Riker-Todd was a Middle Woodland Hopewell Mound located on a glaciated upland in Union Township, Butler County, Ohio. Radiocarbon dating and anthropogenic stratigraphy indicate that there were at least three different mound building episodes between ca. 5 B.C. to A.D. 631. Stylistically distinctive artifacts and mtDNA from Riker-Todd Mound fall within the range of other Middle Woodland Hopewell sites in North America and most closely resemble those from Mound 25 of the Hopewell Mound Group, including a large corner-notched, flaked-stone biface manufactured from Knife River flint. Although maize was part of the Hopewell diet, stable carbon obtained from human bone collagen failed to find an isotopic signature.

Conjoined twins are born when a single fertilized egg partially splits into two fetuses. A hypothetical case of infant conjoined twins from Angel Mounds, a Middle Mississippian site (A.D. 1050-1400) on the Ohio River near Evansville, Indiana, was discovered in 1941. Morphological analysis does not rule out the field interpretation of this double burial as twins. Ancient mitochondrial DNA recovered from both infants demonstrates that they were not maternal relatives, and hence that they cannot have been conjoined twins.