Introduction
Science has accomplished enormous progress and achievements
in genetics since the turn of the 21stcentury. Scientists have sequenced
and mapped the entire genomes of more than 2800 organisms/species including
human, and the count is on.[1]
Macroevolution of evolution theory tells us that humans, as
well as other multicellular forms of life, have evolved from primitive
single-celled organisms that fall under the kingdom of prokaryotes or even more
primitive.[2] Prokaryotes are single-celled
organisms that have no true nucleus as their genome is not contained within a
membrane nor distinct from the rest of the cell. They are the earliest
and most primitive forms of life found on earth.[3] Is there a chance for this
evolution to have taken place from a simple, single cell to a human being
during the age of the universe?
The human genome[4] contains approximately 3
billion chemical nucleotide base pairs (A, C, T, and G).[5]
Approximately 34 million nucleotide bases of the human genome encode for the
production of proteins that are vital to all living processes.[6] These 34 million nucleotides
are called genes. Proteins are made of amino acids. Each amino acid
is encoded for by a codon, and each codon is composed of 3 nucleotides.
You can think of nucleotides as alphabets of 4 letters pool,
and codons as words of 3 letters length.
The sequence of these nucleotides within genes is what
defines the characteristics and functions of a living organism and its nature;
will it be a bacterium, a plant, a fly, a fish, or a human. The sequence
of this coding in human genes, as well as other organisms, is so sophisticated,
precise, and well organized that it is comparable to the sequence of alphabets
in a Shakespeare’s poem, a novel, a thesis, a computer program, or an
encyclopedia of 2 million words (or 2 volumes).
According to macroevolution, this precise sequence, coding,
has come into being by random mutations[7] and natural selection.
Maximum Possible Mutations During the Age of the Universe
We will try to find out here the maximum number of mutations
that can occur during the age of the universe based on assumptions that favor
evolution.
The maximum number of mutations a human genome can undergo
during its course of evolution from a single cell to a human is 3 billion
mutations per generation since that is the largest size the genome of mammals
has reached. This is an extreme assumption in favor of evolution.
In reality, mutation rate ranges approximately between 0.003 and 350 mutations
per genome per generation.[8]
The shortest generation time reported to date is the
generation ofPseudomonas natriegens, a marine bacterium with a generation time
of 9.8 minutes.[9] Nevertheless, going once again
to the utmost in favor of evolution, we can assume that we are getting a new
generation every one second. Thus, during the age of the universe,[10] which is about 15 billion
years,[11] the maximum number of
generations that can be reached is:
Universe age in years × Days per year × Seconds per day
15 billion × 365 × 86400
which equals less than 1018 generations (1 with 18 zeros after it).
15 billion × 365 × 86400
which equals less than 1018 generations (1 with 18 zeros after it).
The last piece of information needed to calculate the
maximum number of possible mutations is the population of these single-celled
organisms. For that we will assume a very large number that leaves no
place for more; the number of atoms in the observable universe that is about 1082.[12]
Thus, based on previous results and generous assumptions,
the maximum number of mutations that may occur in the entire universe and
during its age is:
Mutations per generation × Generations during universe age ×
Population
3 billion × 1018 × 1082
which equals less than 10110 mutations (1 with 110 zeros after it).
3 billion × 1018 × 1082
which equals less than 10110 mutations (1 with 110 zeros after it).
Number of Random Mutations Required for the Evolution into a
Human
The genes of human genome consist of approximately 34
million nucleotides.[13]
The largest genome in simple, single-celled organisms,
prokaryotes, is about 13 million nucleotides.[14]
Thus, there is a difference of at least 21 million
nucleotides between prokaryote organisms and humans. And for a single
cell to evolve into a human, the evolutionary process needs to mutate –which
may include insertion– at least 21 million nucleotides with the correct
nucleotide base and in the correct sequence.
In genes, each amino acid –the building block of proteins
that are vital to all living processes– is coded for by 3 nucleotides, which is
called a codon. 21 million nucleotides means 7 million codons.
