 In 1995, the timeless gene was cloned by Amita Sehgal and partners in the lab of Michael W. Young.Unlike the Drosophila "timeless" gene, homologs have been discovered in other species that are non-essential for circadian rhythm.The discovery of "timeless" followed the discovery of the "period" mutants in 1971 through forward genetic screening, the cloning of "per" in 1984, and an experiment determining that "per" is circadian in 1990.