31 July 2023

The true history of junk DNA

"By the late 1960s, knowledgeable scientists were used to the idea that genes occupied only a small part of the genome, and in 1974 the editor of the journal Cell, Benjamin Lewin, was expressing the consensus view of the experts when he wrote that the C-value Paradox could be resolved by assuming that much of the genome is composed of nonfunctional repetitive DNA (junk DNA)." (Chapter 2 of Laurence Moran (2023) What's in your genome.)

It may be that 'knowledgeable scientists' in the late 1960s knew that much of the genome is composed of junk DNA, but the 'consensus view' was not widely known in all sub-disciplines of the biological research community. Maybe the journal Cell was not read in the evolutionary biologist community. Probably, those experts were experts in a different field with its own journals and conferences.

Eli C. Minkoff (1984) Evolutionary Biology.

I checked the oldest textbook I have, Minkoff (1984) Evolutionary biology. There is no 'junk DNA' and no 'non-coding' DNA in the index, despite the 'consensus view'. Yes, there are tRNA and rRNA (p.16), but these RNAs are not labeled as 'non-coding RNA' or 'non-coding DNA'. They are in the business of producing proteins. They are the very embodiment of the genetic code. Therefore, it would be somewhat counterintuitive to call them 'non-coding'. Yes, there is 'genetic drift', neutral mutations, 'neutralism versus selectionism', 'genetic load', 'mutational load' in his book, but Minkoff did not connect these concepts with 'non-coding DNA'. The concept is absent anyway. 'Centromere' is mentioned once casually (p.19), I could not find 'telomere'. Anyway, 'centromere' is not labeled as 'non-coding DNA'. Why is non-coding DNA absent from the book? 

I think I found part of the answer in the following passage:

"One of the fundamental tenets of modern synthetic theory of evolution is that natural selection operates on the phenotype rather than the genotype. No genetic change can be influenced by natural selection unless it first produces some phenotypic change. It is largely for this reason that modern evolutionary biologists must be aware of the manner in which phenotypes are controlled." (p.114)
This was an eye-opener for me. The phenotype is the most important, the genotype is important only in so far it has an effect on the phenotype. Who cares about DNA that does nothing? Evolutionary biology has the task of explaining the organism.

A second foundational paradigm I found here:

"Proteins are among the most important of all biological molecules. (...) The great intricacies of living systems are all the result of enzyme-controlled activities (...) enzymes are therefore the chemical basis of life". (p.17).

Taken together these two principles explain the mindset of evolutionary biologists in those days. If they did know about non-coding DNA, it simply had no relevance to the goals of their daily research. On page 37 there is a table labeled as 'The Genetic Code for Translation of mRNA Codons into Amino Acid sequences'. The famous table. It makes sense in this context, because the Genetic Code is the link between DNA and proteins. The reason for the existence of the Genetic Code is to produce proteins. The Watson-Crick structure of DNA plus the chemical structure of the four bases is present in the book. Minkoff knows the necessary biochemistry. Unfortunate exception: introns and splicing are absent! Introns were discovered in 1977.

There is one isolated and thus mysterious remark which vaguely suggests something like 'non-coding DNA':

"Not all of the genotype is transcribed and translated into a portion of the epigenotype, nor are all the transcribable genes ever transcribed at the same time." (p.114) ['epigenotype' = "the polypeptides that result from the immediate transcription and translation of the genotype"]

That's all. Probably, Minkoff was vaguely aware of non-coding DNA. But why include it in his textbook? He did not elaborate the concept because in his opinion it was simply not relevant or nothing was known about it. DNA which is not transcribed and translated has nothing to contribute to the phenotype of the organism, consequently nothing to biology and evolution. It doesn't fit in the evolutionary biology paradigm of that time [1].

