Haplogroup K appears in West Eurasia, North Africa, and South Asia and in populations with such an ancestry. Haplogroup K is found in approximately 10% of native Europeans. Overall mtDNA Haplogroup K is found in about 6% of the population of Europe and the Near East, but it is more common in certain of these populations. Approximately 16% of the Druze of Syria, Lebanon, Israel, and Jordan, belong to haplogroup K. It was also found in a significant group of Palestinian Arabs. K reaches a level of 17% in Kurdistan.
Approximately 32% of people with Ashkenazi Jewish ancestry are in haplogroup K. This high percentage points to a genetic bottleneck occurring some 100 generations ago. Ashkenazi mtDNA K clusters into three subclades seldom found in non-Jews: K1a1b1a, K1a9, and K2a2a. Thus it is possible to detect three individual female ancestors, who were thought to be from a Hebrew/Levantine mtDNA pool, whose descendants lived in Europe. recent study suggest these clades originate from Western Europe.
Haplogroup K was found in the remains of three individuals from the Pre-Pottery Neolithic B site of Tell Ramad, Syria, dating from c. 6000 BC. Haplogroup K has also been found in skeletons of early farmers in Central Europe of around 5500-5300 BC. It has long been known that some techniques of farming, together with associated plant and animal breeds, spread into Europe from the Near East. The evidence from ancient DNA suggests that the Neolithic culture spread by human migration.
Analysis of the mtDNA of Ötzi the Iceman, the frozen mummy from 3,300 BC found on the Austrian-Italian border, has shown that Ötzi belongs to the K1 subclade. It cannot be categorized into any of the three modern branches of that subclade (K1a, K1b or K1c). The new subclade has provisionally been named K1ö for Ötzi. Multiplex assay study was able to confirm that the Iceman's mtDNA belongs to a new European mtDNA clade with a very limited distribution amongst modern data sets.
A woman buried some time between 2650 and 2450 BC in a presumed Amorite tomb at Terqa (Tell Ashara), Middle Euphrates Valley, in Syria carried Haplogroup K.
This phylogenetic tree of haplogroup K subclades is based on the paper by Mannis van Oven and Manfred Kayser Updated comprehensive phylogenetic tree of global human mitochondrial DNA variation and subsequent published research.
A study involving Caucasian patients showed that individuals classified as haplogroup J or K demonstrated a significant decrease in risk of Parkinson's disease versus individuals carrying the most common haplogroup, H. 
On an 18 November 2005 broadcast of the Today Show, during an interview with Dr. Spencer Wells of The National Geographic Genographic Project, host Katie Couric was revealed to belong to haplogroup K. 
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^Fernández Domínguez, E., Polimorfismos de DNA mitochondrial en poblaciones antiguas de la cuenca mediterránea. (Doctoral thesis 2005).
^W. Haak, et al, "Ancient DNA from the First European Farmers in 7500-Year-Old Neolithic Sites", Science, vol. 310, no. 5750 (2005), pp. 1016-1018; B. Bramanti, "Ancient DNA: Genetic analysis of aDNA from sixteen skeletons of the Vedrovice," Anthropologie, vol. 46,l no. 2-3 (2008), pp. 153-160; B. Bramanti et al, "Genetic Discontinuity Between Local Hunter-Gatherers and Central Europe’s First Farmers," Science, (published online 3 Sep 2009).
^J. Tomczyk, et al., "Anthropological Analysis of the Osteological Material from an Ancient Tomb (Early Bronze Age) from the Middle Euphrates Valley, Terqa (Syria)," International Journal of Osteoarchaeology, published online ahead of print (2010).
^van der Walt, Joelle M.; Nicodemus, Kristin K.; Martin, Eden R.; Scott, William K.; Nance, Martha A.; Watts, Ray L.; Hubble, Jean P.; Haines, Jonathan L.; Koller, William C.; Lyons, Kelly; Pahwa, Rajesh; Stern, Matthew B.; Colcher, Amy; Hiner, Bradley C.; Jankovic, Joseph; Ondo, William G.; Allen Jr., Fred H.; Goetz, Christopher G.; Small, Gary W.; Mastaglia, Frank; Stajich, Jeffrey M.; McLaurin, Adam C.; Middleton, Lefkos T.; Scott, Burton L.; Schmechel, Donald E.; Pericak-Vance, Margaret A.; Vance, Jeffery M. (2003). "Mitochondrial Polymorphisms Significantly Reduce the Risk of Parkinson Disease". The American Journal of Human Genetics72 (4): 804–811. doi:10.1086/373937. ISSN0002-9297.