Here's why:

* Diploid vs. Haploid: Human cells are typically diploid, meaning they have two sets of chromosomes (23 from the mother and 23 from the father), totaling 46 chromosomes.

* Gametes: Gametes are sex cells (sperm and egg) that are haploid, meaning they contain only one set of chromosomes.

* Fertilization: When a sperm and egg fuse during fertilization, they combine their single sets of chromosomes to create a new diploid individual with 46 chromosomes.