Iasus was the king of Arcadia and father of Atalanta.
Iasus desperately wanted a son so that his bloodline could continue on the throne. However his wife gave birth to a daughter, who he had abandoned in the woods.
Years later he went to the oracle to ask about his daughter. She told him his daughter would return and marry. When Atalanta returned he started talking about marriage but she said she would only marry on her own terms. She had him organize a race to decide who she would marry. The following day she told the suitors her conditions. If they could out run her in a foot race and avoid being killed by her, that is the man she would marry. Many tied and failed to beat her to no avail.
However one day Hippomenes, a prince from a nearby city, came and challenged the princess to the next race and, the following week, won and wed her. Iasus had mixed feelings about it, he was happy that his daughter was finally married, but annoyed that the revenue the death races brought to Arcadia would have to stop.