Featured Research

from universities, journals, and other organizations

Complexity not so costly after all: Moderately complex plants and animals can be better equipped to adapt

Date:
September 28, 2010
Source:
University of Michigan
Summary:
The more complex a plant or animal, the more difficulty it should have adapting to changes in the environment. But if that tenet is true, how do you explain all the well-adapted, complex organisms in the world? This "cost of complexity" conundrum puzzles biologists and offers ammunition to proponents of intelligent design. A new analysis reveals flaws in the models from which the cost of complexity idea arose and shows that complexity can, indeed, develop through evolutionary processes.

Hummingbird and an orchid.
Credit: iStockphoto

The more complex a plant or animal, the more difficulty it should have adapting to changes in the environment. That's been a maxim of evolutionary theory since biologist Ronald Fisher put forth the idea in 1930.

Related Articles


But if that tenet is true, how do you explain all the well-adapted, complex organisms -- from orchids to bower birds to humans -- in this world?

This "cost of complexity" conundrum puzzles biologists and offers ammunition to proponents of intelligent design, who hold that such intricacy could arise only through the efforts of a divine designer, not through natural selection.

A new analysis by Jianzhi "George" Zhang and coworkers at the University of Michigan and Taiwan's National Health Research Institutes reveals flaws in the models from which the cost of complexity idea arose and shows that complexity can, indeed, develop through evolutionary processes. In fact, a moderate amount of complexity best equips organisms to adapt to environmental change, the research suggests. The findings will be published online in the Proceedings of the National Academy of Sciences.

The study focused on a genetic phenomenon called pleiotropy, in which a single gene affects more than one trait. Examples of pleiotropy are well known in certain human diseases, and the effect also has been documented in experimental animals such as fruit flies. Biologists also recognize its importance in development, aging and many evolutionary processes. However, pleiotropy is difficult to measure, and its general patterns are poorly understood, said Zhang, a professor of ecology and evolutionary biology.

Even so, scientists have developed mathematical models of the phenomenon, based on certain assumptions, and have made predictions from the results of the models. Zhang and coworkers decided to test the assumptions against real-life observations by analyzing several large databases that catalog the effects of specific genetic mutations on traits in model organisms (yeast, roundworms and mice). Each data set included hundreds to thousands of genes and tens to hundreds of traits.

For simplicity, mathematical models of pleiotropy have assumed that all genes in an organism affect all of its traits to some extent. But Zhang's group found that most genes affect only a small number of traits, while relatively few genes affect large numbers of traits.

What's more, they found a "modular" pattern of organization, with genes and traits grouped into sets. Genes in a particular set affect a particular group of traits, but not traits in other groups.

In addition, the researchers learned that the more traits a gene affects, the stronger its effect on each trait.

All of these findings challenge the assumptions underlying the classic mathematical models that suggest complexity is prohibitively costly.

When Fisher first wrote about the cost of complexity, he argued that random mutations -- which, along with natural selection, drive evolution -- are more likely to benefit simple organisms than complex organisms.

"Think of a hammer and a microscope," Zhang said. "One is complex, one is simple. If you change the length of an arbitrary component of the system by an inch, for example, you're more likely to break the microscope than the hammer."

In a paper published in 2000, evolutionary geneticist H. Allen Orr of Rochester came up with additional reasons for the cost of complexity. According to his model, even if a mutation benefits a complex organism, it's unlikely to spread throughout the whole population and become "fixed." And even if it does that, the advantage of the mutation is likely to be small.

By incorporating a more realistic representation of pleiotropy, Zhang's analysis found the reverse of Orr's arguments to be true. Although Fisher's observation still holds, reversing Orr's assertions minimizes its impact, thus reducing the cost of complexity.

Further, the analysis showed that the ability of organisms to adapt is highest at intermediate levels of complexity. "This means a simple organism is not best, and a very complex organism is not best; some intermediate level of complexity is best in terms of the adaptation rate," Zhang said.

The new findings help buffer evolutionary biology against the criticisms of intelligent design proponents, Zhang said. "The evolution of complexity is one thing that they often target. Admittedly, there were some theoretical difficulties in explaining the evolution of complexity because of the notion of the cost of complexity, but with our findings these difficulties are now removed."

Zhang's coauthors on the paper are former U-M graduate student Zhi Wang, now at Sage Bionetworks in Seattle, Wash., and Ben-Yang Liao of the National Health Research Institutes in Taiwan.

Funding was provided by the U.S. National Institutes of Health and the Taiwan National Health Research Institutes.


Story Source:

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


Journal Reference:

  1. Zhi Wang, Ben-Yang Liao, and Jianzhi Zhang. Genomic patterns of pleiotropy and the evolution of complexity. Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.1004666107

Cite This Page:

University of Michigan. "Complexity not so costly after all: Moderately complex plants and animals can be better equipped to adapt." ScienceDaily. ScienceDaily, 28 September 2010. <www.sciencedaily.com/releases/2010/09/100927155320.htm>.
University of Michigan. (2010, September 28). Complexity not so costly after all: Moderately complex plants and animals can be better equipped to adapt. ScienceDaily. Retrieved December 18, 2014 from www.sciencedaily.com/releases/2010/09/100927155320.htm
University of Michigan. "Complexity not so costly after all: Moderately complex plants and animals can be better equipped to adapt." ScienceDaily. www.sciencedaily.com/releases/2010/09/100927155320.htm (accessed December 18, 2014).

Share This


More From ScienceDaily



More Fossils & Ruins News

Thursday, December 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Researchers Bring Player Pianos Back to Life

Researchers Bring Player Pianos Back to Life

AP (Dec. 17, 2014) Stanford University wants to unlock the secrets of the player piano. Researchers are restoring and studying self-playing pianos and the music rolls that recorded major composers performing their own work. (Dec. 17) Video provided by AP
Powered by NewsLook.com
Domestication Might've Been Bad For Horses

Domestication Might've Been Bad For Horses

Newsy (Dec. 16, 2014) A group of scientists looked at the genetics behind the domestication of the horse and showed how human manipulation changed horses' DNA. Video provided by Newsy
Powered by NewsLook.com
Mozart, Beethoven, Shubert and Bizet Manuscripts to Go on Sale

Mozart, Beethoven, Shubert and Bizet Manuscripts to Go on Sale

AFP (Dec. 16, 2014) A collection of rare manuscripts by composers Mozart, Beethoven, Shubert and Bizet are due to go on sale at auction on December 17. Duration: 00:57 Video provided by AFP
Powered by NewsLook.com
Old Ship Records to Shed Light on Arctic Ice Loss

Old Ship Records to Shed Light on Arctic Ice Loss

Reuters - Innovations Video Online (Dec. 15, 2014) Researchers are looking to the past to gain a clearer picture of what the future holds for ice in the Arctic. A project to analyse and digitize ship logs dating back to the 1850's aims to lengthen the timeline of recorded ice data. Ben Gruber reports. Video provided by Reuters
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:

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