In our timeline Alexander Fleming accidentally discovered penicillin by accidentally leaving petri dishs out over a long period of time.

If a person from an earlier time, e.g. ancient Rome, woke up and knew of penicillin's existence and significance, could they discover it themselves? For example, would setting out 100 batches of dough work?

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    $\begingroup$ Yes, if you know that penecilin is in mold, gather a 100 doughs, and give each a different mold. Then use the one that works and make another try with more "distilled/dried" versions. It would be even eaier in Rome as Penicilium (the fungus) like to grow on fruits. There is even one called "Penicilium citrus" because it grow on citruses. $\endgroup$ Commented Nov 20, 2019 at 10:31
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    $\begingroup$ @SZCZERZOKŁY not all members of the Penicilium genus produce useful antibiotics, though some are handy for making cheese. $\endgroup$ Commented Nov 20, 2019 at 11:49
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    $\begingroup$ Hmmm. Does this fellow in ancient Rome also wake up with a complete understanding of germ theory and microscopes and sterilization...and all the underlying biology, chemistry, and physics required? Which implies an understanding of the scientific method and basic statistics? Or is this a one-shot divine revelation, and they are going to pray to Juno for lots of magic mold without an understanding of what it does or why? $\endgroup$
    – user535733
    Commented Nov 20, 2019 at 17:31
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    $\begingroup$ For this, I was thinking that they understand the minimum required. Enough for an adequate "explain like I'm five," answer. As far as equipment, I'd like to keep it to things readily available at the time. If I have to "hand wave," one key component (e.x. a convex shaped gem contributed by the temple of Minerva), that would be fine. $\endgroup$
    – GentlemanS
    Commented Nov 21, 2019 at 4:52

4 Answers 4


Yes they could, in fact some ancient civilizations are believed to have experimented with the use of moulds to help cure wounds. The problem being they were not aware of what was going on so their methods might be best described as haphazard. Someone who knew (by some means) of the existence of and presumably the effect of penicillin might well be able to improve on what happened historicaly if they followed an extensive program of trial an error.

The key question is how much does this person know? Do they know the source of the mould and where to find it? If not then they might search for a very long time in the wrong place. But if they did then there is every likelihood that penicillin would have been discovered and used.

Note however that this use would have been far removed from a modern antibiotic as it would have been extremely difficult to purify and concentrate the active substance. Further example of ancient use.

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    $\begingroup$ It was so difficult to purify penicillin from the mold that in the early days, they collected the urine of people treated with penicillin to recover the penicillin and use it again. $\endgroup$
    – Willk
    Commented Nov 20, 2019 at 13:41
  • $\begingroup$ I doubt the Romans would have tried purification, probably just concentration. $\endgroup$
    – Slarty
    Commented Nov 20, 2019 at 13:53
  • $\begingroup$ jamming live mold in a wound and using antibiotics are very different things. $\endgroup$
    – John
    Commented Nov 20, 2019 at 14:21
  • $\begingroup$ It was done. It would not have been nearly as effective as modern antibiotics but thats beside the point sciencedirect.com/science/article/abs/pii/S0269915X89800102 $\endgroup$
    – Slarty
    Commented Nov 20, 2019 at 16:53
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    $\begingroup$ Because something is applied to the skin does not prevent it from being an antibiotic. There are topical antibiotic creams and ointments which are not intended for internal use. And because an antibiotic is not present in a concentrated or pure form does not stop it from being an antibiotic and killing bacteria. $\endgroup$
    – Slarty
    Commented Nov 20, 2019 at 22:19

It can't be done. To understand why you have to know the actual history. Fleming accidentally discovered a contaminating mould killed off his bacterial cultures in Petri dishes.

Did this give the world Penicillin? No, not at all. No-one knew how to produce or culture on any scale.

Come the Second World war and it became imperative to keep wounded soldiers alive. A massive research effort was instigated by Howard Florey and Ernst Chain to find out how to extract and mass manufacture Penicillin. They succeeded and the world now had an extremely effective antibiotic.

Alexander Fleming was given the glory as a discoverer of Penicillin, but he wasn't the first, and a share in the Nobel prize. The real work was done by Florey and Chain.

