In 1998, researchers identified a mouse homolog and a human homolog of the "Drosophila" "timeless" gene. The exact role of TIM in mammals is still unclear. Recent work on the mammalian "timeless" ("mTim") in mice has suggested that the gene may not play the same essential role in mammals as in "Drosophila" as an necessary function of the circadian clock. While "Tim" is expressed in the Suprachiasmatic Nucleus (SCN) which is thought to be the primary oscillator in humans, its transcription does not oscillate rhythmically in constant conditions, and the TIM protein remains in the nucleus.