|
First 'rule' of evolution suggests that life is destined to become more complex
March 18, 2008Scientists have revealed what may well be the first pervasive 'rule' of evolution.
In a study published in the Proceedings of the National Academy of Sciences researchers have found evidence which suggests that evolution drives animals to become increasingly more complex.
Looking back through the last 550 million years of the fossil catalogue to the present day, the team investigated the different evolutionary branches of the crustacean family tree.
They were seeking examples along the tree where animals evolved that were simpler than their ancestors.
Instead they found organisms with increasingly more complex structures and features, suggesting that there is some mechanism driving change in this direction.
"If you start with the simplest possible animal body, then there's only one direction to evolve in - you have to become more complex," said Dr Matthew Wills from the Department of Biology & Biochemistry at the University of Bath who worked with colleagues Sarah Adamowicz from from the University of Waterloo (Canada) and Andy Purvis from Imperial College London.
"Sooner or later, however, you reach a level of complexity where it's possible to go backwards and become simpler again.
"What's astonishing is that hardly any crustaceans have taken this backwards route.
"Instead, almost all branches have evolved in the same direction, becoming more complex in parallel.
"This is the nearest thing to a pervasive evolutionary rule that's been found.
"Of course, there are exceptions within the crustacean family tree, but most of these are parasites, or animals living in remote habitats such as isolated marine caves.
"For those free-living animals in the 'rat-race' of evolution, it seems that competition may be the driving force behind the trend.
"What's new about our results is that they show us how this increase in complexity has occurred.
"Strikingly, it looks far more like a disciplined march than a milling crowd."
Dr Adamowicz said: "Previous researchers noticed increasing morphological complexity in the fossil record, but this pattern can occur due to the chance origination of a few new types of animals.
"Our study uses information about the inter-relatedness of different animal groups - the 'Tree of Life' - to demonstrate that complexity has evolved numerous times independently."
Like all arthropods, crustaceans' bodies are built up of repeating segments. In the simplest crustaceans, the segments are quite similar - one after the other. In the most complex, such as shrimps and lobsters, almost every segment is different, bearing antennae, jaws, claws, walking legs, paddles and gills.
The American biologist Leigh Van Valen coined the phrase 'Red Queen' for the evolutionary arms race phenomenon. In Through the Looking-Glass Lewis Carroll's Red Queen advises Alice that: "It takes all the running you can do, to keep in the same place."
"Those crustacean groups going extinct tended to be less complex than the others around at the time," said Dr Wills.
"There's even a link between average complexity within a group and the number of species alive today.
"All organisms have a common ancestor, so that every living species is part of a giant family tree of life."
Dr Adamowicz added: "With a few exceptions, once branches of the tree have separated they continue to evolve independently.
"Looking at many independent branches is similar to viewing multiple repeated runs of the tape of evolution.
"Our results apply to a group of animals with bodies made of repeated units. We must not forget that bacteria - very simple organisms - are among the most successful living things. Therefore, the trend towards complexity is compelling but does not describe the history of all life."
This work was supported by a Beit Scientific Research Fellowship, a Natural Sciences & Engineering Research Council of Canada Scholarship, an Overseas Research Scholarship and a Biotechnology & Biological Sciences Research Council grant.
The University of Bath
They were seeking examples along the tree where animals evolved that were simpler than their ancestors.
Instead they found organisms with increasingly more complex structures and features, suggesting that there is some mechanism driving change in this direction.
"If you start with the simplest possible animal body, then there's only one direction to evolve in - you have to become more complex," said Dr Matthew Wills from the Department of Biology & Biochemistry at the University of Bath who worked with colleagues Sarah Adamowicz from from the University of Waterloo (Canada) and Andy Purvis from Imperial College London.
"Sooner or later, however, you reach a level of complexity where it's possible to go backwards and become simpler again.
"What's astonishing is that hardly any crustaceans have taken this backwards route.
"Instead, almost all branches have evolved in the same direction, becoming more complex in parallel.
"This is the nearest thing to a pervasive evolutionary rule that's been found.
"Of course, there are exceptions within the crustacean family tree, but most of these are parasites, or animals living in remote habitats such as isolated marine caves.
"For those free-living animals in the 'rat-race' of evolution, it seems that competition may be the driving force behind the trend.
"What's new about our results is that they show us how this increase in complexity has occurred.
"Strikingly, it looks far more like a disciplined march than a milling crowd."
Dr Adamowicz said: "Previous researchers noticed increasing morphological complexity in the fossil record, but this pattern can occur due to the chance origination of a few new types of animals.
