John Cotton's life has primarily been chronicled by Cotton Mather in his Magnalia Christi Americana.
However, Cotton Mather was born ten years after John Cotton died and must have relied on the memory of his mother and uncles to write his account of the life of John Cotton.
During the Victorian era, several genealogists traced Cotton's ancestry back to 11th century England. Though their efforts were well intended; much of their work lacks the rigor of modern genealogy and has been called into question- in part because many records relating to Cotton's father, Roland, were burned in the Great London Fire of 1666.
As a result, Rev. John Cotton's life and ancestry have yet to be fully detailed.
With the aid of modern DNA research, however, Cotton's origins have been traced to the R1b paternal haplogroup that first arrived in Europe 35,000 to 40,000 years ago and a specific Celtic tibe called the Dumnonii that migrated into south western England around the 1st century BC. As a result, it is clear that John Cotton was of paternal Celt orgin.