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Big-brained animals evolve faster
August 15, 2008Ever since Darwin, evolutionary biologists have wondered why some lineages have diversified more than others. A classical explanation is that a higher rate of diversification reflects increased ecological opportunities that led to a rapid adaptive radiation of a clade. A textbook example is Darwin finches from Galapagos, whose ancestor colonized a competitors-free archipelago and rapidly radiated in 13 species, each one adapted to use the food resources in a different way.
This and other examples have led some to think that the progenitors of the major evolutionary radiations are those that happened to be in the right place and at the right time to take advantage of ecological opportunities. However, is it possible that biological diversification not only depends on the properties of the environment an ancestral species finds itself in, but also on the features of the species itself? Now a study supports this possibility, suggesting that possessing a large brain might have facilitated the evolutionary diversification of some avian lineages.
Over 20 years ago, Jeff Wyles, Allan Wilson, and Joseph Kunkel proposed that big brains might favor adaptive evolutionary diversification in animals by facilitating the behavioral changes needed to use new resources or environments, a theory known as the behavioral drive hypothesis. When these authors formulated their hypothesis, evidence that the size of the brain limits the cognitive capacity of animals were scanty. Since then, however, a substantial body of evidence has confirmed that animals with larger brains, relative to their body size, have more developed skills for changing their behavior through learning and innovation, facilitating the invasion of novel environments and the use of novel resources. Despite the progress, the role of the brain in the adaptive diversification of animals has remained controversial, mostly due to the difficulties to demonstrate that big-brained animals evolve faster. Now, ecologist Daniel Sol of CREAF-Autonomous University of Barcelona and evolutionary biologist Trevor Price of the University of Chicago, provide evidence for such a role in birds in an article in the August issue of The American Naturalist. Analyzing body size measures of 7,209 species (representing 75% of all avian species), they found that avian families that have experienced the greatest diversification in body size tend to be those with brains larger than expected for their body size. These include the Picidae (woodpeckers), Bucerotidae (hornbills), Psittacidae (parrots), Strigidae (owls), Menuridae (lyrebirds) and Corvidae (crows). Brain size can promote morphological diversification because it facilitates range expansions and speciation, yet the analyses indicate that the brain-diversification association is statistically independent of geographic range and species richness. "The most likely alternative," Daniel Sol states, "is that big brains enhance the rate of evolutionary diversification by facilitating changes in behavior, which would place new selection pressures on populations and favor adaptive divergence." Thus, in species with high cognitive styles, behavior might be, along with environmental factors, a major driving force for evolution.
University of Chicago Press Journals
University of Chicago Press Journals
Diversification Current Events and Diversification News RSSConserving historic apple trees
The apple trees of yesteryear are slowly disappearing. Many apple varieties common in the United States a century ago can no longer be found in today's orchards and nurseries.
Geologist analyzes earliest shell-covered fossil animals
The fossil remains of some of the first animals with shells, ocean-dwelling creatures that measure a few centimeters in length and date to about 520 million years ago, provide a window on evolution at this time, according to scientists. Their research indicates that these animals were larger than previously thought.
Plant fossils give first real picture of earliest Neotropical rainforests
A team of researchers including a University of Florida paleontologist has used a rich cache of plant fossils discovered in Colombia to provide the first reliable evidence of how Neotropical rainforests looked 58 million years ago.
Water scarcity will create global security concerns
Water scarcity as a result of climate change will create far-reaching global security concerns, says Dr. Rajendra K. Pachauri, chair of the intergovernmental panel on climate change, a co-recipient of the 2007 Nobel Peace Prize.
Genome duplication responsible for more plant species than previously thought
Extra genomes appear, on average, to offer no benefit or disadvantage to plants, but still play a key role in the origin of new species, say scientists from Indiana University Bloomington and three other institutions in this week's Proceedings of the National Academy of Sciences.
Naming evolution's winners and losers
Mammals and many species of birds and fish are among evolution's "winners," while crocodiles, alligators and a reptile cousin of snakes known as the tuatara are among the losers, according to new research by UCLA scientists and colleagues.
A global model for the origin of species independent of geographical isolation
The tremendous diversity of life continues to puzzle scientists, long after the 200 years since Charles Darwin's birth.
Ferns took to the trees and thrived
As flowering plants like giant trees quickly rose to dominate plant communities during the Cretaceous period, the ferns that had preceded them hardly saw it as a disappointment.
Owning too much company stock puts workers' retirement at risk
Congress should ban employer stock from company-sponsored retirement plans to spare workers the risk of putting too much of their nest eggs in one basket, a new study by a University of Illinois legal expert says.
Domestication of Capsicum annuum chile pepper provides insights into crop origin and evolution
Without the process of domestication, humans would still be hunters and gatherers, and modern civilization would look very different.
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