99% of scientists believe in Evolution. This spurious claim is on the lips of every Evolutionist who either loses a debate, or knows they couldn't win one to begin with. It's a lazy and thoughtless argument, not only demonstrating a lack of critical thinking abilities, but worse, the assumption that one's opponent also does not, or at the very least should not, exercise them either.
This kind of argument is so bad that it actually combines two fallacies into one: The appeal to authority (argumentum ad verecundium), and appeal to popular opinion (argumentum ad populum). The former suggests a view is true because an authoritative figure or body says so. The latter suggests a view is true because it is the majority opinion.
The first key to understanding why this is a poor argument is to simply point out that it would have stopped scientific research into literally any topic immediately. In fact, there are arguments which similarly attempt to dismiss Christianity under the cloak of science. Specifically, it is claimed there was a time when Christianity suppressed science.
Long ago, 99% of scientists believed what is now known as the "geocentric model". That is, the Earth is stationary, and the celestial bodies all orbit it, much like we now know the moon actually does. Two scientists, however, disagreed. Galileo Galilei, and before him Nicolaus Copernicus, both believed the Earth actually orbits the sun. Though they were the minority, they were in the correct minority, and their ideas have since been vindicated and refined.
With this in mind, the simple question to ask those who cite the 99% of scientists is "how do you know they're right?" This takes Evolutionists right out of their comfort zone, forcing them to do what they aren't especially fond of doing: Thinking critically about Evolution. See, while it's true that the vast majority of scientists do believe in Evolution (though the figure is not likely anywhere near 99%), that position can be questioned. And when we ask those questions, even hardcore Evolutionists like Eugenie Scott admit it will fail to answer. In fact, Evolutionists like Michael Ruse go as far as to admit it will turn out to be a religion, and one specifically designed as an alternative to Christianity.
My favorite example is when Michael Crichton, famous for writing the Jurassic Park novels, stated that "Consensus is invoked only in situations where the science is not solid enough." I love this quote in particular, not only because it's a true and wise thing said by an Evolutionist who, at the time, was not even referring to Evolution, but because I once silent quoted it to an Evolutionist, and he got so angry, I thought he was going to crawl through the screen just to punch me. Of course, don't let one guy on the internet represent Evolutionists as a whole, but in general, they do not like when this fallacious argument does not work.
In fact, in spite of the above, they will often insist it's not a fallacy in this case. In their view, appeal to authority is only a fallacy when the authority figure is not an expert, and appeal to popular opinion is only a fallacy if it's not the majority of experts. When appealing to the majority of experts, however, it can be reasonably assumed they know what they're talking about, and so we can even dismiss the minority of experts, who by the same reasoning should know what they're talking about, simply because the majority of experts are in a position to know the truth.
We've already shown, by example, why this is ridiculous reasoning. And we could do so many times over. Galileo is not the only correct scientist to suffer the wrath of the consensus mob. Nor is he alone in being vindicated against that mob. But let's concede the tiniest piece of ground to the Evolutionist and admit that yes, it is at least less likely that the majority of scientists would be wrong, and they do have more tools at their disposal to test their theories. Question: Are they infallible?
If scientists were infallible, then not only would consensus reach 100% every time, but it would also never produce examples like, for example, the Great Chromosome Fiasco. But it never does reach 100%, and it does produce what, in some cases, turns out to be major error, some of which persists for centuries. The obvious reason for this is that scientists are, in fact, human.
Human beings are flawed creatures, and there is literally no way to fully erase these flaws. Even experts, and I mean experts in any given field, may make honest mistakes, will have personal bias, may fall prey to deception, will want to fit in with both their fellow experts and society as a whole, may even be tempted by unsavory things such as bribery, and most of all, absolutely will sin.
This is actually one of the purposes of "peer review" in science. Of course, even this doesn't solve the problem. In fact, hilariously, some peer reviewed journals even let prank articles slip through the cracks, which then get cited as a source for later material. Furthermore, Evolutionists must concede that it is not proof positive of reliability. While they constantly claim Creationists don't publish in peer reviewed journals, they actually do, with some peer reviewed journals even being exclusively Creationist in nature. To dismiss these because of their bias is as fallacious as to dismiss Evolutionist journals on the same basis.
Furthermore, occasionally, even peer reviewed journals with an Evolutionist bias allow pro-intelligent design studies to be published. Richard Sternberg, for example, once published such an article in Proceedings of the Biological Society of Washington. For this, he was very aggressively persecuted by his peers, so much so that the Office of Special Counsel had to get involved. Though an Agnostic himself, he was bullied for being a "closet Bible thumper", all because he didn't stick to the status quo. This raises a particularly interesting question: How many scientists would really accept Evolution if they didn't have to?
The answer, of course, is that a fair few still would. After all, it didn't become consensus like that. Rather, it was, itself, initially pushed by a minority of mostly misotheists, such as Charles Lyell. Lyell, according to Warren Allmon, "...sold geology some snake oil". That "snake oil" was the principle of Uniformitarianism: The belief that all past processes occurred at roughly their present rate.
