The core hypothesis of the theory, Evolution, is descent with modification from a common ancestor.(1)
Moving back in time, generation to generation, the theory leads us to the last universal common ancestor; LUCA is the most recent common ancestor of all current life on Earth.(2)
The Theory of Evolution stands falsified because there isn't a single workable hypothesis(3)(4)(5) to show that it's possible for the 'last universal common ancestor' to exist.
There used to be a ton of hypotheses, but they've all been falsified for decades.(3)
Currently, scientist don't have a clue of where to find a clue; "...there's not even a consensus on how to approach the problem..."(4)
Rules of the game: A scientific theory is an explanation of some aspect of the natural world that can, in accordance with the scientific method, be repeatedly tested, using a predefined protocol of observations and experiments. It will have made predictions of phenomena that previous theories could not explain or could not predict accurately, and it will have resisted attempts at falsification.(8)
It's pseudoscientific, system of theories or assertions about the natural world that claim or appear to be scientific but that, in fact, are not, and ignorant, lacking knowledge, information, or awareness about something in particular, to present the Theory of Evolution as a 'scientific' theory, because it fails the definition.
The Theory of Evolution doesn't fulfill the necessary criteria because all hypotheses for LUCA have been falsified; "ability to be supported or refuted through observation and experimentation."
It does qualify as a working hypothesis, provisionally accepted as a basis for further research in the hope that a tenable theory will be produced, but not a 'scientific' theory.
Some try to remove the required existence of the "last universal common ancestor" from the theory, "descent with modification from a common ancestor", to make the theory unfalsifiable. But, buy definition, that turns the theory into pseudoscience. Karl Popper; what is unfalsifiable (testable) is classified as unscientific, and the practice of declaring an unfalsifiable theory to be scientifically true is pseudoscience(6). (lack of openness to evaluation by other experts)(7)
Steve Benner: We have failed in any continuous way to provide a recipe that gets from the simple molecules that we know were present on early Earth to RNA.(5)
(1) berkeley.edu, 'Descent with modification', http://evolution.berkeley.edu/evolibrary/article/evo_15
(2) Wikipedi, 'Last universal common ancestor'
(3) NASA SP-530 An Exobiological Strategy for Mars Exploration Prepared by Exobiology Program Office, NASA HQ April 1995 ; NASA- EXOBIOLOGY - A Program of NASA's Solar System Exploration Division - Written by NASA Exobiology Program Manager: Michael A. Meyer; "A decade and a half ago (written 1995), the study of prebiotic chemistry was dominated by a single paradigm consisting of the following sequential steps: (1) synthesis of organic compounds from reduced gases in the atmosphere and transfer of these compounds to the ocean producing (2) a 'prebiotic soup' of a concentration high enough to lead to (3) chemical evolution of biopolymers corresponding to early versions of DNA and proteins which organize themselves into (4) a heterotrophic organism which could obtain energy from compounds in the soup and lead eventually through Darwinian evolution to (5) autotrophs capable of feeding themselves through photosynthesis. Research in recent years has challenged all aspects of this paradigm as well as the assumptions on which it is based."
(4) www.astrobio.net, Astro Biology Magazine, The Origin of Life Challenge: Searching for How Life Began, by Nola Taylor Redd, Jun 20 2012; 'The scientific study of the origin of life is still early enough that there's not even a consensus on how to approach the problem...'
(5) huffingtonpost, Suzan Mazur, 'Steve Benner: Origins Soufflé, Texas-Style'; 'Steve Benner: We have failed in any continuous way to provide a recipe that gets from the simple molecules that we know were present on early Earth to RNA.'
(6) Wikipedia, 'Falsifiability'
(7) Wikipesia, Pseudoscience
(8) Wikipedia, Scientific theory