London: Whether we admit it or not, the human race seems to be heading for a dumber version of itself -- thanks to the shrinking size of our brains.
The human brain has been gradually getting smaller in size over the last 20,000 years, says a new report. It includes both the genders worldwide.
This decrease follows two million years of growth of the human cranium.
"Over the past 20,000 years, the average volume of the human male brain has decreased from 1,500 cubic centimetres to 1,350 cubic centimetres, losing a chunk the size of a tennis ball," according to a Daily Mail report quoting Kathleen McAuliffe in Discover magazine.
"The female brain has shrunk by about the same proportion."
McAuliffe reported the comments made by John Hawks, anthropologist from the University of Wisconsin, who argues that the fact the size of the human brain is decreasing doesn`t necessarily mean our intelligence is in decline as well.
Some paleontologists agree with this diagnosis that our brains may have become smaller in size, but increasingly efficient.
But others believe that man has indeed become steadily more stupid as he has evolved. Several theories have been advanced to explain the mystery of the shrinking brain.
According to a theory, the big heads were necessary to survive Upper Paleolithic life, which involved cold, outdoor activities. The second theory is that the skulls developed to cope with a chewy diet of rabbits, reindeer, foxes and horses.
As our food has become easier to eat, so our heads have stopped growing, according to the supporters of the theory.
A recent study conducted by David Geary and Drew Bailey, cognitive scientists at the University of Missouri explored how cranial size changed as humans adapted to an increasingly complex social environment between 1.9 million and 10,000 years ago.
They found that when the population density was low, such as during the majority of our evolution, the cranium increased in size. But when a certain area`s population changed from sparse to dense, our cranium size decreased.
They concluded that as increasingly complex societies emerged, the brain grew smaller because people didn`t have to be as smart to stay alive.