Nice to have a (slightly) different voice in here. I wonder if any Sikhs, Hindus and others would care to join?
God's signs in the universe and within ourselves were easier to see 7,000 years (Judaism), 2,000 years (Christianity) and 1,400 years (Islam) ago. Natural cosmic and terrestrial events were not understood. Disease was not understood. Nobody had a clue about psychology, people didn't even know that thoughts originate in the brain. The mechanism of human reproduction wasn't identified until the 17th century.
Having started from entirely reasonable assumptions, given the state of early human knowledge, that things must have been enacted by mysteriously powerful beings, scientific investigation did proceed - but always overlain by assumptions of divinity. Chinese and Assyrian astronomers, for instance, did some incredible work by dint of tracking celestial events over long periods and working out some reliable sequences. This information was used to divine the gods' intentions, which is one way of looking at it but tends to stymie further investigation. Medical traditions such as Ayurveda made useful discoveries but, again, detailed examination of disease and the body was prevented by adherence to the religious building blocks on which they were founded.
The Islamic enlightenment, 8th - 13th centuries, made great strides, building on the classical science of the previous millennium. In every field and nation, gods were the presumed source of all phenomena, and scientists continued to divine godly intent in their findings. This added a confounding element to scientific discovery and impeded progress - the regular indictments for heresy are proof enough of religions' impositions of faith doctrine over intellect.
In this way, priesthoods managed their people's progress from "Everything is a sign of god" to "Science is a sign of god". And there were still plenty of unexamined mysteries which, like it or not, priesthoods guarded on pain of death. The Greek author of On the Sacred Disease (400BC) includes a tirade against priests insisting that epilepsy is a divine punishment. Human cadaveric dissection was banned worldwide for almost 2,000 years, until the Italian Renaissance.
The European Enlightenment period, 17th century onwards, brought a sincere effort to separate the natural and supernatural. This was what William Blake abhorred: a growing recognition that all things may be explained without recourse to "god's will". Worryingly, this separation seems to be going into retreat. It's happened before - and is always followed by Dark Ages.
Sorry about the length of this post; it's very close to my current pet subject, I can't help it! Anyway, the point is that God's signs come from lack of knowledge: a point well recognised by spiritual authorities, who continue to obstruct secular knowledge as far as they are able.