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How Did Insect Metamorphosis Evolve? (2012) (scientificamerican.com)
56 points by vezycash 7 days ago | hide | past | web | favorite | 14 comments





>In the 1830s a German naturalist named Renous was arrested in San Fernando, Chile for heresy. His claim? He could turn caterpillars into butterflies.

If that was his actual claim it would indeed be heretical (or at least academically fraudulent) even today.


In Darwin's telling, Renous left his caterpillars in the care of a girl "that they might turn into butterflies", which isn't quite the same thing.

I suspect there's even more to the story than what is apparent in Darwin's anecdote, both because right or wrong it simply doesn't fall under the category of heresy, and given that metamorphosis had been a well observed and documented phenomenon for hundreds of years prior to the event. For example in De animalibus insectis libri septem by Ulisse Aldrovandi[1][2]

It may even be in the order of thousands of years even though we don't have written accounts of it, given that's how we have practiced apiculture and had the opportunity to closely observe the phenomenon. And apiculture has been widely practiced by monasteries, so churchmen should not have been entirely unfamiliar with the concept.

1. https://archive.org/details/deanimalibusinse00aldr/page/280

2. Coincidentally Aldrovandi was also accused of heresy, but for anti-trinitarianism, not for describing metamorphosis: https://en.wikipedia.org/wiki/Ulisse_Aldrovandi#Heresy


I couldn’t understand exactly but do they assume that the caterpillar came before the butterfly and butterfly evolved from the caterpillar? If so is there evidence for such an assumption?

They actually say the opposite in the article:

> Complete metamorphosis likely evolved out of incomplete metamorphosis. The oldest fossilized insects developed much like modern ametabolous and hemimetabolous insects—their young looked like adults. Fossils dating to 280 million years ago, however, record the emergence of a different developmental process. Around this time, some insects began to hatch from their eggs not as minuscule adults, but as wormlike critters with plump bodies and many tiny legs.


They probably always devoloped like this inside the egg. Eg getting wings and adult features last. So starting evolving metamorphosis might have been as simple as a few dna mutations to make them hatch earlier before being fully developed.

Of course evolving the pupa seems like it would be a lot more difficult.


> Of course evolving the pupa seems like it would be a lot more difficult

Once you have evolved one intermediate form others can follow more easily. It’s always important to remember that genes define recipes that create biological structures, not blueprints of what they look like.

It’s a different mechanism but genetic networks are good at repeating things like body segments, fingers, etc. Biology invented the REPEAT UNTIL loop a long time before we did.


Nitpick to the analogy: biological loops are recursive, not iterative.

I was thinking of genes that are components of signalling pathways that regulate the expression of other genes while a particular condition holds true

ontogeny recapitulates phylogeny, kinda

> ...wormlike critters with plump bodies and many tiny legs. So they are saying, “wormlike” insects ie, not the butterflies, but caterpillars came first. That’s how I read it.

> Fossils dating to 280 million years ago, however, record the emergence of a different developmental process. Around this time, some insects began to hatch from their eggs not as minuscule adults, but as wormlike critters with plump bodies and many tiny legs.

What they mean is: before this developmental change 280 years ago, they hatched as (albeit tiny) fully fledged adults, rather than in their intermediary state.


Still I don't get it. There are two creatures, the caterpillar and the butterfly. Which one came first?...

Complete metamorphosis is a circular process as pictured here: http://burns-classroom.weebly.com/module-6-plants-and-life-c... Caterpillar (or larvae) turns into pupa; pupa turns into butterfly and butterfly (turns?) into egg; and egg turns into larvae and so on... I am curious to know which of these organisms came first. Did the butterfly exist before the caterpillar? Or were they two different species who entered into a symbiosis agreement?

And why is it that the transformation of a seed into a tree not considered a metamorphosis? The seed and the tree are as different as the caterpillar and the butterfly.


They are no more different species than a chicken and an egg are different species.

Neither the butterfly nor it’s larval stage, not it’s egg, came first. They are all one species that evolved from species before them. Originally the adult form was born from the egg, but other stages evolved later.




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