Animals with large brains are smarter, but they have fewer offspring and smaller intestines . This fact, which has been suspected for a long time, has just been experimentally confirmed in guppy fish ( Poecilia reticulata ) by an international team of researchers who publish their work in Science .
To do this, the scientists selected the fish with the largest and smallest brains over two generations, so that in the end they obtained two different lines of fish with differences of more than eight percent in brain size.
On the one hand, they evaluated the intelligence of each group by training them to look for food. "Fish with bigger brains did it," explains Alexander Kotrschal, from the University of Uppsala (Sweden). "When you experimentally manipulate the size of the brain , you get smarter fish," he adds.
However, having more brain is not free. The fish with the largest size of the same also had intestines of 4 milligrams on average compared to 5.5 milligrams of the fish with less brain. In addition, the latter had more offspring: in particular seven young in the first clutch, compared to six in fish with large brains.
