29 July 2019

Frans de Waal: Mama's Last Hug. Emotions, Sentience, Morality, Meat, Vegetarianism, Veganism.

Frans de Waal (2019) Mama's last hug.
Animal Emotions and What They Tell Us about Ourselves

Mama's last hug is about animal emotions. If animals have emotions, this has consequences Frans de Waal says in his new book Mama's last hug. What are those consequences? 
"None of this is to say, however, that we have to keep eating the way we do, or even eat meat at all. Animal protein may be overrated. We live in different times with different possibilities, and we have promising alternatives in the works, such as in vitro and plant-based meats that can be stuffed with all the vitamins we need." (269/357).
And that is not all. De Waal puts his views into practice: "I admire the effort [of vegetarians] though, and have joined it in my own imperfect and undogmatic fashion by banishing practically all mammalian meat from my family's kitchen." (270/357) [4].

I am pleased, but also surprised. This is the first time he says in print that he has taken the first steps to lower his meat consumption. In 2017 de Waal defended his meat eating on Dutch television [3]. But then he said nothing about reducing his meat consumption. Strangely, in chapter 7 he repeats the same already refuted pro-meat arguments. Why repeating pro-meat fallacies, when you have stopped eating cows and pigs? Here we find ourselves in the middle of a confusing mix of contradictory pro- and anti-meat arguments.

Sentience: What Animals Feel

For example, in chapter 7 'Sentience: What Animals Feel', de Waal presents all the usual pro-meat arguments: we humans have a long evolutionary history of hunting and eating animals, we have an omnivore anatomy (multifunctional dentition, relatively short intestine, massive brain), nutritional value (meat provides the optimal mix of calories, lipids, proteins, vitamins), we owe our cooperative nature, our food-sharing tendencies, our sense of fairness, and even our morality to the subsistence hunting of our ancestors, the natural cycle (every animal plays a role by eating or being eaten), and so on. Again, if these facts are true and the arguments are valid, then why stop eating meat?

This is his explanation: "We live in different times with different possibilities." [7]. Well, that is absolutely true! But different times with different possibilities don't have the power to change our long human evolutionary history, isn't it? And our anatomy and physiology did not change either, nor the nutritional value of meat, etcetera. We are still omnivores, I suppose. But all these facts are routinely used to propagate the 'meat-is-natural' theology. If these views contain any truth, how can they stop being arguments for meat eating? De Waal does not notice the problem. I think that the biological and evolutionary facts did not change, but our ethics. Those carnism arguments never were and never can be arguments for meat eating, simply because one cannot infer values from facts. "I am an omnivore, therefore it is morally acceptable to eat meat" is obviously false. Such a conclusion must follow from a moral principle. Living a vegetarian or vegan lifestyle simply does not contradict the facts of our evolutionary history. They are simply facts, and you need a moral system to change your behaviour.

Frans de Waal explains why he eats meat to Janine Abbring
on Dutch television, August 20th 2017 youtube

I am too much a biologist...

There is another story in the same chapter I have no problem with on its own, but I wonder what practical and moral conclusions we are supposed to draw from it. It starts with the infamous "I am too much a biologist to question the natural circle of life...". What follows is a general biological view about what it means to be a living being. A plant lives from the sun. Plants do not need to kill other living beings. Animals need to kill other living beings to stay alive. Carnivores kill other animals. Herbivores kill plants. Omnivores kill both plants and animals. The principle behind all this is the interest in staying alive of each and every creature on earth. In Darwins words: 'the struggle for existence' [1].
Plants defend themselves with toxic chemicals to repel herbivores. Plants don't like to be eaten. He dedicates a few pages to the plants [2]. In order to stay alive every organism must detect attacks. An organism needs sentience. Sentience is defined as the capacity to experience, feel, or perceive. Plants do react to environmental changes, but that is not the same as experiencing them, according to de Waal. Plants do not have a central nervous system. We must assume plants do not feel pain. Plants 'do not cry out in pain'.

