In logic, this is known as the fallacy of Appeal to Numbers.
The factuality of a statement cannot be demonstrated simply by the number of people who subscribe to it. If that were so, the true religion on the Earth would be Hinduism, the correct form of government Communism, and the best language on the planet Chinese.
You're right, it's not that simple. You must observe the qualifications of the population you survey to determine who believes what, and what qualifies them to know the facts.
The fact is that virtually 100% of the professional scientists that study ancient species accept that Evolution is a fact. They discuss and dispute various details of Evolution theory, but they have no doubt as to the fact that Evolution occured.
"Fred Hoyle"
The same Fred Hoyle that thought that life on earth originated with space-born bacteria and viruses?
I'm quite aware of this fallacy, however, you have somewhat misunderstood it. Appeal to numbers is in fact valid when those people are experts on the given subject. In the same way it's not Appeal to Authority fallacy if you say a physicist agrees with you when arguing about physics.