So, that is the 'true history' of non-coding DNA based upon Minkoff (1984) and that was taught to biology students at that time. He did not say that non-coding equals junk, but by omitting non-coding DNA, he implied that non-coding DNA is unimportant. If one makes statements about the history of junk DNA, one has to investigate the evolutionary biology textbooks, especially older ones. Minkoff was an eye-opener for me. I checked more evolutionary biology textbooks: 8 out of 17 do not have 'non-coding DNA' in the index.

"As Sandwalk readers know, there was never a time when knowledgeable scientists said that all non-coding DNA was junk. They always knew that there was functional DNA outside of coding regions." (Sandwalk)

I think one has to take into account that there are different scientific disciplines with their own paradigms, leaders, journals, conferences, and networks. 

Thanks for reading. Have a nice day!



  1. On page 18 he writes: "there are other sequences in each DNA molecule that do not appear to determine the amino acid sequence of any polypeptide. Some of these may function as "spacers", and others are believed to function as regulatory genes, which control the transcription of other genes." (page 18, chapter 2: Basic Principles of Genetics). Here he describes non-coding regulatory genes! He doesn't realize that these non-protein-coding DNA sequences must have indirect effects on the phenotype, and consequently are important for evolutionary biology! In the subsequent development of evolutionary biology, the evolutionary importance of regulatory genes became evident.  Added: 21 Aug 2023


Previous posts

  1. Junk DNA in the Evolution textbooks (2) from 1996 to 2023 26 Jul 23
  2. Junk DNA in the evolution textbooks. Bergstrom and Dugatkin 2023 12 Jul 23
  3. Periannan Senapathy (1994) claimed that the human genome consists of more than 90% junk DNA. 4 Jul 2023
  4. Scientists say: 90% of your genome is junk. Have a nice day! Biochemist Laurence Moran defends junk DNA theory 26 Jun 23

26 July 2023

Junk DNA in the Evolution textbooks (2) from 1996 to 2023


    Futuyma, Kirkpatrick (2023)  Evolution.

fifth edition        

In the previous blog I discussed Bergstrom and Dugatkin Evolution, third and first edition. Today I continue my investigation of 'junk DNA' in the Evolution textbooks with a textbook by Douglas Futuyma and Mark Kirkpatrick (2023) Evolution also published this year

Although "junk DNA" does not occur in the index, on page 86 (chapter 'Mutation and variation'), the authors state: "In humans for example, 98% of the DNA does not code for any gene product." Note: they do not say 'protein product', but 'gene product'. However, the capture of figure 10.13 states: "Less than 2% is devoted to protein-coding sequences." (p.274). So, if that is what they mean by 'gene product' the 98% is OK. They explain these matters in an excellent and up-to-date chapter about genes and genomes (chapter 10). On page 281 the authors ask:

"Does that mean the 98% of our genome that is noncoding is actually junk? We are still far from having a clear answer to this fundamental question. (...) some of the resulting "junk" now plays key roles in regulating gene expression, and the cell's metabolism has coevolved with the total quantity of DNA in the nucleus. (...) Like an addict and his drug, eukaryotes may not be able to break their dependence on a bloated genome. But their is good news in this story. When ancient eukaryotes acquired large amounts of of noncoding DNA, it opened new options for the evolution of gene regulation. That, in turn, may have enables the origin of complex life-forms, including ourselves." (p.281)

In the end-of-chapter section called 'What We Don't Know' (by the way, a nice feature!):

"Also debated is the fraction of the eukaryotic genome that has a function. One large-scale study estimated that 80% of the human genome has a function." [the reference is the ENCODE publication in Nature, 2012]. "That estimate, however, has been criticized as far too high, and many evolutionary biologists would agree that perhaps only about 10% of our genome has a definite function" (p.281).

Figure 10.13. (p.274). Adapted from Gregory (2005)

This seems a fair and correct description of the status of the scientific evidence. What I miss in figure 10.13 is the difference between functional and non-functional DNA (perhaps an unreasonable demand!). The functional sequences outside protein coding sequences will be hidden in the 98%. 'Functional RNA' is not present in the book. One can find a comprehensive treatment of functional and nonfunctional RNA in Moran (2023) (see my blog 26 June).