Again, we must ask the question what moral imperative follows from this analysis? Nothing, unless one has endorsed already a moral principle. De Waal writes: 'Humans should respect all forms of life' (270). It is clearly not a statement of fact, it looks like a moral principle. He gives three reasons for this principle:
  1. the inherent dignity of all living things
  2. the interest every form of life has in its own existence and survival
  3. the capacity to suffer
Unfortunately, there are some problems with these statements. First, 'inherent dignity of all living things' is beautiful, but too vague. It cannot distinguish between good and bad actions. It is too broad, because we kill bacteria with antibiotics to save human lives, we destroy malaria mosquitoes and all dangerous parasites to combat disease, and we eat plants. These actions are rather difficult to avoid. So, the first principle fails as a moral guideline.

The second statement is factual and true. It is fundamental to all life. Interpreted as a moral guideline we violate it as soon as we start eating. So, we cannot follow it.

The third statement 'the capacity to suffer' is a descriptive statement, not a moral principle. That is a important difference. Because, one could rightly claim that the experiencing pain is natural. Above that, 'the capacity to suffer' does not apply to all living beings.
These three statements together are –strictly speaking– not moral principles.

But there is no need to invent a moral principle. Jeremy Bentham remarked 140 years ago:
The question is not, Can they reason? nor, Can they talk? but, Can they suffer? Jeremy Bentham, 1879
This position has been elaborated  by philosopher Peter Singer into a moral philosophy. Singer wrote famous books such as Animal Liberation (1975), and The Expanding Circle (1981). 

De Waal criticised Singer's animal-rights activist position in his book 'Primates and Philosophers' [8]. De Waal objects to the idea of animal rights. We now know that de Waal consumed meat at the time and reasoned accordingly. Remarkably, Peter Singer is missing in Mama's last hug !

De Waal wrote that it is a moral imperative to reduce meat consumption or even ban it altogether (270/357). That is exactly what vegans like Peter Singer practice. The famous chimpanzee researcher Jane Goodall is mentioned in Mama's last hug, but de Waal apparently does not know she is a vegetarian/vegan.

So, if you really want to practice the principle 'do not cause pain to other living beings in so far they are capable of experiencing pain', then it does not make sense to attack vegans [4],[5].

Again, if you really want to commit yourself to this moral principle, then you cannot simultaneously hold:
  1. "it is a moral imperative to reduce meat consumption" (270/357)
  2. "Even if I have no problem with meat-eating per se ..." (269/357).
De Waal does not have a moral problem with meat-eating per se? [6]. Doesn't that contradict his moral imperative?


There is a fundamental tension between the moral principle 'inherent dignity of all living beings'  and the descriptive 'natural circle of life'. De Waal did not resolve this tension. On the contrary. He wants at the same time to legitimize meat consumption with 'the natural circle' philosophy, and legitimize his reduction of meat consumption with a 'inherent dignity' philosophy. 
What we need is a coherent universal moral system that is detached from the 'natural circle of life' and from any personal interests and circumstances. 

As de Waal himself wrote in Primates and Philosophers: "Moral emotions ought to be disconnected from one's immediate situation: they deal with good and bad at a more abstract, disinterested level." [8].

The human species has the biggest brain and is the most intelligent animal ever seen on the face of the earth. That species has the highest self-awareness and the most sophisticated language of all animals. That species wrote holy books with the 'Ten Commandments' and produced an ethics culminating in 'the Golden Rule'. That species uses its superior intelligence for inventing bad excuses for killing members of other species.

Conclusion expanded 17 Aug 2019

Disclosure. I am too much a biologist to question the fact that milk and cheese come from cows, and cows are mammals. I am too much a biologist to question the fact that birds have a central nervous system and that eggs come from birds. I think, we don't have to keep eating the way we do, or even eat animal products at all. I am a vegan. In that sense I am biased. But, I hope without fallacies.

(This blog is an improved version of the previous blog in Dutch.)


15 Aug 2019
By the way, are you vegetarian or vergan?

After writing this blog, I discovered the interview of Michael Shermer with Dr. Frans de Waal (12 mrt. 2019) about the book Mama's Last Hug
Check out the last minutes of the interview about meat (57th min), especially the question "By the way, are you vegetarian or vergan?"(58:46). Frans de Waal: "No. I do eat less meat, and I try to avoid eating mammals." Why, why, why is it so hard to stop, if you know for certain they can feel pain???


