(1) Though it may seem strange, scientists have found that bats actually seem to form friendships. (2) A scientist noticed one bat feeding another. (3) He assumed the two bats were related. (4) He found out that they shared none of the same genes meaning they couldn't possibly be relatives. (4) The bats appear to take care of those around them even if they are not "family". (5) Bats feed on other animals drinking their blood. (6) He concluded that the bonds bats share are like human friendships.

Which sentence in this paragraph should be deleted because it includes information that is not relevant to the main topic of the paragraph?