"Alternative splicing is a major mechanism used by eukaryotes to increase organismal complexity " (p.274). 

Is it really 'a major mechanism'? This is a controversial statement because there is no quantitative estimate of its importance. Futuyma and Kirkpatrick do not mention non-coding tRNA (transfer RNA), but ribosomal RNA (rRNA) is present (p.269).  However, both are not introduced as good examples of non-coding DNA (they do not code for proteins but are functional). 

Note [3] about Futuyma, 1st edition, 1979


Nicholas Barton et al (2007) Evolution 






Nicholas Barton et al (2007) Evolution has a very good discussion of junk DNA, selfish DNA, C-value, non-coding DNA. Fortunately, they also pay attention to the disadvantages of a big genome (p.597). For example, in insects metamorphosis requires rapid cell division and is harder when massive amounts of DNA must be replicated. It shows that natural selection can downsize large genomes. Which is good to know! It brings the burden of large genomes back into focus. This is important:  transposons can by accident acquire a new function. They do not give an estimate how often this happens. "Introns are frequently considered to be junk DNA. However, comparative sequence analysis has revealed that the sequence of some introns is highly conserved, suggesting that functional constraints have played a role in evolution." (p.220). "Overall, about 18% of nucleotides are conserved in introns and intergenic regions, compared with 72% within exons" (546). "Such studies suggest that in that in multicellular eukaryotes, at least as much non-coding as coding sequence is maintained by selection." (p.547). If all possible alternative splicing possibilities are taken into account, species such as humans can make millions of different proteins, even though they each have only 25,000 protein-coding genes. Alternative splicing provides a significant source of novelty for diversification" (p.221). This is regarded as controversial by some. Transposable elements have sometimes been co-opted to aid their host (p.598). Sometimes pseudogenes acquire new functions. These views contrast with those of Laurence Moran (2023). Further research is necessary.



  Freeman, Herron (2007) Evolutionary Analysis





The most recent edition of Freeman and Herron is the fifth edition (2013). I don't have that edition, I used Evolutionary Analysis 4th edition (2007). There is no 'junk DNA' and no 'non-coding DNA' in the index. Unexpectedly and paradoxically, transposons –a prime example of selfish genetic elements– are discussed in chapter 15 'Phylogenomics and the molecular basis of ADAPTATION'. 

But first, read this stunning remark (remember, this book was published before ENCODE 2012):

"In humans only about 1.2% of the genome codes for proteins." (p.576)

They do not comment on this remarkable statement. It is an isolated statement from an unknown source. However, they do state that the "extra" DNA responsible for the C-value paradox consists of transposable elements: "In the human genome, for example, over 44% of the DNA present is derived from transposable elements (p.576). What about the remaining 54%? They do not tell. Unknown?

Fortunately, the authors discuss the burden of these genomic parasites. It costs the cell time, energy and resources to replicate a genome with a lot of transposons (p.577). Funny remark: transposons are present in the genome in "often appallingly large numbers"! Such an emotional remark is really funny for a textbook! Good to know: transposons are not 100% non-coding DNA, because they encode the enzyme transposase. They have further important information: defense mechanisms against transposons (!), and: "work by John Moran (!) (1999) suggested that transposition events in eukaryotes may occasionally result in mutations that confer a fitness benefit." (p.581-583). They conclude:

"Even though most transposable elements function as genomic parasites and most transposition events result in deleterious mutations, it is increasingly clear that at least some transposition events result in important new genes or other changes that have a positive impact on the fitness of organisms." (p.584).

