The biggest threat to humanity is humanity itself.

Tough question.

What I think is, most dangerous is when the two are combined. Weaponry is considered technology, so it's science. That combined with religion can be/is devastating.

But if you just separate them, I'd say science is definitely the most dangerous. People nowadays love science, and think of technology like a mommy or daddy, so they don't want to recognize the dangers. But there are incredible dangers. It will probably become more visible in a few years.

If people would just believe what they want, and allow other's to do the same; all would be well.

But Scientist's want to prove their case via so called "scientific fact"....

Christian's want to stake their claim on the Bible, which is a book written by some old guys, than was packaged by the romans to control the jews.  "Faith" is the answer. (I am a Christian but I am not delusional)

So everyone should just believe whatever helps them sleep at night, because no one knows what' what.

Don't want to offend anyone, but it seems to be as though my generation (I'm 29) and onwards has seen a dramatic decrease of religious people. I live in the US, so I'm basing this on my personal observations, but there are fewer and fewer religious people as time goes on.

Also, the people that do go to church may not even believe the stuff the church is teaching them anyways, and may just do it because they want to feel good about themselves. For example, I had my daughter baptized, possibly just to please my grandparents.

Lastly, and I'm sure that I'm not the only person to think about this, but... There are so many different religions with conflicting views. They can't all be right, so what do religious people think of other religions besides their own? Do they think that what they have been taught is correct and everyone else is living a lie? I'd consider myself to be a very open-minded person so it was rather easy for me to figure things out, but it almost has to take some sort of extreme negligence and ignorance to think that way.

I'd say both religion and science are tools constructed by man, one used to contemplate the rules of nature the other (along with art and philosopy) to contemplate the nature of man an society

Both are not inherently dangerous on the contrary they can be used to achieve great things. They can be dangerous if used by ignorant people or if used for selfish and short-sighted reasons.

the more we know the more a threat we become to the people in power, and the people in power uses religion to keep humanity back from progress.

science is to know.

There is nothing wrong with people getting spiritual enlightenment with religion, the problem is how it is interpreted and used. However religion should stay out of the science lab.

then science is also the only reason why this is happening.

Depends on how they’re used. Both have benefits, both have not so great benefits.

the science and the technology is already here to stop or slow down the effects. It is $$$ that is stopping progress.

ISIS uses fanaticism (a product of religion) plus rifles and bombs (products of technology and science) for attacks. Science and relegion can go hand in hand if the people in power uses them as means for oppression.