# Which came first? Life or DNA?
**URL:** https://boards.straightdope.com/t/which-came-first-life-or-dna/945251
**Category:** In My Humble Opinion
**Created:** [June 29, 2021, 2:17pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251 "2021-06-29T14:17:25Z")
**Posts on this page:** 19
**Page:** 1
### Author:  [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)
#### Post date: [June 29, 2021, 2:17pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/1 "2021-06-29T14:17:25Z")
The title pretty much says it all. Did the earliest one celled animals contain DNA? Which came first the one celled animals or the DNA?
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### Author:  [@Crane](https://boards.straightdope.com/u/Crane)
#### Post date: [June 29, 2021, 2:28pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/2 "2021-06-29T14:28:58Z")
I believe your question is too high on the ladder of evolution. I assume abiogenesis was at the molecular level.
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### Author:  [@IvoryTowerDenizen](https://boards.straightdope.com/u/IvoryTowerDenizen)
#### Post date: [June 29, 2021, 2:47pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/3 "2021-06-29T14:47:05Z")
It’s likely that RNA was the initial molecule of life in proto-cells, and then RNA evolved into DNA, into the types of cells we see as the cellular basis of life.
By the time we get to animal cells, hell even early prokaryotic (bacteria) or eukaryotic cells (algae or protozoa), DNA was the molecule of life.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [June 29, 2021, 3:15pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/4 "2021-06-29T15:15:50Z")
To clarify a bit, “one celled animals” is a contradiction. We’re used to thinking in terms of “things that move” as animals, and “things that don’t move” as plants, and so there’s a temptation to classify (modern) single-celled creatures as “animals”. But of course, real-world taxonomy is much more complicated: Animals and plants are more closely related to each other, than either is to the vast majority of life on the planet (certainly when counted by number of organisms, and even when counted by number of cells). Fungi (such as mushrooms and yeast) and protists (such as amoebas and paramecia) are groups on the same categorical level as animals and plants, and all of them together are in one group, the eucaryotes, that’s one of the three top-level groupings of life.
But back to your original question, it’s very difficult to answer, because there’s not a sharp boundary between what counts as “life” and what doesn’t count. The first molecule of self-replication was probably a variant of what we would now call RNA (similar to but distinct from DNA), but do you call something based entirely on RNA “life”? I’ve seen some definitions for “life” that explicitly include that it be based on DNA; by those definitions, life by definition couldn’t have preceded DNA (but there was a lot of almost-life stuff around before then).
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### Author:  [@Kimera757](https://boards.straightdope.com/u/Kimera757)
#### Post date: [June 29, 2021, 3:23pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/5 "2021-06-29T15:23:03Z")
Even the most primitive viruses (which are frequently described as not being alive) contain genetic material (RNA or DNA) and protein. Genetic material is kind of pointless if it’s not coding for protein. Of course, to assemble DNA/RNA you generally need DNA/RNA polymerase (otherwise replication will be very slow), and the polymerase is a protein, but to code for that protein, you need DNA/RNA.
I think I have to say DNA/RNA came first, because I believe you need both genetic material and protein for life. Having said that, it’s at least theoretically possible to have self-replicating proteins that don’t need genetic material (prions are an example of this). Those aren’t considered alive though.
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### Author:  [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)
#### Post date: [June 29, 2021, 3:50pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/6 "2021-06-29T15:50:03Z")
Science isn’t sure, but it wasn’t DNA. DNA is a more stable form of genetic material than RNA since it lacks the -OH group that can interfere with the phosphate backbone and damage the molecule. DNA evolved out of RNA.
RNA could have come first though.
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### Author:  [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)
#### Post date: [June 29, 2021, 6:10pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/7 "2021-06-29T18:10:09Z")
> [@HoneyBadgerDC](#):
>
> The title pretty much says it all. Did the earliest one celled animals contain DNA? Which came first the one celled animals or the DNA?
