POTENTIALLY HABITABLE WORLDS ORBITING M DWARF STARS CAN EXPERIENCE EXTREME INTERNAL AND EXTERNAL HEATING THAT CAN REMOVE PRIMORDIAL WATER. M DWARFS MAY TAKE UP TO 2 GYR TO REACH THE MAIN SEQUENCE DURING WHICH TIME THE STAR IS MORE LUMINOUS AND HENCE PLANETS IN THE HABITABLE ZONE TODAY WERE INTERIOR TO IT EARLY ON. IN ADDITION TIDAL HEATING CAN BE LARGER THAN ON IO POSSIBLY SUSTAINING A LONG-LIVED MAGMA OCEAN AND INTENSE VOLCANIC ACTIVITY. LIKE THE STELLAR LUMINOSITY THIS TIDAL HEATING IS EXPECTED TO FADE IN MOST CASES AS ORBITS CIRCULARIZE AND ROTATIONS SYNCHRONIZE ELIMINATING THE SOURCES OF FRICTION THAT HEAT THE INTERIOR. THUS THE EARLY EVOLUTION OF THESE PLANETS IS LIKELY CHARACTERIZED BY A RUNAWAY GREENHOUSE ATMOSPHERE ATOP AN ACTIVE SOLID BODY THAT IS OUTGASSING INTERIOR VOLATILES. THE HIGH XUV FLUX FROM YOUNG M DWARFS CAN PHOTOLYZE WATER AND THE RELEASED HYDROGEN CAN ESCAPE TO SPACE. THE LOST WATER CAN BE REPLACED BY OUTGASSING BUT EVENTUALLY THE INTERNAL RESERVOIR IS DEPLETED. HENCE IT IS ESSENTIAL THAT ASTRONOMERS DETERMINE IF THESE PLANETS CAN RETAIN THEIR LIQUID WATER IN SPITE OF THESE PROCESSES.