Complex sentence: Throughout the Paleolithic era the primary economic unit was the band (small kin group), and communication between bands occurred for the purposes of trading tools, foods, skins and other commodities, for warfare and for the trading (or kidnapping) of mates.
Split into simpler sentences: Throughout the Paleolithic era the primary economic unit was the band (small kin group). It is likely that communication between bands occurred for the purposes of trading tools, foods, skins and other commodities, for warfare and for the trading (or kidnapping) of mates.