[HN Gopher] Brain-signal proteins evolved before animals did
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       Brain-signal proteins evolved before animals did
        
       Author : theafh
       Score  : 89 points
       Date   : 2022-06-03 13:28 UTC (9 hours ago)
        
 (HTM) web link (www.quantamagazine.org)
 (TXT) w3m dump (www.quantamagazine.org)
        
       | ddabed wrote:
       | The text says "They point out that, based on their peptide
       | sequences, both precursors are likely to be secreted molecules."
       | How can they tell that from the sequence?
        
       | guerrilla wrote:
       | The important question to answer for me though is whether they
       | originated before or after muscle-like cells though. I'm a big of
       | the saying "the brain is for moving" by, I think, Eric Kandel.
        
       | stevenjgarner wrote:
       | I always wonder about these evolutionary arguments where such and
       | such a feature is discovered in a group of primordial precursor
       | life forms so therefore that's when it originated.
       | 
       | Just to be contrary, is it not at all possible that such and such
       | a feature "evolved" in all the relevant life forms at the same
       | (more recent) time in response to changing external stimuli?
       | 
       | I remember being edified by an evolutionary biologist who stated
       | that humans are not more "evolved" than single-celled organisms -
       | both have been evolving for the same period of time. Both have
       | just evolved into different niches at different levels of
       | complexity. I hope I'm getting that right.
        
         | Udo wrote:
         | _> discovered in a group of primordial precursor life forms so
         | therefore that 's when it originated._
         | 
         | It's a shorthand way of working with incomplete information. In
         | many cases it's not possible to directly point to a concrete
         | organism as a point of origin for a certain molecule. That's
         | why we point to the earliest known implementation and shrug.
         | 
         |  _> Just to be contrary, is it not at all possible that such
         | and such a feature  "evolved" in all the relevant life forms at
         | the same (more recent) time in response to changing external
         | stimuli?_
         | 
         | When a molecule is sufficiently complex and all other factors
         | being equal, we tend to assume there was _one_ common ancestor
         | who first developed it.
         | 
         | It seems to me that Quanta is sometimes a bit biased towards
         | the cosmic inevitability of intelligence, while carefully
         | avoiding full-on Penrose mysticism. That's why the title is
         | phrased as it is when in fact this discovery is congruous with
         | current models.
         | 
         | Signal proteins evolving before the majority of systems they're
         | currently used in is in fact well aligned with prior
         | expectations. Once a way to synthesize a molecule has evolved,
         | it can get re-used quite a lot for similar purposes. That's
         | because evolution is a hill-climbing algorithm which is bad at
         | coming up with complexity from the ground up but has no problem
         | with complexity that has developed over extended periods.
         | 
         |  _> humans are not more  "evolved" than single-celled
         | organisms_
         | 
         | Well, there is a directionality to evolution, and humans are
         | way more complex than single-celled organisms. Biologists tend
         | to avoid labels such as "more evolved" because they can be
         | misleading and because obviously every organism around today is
         | evolved to the same extent, namely to survive in current
         | conditions.
        
         | outworlder wrote:
         | > Just to be contrary, is it not at all possible that such and
         | such a feature "evolved" in all the relevant life forms at the
         | same (more recent) time in response to changing external
         | stimuli?
         | 
         | Depends. Joints can independently evolve. Knees are unlikely.
         | 
         | In other words, nothing is impossible. A structure that
         | performs any given function could evolve independently even if
         | it looks different. The exact same structure or molecule?
         | Unless it's one of the simplest 'solutions' to a problem, it's
         | very unlikely without a common ancestor.
         | 
         | Even things that should have one solution - like eyes - can
         | lead to many different structures. Like our "backwards" retina
         | which is not shared with octopi.
        
         | _Microft wrote:
         | The process you are describing is called "convergent evolution"
         | [0].
         | 
         | [0] https://en.wikipedia.org/wiki/Convergent_evolution
        
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