  1. Charles Darwin, Chapter III in the Origin of Species is entitled 'Struggle for Existence'. I wonder whether de Waal is describing the 'dog-eat-dog view of nature' or 'Nature red in tooth and claw'? That is precisely the view of nature he forcefully and indignantly rejects in other contexts! The useful function of predators in natural predator-prey systems is a well established scientific fact. However, the meat industry of our own species does not resemble the natural prey-predator systems in anyway and is in fact unnatural. Pro-meat advocates forget this.
  2. I have the feeling that the lesson of 'the natural circle of life' story among other things seems to be that vegetarians and vegans infringe upon the interests of plants! Vegans are plant-killers! Above that vegans tell fairy tales! That's why FdW is not a vegan?
  3. Frans de Waal on Dutch television: Frans De Waal uses a fallacy to defend eating meat, 3 Oct. 2017 (fragment)
  4. "...I admire the effort [of vegetarians] though, and have joined it in my own imperfect and undogmatic fashion by banishing practically all mammalian meat". (270/357). Sorry, 'undogmatic'? Vegans are dogmatic? Undogmatic implies be selfish and violate your own moral principle?
  5. Frans de Waal states that the goal will be best accomplished if we honestly face where we come from [our omnivorous past] rather than spinning the fairy tale, often heard these days [where? source please!], that we are meant to be vegan." (270/357). Sorry? How does that help? De Waal criticises those that have gone far beyond his own imperfect attempts to reduce meat intake? You cannot go further than vegans, unless you can live on air alone! [31 July 2019]
  6. Psychologist Naomi Ellemers perfectly describes the behaviour of people like Frans de Waal:
    "Thus, even though being moral implies being honest and reliable, those who are most keen to establish a moral image of themselves tend to be less truthful and reliable in reporting about their own moral behavior" (57/412). Naomi Ellemers (2017) Morality and the Regulation of Social Behavior.
  7. "We live in different times with different possibilities": that is to say, the first prominent modern vegetarian was the Greek philosopher Pythagoras (History of Vegetarianism). Nothing new under the sun! [7 Aug 2019]
  8. Frans de Waal (2006) Primates and Philosophers, p.143 hardback. (quoted by Peter Singer). On page 152 Peter Singer writes: "... make me, I assume, a target of de Waal's criticism of animal rights advocates." De Waal objects to the idea of animal rights for silly reasons. Further, Singer observed that de Waal uses an ad hominem argument against animal rights activists (p.155). That was back in 2006 when de Waal was consuming mammals. [ added 8 Aug 2019 ]

Previous blog

  1. Killing Animals in the Age of Empathy. Frans de Waal, a leading primatologist explains why he eats animals. 26 September 2017.

17 July 2019

Het nieuwe boek van Frans de Waal 'Mama’s laatste omhelzing'

Frans de Waal (2019) Mama’s laatste omhelzing

Het nieuwste boek van Frans de Waal, 'Mama's laatste omhelzing' (Engelse titel: Mama's Last Hug: Animal and Human Emotions) gaat over emoties bij dieren. 

Vlees en sentience

In Hoofdstuk 7 [3] geeft Frans de Waal een diepgaande filosofie over wat het betekent een levend wezen te zijn en met name de positie in de voedselketen. Alle dieren moeten organische materie (=voedsel) in zich opnemen om te kunnen leven. Planten kunnen zelf koolstofverbindingen maken met behulp van zonlicht. Ze maken hun eigen voedsel. Ze hoeven geen ander levend wezen te doden om in leven te blijven. Dieren daarentegen moeten andere levende wezens doden om in leven te blijven. Dat is een fundamenteel gegeven. Daar is niet aan te ontkomen. Het wordt nog interessanter: "Alle levensvormen doen hun best om niet door hongerige vijanden te worden opgegeten. ... Vast houden aan het leven is een deel van het leven." Dat geldt ook voor planten, schimmels, en bacteriën. Planten verweren zich door giftige stoffen te produceren of zich op andere manieren onaantrekkelijk te maken voor herbivoren [17]. Denk aan de brandnetel. Dus ieder levend wezen wil leven en tegelijk moet ieder levend wezen voedsel bemachtigen om in leven te blijven.

Ik vind dit een interessante theoretische analyse. Weliswaar is deze analyse niet nieuw, het is in feite een Darwinistische visie op het leven, en is zeker niet controversieel, maar het interessante zit er in dat juist Frans de Waal deze analyse geeft. Het wordt nog interessanter omdat deze visie beschreven staat in de paragraaf 'Vlees en sentience' (=het vermogen de buitenwereld zintuigelijk  te ervaren).

