Scientists have claimed that the human brain may have reached its full capacity and can't get cleverer.
A team at Cambridge University, led by Professor Simon Laughlin, says this is because the people are unable to provide the amount of extra energy and oxygen needed to become more intelligent.
The scientists have based their findings after analysing the structure of the brain and worked out how much energy its cells use up.
Professor Simon Laughlin was quoted by the British media as saying, "We have demonstrated that brains must consume energy to function and that these requirements are sufficiently demanding to limit our performance and determine design. Far-reaching powers of deduction demand a lot of energy because for the brain to search out new relationships it must constantly correlate information from different sources. Such energy demands mean there is a limit to the information we can process."
The scientists say that the wiring inside the brain would need vast amounts of extra energy to become more efficient. As it's impossible for humans to provide this, they can't become any smarter.
In their research, the team measured the efficiency with which different parts of the brain communicated with each other and found impulses travelled fastest in smarter people and slower in those who were less intelligent.
"High integration of brain networks seems to be associated with high IQ. You pay a price for intelligence. Becoming smarter means improving connections between different brain areas but this runs into tight limits on energy, along with space for the wiring," Ed Bullmore, team member, said.