Simplify the following text for a Grade 12 native English-speaking person.
Original: Similar interchanges occurred earlier in the Cainozoic , when the former Gondwana continents of India and Africa made contact with Eurasia , about 50 and 30 mya respectively .
Simplified: Analogous interchanges occurred earlier in the Cenozoic , when the formerly isolated land masses of India and Africa made contact with Eurasia c. 50 and 30 Ma ago , respectively .