When you think about it, there are probably fewer than you might expect. Obviously, the unknown inventor of the wheel would be one, and we might count people such as Johannes Gutenberg (the printing press), Alexander Graham Bell (the telephone) and James Watt (the steam engine) among those whose inventions basically changed the way society operates.
This year marks the 50th anniversary of the approval of a chemical invention which has arguably had an impact similar to those listed above.
The name of the inventor, Carl Djerassi, may not be familiar to you, but his invention, the contraceptive pill, certainly will be. And its discovery is a fascinating story of mimicry on a molecular scale.
Our bodies contain a vast number of molecules which have an extraordinary range of complexities. One such molecule, of quite modest size and found only in women, is progesterone, the structure of which is shown above.
Progesterone belongs to the family of molecules called steroids, all of which have the same skeleton consisting of one 5-membered and three 6-membered rings of carbon atoms. It is an important molecule because it suppresses ovulation - one could in fact say that it is a natural contraceptive.
However, progesterone cannot be taken orally to perform this function as it is not well absorbed from the gut and can be degraded in the digestive system. It is therefore most effective when injected - never the most pleasant mode of delivery.
In the days before the contraceptive pill, natural progesterone was also extremely scarce; a 1938 paper reported that extraction of 1800kg (1.8 tonnes) of ox adrenal glands yielded a mere 10mg of progesterone - not exactly the stuff of economic viability.
And this is where Prof Djerassi came in. He realised that in order to make an effective oral contraceptive, he needed a synthetic molecule that physically resembled progesterone, but which had none of its drawbacks.
Starting from naturally occurring steroid molecules, in 1951 he prepared and patented a molecule called norethindrone, the structure of which can be seen above.
The structural similarity of progesterone and norethindrone is obvious, and in hindsight, it's probably not surprising that they behave similarly. In fact, norethindrone was found to be even more effective as a contraceptive than progesterone, with the added advantage that it could be taken orally.
However, it wasn't until June 23, 1960 that the "pill", as it became known, was approved for general use as a contraceptive. And, funnily enough, it wasn't Prof Djerassi's molecule that was used in the original pill (which was called Enovid), but a very closely related one, patented by another company. However, by the middle of the '60s, norethindrone had the dominant share of the market.
Many of you reading this will realise just how the pill changed society. And it seems strange to me that its inventor, now in his mid-80s, has not received the Nobel Prize for what was probably the most far-reaching chemical invention of the 20th century. Perhaps the Nobel committee might have a change of heart come October.
• Dr Blackman is an associate professor in the chemistry department at the University of Otago.
