![[Two large sperm cells are coiled up next to each other within a male’s testis (photo by Romano Dallai).]](https://blogs.iu.edu/sciu/files/2023/02/bifurca_sperm.jpg)
The drive to reproduce has led to many of the flashiest traits observed in nature. For instance, male deer use antlers to fight one another for access to female mates, while male peacocks display their extravagant tails to impress peahens. These are examples of sexually selected traits, or traits that increase reproductive success. Sexually selected traits evolve because they increase “fitness”…