Why Turtles Evolved Shells | Hacker News Reader

Why Turtles Evolved Shells

theatlantic.com

123 pointskjhughes39 comments

Beyond explaining the curiosity of a turtle's shell, I really liked this article for introducing me to exaptation:

   The turtle’s shell, then, is a wonderful example of exaptation
   —the evolutionary process where a trait evolves for one function
   and is then co-opted to serve another. They began as digging 
   platforms and then became suits of armor. Feathers are another 
   example. They now help birds to fly, but they probably originated 
   as ways of keeping warm or signaling to mates and rivals.

"Exaptation" has slowly been replacing the older term "pre-adaptation", which biologists avoid using because of its teleological implications.

Exaptation is a product of exaptation.. smirks

Antiteleological principles developed in order to avoid teleological justifications.

There's a really good Stephen J. Gould essay on exaptation titled, "Exaptation - a missing term in the science of form"

For others that are curious, appears to be on-line here:

http://faculty.insead.edu/vibha-gaba/documents/Gould%20%26%2...

Rather a neologism:

https://books.google.com/ngrams/graph?content=exaptation&yea...

Though the antecedants date to the 19th century: https://books.google.com/books?id=0WNVAAAAMAAJ&pg=PA102&dq=%...

It's always interesting to me when evolution is framed in terms of "why" something happened rather than "this mutation was more suited to the environment at the time." In this case, sounds like shells were good for digging, now are good for protection. I suppose such headlines are well-suited to our current popular understanding of evolution. (Also... I like turtles.)

>framed in terms of "why" something happened rather than "this mutation was more suited to the environment at the time."

I simply read "why did turtles evolve shells" as a short form for "why did shells provide a reproductive advantage to some organisms possessing this random mutation".

It's possible that some readers of the article will interpret the phrase that way. For people with a less nuanced understanding of natural selection it suggests that evolution is a directed effort towards certain ends, as though turtles had a say in how their species evolved. Alternatively, that there is some other agency that is deliberately influencing the evolution of species.

Personally I feel like the idea of evolution as a directed effort is a common misunderstanding of natural selection, and I wonder if better science reporting could start to mend those kinds of misconceptions.

Yes, technical people often use shorthand terms that ascribe agency to random or inanimate processes, and I think laypeople take that agency literally more often than we realize.

I had a Swiss professor on my committee who would halt any discussion of evolutionary process if someone hinted at 'purpose' or 'intention'. He would pop up and shout in a thick Swiss accent "noO!dis iz da fallacy uv teleology!"[1] He would never be assuaged with attempts to point out that such references are merely short-hands for longer, more precise, statements. But he consistently held the best post-presentation parties.

[1] https://en.wikipedia.org/wiki/Teleology

I understand the insistence. Here in the US, people think "It's just a theory" is a legitimate refutation of evolution.

Shorthand terms can shape the debate in wasteful ways. By always ensuring you use the correct terms and thinking with evolution it helps shape the debate in more useful ways.

Macroscopic models are crucial. Imagine trying to understand water flow in terms of brownian motion or turbulence, instead of "downhill". Similar for heat flow.

We'll need such models to understand neural activity.

That's not to say that lower-level models are unimportant... or that we have the correct macroscopic model.

re title: click-bait titles are why tl;dr's should be encouraged. It would be interesting to have frontpage-like voting on better titles for each story.

Q: Why shells?

A: More turtles.

Because they wouldn't be turtles if they hadn't evolved shells. Teleology in a (nut) shell...

It's turtles all the way down!

How would you reword the headline?

Excellent question! I'm not sure I could do much better, tbh. Maybe something like, "New theory suggests turtles shells used for digging before protection." Not nearly as succinct, to be sure, but less click-baited. The current title certainly got me to click through...

My original comment really was one of curiosity and theophrastus's link to Teleology above hit on exactly the thought process that I was wondering about.

"Why shells evolved in turtles"

How Turtle Shells May Have Evolved.

I don't see it as anything different than answering the question "Why did you take your sister to the hospital" with an answer other than "Because she needed medical care"

TL;DR:

For digging.

Came here to type this comment. Man, did they ever bury that one. I finally went back to ctrl-f "dig", and it was in fact in the intro, but just in passing…

I wonder if a turtle helped bury it.

And should the turtle flip while digging? Thankfully, we have the assurance of geometry to tell us it will get back to digging in no time.

http://rspb.royalsocietypublishing.org/content/275/1630/11

Similar to a gömböc: https://en.wikipedia.org/wiki/G%C3%B6mb%C3%B6c

Another concept that's useful in this context is that of the adjacent possible. Rather than get bogged down in concepts of teleology, realise that for an adaptation to occur, it must be beneficial, or, at the very least, not disadvantageous.

So, from proto-turtle to current evolved state, the shell had to pass through various forms which were adjacent and possible to their progenitor state, and subsequent state.

While the end result wasn't a goal, it had to exist on the possibility path which lead to it. That is, adaptations are path dependent.

Which applies as well to technological and enterprise progress. For a company to evolve from some precursor state A to some ultimate state C, it's got to pass through some intermediate set of possiblities, B, B', B", etc. Maintaining corporate solvency, existence, some employee retention, etc., are all necessary. And original intent often isn't the final result.

I wish we talked about evolution a bit differently. It's not that "turtles" "evolved" shells. It's that as the population of turtles mutated into various forms, certain ones survived and thrived, and others didn't.

It's almost as if someone decided to give that phrase a name, and decided to use the word "evolution".

It was the only way to escape being used by all other species as drawing tools

How Titles Evolved: It Wasn't for Giving Away the Actual Information in the Article

Thanks to Buzzfeed and others. It's a great psychological tool to get you to click since the curiosity has been tickled and you just have to know now (FOMO).

My positive spin on clickbait titles is that they help me try to train away my FOMO bias.

I learn to learn from them to better create copy that improves conversion rates.

Five Things You Won't Believe BuzzFeed Has Done To This Industry.

One thing you wouldn't believe has existed since far before BuzzFeed.

When a headline exists, on a page, to catch your eye and lead you in a few thousandths of a second to the story, vs. online, where fully loading a weaponised viral clickbait story can take 10-20 seconds, to a minute or more, is a huge difference.

I prefer offering 1) descriptive titles and 2) informative microcontent, as Jacob Nielson has been advocating for nearly 20 years now.

https://www.nngroup.com/articles/microcontent-how-to-write-h... (1998)

https://www.nngroup.com/articles/pogo-sticking/ (2015)

https://www.nngroup.com/articles/does-user-annoyance-matter/ (2007)

https://www.nngroup.com/articles/link-promise/ (2014)

Turtles evolved shells so that they could work from home.

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