To quote the aforementioned Warren Allmon, "This extreme gradualism has led to numerous unfortunate consequences, including the rejection of sudden or catastrophic events in the face of positive evidence for them, for no reason other than that they were not gradual." In other words, because of a particular bias (which, in Lyell's case, was quite explicitly designed to "free the science from Moses"), even genuine evidence is rejected.
With those prior assumptions plugged in, Lyell, who lived in a time when even a few hundred thousand years would have been seen as an extremely exaggerated age for the Earth, actually fudged data in order to exaggerate the age of Niagara falls. When he visited the falls, he was informed that they were retreating by about a yard per year, which, even going by his theory, would mean that the erosion of the whole gorge would have taken around 10,000 years. But this wasn't long enough for Lyell, so he wrote "...the average of one foot a year would be a much more probable conjecture. In that case, it would have required 35,000 years for the retreat of the Falls, from the escarpment of Queenstown to their present site."
The irony here is that even knowing the actual rate of erosion, he decided it wouldn't make the falls old enough, so he decreased the known average rate to increase the alleged age of the falls. Furthermore, we now know that the rate is not constant; certain conditions have been known to increase it. In fact, many processes previously assumed to have taken thousands, even millions of years, have now been observed to occur in much shorter time spans! Even fossils can now be formed relatively easily in a lab.
In other words, we now know, by observation, that Lyell's entire assumption was wrong: The present is not key to the past. Yet still, using his assumptions, we can sincerely draw the wrong conclusions. Using Uniformitarianism as a starting position, we do see an Old Earth.
In fact, the irony is, using present rates of anything, we could go back in time to Adam's first birthday and assume he was, at the very least, in his teens. This is because the heavens and the Earth were created with what is described as "functional maturity". That is, in order to function, virtually nothing could have "looked" as young as it was from the beginning. Otherwise, it wouldn't function. Therefore, a time travelling scientist observing the Earth in its infant stages would, using the wrong assumptions, sincerely believe it was old.
We see, then, that the problem we have isn't even necessarily the evidence. After all, the Creation scientists who do exist (and, frankly, make far better arguments, and without throwing a paddy when their authority, arguments, or worldview are challenged) are looking at the same evidence. The difference is, while Evolutionists expect their authorities to draw the right conclusion based on demonstrably flawed assumptions, Christians believe in an infallible authority figure, and use His testimonies as a guide for interpreting evidence.
By acknowledging God, for whom we have far more reasons than just science to believe in, we see that even first century Jews, like Paul, or pre-Christian prophets, like Moses, and, in particular, Jesus Himself, are all in a far better position to explain the origins of the heavens, the Earth, and all that is in them, than any scientist living today.
Furthermore, by their same testimony, we actually expect the majority of "experts" to oppose God. And not only in the realm of science. From religious leaders and philosophers, all the way to kings, the Bible tells us that Christianity will always be an unpopular opinion, simply because sin, a condition we all suffer with, blinds us.
Furthermore, scripture specifically singles out those who are "wise according to the flesh" as the most likely to oppose God, and that this is deliberate on His part. "For you see your calling, brethren, that not many wise according to the flesh, not many mighty, not many noble, are called. But God has chosen the foolish things of the world to put to shame the wise, and God has chosen the weak things of the world to put to shame the things which are mighty; and the base things of the world and the things which are despised God has chosen, and the things which are not, to bring to nothing the things that are, that no flesh should glory in His presence." (1 Corinthians 1:26-29).
Therefore, although there are many scientists who believe, it is to be expected that many more will be opposed to God. This sets up a bizarre situation in which even the unqualified are capable of humiliating experts, of course being the intellectual equivalent of David, a shepherd boy who had never seen war, and having even rejected Saul's armor, taking down a battle-hardened giant with nothing but a stone in a sling.
In the end, then, it is far more embarrassing for Evolution to cling so desperately to consensus, as it is consistently and reliably defeated by simple arguments, often delivered through the mouths of the simple. In the end, Christians win the origins debate not by being in the majority, but simply because we are standing on the right foundation.
Of course, in the end, the goal is far more lofty than simply winning the argument. The ultimate victory is to be won over that which causes the argument in the first place. It is sin that causes our species to deny our Creator, and so it is sin that must be defeated. This was done not on a debate stage, but on a cross, where the Creator Himself hung and died, receiving in Himself the full wrath of God. Although Jesus knew no sin, scripture tells us He "became sin" for us, that we may become the righteousness of God in Him. Therefore, even blasphemous ideas like Evolution can be fully forgiven, merely by confessing Jesus as Lord, and believing God raised Him from the dead. My advice to Evolutionists, therefore, is to stop arguing yourselves into Hell, swallow your pride, and turn to your Creator in repentance.