Our sun ignited about 5 billion years ago (8.7 billion years after the Big Bang) and our home planet had formed by 4.6 billion years ago. Life first evolved in the primordial seas of Earth about 3.6 billion years ago and, through the process of natural selection, has since diversified into the millions of plant and animal species that we find today; we humans did not appear until 150,000 year ago, at the earliest.
Since life appeared and began to diversify, the great majority of species have become extinct, some as "failed" dead-end species while others morphed into more viable species before they died out; the volcanic and sedimentary rocks of our planet are replete with fossils and preserved impressions of extinct species, most of which we have yet to discover. We humans, endowed with a large brain, imagine that we are a chosen species, the endpoint of evolution on Earth, destined to rule the planet until our God comes to whisk us from our animal life. Unfortunately, this widespread belief distracts us from the importance of protecting our planet and leads many to deny our dependence on its complex ecosystems.
Of course, we also tend to reject the fact that humans are just another species of Planet Earth, subject to extinction like all other forms of life; from a scientific point of view, the only questions are how that extinction will occur and whether we will evolve into another species beforehand. Unless we begin to address our overpopulation and reign in our impact on natural ecosystems, we will likely succumb to environmental pollution and other man-induced problems; perhaps a massive asteroid strike, nuclear war or super-volcanic explosion will hasten our demise. It is conceivable that some humans may escape to another planet or solar system before our species dies out or that the evolutionary offspring of mankind will take that journey before our dying sun destroys the Earth; if neither scenario unfolds, we will die with our planet.