1997XF11 was a reminder that there could be another major impact with earth, and this too could spell the end of humankind. However, contrary to the early reports, there is no real danger of this asteroid colliding with earth in 2028 - though it might do in the distant future.
Humans are only a recent arrival to the earth, having been around for just a few million years.
To date we have been a successful species, thriving and multiplying until we inhabit almost every corner of the globe. We are an incredibly resourceful species, and are able to modify our environment in many ways to make it more comfortable - building houses and cultivating crops. On the other hand, we may be our own worst enemy. Perhaps the biggest threats to humankind will be the results of the immense, and usually negative, effect we are having on the environment - which is, after all, where we live.