SO once every hundred years we see a new species? Why, in 10,00 years do we not have different species of humans?
And something I've thought about for awhile, how do you think the brain was randomly generated? It is a living computer more powerful than anything we have ever created, and for power just put some food into the body, where the body automatically seperates the individual proteins to create completely new proteins for your various protein needs. Bit convenient, isn't it? Also, our eyes are the most advanced lenses ever. They automatically choose the correct aperture depending on the light hitting it, which then flips the picture upside down, to be read and flipped right side up again by the brain. Then, we have the nervous system, which uses tiny electrical impulses to move a limb or to let you know you just stubbed your toe. To believe that these things just exist and happened completly randomly is not just ludicrous, it borders insanity.
Now what you have done is to completely misunderstand speciation. Speciation does not occur *pop* ...new species, it doesn't work like that except in really, really bad strawman arguments.
Evolution is a gradual (from a generational perspective) change in the genetic code of an organism.
Lets look at a hypothetical examination over time.
We know that Amphibians exist.
they lay eggs that requier water to survive. However, they also need a protective (althoguh soft and water permiable) shell to stop them being damaged.
But, if a species of amphibian lived in an area where there were a lot of water born predators that ate their eggs, then it would be advantageous for therm to lay them as close to the shore as possible. However, due to various reasons the shore line can rise and fall. If one of our amphibians laid their eggs too close to the shore, they might avoid all chance of predation, but they run the risk of the eggs being exposed and drying out.
If an amphibian's egg were to have a thicker shell, then it might make it harder for the young to escape the egg, so this would normally be selected against (as they would be weaker and be therefore more susceptible to predation after they hatch and the more vigorous young would be able to out compete them for food).
But, in an area where predation of eggs is high, then eggs not out as far as possible would be at a disadvantage as they would be eaten by the predators, but the eggs on the outside would be safer.
However, in this situation, any egg that had a thicker shell could last longer out of water and not dry out. So in this case a thicker shell is an advantage, even though the young would find it harder to hatch and then find food. They would, though, be able to survive situations which would kill all the other eggs as they could last longer out of water.
Now, if there was any mutation that allowed the young to escape the eggs easier this would be an advantage, say a tooth that develops early. This might not be a disadvantage for the original amphibian, but it would not be an advantage either. But for these new mutant amphibians, this would be a decided advantage as it would enable them to escape the thick shelled eggs easier and so take less energy and they could remain vigorous. They could catch food easier and escape predators easier.
But then this "Egg Tooth" would also allow the shell of the egg to become thicker still, allowing these eggs to last even longer out of water, which give this species even more advantage against the egg predators.
This will continue back and forth for a bit until the shell fo the egg becomes completely water proof. At this point the species is no longer dependent on breeding in the water any more and can lay their eggs completely on land. They would in fact be reptiles as we would classify them.
By small changes We have gone from an amphibian to a reptile. A frog to a lizard if you will. But at no point could we state that there was a new species, except if we look back and compare it to the original amphibian.
This of course is an extremely simplified example to show the process and to highlight how speciation occurs (ie it is an artificial and human created division, not something that actually exists).
Because speciation is a human created definition, it tends to fail in light of real word situations. We can't agree on precisely what a species is because the whole concept of a species is not something that really exists in the real world. So even what constitutes as a speciation event is not well defined either because the real world is not like that.
We tend to think of new species branching off like a branch of a tree. But in reality, this branching takes place over many generations, and in this time there is many links back form the diverging genomes to the old genomes, there is hybridisation, there is large scale mutations, there are extinctions, there are random deaths, there are changes to the environment and so on and so forth.
This concept of a neatly branching tree of life is altogether over simplified, but it is a decent analogy, just don't mistake it for the real thing.
Now, as for the drive for new species to develop:
Evolution create pressures on a species. Over time an equilibrium is reached where the pressures drop. In these situations there will not be much changes, as a key point in evolution is selection. If selection is minimal, then there will not be much drive for the organism to change much. It will, however, change in neutral ways. that is in ways that do not make much changes to the organism.
If you remember my previous post, I explained how a mutation could be neutral and actually not effect the organism at all. However, these are changes, and they do effect what directions the organism could more easily take in evolution.
This is called genetic drift, because the genome of the organisms will drift over time and not much change will be noticed. This will also create a lot of variation in the population as small changes that do have an effect will not be necessarily selected against.
Remember in the amphibian example above how the development of an "egg tooth" in the amphibian with the soft shell did not create any overt disadvantage, but did not create at that point any overt advantage. Something like this could develop and it wouldn't really change the species in any real way.
But things get interesting when some pressure is put on the organisms,say a new predator comes onto he scene, or the climate change. Now these variations that have accumulated in the species might offer some an advantage and others a disadvantage. There might also be more than one variation that offers an advantage but it is not existant in all members of the population.
This would create a strong selection for these traits that offer an advantage and a strong selection away from the traits that offer the disadvantage.
This would create a rapid change (geologically speaking) change in the organism and create a speciation event that would be seen in the fossil record, or even occur within out lifetime for a rapidly reproducing species like finches (the vampire finches of the Galapagos).
ALso, as the original species would go extinct, we would not necessarily see any survivors of this original species survive.
Also...
If there were several different traits that offered an advantage, but these traits were not in every individual, then what we would see occur is that these different traits would lead to different species and we would get two species with a common ancestor.