THE AGE OF ALU SUBFAMILIES

Using Kimura's distance measure we have calculated the average age of all major Alu subfamilies based on the most recent available data. We conclude that AluJ sequences are some 26 Myr older than previously tho ught. Furthermore, the origin of the FLA (Free Left Arm) Alu family ca n be traced back to the very beginning of the mammalian radiation. One new minor subfamily is reported and discussed in the context of seque nce diversity in major Alu subfamilies.