Complex sentence: The French specialists, led by their guru Gabriel de Mortillet, were particularly adamant in rejecting the hypothesis of Sautuola and Piera and their findings were loudly ridiculed at the 1880 Prehistorical Congress in Lisbon.
Split into simpler sentences: The French specialists, led by their guru Gabriel de Mortillet, were particularly adamant in rejecting the hypothesis of Sautuola and Piera. Their findings were loudly ridiculed at the 1880 Prehistorical Congress in Lisbon.