It has been extremely difficult to pin down specific cause and effect in ANY evolutionary development. In fact, this is something that causes Creationists much glee. About the best we can do is look at specific environmental conditions, and try to find single mutations that result in selection. Some examples are Darwin's Finches, antibiotic resistance in bacteria, chemical resistance in insects, and those famous Moths in England.
Now, despite being able to directly observe the pressure, sample the population, and do DNA analyses for mutations, it has proven difficult to attribute clear evolutionary changes. Resistance to toxins are the most clear examples, and most people accept such evidence.
AFAIK, there is absolutely zero agreement on any environmental factors or cultural factors, leading to anything remotely as complex as actual speciation. We have not even a clue yet as to what genetic differences are the fundamental ones between us and chimps, let alone a prayer of a hope of showing why, when, or how they originated.
If you think that support for something like AGW is shaky, the support for a claim as to what drove human speciation is nonexistent by comparison.
At best, one can make some handwaving arguments and link them to data which shows temporal correlation. That is far from looking convincing. |
