Featured Research

from universities, journals, and other organizations

Bigger creatures live longer, travel farther for a reason

Date:
August 24, 2012
Source:
Duke University
Summary:
A biological mystery about the longer lifespans of bigger creatures may be explained by the application of a physical law called the Constructal Law. It proposes that anything that flows -- a river, bloodstream or highway network -- will evolve toward the same basic configuration out of a need to be more efficient. A professor argues that this same basic law applies to all bodies in motion, be they animals or tanker trucks.

A long-standing mystery in biology about the longer lifespans of bigger creatures may be explained by the application of a physical law called the Constructal Law.*

What this law proposes is that anything that flows -- a river, bloodstream or highway network -- will evolve toward the same basic configuration out of a need to be more efficient. And, as it turns out, that same basic law applies to all bodies in motion, be they animals or tanker trucks, says Adrian Bejan, the J.A. Jones Professor of mechanical engineering at Duke and father of the Constructal Law.

In his latest theory paper, appearing Aug. 24 in the journal Nature Scientific Reports, Bejan argues that there is a universal tendency for larger things, animate and inanimate, to live longer and to travel further.

He starts his argument with an examination of the well-known observation in biology that larger animals tend to live longer. Bejan wanted to see if this general rule might apply to inanimate systems as well and proceeded to mathematically analyze the relationship in rivers, jets of air and vehicles.

He found, as a general rule, that bigger rivers are older and that larger jets of air, such as atmospheric jet streams, last longer. By his calculations, larger vehicles should also last longer, but hard evidence of that is lacking, he says, and there are outliers of course, like Subaru Justys with 300,000 miles.

By being larger and lasting longer, all of these systems also travel farther, he says.

If you look at a moving vehicle or animal simply as a mass in motion, that is, something flowing, "the spreading of the mass of vehicles and animals is completely analogous to the flow of water in river channels," Bejan says. "It is the same design."

Interestingly, if the body size and lifespan of known species of animals are plotted on a curve, it falls on a slope of about . And then, following a different line of inquiry, if you plot the frequency of breathing to body size, that is a slope of - .

When combined, these two insights about animal body size work out to a constant for the number of breaths per lifetime, Bejan says. This gives most creatures about the same number of breaths in their lifetime, but the larger, slower-breathing animals use their breaths up over a longer span of time. "So bigger means a longer lifespan," he said. "I was looking at this enigma about body size and longevity from a point of view that hadn't occurred to biologists," Bejan said.

The Constructal Law governs how big an engine a truck needs and how big a heart a whale needs. "There's no difference between a vehicle and an animal," Bejan said. "Being larger means two things, not one: you live longer and you travel farther."

There are, of course, notable exceptions to the rule: The 4-ounce Arctic Tern travels more than 44,000 miles a year.

"The size-effect on travel and life time is the same for the animate and the inanimate," Bejan argues. "Everything that moves enjoys the same design."

* www.constructal.org.


Story Source:

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


Journal Reference:

  1. Adrian Bejan. Why the bigger live longer and travel farther: animals, vehicles, rivers and the winds. Scientific Reports, 2012; 2 DOI: 10.1038/srep00594

Cite This Page:

Duke University. "Bigger creatures live longer, travel farther for a reason." ScienceDaily. ScienceDaily, 24 August 2012. <www.sciencedaily.com/releases/2012/08/120824082532.htm>.
Duke University. (2012, August 24). Bigger creatures live longer, travel farther for a reason. ScienceDaily. Retrieved April 23, 2014 from www.sciencedaily.com/releases/2012/08/120824082532.htm
Duke University. "Bigger creatures live longer, travel farther for a reason." ScienceDaily. www.sciencedaily.com/releases/2012/08/120824082532.htm (accessed April 23, 2014).

Share This



More Plants & Animals News

Wednesday, April 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Monkeys Are Better At Math Than We Thought, Study Shows

Monkeys Are Better At Math Than We Thought, Study Shows

Newsy (Apr. 23, 2014) A Harvard University study suggests monkeys can use symbols to perform basic math calculations. Video provided by Newsy
Powered by NewsLook.com
Raw: Leopard Bites Man in India

Raw: Leopard Bites Man in India

AP (Apr. 22, 2014) A leopard caused panic in the city of Chandrapur on Monday when it sprung from the roof of a house and charged at rescue workers. (April 22) Video provided by AP
Powered by NewsLook.com
Iowa College Finds Beauty in Bulldogs

Iowa College Finds Beauty in Bulldogs

AP (Apr. 22, 2014) Drake University hosts 35th annual Beautiful Bulldog Contest. (April 21) Video provided by AP
Powered by NewsLook.com
805-Pound Shark Caught Off The Coast Of Florida

805-Pound Shark Caught Off The Coast Of Florida

Newsy (Apr. 22, 2014) One Florida fisherman caught a 805-pound shark off the coast of Florida earlier this month. 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:
from the past week

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