The proclamation of the gospel of Jesus Christ is the proclamation of public truth claims about the nature and purpose of the work and person of Jesus Christ. These claims are neither magic nor hocus-pocus nor mystical mush. They are open to rational enquiry, historical and scientific investigation. They may be discussed by philosophers and made subjects worthy of university research.
But some Christians - quite a considerable number in places such as the United States of America - also believe in 'creationism' or 'creation science'. Creationism involves claims that the reality of the beginning of life is closer to a literal reading of Genesis 1 and 2, framed against the chronology of Genesis 4 onwards, than to the scientific discoveries of biology, geology, and cosmology. Thus creationism proposes that the earth (and universe) is young (around 6000 to 10000 years old), and that the first human beings had no biological ancestors. In support of these claims some scientific evidence is advanced. But this evidence is generally not accepted in the broader world of science. Nor are proponents of creationism generally accepting of the evidentially-based conclusions of the broader world of science. Thus creationism involves closure to the normal processes of rational enquiry, and historical and scientific investigation. The potential for creationist Christianity to lead Christianity into a religious cul-de-sac where all sects and cults reside is considerable. In that cul-de-sac there is no evangelism as understood in the New Testament ('Go into all the world'), there is only a furtive gathering up of fugitives from the real world. If evangelism is to succeed, creationism must die.
The case for the fact of evolution is excellently put by Richard Dawkins in an article lauding the publication of a book on evolution by a fellow scientist. Here's an excerpt:
"How can you say that evolution is “true”? Isn’t that just your opinion, of no more value than anybody else’s? Isn’t every view entitled to equal “respect”? Maybe so where the issue is one of, say, musical taste or political judgement. But when it is a matter of scientific fact? Unfortunately, scientists do receive such relativistic protests when they dare to claim that something is factually true in the real world. Given the title of Jerry Coyne’s book, this is a distraction that I must deal with.
A scientist arrogantly asserts that thunder is not the triumphal sound of God’s balls banging together, nor is it Thor’s hammer. It is, instead, the reverberating echoes from the electrical discharges that we see as lightning. Poetic (or at least stirring) as those tribal myths may be, they are not actually true.
But now a certain kind of anthropologist can be relied on to jump up and say something like the following: Who are you to elevate scientific “truth” so? The tribal beliefs are true in the sense that they hang together in a meshwork of consistency with the rest of the tribe’s world view. Scientific “truth” is only one kind (“Western” truth, the anthropologist may call it, or even “patriarchal”). Like tribal truths, yours merely hang together with the world view that you happen to hold, which you call scientific. An extreme version of this viewpoint (I have actually encountered this) goes so far as to say that logic and evidence themselves are nothing more than instruments of masculine oppression over the “intuitive mind”.
Listen, anthropologist. Just as you entrust your travel to a Boeing 747 rather than a magic carpet or a broomstick; just as you take your tumour to the best surgeon available, rather than a shaman or a mundu mugu, so you will find that the scientific version of truth works. You can use it to navigate through the real world. Science predicts, with complete certainty unless the end of the world intervenes, that the city of Shanghai will experience a total eclipse of the sun on July 22, 2009. Theories about the moon god devouring the sun god may be poetic, and they may cohere with other aspects of a tribe’s world view, but they won’t predict the date, time and place of an eclipse. Science will, and with an accuracy you could set your watch by. Science gets you to the moon and back. Even if we bend over backwards to concede that scientific truth is no more than that which enables you to pilot your way reliably, safely and predictably around the real universe, it is in exactly this sense that – at the very least – evolution is true. Evolutionary theory pilots us around biology reliably and predictively, with a detailed and unblemished success that rivals anything in science. The least you can say about evolutionary theory is that it works. All but pedants would go further and assert that it is true."
Read it all here. New Zealand even gets a mention twice (once explicitly, once by implication).