Complex sentence: Fawcett chose only two companions, so they could travel lighter and so they would go more unnoticed with the tribes of the jungle; some being hostile towards explorers; many tribes at the time still had not come into contact with white men.
Split into simpler sentences: Fawcett chose only two companions, so they could travel lighter and so they would go more unnoticed with the tribes of the jungle; some being hostile towards explorers. And many tribes at the time still had not come into contact with white men.