Hij zegt vervolgens "mensen moeten alle vormen van leven respecteren, de inherente waardigheid van alle levende wezens, het belang dat elke vorm van leven heeft bij zijn eigen bestaan en overleving, en de sentience en de capaciteit tot lijden." (30/188).

Dat 'moeten' wijst op een moreel gebod. De rest is beschrijvend. Zijn filosofische analyse is zuiver wetenschappelijk. Uit beschrijvingen volgen geen concrete morele voorschriften. Maar met het 'moeten' geeft hij hier zonder het expliciet te benoemen een moreel gebod. Het probleem is dat zelfs uit 'alle vormen van leven respecteren' volgen geen concrete praktische voorschriften omdat het te vaag is. Hij blijft steeds op twee gedachten hinken met onvermijdelijk verwarring en tegenstrijdigheden als gevolg:
  1. "Ik ben te zeer bioloog om de natuurlijke levenscyclus in twijfel te trekken. Elk dier speelt een rol door te eten of gegeten te worden, en wij zijn aan alle kanten bij dat proces betrokken. ... " [Hoofdstuk 7]
  2. "Weliswaar heb ik geen probleem met het eten van vlees op zich, maar er is veel mis met hoe we dieren behandelen, hoe we hen grootbrengen, transporteren en slachten." [1].
  3. "... Maar ik bewonder het streven en heb mij me er op mijn eigen onvolmaakte en ondogmatische manier bij aangesloten door praktisch alle vlees van zoogdieren uit de keuken van mij en mijn gezin te verbannen." [2]. [vet gedrukt is van mij)
Het meest opvallende is dat hij voor het eerst schrijft dat hij 'geen zoogdieren meer eet' (dus hij eet geen olifanten, giraffes, dolfijnen, chimpansees, bonobo's, koeien, paarden, varkens). Nadat hij zijn hele leven dieren heeft bestudeerd, trekt hij op zijn 70e  morele consequenties. Twee jaar geleden in de beruchte Zomergasten uitzending van 2017 verdedigde hij vlees eten zonder meer tot verbijstering van presentatrice Janine Abbring [9].

Ik vind het een hele vooruitgang dat de Waal bijna geen zoogdieren meer eet. Dat is een grote stap voor een dieren- en vleesliefhebber [18]. Het probleem is echter dat hij vele strijdigheden verkondigt. Bijvoorbeeld: hij heeft in principe [5] geen probleem met het eten van vlees. Hoezo? Waarom heb je dan zoogdierenvlees verbannen? En hoe is dat te rijmen met zijn filosofie dat 'mensen moeten alle vormen van leven respecteren'?

En als je erkent dat 'niet-zoogdieren' zoals vogels en vissen ook pijn kunnen voelen omdat ze een centraal zenuwstelsel hebben [54/188], waarom eet je dan nog kip en vis? Hebben vogels en vissen geen centraal zenuwstelsel? De Waal erkent dat vissen pijn kunnen voelen [6] en toch eet hij zonder gewetensbezwaren paling [16].

En waarom zegt hij "praktisch alle zoogdierenvlees verbannen..."? Dat betekent dat je soms zoogdierenvlees eet? En dat is gebaseerd op het wetenschappelijk inzicht dat praktisch alle zoogdieren een centraal zenuwstelsel hebben?

En dit neem ik hem erg kwalijk: 'ondogmatische manier' in het 3e citaat. Is 'ondogmatisch' een eufemisme voor principeloosheid? Dus hij heeft morele principes, maar hij houdt er zich niet 'dogmatisch' aan? Tegelijkertijd zet hij hiermee vegetariërs en veganisten weg als dogmatici! [11]. Dat zijn nu net de mensen die het verst gekomen zijn met het 'respect voor alle levensvormen'! (zijn eigen woorden). Zo kan hij met een goed geweten vlees blijven eten en tegelijk vegetariërs en veganisten een trap geven. En dat is niet de eerste keer dat hij vegetariërs belachelijk maakt [12]. 