My conclusion: there is no 'junk DNA' and no 'non-coding DNA' in the index, and more puzzling, there is also no discussion of introns and splicing. That is a serious omission for an evolution textbook. The origin of introns is a longstanding evolutionary mystery. However, they have interesting things to say about transposable elements. According to Laurence Moran 37% of our genome consists of introns and according to Futuyma, Kirkpatrick (2023): 26% (see figure above). Obviously, without introns Freeman and Herron don't have a complete overview of non-coding DNA and can't calculate the sum total of functionless DNA in our genome. Yet, they know that 1.2% of the genome codes for proteins! I guess that Freeman and Herron are optimistic about the possibility of finding more useful elements in the uncharted parts of the human genome and therefore avoid the concept 'junk DNA'. Reasonable.


Strickberger's Evolution Fourth edition 2008


Strickberger's Evolution is a famous evolution textbook. The first edition was published in 1990. The fifth edition appeared in 2013. The most recent edition I have is the fourth edition (2008) authored by Brian Hall and Benedikt Hallgrimsson (I don't know whether Strickberger participated in this edition). 'Junk DNA' [1] and 'non-coding DNA' are not in the index. However, 'junk DNA', 'selfish DNA' and 'C-value paradox' are discussed in the text.

"According to some molecular biologists, many transposable elements and other forms of repeated sequences contribute little, if any, function to their host cells. Because the DNA replication process cannot discriminated between functional and nonfunctional sequences, it replicates any introduced sequence. Transposon DNA and repeated sequences may therefore perpetuate parasitically as either "junk" or "selfish" DNA. (p.221).

Important information is present in Box 12.1 'Quantitative DNA measurements'. In connection with the ENCODE project the following paragraph contains intriguing thoughts which I quote in full:

"According to Bird [1995], eukaryotes were able to circumvent such "noise" by a nuclear membrane that separates transcription from protein translation, allowing only translatable messenger RNA sequences to filter into the cytoplasm, and by tightly folding the DNA of functionally unnecessary genes into nontranscribable confirmations, using nucleosomes and their histones. To these transcription-repressing mechanisms, Bird claims that vertebrates added DNA cytosine methylation, formerly used mostly to suppress genomic parasites such as transposons." (p.260). (my bold)

Especially the concept transcription-repressing is intriguing because according to the ENCODE project and Laurence Moran there is pervasive transcription in the cell and most of it is noise! This would disprove the success of transcription-repressing mechanisms? Apparently, the mechanism fails spectacularly. 

My own thoughts are that maybe because transcription is restricted to the nucleus and those RNA transcripts are not exported to the cytoplasm, and consequently are not translated, large-scale transcription can be tolerated by the cell. This assumes that protein synthesis is more costly than transcription. I admit that it is still a burden, but the burden has been halved.

In contrast to Freeman, Herron (2007), in this book 'introns', the "Introns early - Introns late-hypothesis" and alternative splicing are present. Interestingly, they describe introns as mobile DNA sequences that can splice themselves out, acting like transposon-like elements.

Brian Hall and Benedikt Hallgrimsson do not favor the concept 'junk DNA'. It is obvious from this remark: "various biologists have been tempted to consider some or many such sequences as forms of "selfish DNA'." (p.262).



Stephen Stearns, Rolf Hoekstra (2005) Evolution, an introduction, second edition, paperback.

Relevant topics are 'jumping genes', 'transposons', 'introns', 'B-chromosomes'. Not found in other textbooks: B-chromosomes are not transcribed and do not contain information vital to the organism, they are genomic parasites (p.362). This fits the definition of junk DNA, although Stearns and Hoekstra do not use the concept. They make an interesting remark about transposons: several mechanisms have evolved to suppress the deleterious effects of active transposons (p.363). I would like to know more about them! "In humans they [transposons] may account for 45% of the genome". "Transposons illustrate genomic conflict between selection favoring mutants that increase the replication rate of transposons and selection favoring the suppression of transposons through stronger replication control." (p.363). They have a chapter about Genomic Conflict. There is no new edition of this textbook.

