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High IQ reduces the ability to reproduce
Last reviewed: 01.07.2025
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Experiments by scientists at Uppsala University have led to the discovery that there is a direct link between intestinal length, brain size and mental development.
The size of the brain determines the intelligence of a living creature; scientists say that connections between neurons play a major role in mental development. The increase in brain size and the number of neural connections led to an increase in intelligence in primates compared to other animals. However, since the intestines and the function of reproduction previously consumed the most energy in the body, they were partially reduced in order to free up the body's resources for brain growth.
An experiment on the growth of intelligence in animals was conducted by researchers from Sweden. Over several generations of the life of guppy fish, scientists carried out selection based on brain size. Only guppies with the smallest and largest brains were taken for breeding. The two lines of fish bred differed in brain size by an average of 10 percent. The group of fish with a large brain quickly learned to "count" - to distinguish the number of drawn symbols that indicated feeding time. At the same time, guppies with a small brain never learned to distinguish the signs.
It is noteworthy that in the line of stupid guppies, on average, 1 more fish was born. After that, the scientists measured the size of the intestines of both lines of fish; in guppies with a small brain, the intestines weighed 5.5 mg, and in guppies with a large brain, 4 mg.
Thus, scientists can conclude that the smarter the individual, the more difficult it is for it to reproduce.
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