Bigger brains can make animals, well, brainier, but that boost in brain size and ability comes at a price. That's according to new evidence reported on January 3rd in Current Biology, a Cell Press publication, in which researchers artificially selected guppies for large and small brain sizes.
The findings lend support to the notion that bigger brains and increased cognitive ability do go together, a topic that has been a matter of considerable debate in recent years, said Niclas Kolm of Uppsala University in Sweden. They also represent some of the first convincing evidence that large brains are expensive, evolutionarily speaking.
"We provide the first experimental evidence that evolving a larger brain really is costly in terms of both gut investment and, more importantly, reproductive output," Kolm said.
Together, the findings strongly support the idea that relative brain sizes among species are shaped through a balance between selection for increased cognitive ability and the costs of a big brain.
The results in guppies have important implications for us humans. After all, one of the most distinctive features of the human brain is its large size relative to the rest of the body.
"The human brain only makes up 2 percent of our total body mass but stands for 20 percent of our total energy demand," Kolm said. "It is a remarkably costly organ energetically."
But support for the so-called "expensive-tissue hypothesis"—that there is a trade-off between the brain and the energy demands of other organs and reproduction—came only from comparative studies among species and were correlative in nature.
In the new study, Kolm's team took a different, within-species approach. They selected live-bearing guppies for large and small brains relative to the size of their bodies. Under that strong selection pressure, they found that brain size could evolve "remarkably quickly."
After selection, large-brained guppies outscored their smaller-brained peers in a test of numerical learning. With more energy devoted to brain-building, brainy fish—males especially—did have smaller guts. They also left fewer offspring to the next generation.
Those effects were observed despite the fact that the fish were supplied with an abundance of food. The researchers say they are curious to see what will happen in future experiments with fish in a more competitive, semi-natural environment including limited resources and predators.
The findings lead Kolm and his colleagues to suggest that the relatively small family sizes of humans and other primates, not to mention dolphins and whales, might have helped to make our big brains possible.
Cell Press: http://www.cellpress.com
This press release was posted to serve as a topic for discussion. Please comment below. We try our best to only post press releases that are associated with peer reviewed scientific literature. Critical discussions of the research are appreciated. If you need help finding a link to the original article, please contact us on twitter or via e-mail.
The largest specimen among Earth's first flying vertebrates boasted a 10-metre wingspan, dwarfing modern-day giants Continue reading...
How can creatures as different in body and mind as present-day humans and their extinct Neanderthal cousins be 99.84 percent identical genetically?
A mile deep expedition using robots has discovered three ships that sank off the coast of Galveston centuries ago. Archeologists are still unsure of why the vessels sunk.
Scientists based their technique on the one used to create the sheep Dolly years ago. These cells might one day be useful in treating all sorts of diseases.
It turns out the first chili peppers were grown by humans in eastern Mexico. And it's not the same region where beans and corn were first grown, according to new ways of evaluating evidence.
A team of international scientists have found four species of insects with reversed sex organs. The females' anatomy may have to do with their need for nutrients that only males produce.
For all but the shyest of wallflowers, moving to music is a natural human response. But what is it about a catchy tune that makes us groove? Scientists think they've figured out at least part of the recipe: just the right mix of regular rhythms and unexpected beats.
Artists' brains are structurally different to non-artists in areas relating to fine motor movements and visual imagery, a study finds.
Information about who suspects call and when is helping police work out who is linked to which crimes and even their place in the criminal hierarchy
The lead scientist behind a revolutionary method to turn adult cells into stem cells has been found guilty of misconduct, but insists the mistakes were unintentional