A possible order is
RNA \> life \> DNA \> cells
Another is
RNA+DNA \> life \> cells
Or eve (but less likely)
life \> RNA+DNA \> cells
Whichever happened, cells were late in the game.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [June 29, 2021, 6:21pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/8 "2021-06-29T18:21:22Z")
> [@Kimera757](#):
>
> Of course, to assemble DNA/RNA you generally need DNA/RNA polymerase (otherwise replication will be very slow), and the polymerase is a protein, but to code for that protein, you need DNA/RNA.
Current results seem to show that you can make functional (albeit inefficient) enzymes directly from RNA itself: That’s why the current thinking is that RNA probably came first. At some point, proto-life evolved the tricks of coding for proteins (including proteins that act as more efficient enzymes), and of producing genetic material in DNA form as well as RNA form. Which of those (proteins or DNA) came first is so far as I know as yet unknown, and at what point you call the system “life” instead of “proto-life” is a judgement call.
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### Author:  [@Tfletch1](https://boards.straightdope.com/u/Tfletch1)
#### Post date: [June 29, 2021, 6:54pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/9 "2021-06-29T18:54:48Z")
Just a small nitpick here (sorry). The traditional definition of life is the cell. Under this definition, even viruses are not “alive”. To be alive something must reproduce and produce basic materials (making proteins). Viruses don’t have ribosomes to make proteins, so they’re not considered to be alive under the traditional definition. Not everyone agrees with this though.
Anyway, the thought is that RNA building blocks that we now see may not have been around. Plus, self-replicating RNA is not very efficient. So there was probably some kind of proto-RNA. There is even a hypothesis that there were RNA-DNA hybrids to solve the inefficient replication model. Also, isolating your system in a some kind of self-assembled membrane increases efficiency quite a bit.
proto-building blocks → building blocks adhered to a surface or trapped within an oil blob → proto-building blocks self-assemble into proto-RNA → RNA (inefficient replication) —\> RNA/DNA hybrid (more efficient replication) —\> proteins and proto-enzymes to replicate DNA —\> stable DNA genome → mature cell
In this model, I have stable genome late in the timeline because it requires DNA polymerase to replicate. You may be able to make bits of RNA/DNA hybrids using only ribozymes (RNA-based enzymes instead of protein-based enzyme). However, you need to have some kind of DNA polymerase to make DNA as we now know it. I put some kind of membrane very early in this timeline because isolation from surroundings and molecular crowding facilitates the chemical reactions you want.
This TED talk is lots of fun:
> **[The line between life and not-life](https://www.ted.com/talks/martin_hanczyc_the_line_between_life_and_not_life/transcript?language=en)**
>
> In his lab, Martin Hanczyc makes "protocells," experimental blobs of chemicals that behave like living cells. His work demonstrates how life might have first occurred on Earth ... and perhaps elsewhere too.
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### Author:  [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)
#### Post date: [June 29, 2021, 7:11pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/10 "2021-06-29T19:11:47Z")
> [@Tfletch1](#):
>
> The traditional definition of life is the cell.
Cite?
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### Author:  [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)
#### Post date: [June 29, 2021, 7:17pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/11 "2021-06-29T19:17:20Z")
> **[Defining Life](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3005285/)**
>
> Any definition is intricately connected to a theory that gives it meaning. Accordingly, this article discusses various definitions of life held in the astrobiology community by considering their connected “theories of life.” These include ...
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### Author:  [@Tfletch1](https://boards.straightdope.com/u/Tfletch1)
#### Post date: [June 29, 2021, 7:30pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/12 "2021-06-29T19:30:03Z")
> [@Darren\_Garrison](#):
>
> Cite?
I’m saying the traditional introductory textbook view, not that it is correct or that everyone agrees.
> **[1.1: Themes and Concepts of Biology](https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Concepts_in_Biology_(OpenStax)/01%3A_Introduction_to_Biology/1.01%3A_Themes_and_Concepts_of_Biology)**
>
> Biology is the science of life. All living organisms share several key properties such as order, sensitivity or response to stimuli, reproduction, adaptation, growth and development, regulation, …
> ## Properties of Life
>
> All groups of living organisms share several key characteristics or functions: order, sensitivity or response to stimuli, reproduction, adaptation, growth and development, regulation, homeostasis, and energy processing. When viewed together, these eight characteristics serve to define life.
