Weighing in at about three pounds, the human brain is the largest and most complex of any living primate. But just as most human genes are nearly identical among mammals, so too does the human brain bear major similarities in structure and function to the brains of those species most closely related to us on the tree of life. However, even nervous systems from the simplest organisms offer clues about the function of the human brain. Researchers are also working to identify the key brain differences that endow humans with unique cognitive abilities, like speaking and abstraction.
Neuroscientists study a variety of animal models, from zebrafish to songbirds. The simplicity of the nervous system in the roundworm Caenorhabditis elegans allowed scientists to trace all its neural connections. This insight could one day offer clues about connections in the human brain. Researchers also study chemicals in the animal world in hopes of finding new drug targets in the human.