- The improbability of nucleotide precursors of RNA and DNA appearing (no nucleotides have been produced in experiments realistically simulating the early Earth)
- The improbability of most amino acids precursors of proteins appearing (no more than two of the twenty amino acids used by life have been produced in experiments realistically simulating the early Earth)
- The improbability of DNA appearing
- The improbability of protein molecules appearing (see below for some discussion of this)
- The improbability of homochirality, a gigantically improbable coincidence apparently needed for life
- The improbability of a first prokaryotic cell appearing
- The improbability of the leap from a prokaryotic cell to a eukaryotic cell (seemingly harder than a horse cart accidentally turning into a sports car)
- The improbabilty of multicellular life appearing (the appearance of large organized organisms is not predictable from the mere appearance of microscopic cells)
- The improbability of organisms with manual dexterity appearing
- The improbability of intelligent life appearing
A recent paper by astronomer David Kipping estimated the likelihood of extraterrestrial intelligence. But the paper paid no attention to any of the improbabilities involved in extraterrestrial life appearing. The paper also paid no attention to any of the improbabilities involved in extraterrestrial intelligence appearing. Kipping's paper fails to even use the word "cell" or "protein" or "genome" or "DNA" or "complexity." He seems to have paid zero attention to the complexity of life.
A few weeks later there appeared another paper estimating the chance of extraterrestrial civilizations. The paper by Tom Westby and Christopher J. Conselice (entitled "The Astrobiological Copernican Weak and Strong Limits for Intelligent Life") also seemed to follow an approach paying no attention to biological unlikelihoods. Again, we have a paper estimating the chance of extraterrestrial life that fails to use the word "cell" or "protein" or "complexity" or "DNA" or "genome."
Very strangely, the paper evoked the principle that we should simply assume that other habitable planets have been as fortunate as Earth has been. Under such a principle, you ignore all of the improbabilities involved in life appearing and intelligent life appearing, and simply assume that intelligent life has appeared on other habitable planets that have existed as long as our planet as existed. So, for example, if there is an Earth-sized planet the right distance from a sun-like star, then you simply assume that intelligent life appeared on such a planet, if the planet has existed as long as the Earth.
Of course, such a principle is ludicrous. If you have reason to believe that very unlikely luck occurred, you have no business assuming that such luck would always occur. If you fall out of a high-flying airplane, and luckily land safely on a haystack, it would be absurd for you to assume that other people falling out of airplanes must have the same luck you had. And if you are lucky enough to win 100 million dollars after buying five $1 lottery tickets, you would be foolish to think that anyone buying five $1 lottery tickets will have the same luck you had.
We can understand the appeal of this "ignore all improbabilities" principle that some of our astrobiologists seem to be following. The attraction is that things become so much easier for the astrobiologist. Suddenly it becomes okay if our astrobiologist does not know a single thing about cells or proteins or genomes. Now some planetary astronomer can call himself an astrobiologist even if he never took a course in biology, and does not know the difference between an amino acid and battery acid, or does not know the difference between a cell and a cell phone.
But I should not suggest that these astrobiologists taking this "ignore all improbabilities" approach are very different from ordinary mainstream biologists. By taking an "ignore all improbabilities" approach, such astrobiologists are pretty much conforming to the behavior of regular mainstream biologists. For while biology professors have never explicitly advocated a policy of "ignore all improbabilities," they have been pretty much following such a policy for a very long time.
Charles Darwin's works paid no real attention to improbabilities. He simply evoked some principle he called survival of the fittest or natural selection, and assumed that such a principle (along with a principle of "sexual selection") could explain almost all wonders of biology, without calculating the improbabilities involved. In the nineteenth century you could try to justify such ignoring of improbabilities by claiming that it is too hard to calculate the odds of biological innovations.
However, by about the middle of the twentieth century scientists had learned enough to have a good mathematical basis for calculating some of the improbabilities involved if an accidental biological innovation were to occur. Scientists learned that the basic building blocks of cells are protein molecules, and that such molecules are typically built from hundreds of amino acids. Humans have more than 20,000 different types of protein molecules, each fine-tuned to serve some particular function. There are twenty types of amino acids used by living things. The twenty types of amino acids are like the twenty six letters of the alphabet, and a protein molecule is like some functional paragraph.
The median number of amino acids in a protein molecule has been calculated as 361. Referring to random tiny changes in the amino acids in a protein (mutations), a scientific paper stated, "We predict 27–29% of amino acid changing (nonsynonymous) mutations are neutral or nearly neutral (|s|<0.01%), 30–42% are moderately deleterious (0.01%<|s|<1%), and nearly all the remainder are highly deleterious or lethal (|s|>1%).” This amounts to an estimate that a random change to the amino acid sequence of a protein has about a 30% chance of breaking the protein's functionality. Similarly, the paper "Protein tolerance to random amino acid change" suggests that a random mutation will have about a 34% chance of breaking the functionality of a protein molecule in which it occurs.
