Complex sentence: In opposition to what the authors see as the'standard narrative' they contend having multiple sexual parters was common in the mobile self contained groups of hunter gatherers they posit as the human norm before agriculture led to high population density.
Split into simpler sentences: In opposition to what the authors see as the'standard narrative', they contend having multiple sexual partners was common. Mobile self contained groups of hunter gatherers are posited as the human norm before agriculture led to high population density.