Do you deny that gravity exists?
This is a very misleading analogy.
In common usage, gravity is interchangeable as both hypothesis and observation. There's no denying that variation exists within species, just as there's no denying that if I hold my hand out and drop a penny, it will accelerate downward. Both observations are true and self evident.
The hypothesis of common descent, like the many hypotheses of gravity, have yet to be demonstrated. So in accordance with these terms, I would say yes, to your question.
Unless of course, you can demonstrate the gravity hypothesis of your choosing [and in so doing, falsify all the remaining hypotheses] and how it is compatible with relativity, and in particular, the equivalence principle.
So, without further adieu, the stage is yours.
Put up, or shut up...since I'm tired of seeing this inappropriate analogy constantly being bandied about...
The hypothesis of common descent, like the many hypotheses of gravity, have yet to be demonstrated.
We are not talking about common usage. We are talking about how terms are used in science. There is often a substantial difference between the two.
The fact that a penny drops is a...fact. This is matched on the evolution side by the observation that genetic change occurs between one generation and the next. Both are examples of "fact" or "data."
The theory part comes in as an explanation for the many facts (or many thousands of facts). This is done according to the following definitions:
Theory: a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena; "theories can incorporate facts and laws and tested hypotheses." Addendum: "Theories do not grow up to be laws. Theories explain laws." (Courtesy of VadeRetro.)From our past conversations I gather that you do not accept the theory of evolution for religious reasons.Theory: A scientifically testable general principle or body of principles offered to explain observed phenomena. In scientific usage, a theory is distinct from a hypothesis (or conjecture) that is proposed to explain previously observed phenomena. For a hypothesis to rise to the level of theory, it must predict the existence of new phenomena that are subsequently observed. A theory can be overturned if new phenomena are observed that directly contradict the theory. [Source]
When a scientific theory has a long history of being supported by verifiable evidence, it is appropriate to speak about "acceptance" of (not "belief" in) the theory; or we can say that we have "confidence" (not "faith") in the theory. It is the dependence on verifiable data and the capability of testing that distinguish scientific theories from matters of faith.
That's fine. But your religious belief does not constitute scientific data, nor does it negate scientific theory.
The hypothesis of common descent, like ...
You're forgetting some other crucial observations that Darwin's theory explains.
First is the Law of Faunal Succession, the fact that a particular fossil organism is restricted to certain strata, and the more recent fossils more closely resemble living animals and plants. This is evidence of descent within lineages, if not complete common descent.
Another data set that Darwin used was the geographic distribution of species and fossils. Wegener cited some of this in his continental drift hypothesis, now part of plate tectonic theory.
Yet another thing Darwin considered was the experience of animal and plant breeders.