From the description at Ancestry.com:
"The Family Data Collection records were created while gathering genealogical data for use in the study of human genetics and disease. Compiling data for genetic research does not require the same type of documentation as traditional genealogical research. The genes themselves verify relationships and qualify or disqualify a person from a particular study. Citing the source of every genealogical fact in the electronic gene pool was deemed unnecessary and cost prohibitive by medical researchers. Millions of individual records were created from birth, marriage and death records; obituaries; probate records; books of remembrance; family histories; genealogies; family group sheets; pedigree charts; and other sources. The records collected that did not fit a specific study became the project's "by-products" and were schedule to be discarded. After viewing the quality of the source material used to create the gene pool and despite the absence of cited documentation, the electronic rights to the data were purchased, rather than see it destroyed."