Complex sentence: Indirect life cycles likely arose in order to increase the efficiency of spreading to new hosts-by using intermediaries the parasite DNA can spread to several hosts instead of remaining concentrated within a single host, achieving a higher likelihood of DNA continuation.
Split into simpler sentences: Indirect life cycles likely arose in order to increase the efficiency of spreading to new hosts. By using intermediaries the parasite DNA can spread to several hosts instead of remain concentrated within a single host, therefore promising a higher likelihood of DNA continuation.