Humankind has always been inquisitive, needing to understand why things behave in a certain way, and trying to link observation with prediction. For example, since prehistoric times we have observed the heavens and tried to make sense of the seasonal changes in the position of the sun, moon and stars. In about 4000 BC, the Mesopotamians tried to explain their observations by suggesting that the Earth was at the center of the Universe, and that the other heavenly bodies moved around it. Humans have always been interested in the nature and origins of this Universe.
But they weren't only interested in astronomy. The extraction of iron, which led to the Iron Age, is a chemical process which early metallurgists developed without understanding any of the science involved. Nevertheless, they were still able to optimize the extraction by trial and error. Before this, copper and tin were extracted (which led to the Bronze Age) and later, zinc. Exactly how each of these processes was discovered is lost in the mists of time, but it is likely that they were developed using observation and experiment in a similar way to that used by today's scientists.
Early humankind also observed that certain plants could be used to treat sickness and disease, and herbal medicines were developed, some of which are still used by modern pharmaceutical companies to provide leads for new synthetic drugs.
The first people to try and develop the theory behind their observations were the Greeks: people such as Pythagoras, who concentrated on a mathematical view of the world. Similarly, Aristotle and Plato developed logical methods for examining the world around them. It was the Greeks who first theorized that matter was made up of atoms, which are particles that could not be broken down further (not including sub-atomic particles).
But it wasn't only the Greeks who moved science on. Science was also being developed in India, China, the Middle East and South America. Despite having their own cultural view of the world, they each independently developed materials such as gunpowder, soap and paper. However, it wasn't until the 13th century that much of this scientific work was brought together in European universities, and that it started to look more like science as we know it today. Progress was relatively slow at first. For example, it took until the 16th century for Copernicus to revolutionize the way that we look at the Universe, and for Harvey to put forward his ideas on how blood circulated round the human body. This slow progress was sometimes the result of religious dogma, but it was also a product of troubled times!
It was in the 17th century that modern science apppeared, and the world began to be examined more closely, using instruments such as the telescope, microscope, clock and barometer. It was also at this time that scientific laws started to be put forward for such phenomena as gravity and the way that the volume, pressure and temperature of a gas are related. In the 18th century much of basic biology and chemistry was developed as part of the Age of Enlightenment.
The 19th century saw some of the great names of science: people like the chemist John Dalton, who developed the atomic theory of matter, Michael Faraday and James Maxwell who both put forward theories concerning electricity and magnetism, and Charles Darwin, who proposed the controversial theory of evolution (I do not believe that evolution exists. Yes, our genes mutate, but not to an extent that a genus can turn into another genus, even after a long time. For example, there was an experiment where fruit flies have been put under large amounts of radiation to speed up the mutation of their genes. The end result was that they were still fruit flies. Even if they had extra limbs or other defining traits, they are still fruit flies. We can debate about this in the comments section). Each of these developments forced scientists radically to re-examine their views of the way in which the world worked.
The last century brought discoveries such as relativity and quantum mechanics, which, again, required scientists to look at things in a completely different way.
Science has truly revolutionized the world.
TL;DR?
Science changed the way we see the world. It also helped us not die.