Apparently, people with half sized brain can be normal:
http://www.cpsimoes.net/index.php?o...in-anomaly&catid=35:noutras-linguas&Itemid=59
The brains of modern people are roughly 1371 cc (male), and 1216 cc (female).
"20. One report of normal intelligence exists in a brain smaller than Homo erectus. According to Burt Wilder (1911), Daniel Lyon was a nonretarded white watchman who worked for 20 years at the end of the nineteenth century in New York at the Pennsylvania Railway Terminal. He could read, write, and according to legal representatives of the company that employed him 'there was nothing defective or peculiar about him, either mentally or physically'. He was of average weight 65.8 kg though of below average high 1.55 m. After he died aged 46 in 1907 from bronchitis his brain was removed and subject to a professional autopsy with 'accurate scales'. This found it weighed just 680 grams (
624 cc assuming a specific gravity of 1.09 for fresh brain)."
Small brained people can be smart too:
"the brain of the Noble Prize winning novelist Anatole France (1844-1924) weighted 1017 grams (
933 cc) at post mortuum..."
And half of your brain can be removed, no problem:
"a male who started to become paralysed on the right side at five months, having seizures at three years and at five and half years of age had his
left hemisphere removed. In spite of this, he went to a normal school, learned to play the baritone horn and even became a member of his high school band. At 26, he was working as an 'industrial executive (traffic controller)' having completed 'his senior year at a prominent Midwestern university with a dual major in sociology and business adminstration'. His full IQ at that time was 116 (WAIS verbal IQ, 126; performance IQ, 102)."