Mark Ridley (2004) Evolution, 3rd Edition

Non-coding DNA is listed in the index under 'DNA, non-coding' [2]. One relevant paragraph 2.4: 'Large amounts of non-coding DNA exist in some species'. The human genome contains 5% maybe up to 10% of genes. "The function of non-coding DNA is uncertain. Some biologists argue that it has no function and refer to it as "junk DNA". Others argue that it has structural or regulatory functions." "Most non-coding DNA is repetitive." (p.27). Alternative splicing is mentioned (gene slo), but there is no diagram of exon-intron structure of a gene (!). The existence of genes coding for RNA (rRNA, tRNA) is mentioned in a footnote ("some genes code for RNA" ! p.25). Further information in Chapter 19 'Evolutionary Genomics' is about the evolutionary history of transposable elements ("About 45% of the human genome is derived from transposable elements", p.567). I am a little disappointed, I expected more of Ridley. Please note, that the draft Human Genome sequence was published in 2001. No definitive conclusions possible at that time. There is no new edition.

John Archibald (2018) 'Genomics: A Very Short Introduction', Oxford University Press, 135 pages, has a succinct description of the ENCODE project in the paragraph "Jumping genes and 'junk' DNA" (p.50-53): "The ENCODE project's broadest and most controversial claim is that 80 per cent or more of the human genome has a biochemical function. "

Peter Skelton 'EVOLUTION. A biological and palaeontological approach' (1993, 1994, 1996)



Initially, I ignored this book because I did not expect it would contain junk DNA. Surprise. In chapter 3: Heredity and Variation, the C-value paradox is explained and illustrated with the well-known genome size diagram of various groups of organisms (Fig. 3.5). It immediately stands out that all salamanders and lungfish have bigger genomes than all mammals, birds and reptiles. The C-value paradox is explained by differences in the amount of various repetitive sequences, and polyploidy. Bats and birds have a high metabolic rate and their genome size is lower than other mammals (p.84). lntrons were discovered in 1977. There is a diagram (Fig. 3.9) of gene structure (intron-exon structure). This figure shows introns with smaller sizes than exons. Unfortunately, students get the false impression that these are the right proportions. However, introns are generally larger than exons.  Alternative splicing is described (p.90). Transposons are explained (p.92). Conclusion: despite this book appeared before the publication of the human genome in 2001, the ingredients of 'junk DNA' are present. So, it doesn't matter that the word 'junk DNA' isn't used.



The word 'junk DNA' is absent in the index and in the text of 4 of the 9 textbooks I investigated. However, if 'junk DNA' is not in the index of a textbook, it always pays to search for transposons, introns, jumping genes, selfish DNA, pseudogenes or C-value paradox. This review of evolution textbooks is not exhaustive (I could not check all editions of all textbooks). Those listed here are the most interesting and give sometimes additional useful insights and different points of view. Some are pre-2012, some post-2012, but all except Skelton are post-2001. In general authors know that less than 2% of our DNA codes for proteins, but are not sure about the rest. I agree. Nobody can claim to know exactly how much of our genome is useless junk. Even assuming that 90% of our genome is junk, there is no definitive answer to the question why is there so much junk in our genome, and why it hasn't been eliminated.

Not discussed here is John Parrington (2017) 'The Deeper Genome. Why there is more to the human genome than meets the eye'  (OUP paperback). This is a must read. He gives very interesting examples of beneficial non-coding DNA derived from transposons, and has a point of view other than that of Moran (2023). I hope to blog about it in the future.

Thank you for reading!


