Featured Research

from universities, journals, and other organizations

Mammals shrink at faster rates than they grow: Research helps explain large-scale size changes and recovery from mass extinctions

Date:
January 30, 2012
Source:
University of Calgary
Summary:
It took about 10 million generations for terrestrial mammals to hit their maximum mass: that's about the size of a cat evolving into the size of an elephant. Sea mammals, such as whales took about half the number of generations to hit their maximum.

Transformations can happen much faster in animals that live in the water. An increase from rabbit-sized to elephant-sized would take at least five million generations, but the equivalent change in whales takes half as many generations. Becoming smaller is also easier: dwarfing in elephants occurred 10 times faster than the equivalent increase to evolve large elephants.
Credit: Image courtesy of Alistair Evans, David Jones and co-authors of the PNAS paper: The maximum rate of mammal evolution

Just how big can mammals get and how fast can they get there? These are questions examined by an international team of researchers exploring increases in mammal size after the dinosaurs became extinct 65 million years ago.

Related Articles


Research published in the journal Proceedings of the National Academy of Sciences shows it took about 10 million generations for terrestrial mammals to hit their maximum mass: that's about the size of a cat evolving into the size of an elephant. Sea mammals, such as whales took about half the number of generations to hit their maximum.

The team, including Dr. Jessica Theodor of the University of Calgary, also discovered it took only about one hundred thousand generations for very large decreases, such as extreme dwarfism, to occur.

"Our research demonstrates, for the first time, a large-scale history of mammal life in terms of the pace of growth. This is significant because most research focuses on microevolution, which are changes that occur within a specific species," says Theodor, co-author of the study and an associate professor of biology at the University of Calgary.

The research team looked at 28 different types of mammals from the four largest continents (Africa, Eurasia, and North and South America) and all ocean basins for during the last 70 million years. For example, one group would include the mammals related to an elephant, another group would include carnivorous mammals.

Researchers were surprised to learn how quickly body-size decreased: the rate is more than 10 times faster than the increases.

"Many of the species which shrunk, such as the dwarf mammoth, dwarf hippo and dwarf hominids, found in the Indonesian island of Flores, became extinct," says Theodor, whose area of expertise are the artiodactyls, hoofed mammals which include in the present day, cows, pigs, sheep, camels, hippos and whales.

"What caused their dwarfism? They may have needed to be small to survive in their environment or perhaps food was scarce and a small stature would require less nutrients," adds Theodor.

This research will help scientists to better understand mammal evolution: what conditions allow a certain mammals to thrive and grow bigger and what conditions would slow the pace of growth and potentially contribute to extinction.

Researchers used generations instead of time in their study because species have different life spans. A mouse only lives for about two years and elephant for 80. They created a metric using the relationship between body size and generation time in living mammals and used it to reconstruct the life history of the extinct forms.


Story Source:

The above story is based on materials provided by University of Calgary. Note: Materials may be edited for content and length.


Journal Reference:

  1. A. R. Evans, D. Jones, A. G. Boyer, J. H. Brown, D. P. Costa, S. K. M. Ernest, E. M. G. Fitzgerald, M. Fortelius, J. L. Gittleman, M. J. Hamilton, L. E. Harding, K. Lintulaakso, S. K. Lyons, J. G. Okie, J. J. Saarinen, R. M. Sibly, F. A. Smith, P. R. Stephens, J. M. Theodor, M. D. Uhen. The maximum rate of mammal evolution. Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1120774109

Cite This Page:

University of Calgary. "Mammals shrink at faster rates than they grow: Research helps explain large-scale size changes and recovery from mass extinctions." ScienceDaily. ScienceDaily, 30 January 2012. <www.sciencedaily.com/releases/2012/01/120130171911.htm>.
University of Calgary. (2012, January 30). Mammals shrink at faster rates than they grow: Research helps explain large-scale size changes and recovery from mass extinctions. ScienceDaily. Retrieved November 28, 2014 from www.sciencedaily.com/releases/2012/01/120130171911.htm
University of Calgary. "Mammals shrink at faster rates than they grow: Research helps explain large-scale size changes and recovery from mass extinctions." ScienceDaily. www.sciencedaily.com/releases/2012/01/120130171911.htm (accessed November 28, 2014).

Share This


More From ScienceDaily



More Fossils & Ruins News

Friday, November 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

New Dinosaur Species Found in Museum Collection

New Dinosaur Species Found in Museum Collection

Reuters - Innovations Video Online (Nov. 27, 2014) A British palaeontologist has discovered a new species of dinosaur while studying fossils in a Canadian museum. Pentaceratops aquilonius was related to Triceratops and lived at the end of the Cretaceous Period, around 75 million years ago. Jim Drury has more. Video provided by Reuters
Powered by NewsLook.com
Classic Hollywood Memorabilia Goes Under the Hammer

Classic Hollywood Memorabilia Goes Under the Hammer

Reuters - Entertainment Video Online (Nov. 26, 2014) The iconic piano from "Casablanca" and the Cowardly Lion suit from "The Wizard of Oz" fetch millions at auction. Sara Hemrajani reports. Video provided by Reuters
Powered by NewsLook.com
3D Map of Antarctic Sea Ice to Shed Light on Climate Change

3D Map of Antarctic Sea Ice to Shed Light on Climate Change

Reuters - Innovations Video Online (Nov. 24, 2014) A multinational group of scientists have released the first ever detailed, high-resolution 3-D maps of Antarctic sea ice. Using an underwater robot equipped with sonar, the researchers mapped the underside of a massive area of sea ice to gauge the impact of climate change. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com
Ruins Thought To Be Port Actually Buried Greek City

Ruins Thought To Be Port Actually Buried Greek City

Newsy (Nov. 24, 2014) Media is calling it an "underwater Pompeii." Researchers have found ruins off the coast of Delos. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

More Coverage


Mouse to Elephant? Just Wait 24 Million Generations

Jan. 30, 2012 Scientists have for the first time measured how fast large-scale evolution can occur in mammals, showing it takes 24 million generations for a mouse-sized animal to evolve to the size of an ... read more

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins