The burden of proof is always on the arguer, creationist or evolutionist, who is making an assertion. The difficulty for creationists lies in making logical arguments against evidence, and for evolutionists in sifting through voluminous evidence for a pertinent example to illustrate their point.
The construction of a cogent deductive argument begins with acceptable premises (supported by evidence) and proceeds according to the laws of deductive reasoning to a conclusion supported by the premises.
Shifting the burden of proof is a subtype of the argument from ignorance fallacy that shifts the burden of proof onto the person whose argument is attacked. This is the "prove it, or I am correct!" challenge that underlies many creationist taunts.
The source of the fallacy is the assumption that something is true unless proven otherwise. The implied conclusion of creationist demands is that unless the evolutionist can provide an adequate explanation for specifically selected creationist questions, then evolutionary theory is false, biological evolution is no longer a fact, and the existence of God is proven (at another level of implication).
If one follows creation vs evolution debates, one will quickly observe that creationists do mention God, while evolutionists do not attempt to disprove the existence of God. Evolutionists typically defend the experimental justifications of evolutionary theory.
On the other hand, scientists defend, to other scientists, their conclusions based upon experimental results. Scientific reports follow a format of introduction to ideas based upon past research, the question to be addressed, experimental methods, experimental results, and conclusions based upon both current scientific understanding and their experimental results. Science proceeds by incremental gains in understanding. It is the very nature of science that conclusions are acknowledged not to be the final word upon explanation, and that, once a scientific theory is widely accepted, research will move on to yet unanswered questions. Creationists utilize, in their religiously-motivated attacks on science, one of the chief virtues of science – the reluctance of the community of scientists to accept any hypothesis or theory until burden of proof moves to the level of general acceptance.
Labels: argument from ignorance, argumentum ad ignorantiam, biological evolution, creationism, deductive argument, evolutionist, fallacies of logic, intelligent design, science, shifting the burden of proof