Let see at one point in time doctors said smoking was safe, another time cocaine was put into food, ddt was used heavily as the safe pesticide, then have Thalidomide and all the birth defects it caused.
Smoking was considered safe on the grounds that it had been used for centuries (both tobacco and cannabis), and there was a lot of money behind it.
Plus the fact that for the most part, it wasn't readily available to every person, so it wasn't widespread, meaning cases of cancer and lung-disease were uncommon.
On top of that, it wasn't until the increase in average lifespan in that last hundred years that cancers (which are typically an old-age illness) were encountered on mass.
Plus, smoking was supported as traditional and good for an upstanding member of a community.
Cocaine was used during the period of the Great Binge, when god knows how many different drugs were used.
It was the beginning of Chemistry, and wonderful things were being produced. They had unbelievable effects on people, which everyone wanted.
Cocaine was used because it was believed to be a great anaesthetic, and like many drugs and new discoveries that came in the Age of Enlightenment, it was essentially a panacea.
This is the same time when people believed that Radium and Electriticty applied to anything would cure or enhance everything.
Yeah, we know that a lot of these things are bad now, but this is before they were even used on a large enough scale or for long enough to even realise there were risks, and before science had even grown to be able to examine these.
DDT was similarly a wonder-drug for acting as an insecticide, and it's no surprise that people took to it so much without waiting to see what effects it would have on ecology.
Even the likes of Charles Darwin had no concept of conservationism, and these discoverers unwittingly, but happily, caused endangerment and extinction of numerous species or animal, plant and more.
DDT happened to be just as bad for ecology, but no one expected it because such a thing had never happened before.
Thalidomide was an accident, caused purely by a lack of knowledge in synthesising man-made drugs, and the dangers of chemical chirality.
Thalidomide worked absolutely loving perfectly at it's intended job, and it's still used today.
But the scientists producing it at the time had no idea that when making it they made an optical isomer which caused the damage to unborn children that it did. How could they have known that it would produce an isomer of itself that worked differently, or that it would do such a thing to children. It was just a seriously unfortunate chance that it was used to treat morning sickness.
The point isn't that these mistakes were made and will happen again.
It's that these mistakes were made because we knew no better. We didn't have clinical trials and studies, and we didn't have the scientific knowledge to test these materials.
Science hadn't existed in this form yet. We had no experience to go on, so we threw ourselves straight in, with consquences both bad and good.
We have learnt so much from these mistakes, and so little escapes the prying eyes of scientists, sceptics and the media these days.
We work hard not to make these same mistakes.
Come on Harm, I know for a fact that you're good with history. You know full well that "those who cannot learn from history are doomed to repeat it".
We don't study the history of these things so we can make the exact same mistakes.