It's hard enough contemplating one's own mortality, let alone that of the species to which we belong. However, in The Next Species: The Future of Evolution in the Aftermath of Man, Michael Tennesen does just that. After all, we are the only species that keeps a Doomsday Clock, and the hands are only three minutes shy of midnight.
Tennesen starts by looking at previous mass extinctions to examine what caused them. The most famous mass extinction was that of the dinosaurs, which was caused when an asteroid collided with the Earth and raised a giant dust cloud that blocked the sun. However, climate change, such as global warming or cooling, also contributes to extinction, and there are several warning signs already present. Tennesen speculates on our end--and that of other species. However, every end is also a beginning. Quick-growing, "weedy" species often move in to take advantage of cleared niches, but they are gradually replaced by bigger, more specialized species. In time, big animals may return.
Is there no hope for humans? Well, there is the possibility of establishing a colony on Mars as a backup for Earth. Human evolution isn't dead; even if a catastrophe wipes out the vast majority of us, the rest could repopulate and perhaps establish a successor species to Homo sapiens. (There is evidence our species did pass through a genetic bottleneck at one point.) Of course, details about what such a species might look like are best left to the science fiction writers.
Do you think our species is as close to destruction as the Doomsday Clock says, or is there still hope for us and our children? Feel free to discuss in the comments.