The last part did it for me, I just had to explain to them how wrong that last statement was, so I invited them inside for a little chat.
You see you can't believe in science the way you believe in anything else, science is not about belief, revelation, authority or tradition it's about evidence and ONLY evidence! As my example I'll use evolution since it is the flavor of the day in the general public. So basically Darwin came up with the scientific theory of evolution. He then published his evidence and his work was reviewed by other scientists who pretty much tried to disprove his scientific theory because in doing so was the only way to "prove" it.
After the scientific theory of evolution went through numerous reviews by other scientists who could not disprove his evidence it became valid. This is how all scientific theory's function.
The greatest thing about a valid scientific theory? It is reviewed every time scientists find new discoveries or new methods of study that are found to offer more accuracy that could apply to a theory. Take DNA for example, when it was discovered scientists reviewed over and over how this applied OR not to the scientific theory of evolution and once again it actually applied, only re-enforcing the validity of evolution and so like hundreds of previous new discoveries long after Darwin's death his scientific theory keeps standing up.
Even the concept of the earth going around the sun gets reviewed whenever some new discovery in astronomy is made that has a relation to how the earth rotates in space.
When a theory as old as Darwin's evolution has been through constant reviews over the past 180 years and every time it comes out as being even MORE valid by the scientific community it makes no sense to say "I don't agree with that" unless you can scientifically disprove the theory, which not a single human has been able to do, anyone who claims to have done so and has had his work peer reviewed has been flatly rejected, not because the scientific community believes in evolution, it's simply because the evidence shows this person's work is wrong.
THAT! Is how science works, a constant study and re-evaluation of a scientific theory.
Now these two young ladies said something along the lines "but it is a theory". I had to explain that a scientific theory and theory are totally different, they should invent another word for scientific theory because it just confuses people.
The only similarity between a scientific theory and a theory is ONE thing... the word: Theory
A simple theory is pretty much just an opinion or a belief, I can say I have a theory that unicorns once existed but were hunted to extinction because humans wanted the ivory, it's almost believable because we see it today with so many species close to extinction because they are hunted for their ivory.
Now if I were to make a statement that this is a scientific theory then I would need evidence, publish it and this documentation would have to be sent to scientists, probably archeologists in this case and they would review my work and of course in no time flat would disprove my scientific theory and it would simply fall back to being an opinion... or a belief.
This is what is so scary about religious people who are fervent believers in ONE book or doctrine and will not believe common scientific sense whenever it goes against their beliefs which is funny because they have no problems using science to try and spread their message (computers, tv, radio, papers, cars, phones, etc...). They try and remove the parts of science they don't agree with and if they can impose their views on others they do so... imposing values on others is one of the main causes of violence as people rebel when freedom is taken away.
If they don't believe in hard peer reviewed science like evolution, they simply cannot believe in ANY science, because ALL science came from a scientific theory. Which means they should throw out their religious book(s) because they only exist due to science (the invention of paper).... heck even all their synthetic clothes! ;-) .