Complex sentence: Buss found that men place very high importance on youth and hypothesized that modern men do this because of the fertility cues that youthful looks can give away; Singh, D., & Singh, D. (2011).
Split into simpler sentences: Buss found that men place very high importance on youth. He hypothesized that they do this because of the fertility cues that youthful looks can give away; Singh, D., & Singh, D. (2011).