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.
Juhan Sonin is donating his DNA to the hunt for medical breakthroughs. He explains why he decided to share his genome, and why you might want to do the same
The sperm of one nematode species harms the females of other species, perhaps explaining why the species remain distinct
Once-endangered gray seal population is rebounding; Cape Cod fishermen say there are now too many -- and they're taking all the fish
That strong, sturdy handshake your grandpa taught you isn't the cleanest way to greet someone, scientists say. So should doctors and nurses in hospitals start bumping fists?
The Natural Trap Cave in Wyoming may hold specimens of DNA from animals who roamed thousands of years ago. Julie Meachem, a paleontologist leading the expedition into the cave, speaks with Audie Cornish about the secrets she hopes to find.
Scientists are trying to raise prized bluefin tuna completely in captivity. An experiment at a Baltimore college is the first successful attempt in North America.
It’s five o’clock, and your dog is excitedly wagging her tail and nuzzling against you. Your furry friend is hungry and seems to know that this is the hour you usually feed her. But was this performance a simple reaction to a rumbling in Ginger’s tummy or are canines actually able to somehow read the clock?
Birds' eggs show adaptations in pigment concentration and thickness to allow the right amount of sun for embryos, scientists say.
Experiments with a large cannon have shown that fossilised algae could have travelled to the moon intact, providing an exciting window into Earth's past
A newly discovered variant of a protein that helps protect us against cancer may trigger cancer and promote its spread around the body