South African Oscar Pistorius sprinted into Olympic history Saturday in London, becoming the first amputee runner to compete in the Games.

Pistorius, who wears special prosthetics on both legs, finished second in a preliminary heat of the men's 400 meters, qualifying him for the semi-finals.

Pistorius was born without fibulas – the outer bones in the lower legs – and his lower legs were amputated when he was less than one year old, so he would later be able to walk with the help of prostheses attached just below his knees .

Pistorius was cleared to compete in the Olympics after years of scientific and legal debate, over whether the prosthetic legs he uses on the track, which are made of carbon-fiber blades, give him an unfair advantage over sprinters using their natural legs.

In other track competition Saturday, three-time Olympic champion Usain Bolt of Jamaica made his debut in the 100-meter sprint, winning his heat.

Bolt is the world record-holder in the 100, he has faced doubts since losing to the current world champion, Yohan Blake, in Jamaica's Olympic trials.

In women's tennis, American star Serena Williams clinched her first Olympic singles gold medal with a dominating win over Russian Maria Sharapova, 6-0, 6-1. She is now only the second woman to win an Olympic singles title and all four tennis majors. German Steffi Graf also accomplished that feat.