I think in this instance it means that humans are developing artificial intelligence without understanding what the consequences might be. In this case I think the person is saying that if we give artificial intelligence to robots, they may rise up and kill all humans. Therefore "could mark the beginning of our end" means that we may all become extinct because the sentient robots (robots with artificial intelligence) may decide to turn on mankind and kill us all.

thanks Sean. :)

Human would go extinct as the development of AI became out of control.