Given such facts, some elementary improbability calculations can be done. Since it is known that a random small change in a protein molecule will have about a 33% of making the molecule non-functional, it is reasonable to assume that at least half of the amino acid sequence of a protein molecule must exist for the molecule to be functional. Half of 361 (the median amino acid length of a eukaryotic protein) is about 180. Given twenty possible amino acids in any position in the amino acid sequence of a protein molecule, the probability of getting a functional protein molecule can be roughly calculated as 1 in 20 to the 180th power. That is a probability of about 1 in 10 to the 234th power, which is 1 in 10 followed by 233 zeroes. That's about the probability of you correctly guessing the full 10-digit phone numbers of twenty-three consecutive strangers.
So for you to get a functional protein molecule by chance requires a miracle of luck. The odds of it are so small that we should never expect it to occur by chance even given billions of years of random chemical combinations. If we are to believe that earthly life has appeared through accidental processes, we must believe that such a miracle of luck has occurred not just once, but many millions of different times. For in the animal kingdom there are many millions of different types of protein molecules, each a complex invention serving a different function.
This is only one of innumerable cases in which improbability calculations indicate that prevailing biological explanations cannot be correct. Those who teach such explanations ignore such difficulties by typically following an "ignore all improbabilities" policy.
The lack of relevant probability calculations by Darwinist professors bothered the eminent physicist Wolfgang Pauli, discoverer of the subatomic Pauli Exclusion Principle on which our existence depends. Pauli stated the following:
"I should like to critically object that this model has not been supported by an affirmative estimate of probabilities so far. Such an estimate of the theoretical time scale of evolution as implied by the model should be compared with the empirical time scale. One would need to show that, according to the assumed model, the probability of de facto existing purposeful features to evolve was sufficiently high on the empirically known time scale. Such an estimate has nowhere been attempted though."
Pauli also stated the following about Darwinist biologists:
“In discussions with biologists I met large difficulties when they apply the concept of ‘natural selection’ in a rather wide field, without being able to estimate the probability of the occurrence in a empirically given time of just those events, which have been important for the biological evolution. Treating the empirical time scale of the evolution theoretically as infinity they have then an easy game, apparently to avoid the concept of purposesiveness. While they pretend to stay in this way completely ‘scientific’ and ‘rational’, they become actually very irrational, particularly because they use the word ‘chance’, not any longer combined with estimations of a mathematically defined probability, in its application to very rare single events more or less synonymous with the old word ‘miracle’.”
Were our biology professors to start paying adequate attention to probability, they would acknowledge the very important principle that the improbability of a complex innovation appearing accidentally usually rises exponentially and geometrically as the number of parts needed for that innovation undergoes a simple linear increase, in most cases when a special arrangement of the parts is required. Similarly, the improbability of you throwing a handful of cards into the air and having them all form into a house of cards will rise exponentially and geometrically as the number of cards in your hand undergoes a simple linear increase. Getting a two-card house of cards by accident isn't too hard, by having two cards lean together diagonally. But if all the humans in the world spent their whole lives throwing a deck of cards into the air, none of these random throws would ever produce a 40-card house of cards by accident. Similarly, the improbability of a typing monkey producing a functionally useful 100-word paragraph is not merely 100 times greater than the improbability of the typing monkey producing an English word; the improbability is more than quadrillions of times greater.
Because the improbability of a complex innovation appearing accidentally usually rises exponentially and geometrically as the number of parts needed for that innovation undergoes a simple linear increase, in most cases when a special arrangement of the parts is needed, fine-tuned protein molecules consisting of hundreds of amino acids arranged in just the right way to achieve a functional effect are accidentally unachievable. The infinitely more complex arrangements of matter in cells and DNA molecules are also accidentally unachievable. No machines in any conceivable factory could ever assemble molecule by molecule the functional intricacy of a human organism. The fine-tuned biochemistry of living things is functionality more complex than any machine humans have ever built. The visual below helps to illustrate why it makes no sense to believe that such immensely organized arrangements of matter appeared because of accumulations of random mutations.
If it were true that Earth-sized planets in the habitable zone tended to be as fortunate as Earth in regard to intelligent life appearing, our galaxy would be teeming with intelligent life, and would probably have many millions of civilizations. Intelligent life on some planets would become extinct, but the tendency of long-lived civilizations to spread around to other planets and solar systems would tend to make up for such extinctions. But 60 years of attempts to detect signals or signs of other civilizations in our galaxy have been completely unsuccessful. This suggests that the kind of wildly optimistic assumptions made by Westby and Conselice are not correct. Westby and Conselice seem to be ignoring not only biology, but also the history of the search for extraterrestrial intelligence.
Postscript: Another science paper similar to the two papers I mentioned regarding the fragility of protein molecules is the paper "Robustness–epistasis link shapes the fitness landscape of a randomly drifting protein," which you can read here. Figure 1 of the paper has a graph suggesting that the fitness of a protein molecule will decline by about 80% after 4 random mutations, and that the molecule will have no fitness (and become useless) after about 12 mutations. Since eukaryotic proteins have a median amino acid length of about 360, that 12 mutations is a mere 3% of the amino acid sequence. The amino acid sequences in proteins are comparable to the sequences of letters in a functional paragraph, but the protein molecule is more sensitive to changes than the paragraph. A paragraph will become unintelligible and useless after about 10% of its characters are randomly changed, but a smaller change in a protein molecule will be enough to make it useless. Protein molecules seem to be almost as sensitive to random changes as computer code. Making random changes in only a very small percent of the characters in a computer program will cause the whole program to become nonfunctional because the code is rejected by the compiler that reads it.