Quote:
Originally Posted by carlo
What calculation did they use to ascertain the 100,000 years ?
The first thing they do is to presume that evolution will do its thing, and that while it might be random across individual evolutionary events it will when you look at it as a whole be fairly statistically even.
An analogy could be looking at a shower... you might not be able to predict exactly where a drop will be going, but it will be fairly easy to predict how wet your bathroom will be at a given point in time after having turned it on.
Then they look at the genetic fingerprints of a specific type of DNA and then they compare how different they are. If we continue with our shower analogy, right after you turn it on you'd expect to see a fairly centered dispersal pattern with only a few outliers... but the longer it has been turned on, the more random splashes would be landing further away from the initial pattern. Thus by looking at the pattern, you could make a fairly educated guess as to how long your shower has been running.
And these people are reporting a less diverse collection of fingerprints than expected. This basically points to a large scale extinction event having taken place, something that made a lot of species go extinct and left a more equal set of genetic fingerprints behind (presumably more similar species share some traits that make them more resistant to that specific event). To continue with the analogy... we are certain the shower was turned on half an hour ago, but these guys showed us that the main dispersion of water (except a few wet spots here and there) points to it only having run for 2 seconds... thus we presume something happened to most of the previous water before those 2 seconds started.
There are of course caveats to their method. If we continue with our analogy, you would be supposing a very specific type of showerhead, a very specific pressure of water, a specific layout of your bathroom and so forth. It wouldn't fit if any of those presumptions were wrong. This is of course why they use language such as "suggests that" and "requires more research". It is not "this is exactly what happened", it's more "this is worth looking into more closely".