Monday, May 21, 2007

Josh's New and Hot (Week 8)

Where did they all go?

In an exciting twist new twist for human development in the Americas, scientists are unveiling evidence this week that a blast from a comet or asteroid caused cooling in North America about 13,000 years ago. They have gathered geological evidence from 20 sites in North America that contain glass, carbon, iridium and nanodiamonds that could not possibly have come from the earth. All this points to the theory that a 5km object impacted the earth or exploded in the sky causing massive wildfires followed by a 1,000 year cooling period known as the Younger Dryas.

What's really cool about this, though, is the implications it has for explaining extinct species. It seems that the date corresponds perfectly with the extinction of most large mammals in North America at the end of the last Ice Age. Mastodons, giant ground sloths, short-faced bears, sabre-toothed cats, and North American camels could all trace their extinction back to this one event. Since I'm reading about Darwin's explanations for gaps in the fossil record for transitional state animals and such, it is interesting to read about theories that point out that fossil records may be spotty because of these sudden catastrophic events.

While interesting, this theory does have some caveats in it as well as conflicts with other theories on the topic. While this theory states that human populations were largely decimated, much evidence and scholarships has pointed out that early Meso-Americans were moving and growing at this period of time, not declining. Also, some would argue that if this explosion occurred, then where are the crater remains. This of course is explained by the fact that the Laurentide Ice Sheet that covered much of North America masked the impact. Still, this is obviously a theory that still needs some tweaking. Perhaps future research will shed some light on where all the mastodons went.

Click here for the story from BBC

1 comment:

chickenpox said...

The article is really interesting! It's really amazing how scientists can actually find evidence leftover today and put together an event that happened so long ago! Even with all the compiled evidence there is always the possibility that they could be completely wrong, because there is always the question of whether anyone can ever really determine what happened.