Simplify the following text for a Grade 15 native English-speaking person.
Original: The Russian Nobel laureate biologist Ilya Ilyich Mechnikov , from the Institut Pasteur in Paris , was influenced by Grigorov 's work and hypothesised that regular consumption of yoghurt was responsible for the unusually long lifespans of Bulgarian peasants .
Simplified: The Russian Nobel laureate biologist Ilya Ilyich Mechnikov , from the Institut Pasteur in Paris , was influenced by Grigorov 's work and made a hypothesis that eating yoghurt regularly was the reason why Bulgarian peasants lived for so long .