Simplify the following text for a Grade 8 native English-speaking person.
Original: Dobzhansky is credited for having studied the fruit fly in population cages , and discovered that close regional varieties of flies were more similar to each other genetically than to flies from other regions .
Simplified: Dobzhansky took fruit fly research out of the laboratory and into the field . He discovered that regional varieties of flies were more similar to each other genetically than to flies from other regions .