Random mutations have one of three effects: Neutral,
Deleterious (harmful), or beneficial. Only beneficial mutations can
contribute to the evolutionary process.
In living organisms, there are 20 different amino acids and
a stop code,[15] thus, the total is 21.[16] Any mutation will lead to one
of these 20 amino acids or the stop code.[17]
Therefore, each mutation falling inside genes, the coding
region of the genome,[18] has a chance of approximately
1/21 of not altering the amino acid (i.e. coding for the same amino acid) and
thus being a neutral mutation, and a chance of approximately 20/21 of altering
the amino acid.[19] 70% of these 20/21 mutations
are deleterious (harmful) mutations.[20] Nevertheless, for the sake of
evolution, we will assume that all mutations which are altering amino acids are
beneficial mutations. Thus, each mutation has a chance of approximately
20/21 of being beneficial.[21]
Therefore, the probability for 7 million codons to mutate
randomly with beneficial mutations is:
Chance of mutation for being beneficial to the power of
Number of codons
20/21 to the power of 7 million
which equals 1 to more than 10100,000 (1 with 100,000 zeros after it).[22]
20/21 to the power of 7 million
which equals 1 to more than 10100,000 (1 with 100,000 zeros after it).[22]
Could natural selection have enhanced the chances of
mutations in our scenario? Never, since what natural selection basically
does is to sustain lineages with beneficial or neutral mutations and to
eliminate lineages with harmful mutations. Natural selection does not
prevent beneficial mutations from being mutated again. Moreover, in our
scenario, we have already assumed that all mutations are either neutral or
beneficial, and have ruled out harmful mutations. Thus, natural selection
cannot do any better in this scenario.
Conclusion
Therefore, we need more than 10100,000 (1 with 100,000
zeros after it) random mutations to occur so that a simple, single-celled
organisms may evolve into a human, while we can only get less than 10110 (1
with 110 zeros after it) mutations during the age of the universe, even when
the entire universe is a stage for this evolutionary process.
All these calculations were based on human genes –that
constitute less than 2% of the genome– without taking into consideration the
junk region that consumes approximately 98% of the human genome, which turned
out not to be junk anymore. The ENCODE Project Consortium was able to
assign biochemical functions for 80% of the human genome and found that
approximately 20% of it regulates the genes. The results of the five-year
ENCODE project were published in 2012 in the journals Nature, Science, Genome
Biology and Genome Research.[23] The ENCODE consortium’s 442
researchers, situated in 32 institutes around the world, used 300 years of
computer time and five years in the lab to get their results.
Hoping this study was beneficial in shedding some light on
this crucial topic.
[Comments, rebuttals, and critics on this article are
welcomed. You may send them to the author at comments@i-g.org].
Footnotes:
[2] http://jmicro.oxfordjournals.org/content/early/2012/09/28/jmicro.dfs062.full
http://www.bbc.co.uk/nature/history_of_the_earth
http://www.ncbi.nlm.nih.gov/books/NBK9841/
http://www.sciencemag.org/content/323/5911/198.full?sid=d1229251-19db-4c22-ad69-f77105acb632
http://www.nature.com/scitable/content/the-origin-of-mitochondria-and-chloroplasts-14747702
http://evolution.berkeley.edu/evolibrary/article/_0/endosymbiosis_03
http://www.bbc.co.uk/nature/history_of_the_earth
http://www.ncbi.nlm.nih.gov/books/NBK9841/
http://www.sciencemag.org/content/323/5911/198.full?sid=d1229251-19db-4c22-ad69-f77105acb632
http://www.nature.com/scitable/content/the-origin-of-mitochondria-and-chloroplasts-14747702
http://evolution.berkeley.edu/evolibrary/article/_0/endosymbiosis_03
[3] http://www.nature.com/scitable/definition/prokaryote-procariote-18
http://www.nature.com/scitable/content/the-origin-of-mitochondria-and-chloroplasts-14747702
http://biology.about.com/od/cellanatomy/ss/prokaryotes.htm
http://www.nature.com/scitable/content/the-origin-of-mitochondria-and-chloroplasts-14747702
http://biology.about.com/od/cellanatomy/ss/prokaryotes.htm
[4] A
genome is an organism’s complete set of DNA or RNA, including all of its genes.
