Complex sentence: Plough agriculture, in contrast, is associated with private property; marriage tends to be monogamous, to keep the property within the nuclear family; and close family are the preferred marriage partners so as to keep property within the extended family.
Split into simpler sentences: Plough agriculture, in contrast, is associated with private property; marriage tends to be monogamous, to keep the property within the nuclear family. Close family are the preferred marriage partners so as to keep property within the extended family.