Part I: Intellectual obstacles to the notion of early transoceanic contacts -- The myth of the oceans as uncrossable barriers -- Before Columbus, the Earth was "flat"? flat wrong -- Conveyor belts of the seas: the prevailing winds and currents -- Staying alive while crossing the deep -- Getting the drift: accidental voyages and discoveries -- No plague in the land? the alleged American absence of Old World communicable diseases -- Why most domesticated animals and plants stayed home -- Low tech: the absences of many Old World inventions in the New World -- More on the whys of technological absences -- The mystery of the missing artifacts -- The supposed silence of the historical record -- The "silent" historical record speaks: documents possibly describing Pre-Columbian crossings -- Part II: Means: the types and availabilities of watercraft and navigation -- Some nautical myths and issues -- The myth of the inadequacy of Pre-Columbian watercraft -- It's earlier than you think: the antiquity of seagoing watercraft -- Have sail, will travel: the origins, types, and capabilities of sails and rigs -- Products of the Paleolithic: rafts -- Out of the Ice Age: skin boats of the North -- Mesolithic and neolithic legacies: dugouts and lashed-plank watercraft -- Hulled wooden ships East and West: the junk and the nao -- Modern experimental voyages: the empirical approach -- Asea without a compass: celestial way-finding -- A matter of course: seamarks and haven-finding -- Part III: Motives for ocean crossings -- Repellants -- Attractants -- Part IV: Opportunity for exchange: concrete demonstrations of contacts -- Shared physical materials, domesticated animals, and diseases -- Shared cultigens: From New into Old (World) -- Cultivated plants: Old World cropping up in the New -- Tobacco, coca, and cannabis: the mummies speak, but the scientists stand mute -- Old World faces in New World places -- Incongruous genes in America -- Part V: Conclusions -- Mission possible: crossings occurred.