>>I presume that the
cosleeping that has happened for years around the world have included both
parents.

Not necessarily.  Often the mother sleeps with the youngest, and the father
with the older children.  Also in polygynous societies the husband takes
turns sleeping with alternate wives and their children on different nights,
so dad would only be in the room every second or third night.  Other
children would be sleeping with the mom, too though, so you might have a
baby, a 4 year old, an 8 year old, a 12 year old, etc.

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Katherine A. Dettwyler, Ph.D.                         email: [log in to unmask]
Anthropology Department                               phone: (409) 845-5256
Texas A&M University                                    fax: (409) 845-4070
College Station, TX  77843-4352
http://www.prairienet.org/laleche/dettwyler.html