Introductory biology textbooks always have something like the above quote. In this simple context, the cell is defined as the basic unit of life.
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### Author:  [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)
#### Post date: [June 29, 2021, 7:39pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/13 "2021-06-29T19:39:29Z")
> **[How life evolved: 10 steps to the first cells](https://www.newscientist.com/article/dn17987-how-life-evolved-10-steps-to-the-first-cells/)**
>
> If life did evolve in alkaline hydrothermal vents, as many scientists now think, it might have happened something like this
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### Author:  [@Tfletch1](https://boards.straightdope.com/u/Tfletch1)
#### Post date: [June 29, 2021, 8:02pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/14 "2021-06-29T20:02:57Z")
Yes, the iron-sulfide bubbles provide a closed system to facilitate chemical reactions. The lipid membrane wouldn’t be needed right away.
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### Author:  [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)
#### Post date: [June 29, 2021, 9:29pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/15 "2021-06-29T21:29:37Z")
Great posts, appreciate all of them, I wish I could contribute something.
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### Author:  [@Kimera757](https://boards.straightdope.com/u/Kimera757)
#### Post date: [June 29, 2021, 10:35pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/16 "2021-06-29T22:35:23Z")
The information on ribozymes is very interesting. So is the protein-first model, shown here in a 2017 article:
> **[Life’s First Molecule Was Protein, Not RNA, New Model Suggests](https://www.scientificamerican.com/article/life-rsquo-s-first-molecule-was-protein-not-rna-new-model-suggests/)**
>
> The findings add to the longstanding debate over which were the first self-replicating molecules
I guess it’s a chicken and egg thing.
Maybe it’s a bit like evolution of the eukaryote. You need (or want) a combination of a more complex cell and something like a mitochondrion or chloroplast to generate energy efficiently. I wonder if the original “soup of life” contained self-replicating proteins and ribozymes.
So when they put a person on Mars with a shovel to investigate life, the next step is a biologist with a time machine to investigate an alternate version of past Earth 😃
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### Author:  [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)
#### Post date: [June 29, 2021, 10:39pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/17 "2021-06-29T22:39:02Z")
> [@HoneyBadgerDC](#):
>
> Great posts, appreciate all of them, I wish I could contribute something.
Book recommendations:
> [@Biochemistries on other planets](https://boards.straightdope.com/t/biochemistries-on-other-planets/797795/4):
>
> You really need to get a copy of [Life as We Do Not Know It](https://books.google.com/books?id=anth6kuZStsC&printsec=frontcover#v=onepage&q&f=false) by Peter Douglas Ward. (For life as we do know it, you couldn’t do much better than the books of Nick Lane, especially including [The Vital Question](https://en.wikipedia.org/wiki/The_Vital_Question) and Life Ascending: The Ten Great Inventions of Evolution.)
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### Author:  [@Tfletch1](https://boards.straightdope.com/u/Tfletch1)
#### Post date: [July 1, 2021, 5:27pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/18 "2021-07-01T17:27:11Z")
> [@Kimera757](#):
>
> I guess it’s a chicken and egg thing.
Sure. I supposed little peptides with positive charges on the outside could help stabilize and even catalyze the formation of bits of RNA or proto-RNA. Those, in turn, could help catalyze small polypeptide.
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### Author:  [@dropzone](https://boards.straightdope.com/u/dropzone)
#### Post date: [July 4, 2021, 10:55pm UTC](https://boards.straightdope.com/t/which-came-first-life-or-dna/945251/19 "2021-07-04T22:55:20Z")
> [@HoneyBadgerDC](#):
>
> Great posts, appreciate all of them, I wish I could contribute something.
(confused look) That never stopped me. 😉
This looks like a good topic for YouTube videos to play all night. FTR, sleep learning doesn’t work.