Complex sentence: The results showed weak ancient human-Neanderthal hybridization, strong ancient human-modern human hybridization, and the human-chimpanzee & neanderthal-chimpanzee hybridization are of similarly weak strength.
Split into simpler sentences: The results showed weak ancient human-Neanderthal hybridization and strong ancient human-modern human hybridization. The human-chimpanzee and neanderthal-chimpanzee hybridization are of similarly weak strength.