For centuries, people believed that maggots and fungi magically sprung from inanimate objects out of thin air. Spontaneous generation! How babies happened was also shrouded in myth, and by the mid-1600s, people had yet to figure out that, in humans, barely visible eggs and microscopic sperm were part of the process. Turns out, all it took was a pair of frog pants to get the ball rolling in the right direction.
A happy day for science: frogs in pants, the first empirical demonstration of barrier contraception, and spontaneous generation went the way of the powdered wig.
Katie L. Burke is an ecologist-turned-science-journalist, who writes about all things biology. Currently an editor at American Scientist, she also blogs at The UnderStory (www.the-understory.com). Follow her on Twitter: @_klburke.
Image Attributions 1.PG 1 Scientists: Original illustration utilizing source image of Anton van Leeuwenhoek from the Library of Congress (http://www.answers.com/topic/anton-van-leeuwenhoek) and source image from Wikimedia Commons for Lazzaro Spallanzani (http://commons.wikimedia.org/wiki/Lazzaro_Spallanzani). 2.PG 2 Frog in pants: Original illustration utilizing multiple sources.3.PG 3 Frogs mating: Original illustration based on source image from Peter Chen, available through GNU General Public License (http://bio1151b.nicerweb.net/Locked/media/ch46/). 4. PG 4 Tadpoles: Original illustration based on source image from Geoffrey Gallice, available through Creative Commons license (http://www.flickr.com/photos/dejeuxx/6407253419/) 5. PG 5 Eggs: Original illustration; source is artist’s photograph.
Let’s call it “Science! The Kermit Couture Edition”
Nice illustrations! But you’ve missed the point of all this. Firstly, although it’s true that Leeuwenhoek initially assumed spermatozoa (= ‘animals that live in sperm’) were animals (not parasites), he very soon decided they were the basis of the next generation, and argued that the egg was merely food. On the other hand, thinkers like his contemporary Swammerdam thought that the egg was the thing. For the next 160 years people were divided into ‘spermists’ or ‘ovists’ (these were the majority). No one thought that both egg and sperm were necessary.
What Spallanzani did was to show that sperm were necessary, BUT he remained a convinced ovist! He thought that sperm merely awoke the egg, setting the foetal heart beating. He did not have anything like a modern understanding of reproduction. So sadly ‘frogs in pants’ did NOT finally explain sex!
It took a remarkably long time for this to develop – von Baer, who was the first to see the human egg in 1827, was a convinced ovist who thought that sperm were animals – he coined the term ‘spermatozoa’ and classified them amongst the parasitic worms.
It was only in the 1840s when people had a) gradually realised that there was such a thing as heredity (this had no biological meaning until the 1830s) and b) had developed the cell theory that it was realised that egg and sperm were equivalents and that both were required for future live to appear. This is not quite as neat a story, but it is nearer the truth.
Thanks for adding these extra details to my brief summary, Matthew. For those interested in further reading, the source for this particular overview is Robert Martin’s 2013 book “How We Do It” (pp. 1-2).
PS The experiment didn’t do for spontaneous generation, either! For animals, that had been proven wrong by Swammerdam and Redi in the 1660s; for micro-organisms, you had to wait until Pasteur did his experiments nearly a century after Spallanzani….
this frog hates rubbers too
It seems you’ve missed the point of all of this. To me, it looks like the artist and writer is highlighting a snapshot in the history of understanding how sex works. They clearly stated that the frog pants got the “ball rolling in the right direction,” not that they finally understood what sperm did versus what eggs did in relation to conception. I mean, it’s cool that you have this extra info to add to the piece, but just because there is more to the story does not mean the story presented here is incorrect or that the authors missed the point.
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A great explanation of one of the nicest experiments in science. I think you’ve “toadily” nailed it (groan)! I love the illustration of the frog in pants.
I featured this cute experiment in my book Rebel Science as “Frogs in Togs”, illustrated by the superlative David Lyttleton. True to what Matthew Cobb says further up, Spallanzani’s experiment showed that sperm was necessary to fertilisation of an egg.
The “frogs in togs” produced no new little jumpers, but – crucially –Spallanzani took some sperm out of their trousers and found he was still able to fertilise the eggs. Neat. Check out Rebel Science on Amazon or at my website.