Simplify the following text for a Grade 10 native English-speaking person.
Original: At first , scientists thought they had found mandibles and skulls belonging to Homo ergaster , but size differences led them to name a new species , Homo georgicus , which would be the descendant of Homo habilis and ancestor of Asian Homo erectus .
Simplified: At first , scientists thought they had found mandibles and skulls belonging to Homo ergaster , but size differences led them to name a new species .