Earlier civilizations lacked two things to discover and produce Penicillin. One, a knowledge and understanding of bacteria. two, the necessary industrial capacity to manufacture the antibiotic. Basically discovering an antibiotic is only the merest beginning. A brilliant person in an ancient Roman society wouldn't have a chance of doing so. Sorry, about that.

EDIT added 21/11/2019:

The history of Penicillin is complex, long and full of turnings in many different directions. The short story is not find mouldy bread, now make penicillin.

First up, what our forebears knew.

Many ancient cultures, including those in Egypt, Greece, and India, independently discovered the useful properties of fungi and plants in treating infection.[7] These treatments often worked because many organisms, including many species of mold, naturally produce antibiotic substances. However, ancient practitioners could not precisely identify or isolate the active components in these organisms.

Please note: identifying and isolating the active components is the key idea.

The history of penicillin follows a number of observations and discoveries of apparent evidence of antibiotic activity in molds before the modern isolation of the chemical penicillin in 1928. There are anecdotes about ancient societies using molds to treat infections, and in the following centuries many people observed the inhibition of bacterial growth by various molds.1 However, it is unknown if the species involved were Penicillium species or if the antimicrobial substances produced were penicillin.

The early scientific evidence for antibiosis and antisepsis starts with this work.

The modern history of penicillin research begins in earnest in the 1870s, in the United Kingdom. Sir John Scott Burdon-Sanderson, who started out at St. Mary's Hospital (1852–1858) and later worked there as a lecturer (1854–1862), observed that culture fluid covered with mold would produce no bacterial growth. Burdon-Sanderson's discovery prompted Joseph Lister, an English surgeon and the father of modern antisepsis, to discover in 1871 that urine samples contaminated with mold also did not permit the growth of bacteria. Lister also described the antibacterial action on human tissue of a species of mold he called Penicillium glaucum.[10] A nurse at King's College Hospital whose wounds did not respond to any traditional antiseptic was then given another substance that cured her, and Lister's registrar informed her that it was called Penicillium. In 1874, the Welsh physician William Roberts, who later coined the term "enzyme", observed that bacterial contamination is generally absent in laboratory cultures of Penicillium glaucum. John Tyndall followed up on Burdon-Sanderson's work and demonstrated to the Royal Society in 1875 the antibacterial action of the Penicillium fungus.[11] By this time, Bacillus anthracis had been shown to cause anthrax, the first demonstration that a specific bacterium caused a specific disease.

I refer interested persons to this article for more information about early precursor research.

This eventually led to Sir Alexander Fleming's accidental discovery and subsequent research.

In 1928, Scottish biologist Alexander Fleming noticed a halo of inhibition of bacterial growth around a contaminant blue-green mold on a Staphylococcus plate culture. He concluded that the mold was releasing a substance that was inhibiting bacterial growth. He grew a pure culture of the mold and subsequently concentrated what he later named "penicillin". He soon began treating infections in patients with penicillin. One of the first was his assistant Stuart Braddock. Fleming applied penicillin to his Sinus infection. Within three hours, most of the bacteria in the infected area had disappeared.[21] In 1929, he reported his findings in an article for The British Journal of Experimental Pathology.[22] During the next twelve years, Fleming grew and distributed the original mold, which was eventually identified as Penicillium notatum (now known as Penicillium chrysogenum). He was unsuccessful in making a stable form of it for mass production.[23] Although Fleming did some research with penicillin directly on patients and greatly contributed to its medical use, he did not realize its revolutionary potential, due to the impurity of the penicillin he made and the difficulty in mass producing it. Most of his further research with penicillin was focused mostly on the properties of penicillin rather than medical treatment with penicillin.

Please note that Fleming's main problem with his research was in isolating pure enough samples of penicillin. Also, he was investigating its properties, like a good biologist, rather than its medical application.

It was only when the development of techniques for its mass manufacture that the full medical potential of penicillin was realized.

