MÛR-DE-BRETAGNE, France — All manner of flags are waved at the Tour de France. But at the start in Rennes on Saturday there were a few dozen examples of one that had probably not made an appearance: the red, blue and green of Eritrea.

Those flags appeared because of Daniel Teklehaimanot and Merhawi Kudus, who are Eritreans of many firsts. In a sport in which black riders from any continent are rare, Teklehaimanot and Kudus are the first black Africans to compete in the Tour. Teklehaimanot is the first African rider to wear the red polka dotted jersey as the Tour’s best climber. And perhaps most important, they ride for the Tour’s first modern African team, MTN-Qhubeka, which hopes to make Africa as important a force in cycling as it is in endurance sports like long-distance running.

Despite his status as the leader of the climbing competition, Teklehaimanot faltered Saturday on what was arguably the most difficult climb of this Tour so far, the dramatically named Mûr-de-Bretagne, or Wall of Brittany. While relatively short, it included a grueling 10 percent grade at one point, which swiftly sorted out the field.

Alexis Vuillermoz, a French rider who started out in mountain biking, launched an attack against the race leader, Chris Froome, near the top of the hill and went on to win the 181.5-kilometer (112.5-mile) eighth stage in 4 hours 20 minutes 55 seconds. Dan Martin, who rides for the American Cannondale-Garmin team, was second.