• Question: Where do you think our population would be without discoveries such as penicillin?

    Asked by hannaalmetrami to Chris, Dave, David, Fiona, Jack on 20 Jun 2013.
    • Photo: Jack Miller

      Jack Miller answered on 20 Jun 2013:


      Hi Hannaalmetrami,

      This is a great question, and one that’s quite hard to answer. The best thing to do (I think) is to look at the growth of the world’s population before about 1900, and then try to estimate based on that. Of course, even today we’re not certain exactly how many people there are — we’re even less sure how many there were 150 years ago!

      Let’s have a look at this graph of population over time: http://en.wikipedia.org/wiki/File:World_population_growth_(lin-log_scale).png. You’ll notice two things about it: one, the ‘y-axis’ is a bit unusual, and two, population really has increased a lot recently. This graph is plotted on what’s called a ‘lin-log’ scale, where population is shown in powers of ten rather than just a linear scale. There’s a period between ~-4000 BC to ~1000 AD where it looks like a straight line. A straight line on a log-graph actually corresponds to exponential growth on a linear graph, and if we can work out the gradient of that line, we can get an estimate for the world’s population without the development of medicine (and the industrial revolution).

      As the figure I linked to lists its data, I’ve just done this accurately, for the period 1000-1800, and developed an estimate for the population of the present day without medicine of around 930 million people, rather than the ~7000 million people alive today.

      That’s a big difference!

      — Jack

    • Photo: David Freeborn

      David Freeborn answered on 20 Jun 2013:


      Hi hannaalmetrami,

      This is a really interesting question. You can take a look directly at (estimates) how many lives we think different things have saved here:
      http://www.scienceheroes.com/index.php?option=com_content&view=article&id=258&Itemid=27

      As you see, the biggest advances (saving billions of lives) have been advances in agriculture (saving several billion lives), followed by advances in public health like chlorinating water, and the development of vaccines. They estimate that Penicillin itself has saved 82 million lives in the 60 years since its discovery- not as many as some of these other inventions, but still a very big number. To put it in perspective, that’s about the population of Germany.

      Saving lives is a complicated business though. We might cure people of one disease, only to see them die of another a few years later. For this reason, it’s very difficult to guess how different the world’s population would be. If we ignore that, and take into account each of these people may have had children, I would guess that the world’s population might be a couple of hundred million lower if we didn’t have penicillin, perhaps 6.8 billion instead of 7 billion.

      Vaccination against infectious diseases is even more important- especially as these are most likely to affect children before they’ve had any children of their own. Looking at the figures, and considering how long different vaccines have been around, my best guess is the world’s population would be half the present figure, about 3 billion, without vaccines.
      These are only very, very rough estimates though!

      Changes to agriculture and industrialisation have been even more important, though. Some of the most important people in history have been plant scientists like Norman Borlaug, who helped to end famine in countries like India and Mexico who helped to start the “Green Revolution” by developing a new high-yield, disease-resistant strain of wheat.

    • Photo: Dave Farmer

      Dave Farmer answered on 21 Jun 2013:


      If you look at how the average life expectancy of the world has increased over the last hundred years (https://en.wikipedia.org/wiki/Life_expectancy) then you get some idea of how our medical advances have affected our population.

      Safe to say without inventions like penicillin you’d have to be a lot more used to people dying suddenly, or very young so all in all it’s probably a good thing we’ve got them!

    • Photo: Chris Mansell

      Chris Mansell answered on 21 Jun 2013:


      The 1918 flu pandamic infected about 1/3 of the world’s population. It killed between 3% and 5% of the world’s population. Considerations such as these lead me to think that the human population would be much lower if it weren’t for the human ingenuity that leads to medical discoveries and advancements.

    • Photo: Fiona Coomer

      Fiona Coomer answered on 21 Jun 2013:


      Undoubtedly the discovery of penicillin has saved millions lives worldwide, which is pretty phenomenal. I think that the most exciting thing about penicillin was the way it was discovered – it wasn’t targeted research, but something that Alexander Fleming came across, and realised the value of. This shows us that although targeted research has real value, so does so called blue sky research, and that we all need to have an open mind and look for the potential in even unexpected results.

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