Sizing Up the Brain
Mutations that produce small brains may reveal how human intelligence evolved
By John Travis
In the 1960s, Pakistan built a mammoth dam on the river Jhelum to generate electric power and store water for irrigation. Known as Mangla, the dam created an upstream lake that displaced about 20,000 families from the district of Mirpur. Around the same time, England’s textile industry was facing a major shortage of skilled laborers, especially in the county of Yorkshire. Many of the people from Mirpur who were displaced by Mangla traveled to Bradford and other Yorkshire districts.
The coincidental timing of the dam’s construction and Yorkshire’s need for workers has, nearly 4 decades later, provided scientists with insight into how the human brain develops and, possibly, into how it evolved from the smaller brains of our hominid ancestors. A few years ago, a physician from St. James’ University Hospital in Leeds, England, noticed something unusual among the Pakistani families he examined at a Bradford clinic. “I was seeing a lot of children who had microcephaly with moderate mental retardation but no other disease features,” recalls clinical geneticist C. Geoffrey Woods.