The human brain has been shrinking since the last 20,000 years, suggesting that we may be getting dumber day by day, a new study said.
"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," the Daily Mail quoted Kathleen McAuliffe as writing in the Discover magazine.
"The female brain has shrunk by about the same proportion," she added.
Dr John Hawks, an anthropologist from the University of Wisconsin, argued that this shrinking doesn't necessarily mean our intelligence is in decline as well.
In fact, many scientists believe that it may be making us more intelligent.
There are many theories to this decreasing brain size - the first one says that big heads were necessary to survive Upper Paleolithic life, which involved cold, outdoor activities. Another is that skulls developed to cope with a chewy diet of rabbits, reindeer, foxes and horses.
Other experts believe that a gradually decreasing infant mortality rate has led to a proportionate decrease in the size of our brains.
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 1.9million and 10,000 years ago.
Geary warned against stereotyping our ancestors as being more intelligent than us.
"'Practically speaking, our ancestors were not our intellectual or creative equals because they lacked the same kind of cultural support," he said.
"The rise of agriculture and modern cities based on economic specialisation has allowed the very brightest people to focus their efforts on the sciences, the arts and other fields. Their ancient counterparts didn't have that infrastructure to support them. It took all their efforts just to get through life," Geary said.
Hawks, on the other hand, believes that the decrease in the size of our brains may actually show we are getting more intelligent. The brain, he says, uses up to 20 per cent of all the fuel we consume.