"It seems that whenever evidence challenges current evolutionary theory, the theory just changes to accept the new data, but the presuppositions don't change.  What evidence would scientists accept that would cast doubt on evolution itself?

[An excerpt Faith and Science, Falsely So-Called by John MacArthur] "Over the course of human history, all kinds of speculative ideas have been falsely labeled “science” and mistakenly accepted as true and reliable knowledge by otherwise brilliant people. The now-discredited dogmas of older scientific theories are numerous—and in some cases laughable. They include alchemy (the medieval belief that other base metals could be transmuted into gold); phrenology (the Victorian belief that the shape of one’s skull reflects character traits and mental capacity); astrology (the pagan belief that human destiny is determined by the motions of celestial bodies); and abiogenesis (the long-standing belief that living organisms are spontaneously generated by decaying organic substances). All those false beliefs were deemed credible as “science” by the leading minds of their times...

...evolution is a dogma, not a demonstrable “fact.” I stand by the position I took in The Battle for the Beginning: “Belief in evolutionary theory is a matter of sheer faith. [It is] as much a religion as any theistic world-view” (The Battle for the Beginning, p. 12).

I’ll go even further: science cannot speak with any authority about when the universe began, how it came into being, or how life originated on earth. Science by definition deals with what can be observed, tested, measured, and investigated by empirical means. Scientific data by definition are facts that can be demonstrated by controlled, repeatable experiments that always yield consistent results. The beginning of the universe by its very nature falls outside the realm of scientific investigation.

To state the case plainly: there is no scientific way to explain creation. No one but God actually observed creation. It did not happen by any uniform, predictable, observable, repeatable, fixed, or natural laws. It was not a natural event or a series of natural events. The initial creation of matter was an instantaneous, monumental, inexplicable miracle—the exact opposite of a “natural” phenomenon. And the formation of the universe was a brief series of supernatural events that simply cannot be studied or explained by science. There are no natural processes involved in creation; the act of creation cannot be repeated; it cannot be tested; and therefore naturalistic theories purporting to explain the origin and age of the universe are unverifiable.

In other words, creation is a theological issue, not a scientific one. Scripture is our only credible source of information about creation, because God Himself was the only eyewitness to the event. We can either believe what He says or reject it. But no Christian should ever imagine that what we believe about the origin of the universe is merely a secondary, nonessential, or incidental matter. It is, after all, the very starting point of God’s self-revelation.

In fact, in its profound brevity, Genesis 1:1 is a very simple, clear, and unequivocal account of how the universe, the earth, and everything on the earth came to be: “In the beginning God created the heavens and the earth.” That is not an ambiguous statement. Until Darwinian evolution undertook a campaign to co-opt the story of creation and bring it into the realm of naturalistic “science”—and especially before modernist skepticism began to seep into the church—no one who claimed to be a Christian was the least bit confused by the Genesis account...

[W]e must not seek ways to circumvent the clear meaning of God’s Word, compromise our trust in the Creator, or continually yield ground to every new theory of falsely-so-called science...

Too many Christian leaders, evangelical schools, and Bible commentators have been willing to set aside the biblical account of a relatively young earth in order to accommodate the ever-changing estimates of naturalistic geologists and astronomers. They have thrown away sound hermeneutical principles—at least in the early chapters of Genesis—to accommodate the latest theories of evolution.

When I encounter people who think evolutionary doctrine trumps the biblical account of creation, I like to ask them where their belief in the Bible kicks in. Is it in chapter 3, where the fall of Adam and original sin are accounted for? In chapters 4-5, where early human history is chronicled? In chapters 6-8, with the record of the flood? In chapter 11, with the Tower of Babel? Because if you bring naturalism and its presuppositions to the early chapters of Genesis, it is just a short step to denying all the miracles of Scripture—including the resurrection of Christ. If we want to make science the test of biblical truth rather than vice versa, why would it not make just as much sense to question the biblical record of the resurrection as it does to reject the Genesis account? But “if Christ is not risen, your faith is futile; you are still in your sins! . . . If in this life only we have hope in Christ, we are of all men the most pitiable” (1 Corinthians 15:17-19)..." full text:  Faith and Science, Falsely So-Called by John MacArthur http://www.gty.org/Blog/B100513