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There's an unbroken chain between everything current living thing and the first living thing, so don't we share DNA with well... everything?
by jeletonskelly 8y ago
There's an unbroken chain between everything current living thing and the first living thing, so don't we share DNA with well... everything?
- Xophmeister 8y agoGiven DNA is quantised into just four nucleotides -- and I suspect that there is no organism that uses, say, just three -- then wouldn't your statement be trivially true? That is, pick a 1mer of a random nucleotide (A, C, G or T) and there you go. What I suspect you're getting at is, rather, if our DNA contains virus DNA, then presumably that virus' DNA also contains the DNA of organisms it encountered (using the same mechanism), etc. Thus, there ought to be an unbroken history -- albeit probably highly corrupted from successive adaptive mutations -- in our DNA to the first living thing. This wouldn't necessarily be everything, though; just everything we've assimilated.
- jeletonskelly 8y agoYes, that's sort of what I'm getting at with that leading question. If we accept evolutionary biology then a headline like this wouldn't be all that surprising. All living things converge at the root.
- fifnir 8y ago> If we accept evolutionary biology then a headline like this wouldn't be all that surprising.All living things converge at the root. That doesn't mean that everything has already been "invented" at the root.
- Thrymr 8y ago> That doesn't mean that everything has already been "invented" at the root. Exactly. The "classical" view of evolutionary genetics is that new genes develop by mutation, are favored (or eliminated) by natural selection, and exchanged only within the same species by interbreeding. So the family tree of life is a map of how closely organisms are related, and they would share a gene only with the nearby branches of the tree descended since that gene arose. We have long known that the simple model is not complete, prokaryotes (bacteria and archaea) exchange lots of genetic material outside their own "species" (trickier to define for bacteria in any case), but it is becoming more widely recognized that lateral gene exchange happens a lot in all organisms. A recent popular book on the subject is "The Tangled Tree: A Radical New History of Life" by David Quammen.
- Xophmeister 8y agoWhat this article is saying, though, is stronger: It's not just convergence to the root, but also branch merges. While those branches will converge to the same root, they may have diverged significantly (such that today, we recognise them as from totally separate organisms).
- fifnir 8y agoYes, generally speaking, but there are genes that were evolved on branches after they separated from ours. We don't produce chlorophyll even though we share some DNA with plants. Imagine in languages: Indoeuropean languages share a common ancestor, but we can say that suchandsuch word is originally from some language and then adapted into another language and used for potentially different meaning.
- narag 8y agoThere's an unbroken chain between everything current living thing and the first living thing... I don't think that's an established fact at all. DNA is a very complex system so it's reasonable to think that simpler systems predated it. Not that it affects your reasoning at all, since every current living thing that we know of does use DNA.
- agumonkey 8y agoI do believe there's an abstract principle that we share with anything that sustained its structure. Not a specific thing like a set of genes but the underlying set of chaos-avoiding rules that makes living forms living forms.
- asdff 8y agoThe RNA world hypothesis proposes that self-replicating RNA molecules proliferated before DNA, which would be that simpler system as it doesn't require complex protein machinery.
- Simon_says 8y agoThe truth of that statement is presently unknown. All that's known for sure is that all life we've found so far shares a common ancestry. It's possible there were multiple abiogenic sources of life and the one we see now just out-competed everything else. So maybe the first living thing has no ancestors alive today.
- User23 8y agoWhat's the argument that life couldn't have arisen multiple times? If the conditions for spontaneous generation existed on the primordial Earth, why wouldn't they have held in more than one place and why couldn't genesis have occurred more than once?
- Emma_Goldman 8y agoThere is no consensus about how life originated on earth. It's perfectly possible that life has arise multiple times.
- fifnir 8y agoAnd how do we come to share genetic code and genes with the most distant organisms?
- bookofjoe 8y agoRefer to the Singularity & Big Bang some 13 billion years ago, when we and everything in the (known) universe were all crunched together for just the smallest possible length of time....