Ancestry of Bees

Sally knows the following about the reproduction of bees:

• If a bee is male, it has just one parent who is female.
• If a bee is female, it has two parents: one male and one female.

She observes that a male bee has 1 parent, 2 grandparents, and 3 great-grandparents.

How many great-great-grandparents does a male bee have?

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Clarification: The reproduction of bees doesn't behave in the same way as that of humans. Fertilized eggs will hatch into female worker bees, while unfertilized eggs will become drones or honey bee males.