Haplogroup T is a humanmitochondrial DNA (mtDNA) haplogroup. Haplogroup T derives from the haplogroup JT, which also gave rise to Haplogroup J. Haplogroup T is believed to have originated in Mesopotamia approximately 10,000 years before present, and to have moved northwards. It is found with particularly high concentrations around the eastern Baltic Sea.
Studies, which have since been proven wrong, had shown mitochondrial haplogroup T to be associated with reduced sperm motility in males.[1] Such studies were not studies on fertility, and reduced fertility needn't be inferred from such results.