by Matthew Cobb
Today’s Google doodle (above) is in honour of Nicolas Steno (1638-1686) – it would be his 374th birthday today (in fact it’s a bit more complicated than that, because he was actually born on 1 January 1638, but under the old Julian calendar…).
The doodle fetes Steno’s principle of superposition, which is the idea that, in any geological strata, the lower layers are older than the upper layers. Furthermore, it shows fossils in the rocks – Steno was the first person to clearly show that fossils were actually the remnants of long-dead animals.
But Steno was not just the father of geology. He was one of the most amazing thinkers who participated in the Scientific Revolution that took place in the 17th century. He also made lasting contributions to anatomy and physiology, and above all to our understanding of where we come from. All in the space of about 12 years.
Between 1662 and 1667, in Amsterdam, Leiden, Paris and Florence:
- He discovered the duct that takes saliva from the parotid gland to the mouth – this is still called ‘Steno’s duct’.
- He made the first scientific dissection of the human brain.
- He showed how muscles work.
That would be enough for anyone. But Steno’s big breakthroughs came after his 1667 book on muscles (Elementorum Myologiae Specimen) had been approved by the Holy Office (the church censor). Just before it went to press, Steno added two brief pieces to his book, both of which had the same origin: the dissection of a shark.
In October 1666, French fishermen landed a gigantic great white shark at the port of Livorno. They weighed it (1200 kg), took out its liver, hacked its head off and then rolled the rest into the sea. The head was then brought to Florence for Steno to dissect in front of the Duke Ferdinand’s court.
Steno noticed that the sharks’ teeth looked remarkably like glossopetrae (tongue-stones) which could be found on exposed rocks in the region, and which were thought to be vipers’ tongues. Like a number of previous thinkers, Steno suggested that glossopetrae looked like sharks’ teeth because that is what they were. His dramatic drawing (in fact of another shark) shows the teeth:
The problem, of course, was how they got into rocks on the top of mountains.
Steno was a good Christian – at this stage he was still a Protestant – and he had a simple answer: the flood. Fish, like sharks, would have been stranded on the top of mountains when the waters receded. He also pointed out that during earthquakes, huge bits of land could move up or down, and that over time, this might also explain how the remains of marine organisms could be found at high altitudes.
Now Steno didn’t have any idea of deep time – if he thought about how old the world was, I assume he would have agreed with something like Bishop Ussher’s view that it was all in the Bible, and so around 6,000 years old. And he was also wily enough to know that his suggestion could be a problem for the Churh, so he used Galileo’s device of claiming that the view he had outlined was merely one possibility amongst many:
‘While I show that my opinion has the semblance of truth, I do not maintain that holders of contrary views are wrong. The same phenomenon can be explained in many ways; indeed Nature in her operations achieves the same end in various ways. Thus it would be imprudent to recognise only one method out of them all as true and condemn all the rest as erroneous.’
In the final part of Elementorum Myologiae Specimen, entitled Historia Dissecti Piscis ex Canum Genere (Study of the dissection of a dogfish) – which is a mere nine pages long – Steno described the dissection of a small female dogfish that gives birth to live young. Most of this is is pretty unexceptional, and then in the final couple of pages, Steno used an a simple analogy and, in a few lines, made a huge break-through in humanity’s understanding of ‘generation’ – where animals come from, and in particular the role of the female ‘testicles’ (what we would now call ovaries).
First he noted that much of the internal anatomy of this shark was very similar to that of an egg-laying ray that he had previously dissected. Then he went on to muse about the nature of ‘generation’ in oviparous and viviparous animals, before coming to this amazing conclusion:
‘having seen that the testicles of viviparous animals contain eggs and having noticed that their uterus opened into the abdomen like an oviduct, I have no doubt that the testicles of women are analogous to the ovary, whatever the manner the eggs themselves, or the matter that they contain, pass from the testicles to the uterus.’
‘The testicles of women are analogous to the ovary’: in other words, women have eggs. This amazing statement – almost a throwaway comment in a brief section on sharks – was the start of our modern understanding of both human reproduction, and on the essential unity of the animal kingdom.
Over the next couple of years, Steno found ovaries in deer, guinea pigs, badgers, wolves, asses and mules, but he never published anything further on the question.
Four years later, two of Steno’s old student friends, Jan Swammerdam and Reinier de Graaf, were slugging it out in public over who had been the first to discover that women have eggs – Swammerdam did some neat dissections, de Graaf did some neater experiments. The Royal Society of London was called in to adjudicate the matter. It took them so long that by the time they issued their verdict, de Graaf was dead, and Swammerdam and Steno had both become obsessed with religion (Swammerdam went all mystic, Steno became a devout Catholic and ended up a bishop; both men abandoned science because of their beliefs). And the Royal Society rightly gave the credit to Steno – the man who discovered that women have eggs.
Five years later, our understanding of what is going on in ‘generation’ became even more complex when Antoni Leeuwenhoek, an uneducated Dutch draper who had known de Graaf, discovered spermatozoa. But for reasons that will have to be dealt with at another time, it would not be until 1827 until von Baer actually saw a human egg, and not until the 1850s that it was realised that egg and sperm were complementary halves of the future organism, and that both were necessary for life to arise.
Google’s doodle rightly commemorates Steno’s principle of superposition. I would like to have seen some eggs floating around in the doodle, too. Without Steno’s brilliant insight, we would not have discovered what we know in the same way, or at the same pace. Maybe they can include a shark and an egg next year.
If you want to know more about Steno or about the discovery of the human egg, the best place to start is either of these two books:
Matthew Cobb (2007) The Egg & Sperm Race (published in the US as Generation)
Alan Cutler (2003) The Seashell and the Mountaintop
Thanks, Matthew, fascinating.
