A few thoughts from a different set of eyes for your consideration.
"To be a Christian" would need some sort of mutually agreeable definition. To "believe in Christ" is quite vague. I'd think that Jesus said a lot about who it is who loves Him, and it's the one who does according to His teaching, as Jesus Himself did according to the teaching of JHWH, The I Am. So Jesus didn't come into a separate story: He is integral with what the whole of the the Bible is about. Jesus referenced the Genesis account of the creation of mankind and the story of Jonah without critical commentary, implying that we can accept what was said. We can live by every word out of the mouth of God, so I would personally lean on believing what was written in both old and new testaments for the message it conveys. An additional thing that "Christians" believe in is the atonement by Jesus's sacrifice of His flesh and His bodily resurrection to pay for the sins of anyone who repents and turns to Him. All the behaviors describing how Christians should live in the new testament are fully supported in the Ten Commandments and the law given in the old testament.
Because of that I often recommend reading the whole of the Bible, comparing the history with the prophecies to get an idea of how the middle fits in with the beginning and the end of the Book. Religion is a totally different thing: apart from relationship it is empty and useless, so I don't have much use for a term of being a "Christian" as someone who warms a pew, observes rituals, or goes through the motions without interest in what Jesus said. I've been amazed at how a deeper study of the parts of the Bible most Christians never see makes so much sense and shows how life is supposed to work. I realize I really can live by His words to make sense out of life more effectively than science alone. Science is limited by our view of the facts. It's good, but it's limited. We should keep at a logical study of what is around us but we shouldn't stop short with strange conclusions such as the theory of evolution. The facts exist that many life-forms have similarities of patterns; but to be bluntly honest, we weren't there to know for sure that our theories, our time dating analyses, or anything else on which evolution depends, is really reflective of what actually happened. I'm not anti-science at all, but I do think it's a bit arrogant to take a stand based on the limited understanding that we've been able to theorize about. Also the theory of evolution is useless in encouraging us to be all that we are called to be. Wouldn't a Christian agree with the Bible that people were made in the image of the Almighty and called to voluntarily behave in kindly oversight to the rest of creation and in fairness, justice, and caring to others as the Ten Commandments and the Law spells out and that to do otherwise makes communities unsafe? In my view it would probably behoove us to seek the One Who put such a wonderful curiosity in us when we were created. I encourage everyone to seek this Creator Who gave you this great gift of life, take time to find out what He's already told us (it's in the Bible) and see how that impacts your thinking. I think at that point it will clearly show the answer to your question.