February 12, 2005
Darwin Day Celebration
Dr. Leah Krubitzer
How Evolution Built a Brain
The annual Darwin Day celebration, jointly sponsored by HAGSA, AOF, and several other Sacramento area organizations and university departments, was held on the 196th anniversary of Charles Darwin’s birthday. The venue was John Smith Hall at the La Sierra Community Center in Carmichael. In the opinion of this writer, the hall was the ideal size and layout for this function.
The keynote speaker was Dr. Leah Krubitzer, a Professor in the Department of Psychology at the University of California at Davis. She was preceded by Paul Geisert and Mynga Futrell, who made some preliminary remarks about the threat of “intelligent design” to a proper understanding of science. Dr. Krubitzer was introduced by Bronda Silva.
Dr. Krubitzer spoke on the evolution of the brain. She first gave us some of her personal background. She went to Roman Catholic schools, where the nuns treated evolution as the idea of the Devil. (Roman Catholic schools are today much more enlightened on that score.) She read “The Origin of Species” in college and it opened up new vistas for her. She earned a BS in Speech Pathology, with High Honors, at Pennsylvania State University, and a PhD in Psychology at Vanderbilt University. After receiving her doctorate she went to Australia to study the brains of primitive mammals. She later received a MacArthur Foundation grant (i.e., she became a MacArthur Fellow).
Dr. Krubitzer posed the question of how evolution built a complex brain, especially the neo-cortex. She took two approaches. For the first 15 years of her career she primarily took the comparative approach. She looked at homologous features in the brains of different species to deduce the likely brain structure of a common ancestor. She has more recently taken the developmental approach. She looked at the changes in the number of cortical fields and the effects of those changes. Complex, intelligent animals require a large, complex neo-cortex; less complex animals can get by with a lot less. She did extensive experiments with the brain of a South American marsupial. She surgically reduced the size of the cortical sheet and noticed that the thalamus also became smaller even though it had not been operated on. The cortical sheet can also be modified by making the lab animal blind or deaf. In those cases the brain itself can become more sensitive to those senses that were not impeded. This is analogous to blind humans compensating for their disability by becoming more sensitive to touch or sound. The brain has a lot of plasticity.
Report prepared by Wayne Luney, Recorder