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Comparisons of different animals have shown that larger brains provide greater intelligence, but they also guzzle more energy and have other consequences. Now scientists have observed the effects of varying brain size within a single species: guppies. The work is in Current Biology. [Alexander Kotrschal et al., Artificial Selection on Relative Brain Size in the Guppy Reveals Costs and Benefits of Evolving a Larger Brain]
Swedish researchers bred two different lines of guppies, selecting one for larger brains and one for smaller. The fish quickly modified until brains were nine percent larger in the big-brained line than in the other.
Not surprisingly, when 48 guppies were given learning tests, large-brained female fish outperformed small-brained females. However, males from both lines scored about the same, possibly because the female guppies' visual system was more suited to the type of intelligence test used.
But big brains also had a downside—the brainier fish had smaller guts, by 20 percent for males and 8 percent for females. Plus, the large-brained guppies produced 19 percent fewer offspring. In order to provide energy to their bigger brains, the egghead fish made sacrifices that may be evolutionary disadvantages. It may indeed be possible to be too smart for your own good.
—Sophie Bushwick
[The above text is a transcript of this podcast.]
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8 Comments
Add CommentSo, it isn't surprising that large brained females scored higher, shouldn't be surprising that large brained males didn't? If it had to do with the type if "IQ" test, perhaps this invalidates all of this research. Does this have anything to do with evolution, does 19% fewer offspring actually mean 19% fewer reaching adult size? Seems that 80% of a brood with intelligence 20% greater than stupid guppies is advantageous evolution wise. Does a smaller gut mean fewer calories? More efficient use of food? Or is there something in this study showing a bad effect from a smaller gut? Guppies don't need bigger brains, they sit in a bowl and get plenty of food, so "forcing" a big brain line doesn't tell us much except someone can make a "smartie pants" fish.
Reply | Report Abuse | Link to thisThis article would be more appropriate if published on April 1. Is there are no more interesting science being conducted?
Reply | Report Abuse | Link to thisTo enlarge the brain: you must sacrifice some organ because our body only produce a limited energy output. Usually we sacrifice our guts because it is the only one who consume the most energy.
Reply | Report Abuse | Link to thisInteresting.
Reply | Report Abuse | Link to thisNow what happens if they keep selecting for intelligence & slightly restrict feed. I'd expect intelligence to slowly increase & brain size slightly decrease as conditions favor efficient brains over big brains.
Indeed. But would this not depend on the richness of the environment? A static environment with little diversity and few stressors, would surely lead to reversion to the wild-type, favouring only routine behaviour and little evolutionary drive to develop intelligence rather than simple food-aquisition.
Reply | Report Abuse | Link to thisWell I have a large brain and a large gut.
Reply | Report Abuse | Link to thisPerhaps guppies are not the best test subjects.
I have not been able to download the podcast since December 20, via iTunes. I tried to go to iTunes and maybe resubscribe but iTunes tells me that this podcast is no longer available in the U.S. iTunes store.
Reply | Report Abuse | Link to thisBigger ain't always better it seems; remember the Neanderthals who could boast about brains bigger-than-ours'!
Reply | Report Abuse | Link to thisPerhaps it was the sheer oversize of their babies' skulls that made for highly risky deliveries, considering the given narrowness of the female birth canal...