Hopeloos ambivalent

De Waal is dus ontzettend ambivalent. Er is een grote discrepantie tussen zijn kennis en zijn gedrag, tussen wat hij zegt en wat hij doet. Op het ene moment leidt hij uit de natuur af dat je vlees mag eten, want hij is bioloog genoeg om dat te weten. Op een ander moment leidt hij uit de natuur af dat ieder organisme wil leven en dus moet je geen dieren eten. En uit diezelfde filosofische analyse volgt logischerwijze dat je geen planten mag eten, want broccoli wil ook leven. Als je geen planten mag eten, dan zou je paddestoelen kunnen eten want dat zijn schimmels. Uit zijn filosofische analyse volgt dat je geen aardbeien mag eten, want ieder levend wezen wil zich voortplanten. En dat wordt gefrustreerd door het eten van vruchten en granen in het algemeen. Uit zijn analyse volgt dat je helemaal geen levende wezens mag eten, want ieder levend wezen wil leven [14]. Hij heeft een ambivalente theorie en bijbehorend ambivalent gedrag.

Duidelijk principe nodig

Je moet een duidelijk moreel principe formuleren dat je consequent in de praktijk kunt brengen. Zijn natuurfilosofie is goed maar ongeschikt om een moreel principe te formuleren. Er bestaat al meer dan een eeuw een geschikt principe. Jeremy Bentham (1748–1832) had als eerste het morele principe geformuleerd dat vandaag nog steeds de morele onderbouwing is voor vegetarisme en veganisme:
The question is not, Can they reason? nor, Can they talk? but, Can they suffer? (wikipedia)
Met dit principe ben je ook af van de vraag of je planten mag eten, want planten hebben geen centraal zenuwstelsel en kunnen geen pijn ervaren. Helaas komt Jeremy Bentham niet voor in zijn boek. Evenmin de filosoof en dierenrechtenpionier Peter Singer, die er in een eerder boek [7] van langs kreeg (we begrijpen nu waarom). En dicht bij huis: filosoof Floris van de Berg heeft het vermogen te kunnen lijden als  basis van zijn moraal gemaakt: het is moreel niet acceptabel om pijn te veroorzaken [10]. Filosofen die duidelijkheid kunnen verschaffen komen niet voor in zijn boek. Zijn internationaal bewonderde collega Jane Goodall (mooie naam!) komt wel in het boek voor, maar hij vergeet te melden dat ze vegetariër is...

Al dit gedrag, al zijn drogredenen, het aanvallen van vegetariërs en veganisten, het negeren van de filosofen met duidelijke morele principes, de halfslachtige praktijk van vleesloos eten, het zwijgen waar hij zou moeten spreken [13], zijn volgens mij symptomen van zijn worsteling om van zijn vleesverslaving af te komen. Het wordt tijd -hij is nu 70 jaar!- dat hij dat eerlijk onder ogen ziet en zichzelf en zijn publiek geen sprookjes meer zit te vertellen. Tijd om empathie in de praktijk te brengen.

"Als je niet meer bang bent voor een leven zonder vlees,
komt er ruimte voor de moraal."



