nygreenguy wrote:goat wrote:
Not all the time. There was the bottle neck as evident in the human population some 70,000 years ago.
You will see a 'bottleneck' anytime you have a 'founder' effect. Of course, since the vast majority of species that have existed are now extinct, just existing 'almost' always ends in extinction.
Which is why I said "almost" always. The founder effect is a different type of bottleneck. When you have mass extinctions, whats happening is you are loosing the ability to survive in your niche, and there isnt enough genetic diversity to allow you to adapt.
Now, with humans we have somewhat circumvented this process in that our minds make up for the shortfalls of our body. We dont require as much genetic change in order to adapt as something like a plant does.
Founders tend to have it different. Yes, they have become reproductively isolated from the main population, but they are also in a novel niche. In these novel niches we usually see one of 3 things.
1) Death. The population simply isnt able to cope with the new area.
2) Exploitation. This novel new areas have open niches which the population can fully exploit. There is where our invasive species fall. No natural predators or diseases mean they are able to outcompete almost everything else around.
3) Rapid evolution. This is often seen on islands, and this explains why island species are just so strange. In these novel new areas, traits which may have not been beneficial in the main population may be highly beneficial in the new area. Take for example the old birds of new zealand. 9 foot high flightless birds, and no mammalian predators. No need to fly.
Now, if there was a global flood, the post flood conditions would be devastating. The soil would be washed away, the vegetation would be dead. Where would there even BE freshwater? Even a little bit of salt would be toxic to almost anything which survived. So, we have ALL of this AND competition for space. How would animals such as deer not only be able to survive all this, but still somehow manage to migrate all the way to the americas? Do you know how much FOOD a deer would need to consume to make this journey?
The list goes on, and on, and on, and on to how the flood could have NEVER happened.
