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ChristianInvestigator

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How does evolution explain symmetry?
« on: October 28, 2020, 10:26:20 am »
This isn’t supposed to be a YEC argument against evolution (I lean towards Evolutionary Creationism), I’m genuinely curious. Is there something inherent to DNA that causes symmetry? Or is it a consequence of cellular structure? I’d be interested in knowing the answer.
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lancia

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Re: How does evolution explain symmetry?
« Reply #1 on: October 28, 2020, 11:46:11 am »
This isn’t supposed to be a YEC argument against evolution (I lean towards Evolutionary Creationism), I’m genuinely curious. Is there something inherent to DNA that causes symmetry? Or is it a consequence of cellular structure? I’d be interested in knowing the answer.

Like most morphological characteristics in organisms, symmetry is a function of genetics. In plants, cycloidea genes are responsible. In animals Hox and dpp genes seem to be involved.

Consequently, to the extent evolution explains genetics, it explains symmetry.

« Last Edit: October 28, 2020, 12:18:19 pm by lancia »

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kurros

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Re: How does evolution explain symmetry?
« Reply #2 on: October 28, 2020, 02:25:29 pm »
I would also add that symmetry is efficient in terms of information encoding. You only have to code up half the information, and then duplicate it. Of course we have plenty of assymetry on top of that, heart on the left, liver on the right etc., but it is just a little extra on top.

Also interesting is that some early life seems to have been even more symmetric, for example rangeomorphs had a cool fractal body plan. It seems logical that these kind of designs that re-use a lot of information were probably easier to "find" in the space of genetic possibilities, and life has gotten less symmetric over time as more complex structures evolved.

Though there are probably also selection forces that favor the kind of symmetry we see a lot, e.g. our bilateral symmetry is good for balance, probably easier to run and jump and climb etc with this kind of symmetric body.
« Last Edit: October 28, 2020, 02:30:13 pm by kurros »

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ChristianInvestigator

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Re: How does evolution explain symmetry?
« Reply #3 on: October 29, 2020, 09:58:26 am »
@ Lancia and Kurros:

Very interesting, thanks!
"This year, though I'm far from home
In Trench I'm not alone.
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kurros

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Re: How does evolution explain symmetry?
« Reply #4 on: October 30, 2020, 02:05:56 am »
I possibly should clarify that by "duplicate it" I don't mean in DNA. I mean there are other genes that mean code for e.g. a leg just gets used/expressed twice. So more symmetry literally requires less DNA*.

* To be honest I never read or heard this anywhere (that I can remember) I just assume it to be the case because it makes sense. I'll let lancia correct me if I am completely making it up ;).

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lancia

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Re: How does evolution explain symmetry?
« Reply #5 on: October 30, 2020, 09:07:09 am »
I possibly should clarify that by "duplicate it" I don't mean in DNA. I mean there are other genes that mean code for e.g. a leg just gets used/expressed twice. So more symmetry literally requires less DNA*.

* To be honest I never read or heard this anywhere (that I can remember) I just assume it to be the case because it makes sense. I'll let lancia correct me if I am completely making it up ;).

I think you are right. If the Hox gene codes for constructing a leg, two legs are made, one arranged on each of the two sides of the body symmetrically. A particular Hox gene mutation in Drosophila produces an extra pair of wings, not just one extra wing.
« Last Edit: October 30, 2020, 11:49:33 am by lancia »