Ditto – excellent post!
I just (very belatedly) finished reading your book “Generation” a few days ago–absolutely fascinating and a fun read. My husband also greatly enjoyed it.I highly recommend it to anyone interested in the history of science and anyone harboring eggs or sperm in their bodies.
Leslie
It is fascinating how he went from layng the foundations of a new science, and chipping away at the old faulty view of the world to reject all that in favour of becoming religious.
Well, back in those days, contradicting the church too much could get you an unexpected visit from someone who wasn’t nearly as funny as John Cleese.
*NOBODY* expects the English Cleese in that sketch though. At least not in the original, IIRC.
Btw, fascinating subject. (Science of procreation, not Cleese, in this context. =D)
Not funny at all if you lived in that era and place. Ranting against religion back then could have gotten you executed. Plus loking at Steno’s life, he seems to have always been scholarly and at the time the Church was this educational institution.
Nice plug for your book, Matthew! I already have it in my “to read” pile (i.e., my bookshelf).
/@
PS. I guess the U.S. publishers were squeamish about the “egg & sperm” in the original (?) title… ?
I think it was more that they didn’t get the joke (egg and spoon races are more common in the UK than in the US, it appears).
We Americans still like our sex dirty and hidden, thank you very much.
…who doesn’t?! 😉
Maybe not entirely: according to his Wikipedia entry:
Yay!
The illustration of the shark’s head stands out to me by the severe wrinkling (?) and misshapen form of the head. I think of the outsides of sharks’ bodies as being smooth, from photographs I’ve seen (and one dissected dogfish during my undergrad).
In the days before effective preservation (freezing, high-concentration ethanol, formaldehyde), I imagine a dissection of an animal killed several days previously would be both a smelly and messy event. It’s pretty amazing to consider the discoveries of soft tissue anatomy (such as the salivary duct) under those conditions.
Also, I’ll have to look up those books – sounds interesting!
This was in the pre-Jaws era. No Landshark jokes, either.
I’m very confused about what we knew before Steno, and what Steno found out.
First, if Steno uses “testicles” to mean “ovaries,” what does it mean when he uses both in the same sentence?? (“I have no doubt that the testicles of women are analogous to the ovary”)
Before Steno, did scientists know that *any* animals had eggs, or did they think males supplied the whole kit and caboodle?
OK, sorry not to have been clearer. What he means here is that the ‘testicle’ in women (which had no known function) is analogous to the ovary in egg-laying animals. He’s seen the similarity of structure in form in egg-laying and live-bearing fish and said ‘those things that we think are testicles in women are in fact like ovaries in chickens’.
On your second point clearly they knew that chickens had eggs, and many fish too. The problem was mammals didn’t seem to have eggs (ie nothing like a chicken egg). So where did babies come from? No one knew. Aristotle argued that the female provided the matter, in the shape of the menstrual blood, while the male provided the ‘shape’ of the new offspring, through the semen. Galen argued that there were two kinds of semen – the obvious male kind and the female kind, which you couldn’t seen.
The weird thing is that by 1678 everyone knew that women had eggs and that there were tiny wriggling things in semen, but they still didn’t ‘get it’ and realise that the two things were equivalent. If you want to know why not, read this earlier post:
http://whyevolutionistrue.wordpress.com/2009/10/04/the-discovery-of-heredity/
Aaaah, okay I get it now. Thanks for the explanation!
You also have to realise that “testes” is the Latin for “witnesses”. Originally the testes and the ovaries were thought to bear witness to whether someone was male or female by their position in the body.
Hey, that’s fun to know! Thanks.
Nice article, learnt a few things from it.
But if I my be so bold, my compatriot Antonie van Leeuwenhoek deserves a better description than ‘uneducated draper’. True, he was autodidact. We honour him as prestigious microbiologist and bacteriologist, one of the finest scientist our country has produced.
Thanks for the illuminated article. When I saw the google header this morning I thought: I should look this guy up but here it is all done for me with commentary!
Cheers!
Alan Cutler’s “Seashell on the Mountaintop” is a fantastic read. The subject matter is of course fascinating, but it’s written with wit and grace. My favorite line from the book:
“It is so rare,” said the duchess of Orleans after meeting Leibniz, for an intellectual “to be smartly dressed, and not to smell, and to understand jokes.”
What a fascinating blog post! Thank you for that Matthew. I note that Brisbane City Council has five copies of your book on its shelves; I shall pick up one tomorrow 🙂
Thanks, this is much better than what I managed to glean from Wikipedia this morning.
And is it just me, or is that drawing of the shark’s head more menacing than the real thing? 🙂
Ooohhhh – nice. We had a nice little Dane-fest on facebook yesterday because of that Google-doodle. Quite proud of him we are. (Though he only did a minimal amount of his research and studies in his homeland.) Oh, and here he is known by his “real” name: Niels Steensen.
Blessed Steno was also a Catholic priest and bishop, and beatified by Blessed John Paul II (http://en.wikipedia.org/wiki/Nicolas_Steno).
So if they move him on to sainthood, what should he be patron of? I think Mary’s got fertility covered, Peter fishermen of course, and (I looked it up) St Apollonia has teeth (her martyrdom included a total extraction)…
Beatification is one step short of canonisation. He’s only the Blessed Nick Steno, not yet a saint.
A fascinating discussion is definitely worth comment. I do believe that you should write more on this subject matter, it may not be a taboo matter but typically folks don’t talk about these topics. To the next! Kind regards!!
It’s difficult to find knowledgeable people on this topic, but you seem like you know what you’re talking about! Thanks