Mitochondrial haplogroups are classifications of the maternal lineage based on specific mutation patterns in mitochondrial DNA. They trace a single line of inheritance — the mother’s mother’s mother’s line — and they can establish whether two individuals share a common matrilineal ancestor. They can also indicate, in a general sense, which broader population a person’s maternal line is associated with.
Haplogroup U5 is one of the oldest European mitochondrial haplogroups, associated with some of the earliest anatomically modern humans to enter Europe. Subgroup U5b1 is found today in a small percentage of modern Europeans, with somewhat higher frequencies in Scandinavia and the Baltic regions and lower frequencies elsewhere. It is not, however, common — and the fact that Adrian Targett in 1997 shared Cheddar Man’s U5b1 haplogroup indicates only that Targett and Cheddar Man fall within the same broad maternal lineage, not that Targett is a “direct descendant” in any genealogically meaningful sense.
The Natural History Museum’s FAQ is explicit on this point: Cheddar Man’s mitochondrial haplogroup “has no bearing on his skin pigmentation and says little about how the haplogroup is distributed among modern populations.” The U5b1 designation is useful for placing Cheddar Man in the context of European maternal lineages but is not in itself evidence about ancestry proportions or about the physical traits of any modern population.
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## The Vitamin D Question: Why Skin Lightened Later
Among the questions that the Cheddar Man findings helped sharpen — without definitively answering — is the question of why lighter skin evolved in European populations, and why it apparently did so relatively recently.