Because humans have 23 chromosome pairs, independent assortment alone gives roughly:

1. The count is two raised to the number of pairs. 2. With n equal to 23, that is 2 to the power 23. 3. Humans have 23 chromosome pairs, which results in over eight million possible genetically distinct gametes. 4. Crossing over multiplies that variety further still. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 11 'Meiosis and Sexual Reproduction', sections 11.1-11.2_