Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Carnivores - Smart and social?

27.05.2009
Comprehensive analysis questions link between sociality and brain increase in carnivores

Packs of hunting dogs, troops of baboons, herds of antelope: when people observe social animals, they are often struck by how intelligent they seem, and recent studies suggest that sociality has played a key role in the evolution of larger brain size among several orders of mammals.

But new research from two evolutionary biologists, John Finarelli of the University of Michigan and John Flynn of the American Museum of Natural History, calls this hypothesis into question—at least for the Carnivora. After a sweeping analysis of many living and fossil carnivore species that places relative increases in brain size in an evolutionary context, Finarelli and Flynn found that increased brain size is not routinely associated with sociality. Their new research paper is being published in this week's Proceedings of the National Academy of Sciences.

"The universality of the Social Brain Hypothesis does not apply," says Finarelli. "When you look at relative brain size from the point of view of the entire evolutionary history of the clade, the story starts to fall apart—at least in carnivores. This study shows that, almost assuredly, brain size is increasing for different reasons in different groups of carnivores."

Flynn adds "When you analyze carnivores group by group, canids alone are responsible for the pattern seen in the recent analysis of the Social Brain Hypothesis." Flynn is referring to a 2007 paper in Evolution that tested the Social Brain Hypothesis, which proposed that sociality has driven the relative increase in brain size among mammals in three speciose orders: carnivores, primates, and ungulates. The evolution of relative brain size is of broad interest in biology, with important implications for ecology, energetics, and life history, and the previous study found correlations between sociality and relative increase in brain size to body size for all three groups.
As part of their broader study of how brain size evolved throughout the Carnivora, Finarelli and Flynn tested the idea in further detail by analyzing 289 terrestrial carnivores, about half of which were fossil species. The fact that so many fossils were included makes this the first study to reconstruct relative brain size across the full span of the evolutionary tree for this group of mammals. Extant carnivores span 15 families and include bears, weasels, cats, dogs, and related species. For all terrestrial carnivore groups, the authors compiled data on endocranial volume (brain size) and body mass, to estimate relative brain size or encephalization. Encephalization data was then used to map changes in relative brain size within specific clades (known as reconstructing a scaling allometry).

Their detailed analysis of the evolutionary history of carnivores documents at least six separate changes in brain sizes for the group, suggesting that the story of brain size increase is far more complex than previously assumed. Some lineages of carnivores have been remarkably stable in relative brain size (for example, one of the two major groups of living carnivores, the feliforms, except for small cats), while others like the extinct bear-dogs (Amphicyonidae) got progressively smaller brains though time when compared to their ancestors. Dogs, on the other hand, have undergone a relatively recent increase in brain size. Finarelli and Flynn determined that this clade skews the data for the modern carnivores that were analyzed in the previous test of the Social Brain Hypothesis; deleting them from the analysis removes any correlation between brain size and sociality in other carnivores. But even though modern canids have large brains, the reason for the relative increase remains unclear: was larger brain size co-opted for sociality, or did sociality drive the brain size increase? The answer might partly lie in previous research by Finarelli analyzing evolutionary changes among dogs. That 2008 study found that the increase in brain size began around 10 million years ago with the appearance of the first representatives of modern dogs.

The relationship between brain size and sociality is variable among living carnivores as well. If social living is the cause of brain size increase for the carnivore order, or evolution of large brains fosters sociality, then the large-brained bears, small cats, and weasels should be social—but they are not. Carnivores retaining the ancestral condition also do not fit within the picture that the Social Brain Hypothesis would paint; relatively small brained hyenas and mongooses both have social and nonsocial taxa.

"This is a sophisticated and powerful analysis that integrates fossils with extant species of carnivores," says Flynn. "If you only analyze living forms, you often don't correctly reconstruct the evolutionary transformations. Our research shows another example of this, and indicates that the Social Brain hypothesis does not hold for all Carnivora."

John Finarelli is an Assistant Professor in the Department of Geological Sciences at the University of Michigan, and John Flynn is the Frick Curator of Fossil Mammals and Dean of the Richard Gilder Graduate School at the American Museum of Natural History. The research was funded by the National Science Foundation, an AMNH Collections Study Grant, the Brown Family Foundation Graduate Fellowship, and the University of Michigan's Society of Fellows.

Kristin Elise Phillips | EurekAlert!
Further information:
http://www.amnh.org

More articles from Life Sciences:

nachricht Hunting pathogens at full force
22.03.2017 | Helmholtz-Zentrum für Infektionsforschung

nachricht A 155 carat diamond with 92 mm diameter
22.03.2017 | Universität Augsburg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Pulverizing electronic waste is green, clean -- and cold

22.03.2017 | Materials Sciences

Astronomers hazard a ride in a 'drifting carousel' to understand pulsating stars

22.03.2017 | Physics and Astronomy

New gel-like coating beefs up the performance of lithium-sulfur batteries

22.03.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>