Why do human egg and sperm cells contain 23 chromosomes?

Human egg and sperm cells, known as gametes, contain 23 chromosomes because they are haploid cells, meaning they carry exactly half the number of chromosomes found in a typical human body cell.12

In humans, somatic (body) cells are diploid, containing 46 chromosomes arranged in 23 homologous pairs—one set inherited from each parent. During meiosis, a specialized form of cell division, these pairs are separated to produce gametes that possess only one chromosome from each pair.1342

This reduction is essential for sexual reproduction. When fertilization occurs, the sperm and egg fuse, combining their respective sets of 23 chromosomes to restore the full diploid number of 46 in the resulting zygote. This process ensures that each generation maintains a consistent chromosome count while promoting genetic diversity through the inheritance of material from both parents.256