Each genome contains all of the hereditary information needed to build and
maintain that organism.
[7] Mutation
types include: substitution, insertion, deletion, frameshift, as well as other
types (http://evolution.berkeley.edu/evosite/evo101/IIIC3aTypes.shtml).
[8] http://www.genetics.org/content/148/4/1667.full
http://www.genetics.org/content/156/1/297.full
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2910838/ [Table 1]
http://sandwalk.blogspot.com/2007/07/mutation-rates.html
http://www.genetics.org/content/156/1/297.full
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2910838/ [Table 1]
http://sandwalk.blogspot.com/2007/07/mutation-rates.html
[10] Why
not during the age of the earth alone? Simply, to eliminate any
assumption that genome codes were passed down to the earth from outer space.
[12] http://www.universetoday.com/36302/atoms-in-the-universe/
http://plato.stanford.edu/entries/computability/
http://plato.stanford.edu/entries/computability/
[15] There
are 64 codons. On average, each amino acid and the stop code can be coded
for by one of three codons [see references in footnote # 17].
[16] http://www.ncbi.nlm.nih.gov/books/NBK21950/ [Figure
10-27]
http://www.nature.com/scitable/definition/genetic-code-13
http://hyperphysics.phy-astr.gsu.edu/hbase/organic/gencode.html
http://www.nature.com/scitable/definition/genetic-code-13
http://hyperphysics.phy-astr.gsu.edu/hbase/organic/gencode.html
[17] http://www.ncbi.nlm.nih.gov/books/NBK22358/ [Table
5.4]
http://en.wikipedia.org/wiki/DNA_codon_table
http://www.nature.com/scitable/topicpage/nucleic-acids-to-amino-acids-dna-specifies-935
http://en.wikipedia.org/wiki/DNA_codon_table
http://www.nature.com/scitable/topicpage/nucleic-acids-to-amino-acids-dna-specifies-935
[18] If
mutation falls outside genes then obviously it is neutral to genes. It is
noteworthy that for most multicellular organisms with a genome size larger than
100 million nucleotides, their genes consume only less than half of the genome
(http://www.ncbi.nlm.nih.gov/pubmed/18384817 andhttp://www.tcm.phy.cam.ac.uk/~tmf20/PUBLICATIONS/jtb_07.pdf).
[19] To
be more precise, the chance of altering the amino acid is between 20/21 and
20.318/21 but cannot exceed that. It is not exactly 20/21 because a codon
doesn’t mutate to itself. The upper limit of chance was obtained by the
equation: (63-((64/21)-1))/(64-1) = 20.318/21. In all cases, the final
result of probability reached in this study is the same.
[21] This
chance of 20/21 of being beneficial can also be applied in the rare case of
inserting complete codons or large scale coding. Because all studies have
confirmed that only a small portion of random mutations (in all their kinds)
are beneficial, while the majority of them are either harmful or neutral.
That is obvious since they are random. Thus, giving it a chance of
20/21 for being beneficial is a very generous assumption (http://www.nature.com/scitable/topicpage/genetic-mutation-441,http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1871816/,http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1617134/,http://global.britannica.com/EBchecked/topic/399695/mutation,http://www.nature.com/hdy/journal/v84/n4/abs/6887250a.html,http://www.genetics.org/content/148/4/1667.full.pdf,
andhttp://www.sciencemag.org/site/feature/data/pharmacia/1999/Cascalho.xhtml).
[22] To
calculate large digits, you may need a special calculator such as the one athttp://www.ttmath.org/online_calculator.
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