The sphinx's riddle goes: What walks on four legs in the morning, two legs in the day, and three legs in the evening? (Not the exact wording but close enough.)
The answer is "man" because: in early life a baby crawls on four legs, an adult man walks upright on two, and an old man walks with a cane - making three legs.
Greek mythology is cool and tragic, if your looking for something to read.
FYI: google might suspend and eventually delete your Google account if you don't verify your age within a set period of time.
They say it's to "prevent minors from having access to an account that isn't monitored by parents".
Seems more like unecessary corpo powertripping, to me.
(If you decide to go through with the age verification: the credit card method is probably the least invasive. Just be sure to unlink your card from the account afterwards.)