The period discussed in the passage is referred to as an "explosion" because itSPECULATION

The period discussed in the passage is referred to as an "explosion" because it

SPECULATION ON THE ORIGIN OF THESE PACIFIC ISLANDERS BEGAN AS SOON AS OUTSIDERS ENCOUNTERED THEM; IN THE ABSENCE OF SOLID LINGUISTIC, ARCHAEOLOGICAL, AND BIOLOGICAL DATA, MANY FANCIFUL AND MUTUALLY EXCLUSIVE THEORIES WERE DEVISED. PACIFIC ISLANDERS WERE VARIOUSLY THOUGHT TO HAVE COME FROM NORTH AMERICA, SOUTH AMERICA, EGYPT, ISRAEL, AND INDIA, AS WELL AS SOUTHEAST ASIA.MANY OLDER THEORIES IMPLICITLY DEPRECATED THE NAVIGATIONAL ABILITIES AND OVERALL CULTURAL CREATIVITY OF THE PACIFIC ISLANDERS.FOR EXAMPLE, BRITISH ANTHROPOLOGISTS G. ELLIOT SMITH AND W. J. PERRY ASSUMED THAT ONLY EGYPTIANS WOULD HAVE BEEN SKILLED ENOUGH TO NAVIGATE AND COLONIZE THE PACIFIC.THEY INFERRED THAT THE EGYPTIANS EVEN CROSSED THE PACIFIC TO FOUND THE GREAT CIVILIZATIONS OF THE NEW WORLD(NORTH AND SOUTH AMERICA).IN 1947 NORWEGIAN ADVENTURER THOR HEYERDAHL DRIFTED ON A BALSA-LOG RAFT WESTWARD WITH THE WINDS AND CURRENTS ACROSS THE PACIFIC FROM SOUTH AMERICA TO PROVE HIS THEORY THAT PACIFIC ISLANDERS WERE NATIVE AMERICANS(ALSO CALLED AMERICAN INDIANS). LATER HEYERDAHL SUGGESTED THAT THE PACIFIC WAS PEOPLED BY THREE MIGRATIONS: BY NATIVE AMERICANS FROM THE PACIFIC NORTHWEST OF NORTH AMERICA DRIFTING TO HAWAII, BY PERUVIANS DRIFTING TO EASTER ISLAND, AND BY MELANESIANS. IN 1969 HE CROSSED THE ATLANTIC IN AN EGYPTIAN-STYLE. REED BOAT TO PROVE EGYPTIAN INFLUENCES IN THE AMERICAS. CONTRARY TO THESE THEORISTS, THE OVERWHELMING EVIDENCE OF PHYSICAL ANTHROPOLOGY, LINGUISTICS, AND ARCHAEOLOGY SHOWS THAT THE PACIFIC ISLANDERS CAME FROM SOUTHEAST ASIA AND WERE SKILLED ENOUGH AS NAVIGATORS TO SAIL AGAINST THE PREVAILING WINDS AND CURRENTS. LOOK AT THE FOUR SQUARES[]THAT INDICATE WHERE THE FOLLOWING SENTENCE CAN BE ADDED TO THE PASSAGE. LATER THEORIES CONCENTRATED ON JOURNEYS IN THE OTHER DIRECTION. WHERE WOULD THE SENTENCE BEST FIT？