Anne,
Betty Crase did a literature review at the 1995 LLLI conference in Chicago
that addressed this issue. Apparently there is no trail of references to
discover where this figure came from. The only source we have is in the book
Breastfeeding: A guide for the medical Profession. A more thoroughly
documented statement comes from Katherine Dettwyler.
What a great opportunity you have to pass on little known and useful
information.
Jeanne Fisher
Austin, TX