  1. Later I found 'junk DNA' listed under 'Deoxyribonucleic acid' - "junk DNA" in the index! [30 Jul 23]
  2. Non-coding DNA is listed in the index under 'DNA, non-coding' [30 Jul 23]
  3. Futuyma (1979) Evolutonary Biology (1st edition). page 439: "Nonetheless, there is an enormous amount of redundancy in the genome, and its significance is obscure. In may animals as much as 60% of the genome seems to consists of short (less than 300 nucleotide pairs) repeated sequences, some present in thousands of, even a milion, copies". That's all. (personal communication Gerdien de Jong) [1 Aug 23]

12 July 2023

Junk DNA in the evolution textbooks. Bergstrom and Dugatkin 2023

Dugatkin 2023

In a previous post I discussed Larry Moran (2023) 'What's in Your Genome? 90% of Your Genome Is Junk'. He argued that 90% of our genome is junk and has no function until proven otherwise. What about the textbooks? Is 'junk DNA' discussed in the Evolution textbooks? What do they say? 

The latest Evolution textbook was published this month: Bergstrom and Dugatkin (2023) Evolution, third edition. There is no 'junk DNA' in the Index, but non-coding DNA is present and  'junk DNA' is mentioned once in chapter 10: Genome Evolution (page 371). There is a lengthy and excellent discussion of the C-value paradox (differences in genome size do not correlate with organism complexity) and the G-value paradox (multicellular eukaryotes tend to have very similar numbers of protein-coding genes despite large differences in organismal complexity). According to the authors the C-value paradox is solved by the observation that most of the genome is non-coding DNA. 

"Nonetheless, the additional genetic material may be co-opted in any number of ways, allowing subsequent evolution by natural selection of complex genome organization". 

The solution of the G-value paradox is that regulatory networks matter more than the total number of genes. Humans have 2000 transcription factors whereas the nematode has 500. The authors don't speculate about it, but I'd love to know how many transcription factors chimpanzees have! Then we would know what a difference they make. They could be redundant.

Bergstrom and Dugatkin don't seem to believe in 'junk DNA': 

"the noncoding regions of our genome are extensively transcribed and are heavily involved in regulation of gene expression (Mattick et al, 2010)".

According to Moran, John Mattick is one of the ENCODE leaders and one of the most prominent opponents of junk DNA. The authors could not have read Moran, but they could have encountered strong criticism of the ENCODE conclusions. In line with their adaptionist views, and contrary to the view that most alternative spliced genes are splicing errors, the authors think alternative splicing is important in producing different protein products from the same gene. So, introns can have advantages. Further, they argue that transposition (transposons) can potentially have advantages as well. Because the authors think much noncoding DNA could be useful, they do not take the burden of junk DNA serious. If it is functional, there is no burden. Yet, they write that introns impose substantial fitness costs. They do not attempt to quantify the costs. As a consequence they don't have an idea of the magnitude of nonfunctional DNA and the magnitude of the evolutionary costs of junk. 

Figure 10.20 Composition of the human genome.
Adapted from Gregory (2005)

In figure 10.20 in chapter 10 protein-coding genes contribute only 1.5% of the total DNA of the human genome. There is a category 'Other' which contributes 11.6% to the total DNA but it is not clear whether it is junk or functional DNA. The authors do not state what the total percentage of junk DNA is. One cannot derive if from this figure because for example the 'Introns' and 'Other transposons' category could contain some useful DNA. My impression is that for the authors junk is an open question. They do not claim that most of our genome is functional.

Bergstrom, Dugatkin 2012

In Bergstrom and Dugatkin (2012) I found interesting remarks about the disadvantages of introns:

"Yet, introns may impose substantial fitness costs as well. First, introns increase the total size of the genome, thereby increasing metabolic costs and decreasing the maximal rate of cell replication. Mutations to the spliceosomal recognition sites can disrupt RNA processing, and thus they can create nonfunctional proteins. Introns also offer refuges for active transposons and other selfish genetic elements that can subsequently cause deleterious mutations." (p.364)

Unfortunately, they do not attempt to calculate the costs. 'junk DNA' is not in the text.

[added 22 Jul 2023]

In a next blog I will discuss other Evolution textbooks.

