Thursday, November 6, 2014

What are the odds of life? Beyond mere astronomical

 Lecompte de Nouy
The French biophysicist and mathematician Lecompte de Nouy was an internationally-regarded scientist whose work on surface tensions and other properties of liquids is still studied today. 

During his work, which started in World War One in trying to mathematically describe the healing of wounds, he examined the laws of probability for a single molecule of high dissymmtery to be formed by chance. De Nouy found that the time needed to form one such molecule worked out to be 10^253 years, or countless trillions of years. (This in a universe that scientists today say is a mere 14.5 billion years old.)

"But," continued de Nouy, "let us admit that no matter how small the chance it could happen, one molecule could be created by such astronomical odds of chance. However, one molecule is of no use. Hundreds of millions of identical ones are necessary. Thus we either admit the miracle or doubt the absolute truth of science." 

I posted before a lecture by James Tour, one of the 10 most cited chemists in the world, whose particular specialty is making molecules from scratch, ab initio, from atoms. 
… I will tell you as a scientist and a synthetic chemist: if anybody should be able to understand evolution, it is me, because I make molecules for a living, and I don’t just buy a kit, and mix this and mix this, and get that. I mean, ab initio, I make molecules. I understand how hard it is to make molecules. I understand that if I take Nature’s tool kit, it could be much easier, because all the tools are already there, and I just mix it in the proportions, and I do it under these conditions, but ab initio is very, very hard.
Think about this: the simplest form of life is the single-cell creature. There is, after all, no such thing as a "half-cell" creature. Of such organisms, prokaryotes "are the earliest and most primitive forms of life on earth." 

As organized in the Three Domain System, prokaryotes include bacteria and archaeans. Prokaryotes are able to live and thrive in various types of environments including extreme habitats such as hydrothermal vents, hot springs, swamps, wetlands, and the guts of animals. Prokaryotic cells are not as complex as eukaryotic cells . They have no true nucleus as the DNA is not contained within a membrane or separated from the rest of the cell, but is coiled up in a region of the cytoplasm called the nucleoid. 
Study that diagram and try to answer Dr. Tour's simple question: 
How do you get DNA without a cell membrane? And how do you get a cell membrane without a DNA? And how does all this come together from this piece of jelly?” We have no idea, we have no idea.
Prokaryotes did not evolve. Taking Dr. Tour's point, the cell's DNA contains the coding for the  formation and structure of the cell wall. But the cell wall could not have come after the DNA because without the cell wall to begin with, the DNA could not have either formed or survived its environment if it had formed. The DNA and cell wall had to have formed simultaneously, but how could that be if forming any organic matter at all is nothing but random chance combinations of atoms that have, in some vital cases, one chance in 10^253 to have formed at all? 

A prokaryote cell cannot have come into existence bit by bit because no bit could have survived without the rest of the cell to support it and give it life. And scientists have neither discovered nor described a potential, simpler pre-prokaryote. No, such a cell not only came into existence all at one time, it had to do so already capable of reproduction through binary fission, else the first would have been the only. 

And of course, this all happened by random chance, right? Which begs the question, What are the odds? 

No wonder that Freeman Dyson, one of the most celebrated scientists of the last 100 years, wrote in his essay, "How We Know," 
The public has a distorted view of science, because children are taught in school that science is a collection of firmly established truths. In fact, science is not a collection of truths. It is a continuing exploration of mysteries. Wherever we go exploring in the world around us, we find mysteries. Our planet is covered by continents and oceans whose origin we cannot explain. Our atmosphere is constantly stirred by poorly understood disturbances that we call weather and climate. The visible matter in the universe is outweighed by a much larger quantity of dark invisible matter that we do not understand at all. The origin of life is a total mystery, and so is the existence of human consciousness. We have no clear idea how the electrical discharges occurring in nerve cells in our brains are connected with our feelings and desires and actions [boldface added].
Then we have this observation by GK Philip & SJ Freeland, NASA Astrobiology Institute, University of Hawaii, in considering that of the 80 amino acids that could be used to build genetically encoded protein polymers, nature uses a “standard set” of 20 identified amino acids.
“Specifically, we show that the standard set of 20 amino acids represents the possible spectra of size, charge, and hydrophobicity more broadly and more evenly than can be explained by chance alone.” (emphasis added)
Amino acids, of course, are the building blocks of proteins, without which there is no life. But, "What are the odds of getting a functional protein by chance?" Well, see for yourself:
  • BONDING: You need 99 peptide bonds between the 100 amino acids. The odds of getting a peptide bond is 50%. The probability of building a chain of one hundred amino acids in which all linkages involve peptide bonds is roughly (1/2)^99 or 1 chance in 10^30.
  • CHIRALITY: You need 100 left-handed amino acids. The odds of getting a left-handed amino acid is 50%. The probability of attaining at random only L–amino acids in a hypothetical peptide chain one hundred amino acids long is (1/2)^100 or again roughly 1 chance in 10^30.
  • SEQUENCE: You need to choose the correct amino acid for each of the 100 links. The odds of getting the right one are 1 in 20. Even if you allow for some variation, the odds of getting a functional sequence is (1/20)^100 or 1 in 10^65.
The final probability of getting a functional protein composed of 100 amino acids is 1 in 10^125. Even if you fill the universe with pre-biotic soup, and react amino acids at Planck time (very fast!) for 14 billion years, you are probably not going to get even 1 such protein. And you need at least 100 of them for minimal life functions, plus DNA and RNA.
But the difficulties of "random chance" continue. E.V. Koonin and A.S. Novozhilov, National Center for Biotechnology Information, National Institutes of Health, Bethesda, MD, wrote:
A real understanding of the [genetic] code origin and evolution is likely to be attainable only in conjunction with a credible scenario for the evolution of the coding principle itself and the translation system.
Which is to say: 
  • The origin of the genetic code is unknown
  • The code operates according to a coding principle but no one knows how the principle started
  • No one understands how the coding principle could have preceded the code itself, or even whether it did so.
But it all started randomly and uncaused, right? It just happened. Lucky us! British cosmologist (and ETI enthusiast) Paul Davies observed that there are just three possibilities of how life started on earth: 
  1. A fluke (random chance), 
  2. Unknown laws that make life a cosmic imperative, 
  3. A miracle (that is, intentional acts by an outside agency)
Of number 1, Davies says this is the "ultimate just-so story." Of number 2, there is no evidence at all and of number 3, well, he doesn't say much. 

I am going with number 3 myself. I do not have enough faith to believe the other two.

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