Leon R. Kass, the University of Chicago medical ethicist who four years ago today was named by President Bush to head the newly created President’s Council on Bioethics, will step down as chairman Oct. 1, the White House announced late Wednesday.Kass, who led the 18-member group of philosophers, scientists, theologians and legal scholars as it plumbed the turbulent debates over human cloning, embryonic stem cell research, the creation of animal-human hybrids and other topics raised by rapid advances in biotechnology, asked to be relieved of the chairmanship, council spokeswoman Diane Gianelli said.
