Is evolutionary science biased?

Science is supposed to be our observations that give an answer to the world around us. Since Darwin there have been many scientists who have sought to explain natural history through theories that exclude God, or limit His ability to create. If this is the case than psychologically couldn't we assume that their findings are biased? They often will point to the fact that since there are fossils that have been found with striking similarities, there must have been an evolutionary leap from one species to another. How can we justify this position since we can only observe the fossils, rather than first hand observation of the process? On top of this some Christians have adopted a position of theistic evolution. Again I would as how this is not contrary to this Biblical account? Why is this not considered a concession to the scientific community in an effort to appear more legitimate? If you start a study with the presupposition that there can be no supernatural causes you have automatically dismissed half of the argument. If you explanation for this is because supernatural theories are to difficult to believe you have missed the point of the word supernatural. Supernatural simply put means the cause of some event cannot be explained by a natural cause and thus since we cannot observe this would mean we might have a difficult time understanding it. Thus it might appear to be illogical, but when you observe it from a philosophical view it begins to make a bit more sense.