  1. Ik gebruik het ebook en heb daarom niet de paginanummers van de papieren editie. In het ebook: 26/188 (=13% van Hoofdstuk 7 'Sentience. Wat dieren voelen')
  2. In het ebook: 27/188 (=14% van Hoofdstuk 7 'Sentience. Wat dieren voelen')
  3. In het ebook: 37/188 (=19% van Hoofdstuk 7 'Sentience. Wat dieren voelen')
  4. NEMO Kennslink: "Ik heb altijd geweigerd om dieren op afstand te houden", interview met Frans de Waal naar aanleiding van zijn nieuwe boek. Een lezeres schrijft "Frans de Waal is een zegen voor dieren en ik hoop dat de koude wetenschappers veranderen van gedachten."! Zij is er in getrapt.
  5. Vergelijk: op zich heb ik niets tegen vreemdgaan, ... in de praktijk ... Of: op zich heb ik niets tegen oorlog, als het maar netjes gebeurt, er zouden camera's bij moeten staan. 
  6. Hij citeert het boek Do Fish Feel Pain? van Victoria Braithwaite en erkent dat de algemeen heersende visie is dat vissen inderdaad pijn kunnen voelen. [153/188 = 81%].
  7. Frans de Waal (2006) Primates and Philosophers. How Morality Evolved.  Hierin heeft Peter Singer een hoofdstuk. Het helpt allemaal niet.
  8. (vervallen)
  9. In dit video fragment: Frans De Waal uses a fallacy to defend eating meat, 3 oktober 2017. Inmiddels 612 hits.
  10. Floris van den Berg (2013) 'De Vrolijke Veganist'. pagina 19 over Bentham en Peter Singer.
  11. Frans de Waal zegt dat 'jongeren experimenteren met vleesloos eten' [26/188]. Pardon? Experimenteren? Is het gevaarlijk? Kun je er aan dood gaan? Vegetarisme/veganisme is geen trend of experiment onder jongeren! Het is gewoon consequenties trekken. We hebben in Nederland een Partij voor de Dieren, een Vegetariërsbond en een Nederlandse Vereniging voor Veganisme, de Vegetarische Slager (levert aan de Europese markt), er zij inmiddels vele succesvolle vleesvervangers (JUMBO heeft 200 vega producten in de schappen!) en Plantaardige Beyond Burger te koop bij AH, en een zeer goed lopend veganistisch restaurant in Utrecht. Sporters en zelfs topsporters eten zuiver plantaardig (nrc 15 aug 19). Kortom: zijn opmerkingen zeggen meer over zijn gebrek aan kennis dan over vegetarisch leven. Door het woord 'experimenteren' probeert hij veganisme op afstand te houden. In moreel opzicht is hij zwak.
  12. FdW: "...maar we komen het verst als we eerlijk onder ogen zien waar we vandaan komen in plaats van het sprookje te verzinnen, zoals dat tegenwoordig vaak te horen is, dat we bedoeld zijn om veganistisch te leven." [29/188].
    Pardon? Eerlijk? Dus veganisten zijn niet eerlijk? Ze vertellen sprookjes? Peter Singer vertelt sprookjes? Graag bronnen! En hoe ver wil Frans de Waal eigenlijk komen? Verder dan veganisten? Of wil hij nooit veganist worden vanwege de zgn. sprookjes? Ondertussen heeft hij dus een goede reden voor zichzelf bedacht om vlees te blijven eten: hij is 'eerlijk' en hij 'gelooft niet in sprookjes' en hij eet zoals de natuur 'bedoeld' heeft. (Probleempje: onze voorouders aten zoogdieren!). FdW is goed in het verzinnen van excuses en smoesjes.
  13. In Pauw 23 mei 2019 zegt Frans de Waal tot tweemaal toe dat moderne inzichten over emoties bij dieren morele consequenties hebben, maar zegt niet welke! De zeer ervaren interviewer Pauw vraagt niet door! Zit hij te slapen? Is hij een vleeseter? een gemiste kans voor beiden.
  14. In de filosofie staat dit bekend als conatus: an innate inclination of a thing to continue to exist and enhance itself. Het begrip speelt een belangrijke rol in de filosofie van Spinoza. Conatus geldt ook voor dode dingen. [donderdag 18 juli 2019]
  15. Gouden uitspraak van Jaap Korteweg (De Vegetarische Slager) in nrc 19 juli 2019. [toegevoegd: 20 juli 2019]
  16. nrc 6 juli 2018: "De Waal had in zijn mail vooraf ook een verzoekje voor het diner: 'Graag een visrestaurant: ik ben gek op paling en krijg het hier nooit'." Hypocrisie, nihilisme. [toegevoegd: 22 juli 2019
  17. Planten: "Mais, rijst, tarwe en sojaplanten activeren allemaal hun immuunsysteem wanneer ze besproeid worden met de feromonen van plantenetende aaltjes. Dat maakt planten weerbaarder tegen een aanval van deze dieren, maar ook tegen andere bedreigingen, zoals virussen, bacteriën en schimmels." NEMO Kennislink 6 aug 2019
  18. In een interview in de Volkskrant 22 december 2007 zegt de Waal:
    Ik heb niets met het idee dat je dieren hetzelfde moet behandelen als mensen. Er zijn dierbeschermers die vinden dat ik geen konijn mag eten. Maar waarom is het wel oké als een vos een konijn eet?.
    Een gewledige textbook fallacy: Ik eet konijn omdat vossen konijnen eten. Mijn  moraal is: ik kopieer dierengedrag. Correctie (1): ik kopieer carnivoren. Correctie (2): ik eet alleen spieren, en geen organen, etc. Correctie (3): ik jaag, dood en vil geen konijnen, ik betaal anderen om dat te doen. Correctie (4): ik eet geen rauw vlees, mijn vrouw braadt het vlees. Correctie (5): ik eet met vork en mes en poets daarna mijn tanden. Maar voor de rest gedraag ik me helemaal als een vos!  [ toegevoegd: 23 aug 2019 ]

