Complex sentence: Ernest Stanley "Stan" O'Neal is an American businessman and a former Chief Executive Officer and Chairman of the Board of Merrill Lynch & Co. Inc., having served in numerous senior management positions at the company prior to this appointment.
Split into simpler sentences: Ernest Stanley "Stan" O'Neal is an American businessman. He currently serves on the board of Alcoa Inc. and is a former Chief Executive Officer and Chairman of the Board of Merrill Lynch & Co. Inc., having served in numerous senior management positions at the company prior to this appointment.