I don't know if you realize this or not, but humans are capable of living in entirely self-contained biodomes, outer space, and deep under the ocean for months at a time. Humans have invented nuclear energy, a nearly infinite energy source, along with countless other forms of electrical energy. Humans have perfected the science of agriculture and can even grow plants underground and even grow tropical plants in Canada. This is hyperbole. If you had to put the odds at humans going extinct, you'd have to place the odds at something like 1 in a trillion chance, short of an interstellar disaster or nuclear war.