According to published work, 10 out of 60 genes involved in recognizing the glycoprotein in question show evidence of rapid evolution (multiple mutations), dating back to around 1 to 1.2 million years ago. Even more interesting, the expression pattern of the replacement glycoprotein has changed—now it is expressed in the brain. Furthermore, the inactivation of the enzyme to make the original glycoprotein apparently happened after our lineage split from chimps, and before the most rapid enlargement of our brains. Is there a causal relationship? Who knows? More.