Vorige blogs over Frans de Waal

20 June 2019

DNA is the most beautiful molecule in the universe and Gareth Williams 'Unravelling the Double Helix' made it even more interesting

Gareth Williams(2019)
Unravelling the Double Helix. The Lost Heroes of DNA

James Dewey Watson and Francis Harry Compton Crick, 1953
Suddenly I realized that the famous picture of Watson and Crick standing before their 3D model of DNA, subtly suggests that they built their double helix model from scratch. Well, yes, they did build the physical model. But, I did not realize that, long before Watson and Crick, researchers established the building blocks of DNA: P, ribose and the 4 bases A, T, C, G. So Watson and Crick discovered neither the building blocks nor the structure of the building blocks. Amazingly, they did not even do any lab work on DNA. And at the time when they started thinking seriously about the structure of DNA, it had already been established that DNA, and not protein, is the carrier of heredity. So, they did not come up with that idea either. They copied the DNA building blocks from the scientific literature of their time. That means others have elucidated the components of DNA.

I did not know (or forgot) that 40 years before Watson and Crick, a researcher called Phoebus Levene established the structure of the sugar and the 4 bases in DNA in the course of  decades of research and put it together in a model of DNA:

figuur 7.2 in Gareth Williams (2019)
DNA according to Phoebus Levene.
The connections between P – Ribose – Base are correct. And Levene introduced the word 'nucleotide', which is still in use today. Yes, it was single-stranded DNA [11]. Poor Levene was written out of history [8], [9] because he came to believe that the bases A, C, T, G were present in equal proportions (tetranucleotide hypothesis). Therefore it was difficult to see how DNA could contain sufficient genetic information.

In the famous textbook  Molecular Biology of The Gene  (James D. Watson, et al) Levene is not even mentioned. Yes, Levene's model was not a double helix, but he got the building blocks and the links right. This puts the achievements of Watson and Crick in the right historical context. They have become famous for putting the last pieces of the puzzle together and got the Nobel price for it. But without the work of Levene they could never have done it.

I discovered this thanks to medical historian Gareth Williams. In his book Unravelling the Double Helix, Gareth Williams shows that 85 year of DNA research by hundreds of scientists preceded Watson and Crick's discovery. That is the period 1868 up to 1953. His book is very entertaining and easy-going with special attention to the characters and personalities involved including conflicts between scientists, their prejudices, failures and successes.

Levene dogmatic?

I think the most interesting and controversial researcher was Phoebus Levene. Levene produced a wrong structure of the DNA model (tetranucleotide) and believed that nucleic acids have nothing to do with heredity [12]. He is supposed to have defended his (wrong) ideas at all costs, and has been accused of obstructing the progress of the science of DNA. On its own it should not be a disaster to publish a wrong hypothesis [13]. The famous Linus Pauling published a faulty DNA model. And the first physical model of DNA created (but not published) by Watson and Crick was hopelessly wrong. This kind of mistakes are usually corrected by subsequent research. But Levene's hypothesis was not corrected quickly. Prof. Levene was an authority. He had great technical skills. Not many others had the skills to repeat his experiments and refute him. According to Williams he ignored criticism and inconvenient facts. As a consequence research into DNA came to a halt. DNA was a boring molecule. Therefore, scientists focussed on proteins as the carrier of heredity [12]. That is tragic indeed. But, it is highly unfair to judge Levene after 1953 with the correct DNA structure at hand. The question is: was he unreasonable given the data at the time? Does Williams think that Levene is one of the 'lost heroes of DNA'?