"Our study uses information about the inter-relatedness of different animal groups - the 'Tree of Life' - to demonstrate that complexity has evolved numerous times independently."
Like all arthropods, crustaceans' bodies are built up of repeating segments. In the simplest crustaceans, the segments are quite similar - one after the other. In the most complex, such as shrimps and lobsters, almost every segment is different, bearing antennae, jaws, claws, walking legs, paddles and gills.
The American biologist Leigh Van Valen coined the phrase 'Red Queen' for the evolutionary arms race phenomenon. In Through the Looking-Glass Lewis Carroll's Red Queen advises Alice that: "It takes all the running you can do, to keep in the same place."
"Those crustacean groups going extinct tended to be less complex than the others around at the time," said Dr Wills.
"There's even a link between average complexity within a group and the number of species alive today.
"All organisms have a common ancestor, so that every living species is part of a giant family tree of life."
Dr Adamowicz added: "With a few exceptions, once branches of the tree have separated they continue to evolve independently.
"Looking at many independent branches is similar to viewing multiple repeated runs of the tape of evolution.
"Our results apply to a group of animals with bodies made of repeated units. We must not forget that bacteria - very simple organisms - are among the most successful living things. Therefore, the trend towards complexity is compelling but does not describe the history of all life."
This work was supported by a Beit Scientific Research Fellowship, a Natural Sciences & Engineering Research Council of Canada Scholarship, an Overseas Research Scholarship and a Biotechnology & Biological Sciences Research Council grant.
The University of Bath
Evolution News and Current Evolution Events RSSCrossed (Evolutionary) Signals?
What do humans and single-celled choanoflagellates have in common? More than you'd think. New research into the choanoflagellate genome shows these ancient organisms have similar levels of proteins that cells in more complex organisms, including humans, use to communicate with each other.
New oral angiogenesis inhibitor offers potential nontoxic therapy for a wide range of cancers
The first oral, broad-spectrum angiogenesis inhibitor, specially formulated through nanotechnology, shows promising anticancer results in mice, report researchers from Children's Hospital Boston.
Plants in the fourth dimension
As anyone who has suffered from jetlag knows, we have internal clocks that tell us when to sleep and wake, and we can be miserable when these are disrupted.
Special topics in environmental mechanics
With rapid development of economics since the 1980s, people have been increasingly realized that the environment plays an important role in the sustainable development of society and economy.
Early origins of maize in Mexico
The ancestors of maize originally grew wild in Mexico and were radically different from the plant that is now one of the most important crops in the world.
Drought tolerance in potatoes
Climate change is expected to exacerbate drought events throughout the world, resulting in large-scale ecosystem alteration and failure of drought-sensitive crops.
Mechanism and function of humor identified by new evolutionary theory
A new publication answers centuries' old questions regarding the mechanism and function of humour, identifying the reason humour is common to all human societies, its fundamental role in the evolution of homo sapiens and its continuing importance in the cognitive development of infants.
SEX4, starch and phosphorylation
Energy from the sun and carbon dioxide fuel photosynthesis in plants and algae, making life on earth possible. Carbon that is fixed by plants is converted to starch and sucrose, which are utilized by plants for energy and to build biomass.
Ancient Mexican maize varieties
Maize was first domesticated in the highlands of Mexico about 10,000 years ago and is now one of the most important crop plants in the world.
Weizmann Institute scientists discover how an injured embryo can regenerate itself
More than 80 years have passed since the German scientist Hans Spemann conducted his famous experiment that laid the foundations for the field of embryonic development.
More Evolution News Articles
 | The Power of Now: A Guide to Spiritual Enlightenment by Eckhart Tolle |
 | The God Delusion by Richard Dawkins |
 | Eat Right 4 Your Type: The Individualized Diet Solution to Staying Healthy, Living Longer & Achieving Your Ideal Weight by Peter J. D'Adamo |
 | Guns, Germs, and Steel: The Fates of Human Societies by Jared Diamond |
 | Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body by Neil Shubin |
 | Biology by Neil A. Campbell, Jane B. Reece |
 | The Selfish Gene: 30th Anniversary Edition--with a new Introduction by the Author by Richard Dawkins |
 | God Is Not Great: How Religion Poisons Everything by Christopher Hitchens |
 | Only a Theory: Evolution and the Battle for America's Soul by Kenneth R. Miller |
 | The Portable Atheist: Essential Readings for the Nonbeliever by Christopher Hitchens |
| © 2008 BrightSurf.com |