The real problem faced by the OP's person in the past who is endowed with a magical foreknowledge of penicillin is in their ability to isolate sufficiently pure quantities of penicillin. They would also need to be granted magical foreknowledge of microbiology, microbiological laboratory techniques, foreknowledge of the uses and manufacture or production of glassware, and to be magically endowed with the financial and person-power resources to accomplish all this. Knowledge alone of what penicillin is, and what it can do isn't enough.

It took several generations of scientists and research to find useful species of Penicillium and then to develop the techniques for its isolation and purification. It would be wonderful if a, say, Roman who investigating nature, and armed with foreknowledge, could introduce penicillin to the ancient world. The barrier is a legion of practical and technical problems which cannot be whisked away with the notion of oh! that might just work!

To quote Thomas Alva Edison: "Genius is one percent inspiration, and ninety-nine percent perspiration."

The ancient world may have known about applying moulds and poultices to cure wounds, but lacked the technical ability to make penicillin usefully. The amount of perspiration required would fill a large lake.

While I applaud the ingenuity of the OP's concept of penicillin in the ancient world, I cannot believe in it as a practical possibility. YMMV.

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    $\begingroup$ It was possible to produce it on a small scale before the mass poduction problem was solved, though what you end up with is a stockpile that's maybe big enough to treat one person, if youre lucky, and that's after quite a bit of work with a decent bit of biochemical knowhow and reasonable equipment. It'd be simpler and more effective to start off with germ theory, sterilisation, aseptic technique and anaesthetics, but they're just not as cool as antibiotics... $\endgroup$ Commented Nov 20, 2019 at 12:52
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    $\begingroup$ Even if you can't mass produce, having enough to treat just one person could still be extremely valuable if that one person is, say, the emperor. $\endgroup$
    – tylisirn
    Commented Nov 20, 2019 at 19:40
  • $\begingroup$ @StarfishPrime You have to have microscopy first to see that microbes. Before that noxious vapors was the putative cause of most diseases. Remember how hard it was to get medical doctors to wash their hands. Not simpler & more effective. If only it was. $\endgroup$
    – a4android
    Commented Nov 20, 2019 at 23:07
  • $\begingroup$ @tylisirn And you get to the Emperor, how? The problem always getting Penicillin pure enough form to treat someone. Fleming couldn't do that, that's Florey & Chain's great achievement. Romans never had the technical capacity. $\endgroup$
    – a4android
    Commented Nov 20, 2019 at 23:11
  • $\begingroup$ @a4android with sealed glass containers and a careful approach to experimentation, it can be made clear that vapours could not be the sole cause of the cultures. Blooms in the shape of handprints can be reaily made, for example, and cleaner hands will produce quite different results. Semmelweis faced a different set of cultural issues than the propose anachronistic scientist. $\endgroup$ Commented Nov 20, 2019 at 23:11

That certain substances might have an antibiotic effect, though it was not called under that name, was known and could have been known in ancient time.

For example honey has some antibiotic properties, and it was used in the past to hygienize wounds.

Another example is birds using laurel leaves to keep their nests clean, and back in the time my grandmather used laurel leaves to help preserving dried fruits or bread crumbs.

There are also accounts of ancient medical books prescribing what sound like disinfecting routines before surgeries. I think I remember of an old Hebrew book prescribing to lay the sick person on a stone bed only after having washed it by pouring 100 times water on it, and then doing the same with the body of the sick.

All in all the results were empirically known, though there was a lack of general understanding of the underlying phenomena.

Therefore it is possible that someone could have noticed that a certain mold could prevent other spoiling to happen, and then attempt using it on wounds.

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    $\begingroup$ disinfectant and antibiotic are very different things. $\endgroup$
    – John
    Commented Nov 20, 2019 at 14:20

Depending to what extent these ancients cultures develop the ideas of moulds as medicine you would need to clarify their understanding of microbiology. Whilst we’ve been brewing alcohol for a long time it’s only in the last 200 years or so that we’ve come to appreciate that these tiny ingredients are actually alive. Without that comprehensive knowledge arriving at penicillin from a few mouldy melons would take a lot of ‘happy accidents’. Doesn’t mean it’s impossible, you might need to invent a few wild rationalisations for the characters who are making the discoveries (assuming they don’t realise they’re dealing with complex living things).


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