molecular insights into human brain evolution分子洞察人类大脑进化.pdfVIP

Open access, freely available online Feature Molecular Insights into Human Brain Evolution Jane Bradbury s a species, we pride ourselves on the uniqueness of our brain. Relative to our body size, the human brain Ais bigger than that of any other animal. It may also contain unique structures and patterns of organisation that presumably underlie our intelligence and ability to manipulate our environment. But how did our unique brain originate, and under what selective pressures did it evolve? Some of the answers may lie in the genetic differences that researchers are now uncovering between us and our closest relatives. What Is So Different about the Human Brain? When we compare our brain to those of other animals, the fi rst thing that strikes us is its size. Human brains weigh on average 1,300 grams; a squirrel brain weighs six grams. Some of this difference is because, as larger animals, we need more brain to run our bodies. However, the brains of our nearest relatives, the great apes, weigh only 300–500 grams, even though their body size is similar to ours (Figure 1). “Humans sit on the top of the pile when it comes to relative brain size”, notes geneticist Bruce Lahn (University of Chicago, Illinois, United States) (see Box 1). Throughout mammalian and primate evolution, there has been a gradual increase in brain size, superimposed with “spikes” of fast growth such as the tripling in human brain size that occurred about 1.5 million years ago, 4 million years after the human lineage diverged from that of the great apes. “Even in the ape lineage, the brain has been expanding but along the human lineage it has really taken off”, says Lahn. In addition, over time, different parts of our brain have increased in size at different rates. The cerebral cortex has DOI: 10.1371/journal.pbio.0030050.g001 expanded more than other areas, an