04 July 2023

Periannan Senapathy (1994) claimed that the human genome consists of more than 90% junk DNA

"Most of the DNA in a genome is junk: The genes exist only as small islands in large oceans of meaningless DNA" (p.544) [1]

These beautiful poetic and prophetic words were written by genome scientist Periannan Senapathy in 1994 [1]. But he made a more precise claim:  the human genome consists of 90-99.5% junk DNA. This is his most extreme claim. Elsewhere in his book he writes "When we know that greater than 90% of the genome is junk (unused) DNA." He further notes that ""Introns are similar to intergenic junk DNA, except introns occur within individual genes rather than between genes. The average length of an intron is approximately ten times longer than the average length of an exon." Elsewhere he writes: "the proportion of introns in a gene is greater than 90%". He does not refer directly to a specific source for this estimate [3].

Figure 8.11. Assembly of a genome by random combinations
of DNA sequences in the primordial pond
leads to long “junk” DNA between islands of genes.

In 1994 when he published his book no whole genome sequence was available, let alone a human genome. The sequence of one chromosome of the eukaryote yeast Saccharomyces cerevisiae was published in 1994 and two years later the complete genome was published. Senapathy based his claim on an estimate of evolutionary biologist and textbook author Douglas Futuyma (1986) that the protein coding genes of an eukaryote would account for less than 10 percent of the average genome [2].  Futuyma himself did not use the term 'junk', instead he used 'non-coding DNA' of unknown function, but Senapathy interpreted that as junk.

This is very remarkable estimation. This year Laurence Moran wrote a book with the title 'What's in Your Genome? 90% of Your Genome Is Junk' (see my previous blog). So, Senapathy's 90% junk claim predates Moran's claim by almost 30 years.  In that sense Moran' was not the first. But, note that Moran's claim is extensively documented, whereas Senapathy's claim is a rough estimate.

Senapathy was aware of the C-value paradox. The C-value is the haploid amount of DNA in a species. The C-value paradox is "the lack of correspondence between C values and the amount of genetic information in the genome." He knew for example that the amount of DNA in each cell of many amphibians and plants is 50 to 100 times larger than that of human beings. He explains the origin of junk DNA and the C-value paradox by random assembly of random DNA in genomes in the 'primordial pond' (Figure 8.11). It follows from his theory that "The genome sizes in various organisms are randomly distributed." 

The 90% claim is intimately connected with his theory about the origin of eukaryotes. I will not explain nor criticize his theory here because I did it extensively on my website. Here I only want to point out that junk DNA and random DNA are the cornerstone of his theory. He defines junk DNA thus: "junk DNA and introns do not have any function" and "any change in the junk DNA should, by nature, be necessarily neutral as far as the function of any gene or the whole genome is concerned". This is still correct today. He claims on the basis of statistical analysis of gene sequences in the GenBank database that "today’s eukaryotic genes are almost random in sequence." (!). It perfectly fits in his theory and it is consistent with Moran's 90% claim. Finally, considering his own theory, it is no surprise that Senapathy fully accepts junk DNA. However, I think it is a biased view. In my next blog I shall have a look at what the Evolutionary biology textbooks have to say about 'junk DNA'.


  1. Periannan Senapathy (1994) "Independent Birth of Organisms. A New Theory That Distinct Organisms Arose Independently From The Primordial Pond Showing That Evolutionary Theories Are Fundamentally Incorrect"
  2. His sources are: D. J. Futuyma (1986) Evolutionary Biology, Sinauer Associates, page 48  and database GenBank (Center for Biotechnology Informatics, National Institutes of Health, Bethesda, Maryland).
  3. In humans, intron lengths contribute 95% of the average gene’s sequence (Venter et al. 2001 'The sequence of the human genome'). That is 7 years after Senapathy's claim. [ 3 Aug 2023 ] According Laurence Moran (2023) 3% of a gene is exon, and 97% is intron. [ 7 Aug 2023 ]