[lutusp]

>> Either DNA is the source of heredity or it isn't.

> As always, it's more complicated than that.

No, it isn't. All one need do is demonstrate that DNA is not the source of heredity, i.e. falsify the claim. That's how science works. Epigenetics doesn't disprove the role of DNA, it augments it, in the same way that conduction and convection stand alongside radiation as mechanisms for the transport of heat energy.

> But biological proofs are weaker than physics proofs.

Not the scientific ones.

> And speaking about physics, light was a wave and this had been tested and verified multiple times. Until it wasn't.

That's misleading. There was a debate about whether light was a wave or a particle -- evidence supported both views. Eventually a new theory combined and fully validated all the prior observations by showing that light is both a wave and a particle. That theory is the best-supported and most powerful theory devised to date, and is the crowning achievement of 20th century physics. And it will eventually be replaced by an even better theory, one that explains more, with fewer preconceptions and arbitrary axioms.

That is science at its best, science driven by evidence, evidence that shapes theories, theories that must survive testing or be discarded.

[notahacker]

Epigenetics might augment theories of heredity, but the causal role of incompletely penetrant alleles in expressing a particular phenotype is falsified in the absence of any auxiliary hypotheses to explain their level of penetrance (especially if that phenotype may also be expressed without that allele). If naive falsificationism is the distinguishing characteristic of science, then an awful lot of biology, including some very useful statistical associations between allele X and phenotype Y (supported by statistical hypothesis testing that looks remarkably like that in social sciences...) gets discarded. If you had to throw away every theory whose counterexamples couldn't be adequately explained there wouldn't be much biology left. The AIDs denialists would have the right idea. Koch's postulates would, if anything, be too low a standard. Popper even had his doubts about the scientific validity of natural selection...

[raverbashing]

> All one need do is demonstrate that DNA is not the source of heredity

Oh, I'm not saying DNA isn't the source of heredity. I'm saying that there are other smaller factors. (you can google them). Heredity in the strict sense, yes, it's DNA, in the broader sense, well, you can have two different fenotypes with the same genotype.

> There was a debate about whether light was a wave or a particle -- evidence supported both views.

Not before the 20th century, diffraction of light (amongst others) firmly put it as a wave. http://en.wikipedia.org/wiki/Light#Wave_theory

And the wave theory of light is still widely used (when it's applicable of course).

[lutusp]

>> There was a debate about whether light was a wave or a particle -- evidence supported both views.

> Not before the 20th century,

Yes before the 20th century. I refer you to the debate between Newton and Huygens as well as Hooke, his contemporaries with respect to these ideas.

http://www.studyphysics.ca/newnotes/20/unit04_light/chp1719_...

Such debates persisted from then until the shaping of quantum theory.