Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Last universal ancestor

en.wikipedia.org

Post reply on HN
Print view View original

21–26 of 26 posts

Re: Last universal ancestor

#21

Post by arh68 »

All I hear is most stupendous badass of all time: (forgive the long quote)

  ... self-replicating organisms came into existence on this planet 
  and immediately began trying to get rid of each other, either by 
  spamming their environments with rough copies of themselves, or by 
  more direct means which hardly need to be belabored. Most of them 
  failed,... Like every other creature on the face of the earth, 
  [Godfrey Waterhouse IV] was, by birthright, a stupendous badass, 
  albeit in the somewhat narrow technical sense that he could trace 
  his ancestry back up a long line of slightly less highly evolved 
  stupendous badasses to that first self-replicating gizmo — which, 
  given the number and variety of its descendants, might justifiably 
  be described as the most stupendous badass of all time. Everyone 
  and everything that wasn't a stupendous badass was dead. 
  As nightmarishly lethal, memetically programmed death-machines 
  went, [his parents] were the nicest you could ever hope to meet....
[1] Cryptonomicon, also found here http://tvtropes.org/pmwiki/pmwiki.php/Main/WorldOfBadass

Re: Last universal ancestor

#22

Post by KMag »

codemac wrote: post #19
streptomycin wrote: post #12

Earlier quoted context omitted.

Fortunately, a citation is provided. I guess that's wikipedia for you.

> For starters, LUCA may not have used DNA. Poole has studied the history of enzymes called ribonucleotide reductases, which create the building blocks of DNA, and found no evidence that LUCA had them (BMC Evolutionary Biology, DOI: 10.1186/1471-2148-10-383)[0]. Instead, it may have used RNA: many biologists think RNA came first because it can store information and control chemical reactions (New Scientist, 13 August…

In order to produce the proteins encoded in DNA, cells first make messenger RNA (mRNA) copies of the information in the DNA and then the rhibosomes translate the mRNA into amino acid sequences. So, while DNA is much more stable than RNA, it's not obvious that an organism couldn't just get rid of DNA, work with RNA, and deal with a higher mutation and degredation rate. Plenty of viruses use only RNA to carry their genetic material.

There's a long-standing debate over whether enzymes or nucleic acids came first. In modern cells, enzymes are necessary to catalyze energy-producing reactions and other chemical reactions, and nucleic acids are necessary to store the information necessary for self-replication. It seems unlikely that nucleic acids and enzymes both were randomly spontaneously generated and worked together in the first self-replicating chemical reactions. Instead, most people have theorized that either early cells used proteins to store information or used nucleic acids to catalyze reactions. It has been shown in the lab that some reactions can be catalyzed by RNA.

So, the theory goes something like (1) self-replicating RNA spontaneously arises that both catalyzes reactions and carries information (2) mutations in some of the RNA causes it to create enzymes, which make much better catalysts and out-compete RNA-only life (3) RNA-enzyme life mutates and starts using DNA as a more stable storage format than RNA, making those DNA-RNA-enzyme organisms more robust and these out-competed all RNA-enzyme organisms.

Re: Last universal ancestor

#23

Post by sumitviii »

b08aa8b0dcfce wrote: post #20
sumitviii wrote: post #14

Earlier quoted context omitted.

The possibility of 2 non-monozygotic twins having identical genes is not zero, just astronomically low. Its the same for LUA.

The possibility of you turning into a teapot is non-zero, just astronomically low.

Is it really possible?

Re: Last universal ancestor

#24

Post by b08aa8b0dcfce »

sumitviii wrote: post #23
b08aa8b0dcfce wrote: post #20

Earlier quoted context omitted.

The possibility of you turning into a teapot is non-zero, just astronomically low.

Is it really possible?

Mathematically speaking, yes, it is. The probability of any event in this universe is non-zero.
Post reply on HN