Aristotle spent serious time on this and concluded eels spontaneously generated from mud, that's not a knock on him, you genuinely cannot find reproductive organs in a wild eel because they don't develop until the final migration, it took satellite tagging in 2018 to actually confirm what was happening. A 2,300 year old mystery closed by a GPS tracker is a good reminder that some problems just had to wait for the right instrument
That is a very big deal observer. Philosophers of science have a concept called "theory ladenness". Until the right tool arrives you may not even be able to formulate the question, and you don't know it.
The history of heat versus temperature is quite enlightening. The absence of thermometers means you don't really what heat capacity means. Same with mass versus weight; the difference isn't hard to measure once it occurs to you to measure it.
These can be great aha moments in the history of science. It's both daunting and inspiring.
In the satellite tracking experiment, I wonder how they sexed the eels to determine they were female before tagging, given the lack of primary sex organs at that time. Are there obvious secondary characteristics like size?
> The researchers behind this recent discovery used satellite tags to follow 21 female European eels as they navigated the final phase of their incredible journey southwest from the Azores, the volcanic archipelago of the North Atlantic Ocean west of Portugal.
I remember being fascinated by animals as a kid and the mystery of where eels went was one of the big unsolved puzzles I remember hearing about.
Much more recently I heard on QI about how medieval people, not knowing about migration, believed, through a lot of leaps, that it was ok to eat barnacle geese at lent. Worth investigating if you are curious :)
Fascinating how certain animals have evolved with complex migration patterns to breeding grounds. And unfortunate that 95% of the population has already collapsed.
Makes me wonder what the world was like before this last great extinction.
tl;dr Eels have a long lifecycle with several stages. They do not develop sexual organs until late in their life, when they migrate back to the Saragossa Sea. This meant earlier autopsies of eels revealed no sexual organs, even though scientists could provoke them with hormone therapy. So, a team lead by Jose Azevedo tagged female eels in the Azores in 2018, and tracked them via satellite [0].
I sometimes think about the selection pressures that lead to complex life cycles, like fig wasps. I find myself thinking about it naively, like one existed and the other grew into the niche. But, realistically, everything is changing (slowly) all the time. I just notice it for, say, influenza because their cycle time is so short.
The important part of the story is that it took so long. People actively searched for an answer for thousands of years.
The answer itself is interesting, but more remarkable to me is how doggedly people pursued it for so long. It seems so basic that they must reproduce the way other vertebrates do, and yet the lack of apparent organs was baffling.
Aristotle spent serious time on this and concluded eels spontaneously generated from mud, that's not a knock on him, you genuinely cannot find reproductive organs in a wild eel because they don't develop until the final migration, it took satellite tagging in 2018 to actually confirm what was happening. A 2,300 year old mystery closed by a GPS tracker is a good reminder that some problems just had to wait for the right instrument
That is a very big deal observer. Philosophers of science have a concept called "theory ladenness". Until the right tool arrives you may not even be able to formulate the question, and you don't know it.
The history of heat versus temperature is quite enlightening. The absence of thermometers means you don't really what heat capacity means. Same with mass versus weight; the difference isn't hard to measure once it occurs to you to measure it.
These can be great aha moments in the history of science. It's both daunting and inspiring.
In the satellite tracking experiment, I wonder how they sexed the eels to determine they were female before tagging, given the lack of primary sex organs at that time. Are there obvious secondary characteristics like size?
> The researchers behind this recent discovery used satellite tags to follow 21 female European eels as they navigated the final phase of their incredible journey southwest from the Azores, the volcanic archipelago of the North Atlantic Ocean west of Portugal.
They swabbed them and sequenced their DNA.
Thank you, I forgot that's cheap enough these days.
"figured out how" seems a little strong, when:
> questions remain about the timing and navigation of the eels across thousands of kilometers of open water
I remember being fascinated by animals as a kid and the mystery of where eels went was one of the big unsolved puzzles I remember hearing about.
Much more recently I heard on QI about how medieval people, not knowing about migration, believed, through a lot of leaps, that it was ok to eat barnacle geese at lent. Worth investigating if you are curious :)
This is a good video on that medieval belief:
Medieval Science was Baffled by Birds - CuriousCabinet123
https://youtu.be/vgFj-MMTqIc
The click bait version adds “and it’s electrifying”.
everyone here is talking about eels but i prefer icktok
I'm just glad that somebody solved this very slippery problem.
Fascinating how certain animals have evolved with complex migration patterns to breeding grounds. And unfortunate that 95% of the population has already collapsed.
Makes me wonder what the world was like before this last great extinction.
tl;dr Eels have a long lifecycle with several stages. They do not develop sexual organs until late in their life, when they migrate back to the Saragossa Sea. This meant earlier autopsies of eels revealed no sexual organs, even though scientists could provoke them with hormone therapy. So, a team lead by Jose Azevedo tagged female eels in the Azores in 2018, and tracked them via satellite [0].
[0] https://www.nature.com/articles/s41598-022-19248-8
I sometimes think about the selection pressures that lead to complex life cycles, like fig wasps. I find myself thinking about it naively, like one existed and the other grew into the niche. But, realistically, everything is changing (slowly) all the time. I just notice it for, say, influenza because their cycle time is so short.
The important part of the story is that it took so long. People actively searched for an answer for thousands of years.
The answer itself is interesting, but more remarkable to me is how doggedly people pursued it for so long. It seems so basic that they must reproduce the way other vertebrates do, and yet the lack of apparent organs was baffling.