Complex sentence: Both are defined as independent of Mesoamerica and in turn are apparently differentiated from one another by cultural traits, one said to be composed of hunter-gatherers and the other in possession of agricultural techniques.
Split into simpler sentences: Both are defined as independent of Mesoamerica and in turn are apparently differentiated from one another by cultural traits. One group is said to be composed of hunter-gatherers and the other to be in possession of agricultural techniques.