Are we getting more stupid? According to Genld Crabtree, a scientist at Standord University in the US, we are. 

You may not want to hear this, but Crabtree believes that human intelligence reached its peak more than 2000 years ago and ever since then has been going downhill. "If an average Greek from 1,000 BC were transported to modern times, he or she would be one of the brightest among us," Crabtree told The Guardian.

At the heart of Crabree's thinking is a simple idea. In the past, intelligence is critical for survival when our ancestors had to avoid dangerous animals and hunt for food. The difference of being smart or stupid is often life or death. However, after the spread of agriculture, when our ancestors began to live in dense farming communities. The need to keep their intelligence in peak. -condition gradually reduced. 

This is not hard to understand. Most of the time, pressure is what keeps us going-you need the pressure from your teachers to finish your homework; the pressure of looking pretty encourages you to lose weight when summer comes. And the same is also true of our intelligence -if we think less, we become less smart

These mutaions (变异) are harmful to our intelligence and they were all developed in the past 3. 000 yean. The other evidence that Crabtree holds is in our genes. He found that among the 20000 to 50000 genes that we have that determine human intelligence, there are two or more mutations in each of us. 

However, Crabtree's theory has been criticized by some who say that early humans may have better hunting and surviving abilities but people today have developed a more diverse intelligence. For example, paring (用矛刺)a tiger doesn't necessarily require more brainpower than playing chess or writing a poem. Moreover, the power

of modern education means a lot more people have the opportunity to learn nowadays. 

"You wouldn't get Stephen Hawking 2, 00 years ago. He just wouldn't exit. " Thomas Hills of the University of Warwick. UK, told Live Science "But now we have people of his intellectual capability doing things and making

Insights(洞察力) that we would never have achieved in our environment of evolutionary adaptation. (进化适应)"