[geoschmo]

I guess it all depends on how you want to define threat. If we are talking about capital T threat as in, the end, no more people, then about the only thing that's likely going to do that is a really big asteroid.

On the other hand, while there's a chance of us all getting done in by a big space rock, there's pretty much a certainty that a whole lot of us are going to get done in by all those self inflicted issues we are talking about, pollution, lack of resources, bad hair days, etc. If things keep going the way they are that is. About the worst we could do to ourselves though is probably knock ourselves back a few hundred years on the civilizational scale. It would really suck, but as a species we'd survive it.