According to this BBC article, we’re actually quite lucky to be here.
Based on the results of analyzing human DNA, some scientists are starting to believe the human race had dwindled down to a worldwide population of around 2000 people sometime within the past 100,000 years. Though the date when the population reached its lowest point cannot be specified with complete certainty, it appears the low population level was reached about 70,000 years ago. The BBC article discusses some of the factors that may have lead to this brush with extinction.
Speaking of threats to humanity, it seems Yellowstone’s underlying pressurized magma, also known as a volcano, may be overdue for an eruption; this could potentially impact almost half of the United States.