndossantos

Posts: 8

February 1, 2012

Looks like they've corrected it to 3 million generations.

Avatar of: TheSciAdmin

TheSciAdmin

Posts: 56

February 1, 2012

Thanks for catching the typo, Ken. It's now comparing generations to generations.

Avatar of:

Posts: 0

February 1, 2012

"While it took about 5 million generations for land mammals to increase
in size 1000-fold, cetaceans increased by a similar factor in just 3
million years."

Is the comparison between 5 million generations and 3 million years a typo? Or am I missing something?

Ken

Avatar of:

Posts: 0

February 1, 2012

Looks like they've corrected it to 3 million generations.

Avatar of:

Posts: 0

February 1, 2012

Thanks for catching the typo, Ken. It's now comparing generations to generations.

Avatar of:

Posts: 0

February 1, 2012

"While it took about 5 million generations for land mammals to increase
in size 1000-fold, cetaceans increased by a similar factor in just 3
million years."

Is the comparison between 5 million generations and 3 million years a typo? Or am I missing something?

Ken

Avatar of:

Posts: 0

February 1, 2012

Looks like they've corrected it to 3 million generations.

Avatar of:

Posts: 0

February 1, 2012

Thanks for catching the typo, Ken. It's now comparing generations to generations.

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