Darwin proposed a hypothesis. In the last 150 years the mountain of evidence for evolution has become overwhelming. It is no longer a hypothesis its a fact.
“ Evolution is a fact. Beyond reasonable doubt, beyond serious doubt, beyond sane, informed, intelligent doubt, beyond doubt evolution is a fact. - Dawkins in The Greatest Show on Earth
It is only possible to deny the fact that every living thing descended from a common ancestor by avoiding the evidence.
Cofty, I also accept evolution as a fact, but to be pedantic, technically Natural Selection (which readers of your comment might assume you are refering too) has become a scientific theory, not a "fact." I know you probably realize this and I'm responding late to this thread, but I wanted to make sure this is crystal clear to others that may not be as familiar to this topic. To use Dawkin's words in that same book:
“Our present beliefs about many things may be disproved, but we can with complete confidence make a list of certain facts that will never be disproved. Evolution and the heliocentric theory weren’t always among them, but they are now.
Biologists often make a distinction between the fact of evolution (all living things are cousins), and the theory of what drives it (they usually mean natural selection, and they may contrast it with rival theories such as Lamarck’s theory of ‘use and disuse’ and the ‘inheritance of acquired characteristics’). But Darwin himself thought of both as theories in the tentative, hypothetical, conjectural sense. This was because, in those days, the available evidence was less compelling and it was still possible for reputable scientists to dispute both evolution and natural selection. Nowadays it is no longer possible to dispute the fact of evolution itself – it has graduated to become a theorum or obviously supported fact – but it could still (just) be doubted that natural selection is its major driving force.” (Greatest Show on Earth p. 17)
He also mentions:
“Darwin came to publish On the Origin of Species in 1859, he had amassed enough evidence to propel evolution itself, though still not natural selection, a long way towards the status of fact. Indeed, it was this elevation from hypothesis towards fact that occupied Darwin for most of his great book. The elevation has continued until, today, there is no longer a doubt in any serious mind, and scientists speak, at least informally, of the fact of evolution. All reputable biologists go on to agree that natural selection is one of its most important driving forces, although – as some biologists insist more than others – not the only one.” (Greatest Show on Earth p.18)
And Jerry Coyne agrees:
“Because a theory is accepted as “true” only when its assertions and predictions are tested over and over again, and confirmed repeatedly, there is no one moment when a scientific theory suddenly becomes a scientific fact. A theory becomes a fact (or a “truth”) when so much evidence has accumulated in its favor – and there is no decisive evidence against it – that virtually all reasonable people will accept it. All scientific truth is provisional, subject to modification in light of new evidence. There is no alarm bell that goes off to tell scientist that they’ve finally hit on the ultimate, unchangeable truths about nature. As we’ll see, it is possible that despite thousands of observations that support Darwinism, new data might show it to be wrong. I think this is unlikely, but scientists, unlike zealots, can’t afford to become arrogant about what they accept as true.” (Why Evolution is True p. 16)
"Obvious conclusion: we can provisionally assume that natural selection is the cause of all adaptive evolution – though not of every feature of evolution." (Why Evolution is True p. 143)