Levene in Wikipedia

Was Levene wrong in all respects? The DNA structure in figure 7.2 (above) has its merits. The structure is linear and not closed. It can be extended indefinitely in both directions, which is a promising feature for information storage. However, wikipedia shows a different structure [1]:

Tetranucleotide in wikipedia

This is the Tetranucleotide according to wikipedia. It is a visually powerful image with a clear message [3]. It clearly is a closed molecule containing each of the 4 bases A, T, C, G only once. It has no possibilities for extensions. This model is not in Williams' book, but he informed me that it originates from H. Takahashi (1932) Uber fermentative Phosphorierung der Nucleinsaure. So, wikipedia attributes the figure to Levene incorrectly [4].

The problem is that we are not sure what Levene really thought. There is evidence that Levene thought DNA has a closed structure or consists of a stack of closed structures. But there is also evidence that he thought DNA was linear [2]. As far as I can see, Levene never published the closed tetranucleotide structure himself and the models he did publish are linear [5]. Does that tell us something? This requires investigation of the primary sources, his own publications, not what others tell about him. Finally, why would he spend so much time on a boring molecule?

With the benefit of hindsight

With the benefit of hindsight, the linear model, but even the cyclic model had more potential than Levene had realised. The linear model has the potential to be extended in both directions infinitely because it is an open structure. Allowing for any order of the bases would fulfil the requirements for information storage. OK, it is not a double helix, but that does not affect information storage capacity [11].

In Williams' figure 7.2 (above) the bases T, A, C, G are present, but in figure 4.8 and 4.9 of Portugal and Cohen (1979) only pyrimidine (T or C) and purine (A or G) are present. I guess that the illustrations of Portugal and Cohen are close to the original. So, that suggests Levene had no fixed order of the 4 bases in mind. In my view Levene could not have evidence that there is only one fixed order of the bases in his tetranucleotide or linear model. Then (if he did not impose a purine - pyrimidine alternation), 6 possible tetranucleotides are possible:

6 different closed tetranucleotides (simplified) ©GK

Because of the cyclic nature, no more than 6 different tetranucleotides are possible. Six different tetranucleotides is slightly less boring than one, but by far not enough. But maybe this kind of thinking could trigger further thoughts. For example, even with one cyclic tetranucleotide ACGT with fixed order of the bases, one could stack it while turning the next one 45° or 90° or 135° clockwise. A reading mechanism could read bases along one (or even all 4) vertical axis, resulting in unlimited information storage capacity. So, the tetranucleotide on its own need not restrict storage capacity. In fact, pure logic makes this possible.

What could cast doubt on the strict tetranucleotide hypothesis is experimental data suggesting unequal amounts of A, T, C, G in DNA samples (A:T:C:G = 1:1:1:1). At the time scientists accepted that the 4 bases occur in equal amounts in DNA. However, do equal amounts of A, T, C, G really kill information storage capacity? No, because A, T, C, G could be distributed in many different ways in a linear single-stranded sequence. For example these two 8-base-sequences



have the same number of the four bases: 2xA, 2xT, 2xC, 2xG, but they are obviously different sequences. Why didn't this occur to people (Levene) at the time? Could it be that they simply did not have the concepts of information storage and digital coding like we do nowadays with computers in every pocket? [6]. If so, the problem was a conceptual problem. In that case Levene was not dogmatic, but a general conceptual barrier prevented Levene and others to solve the DNA puzzle. Maybe another conceptual barrier was the idea of a helix or the idea of a double helix because these concepts were not yet invented in chemistry? [7]. Today we are used to the idea that DNA is a very long molecule. In fact the longest molecule in the universe. The shortest human chromosome is 46 million and the longest is 248 million base pairs [14]. This is far beyond the imagination in those days, I guess.
A technical problem in those days was the fact that, after analysis of the macromolecule DNA many breakdown products were to be found in the test-tube. There are many ways to reconstruct DNA from the breakdown products. That's the problem.

The most beautiful molecule

All these possible barriers make the history of the discovery of DNA fascinating. Although that history has been written at length by others, including Watson, Crick and Wilkins [8], and I read them years ago, Gareth Williams managed to renew my interest in the subject. I started rereading the older books because I had questions and wanted answers.

Scientists of DNA timeline (source).

I found a time-line of the discovery of DNA on the internet. Amazingly, the period between Miescher (1869) and Chargaff (1950) is completely blanc! As if nothing had been done. Gareth Williams did a great job filling in that empty space.

But Gareth Williams did more than that. For example, for me Miescher was just a name. But  Friedrich Miescher did his discovery at a very young age and at first his boss was not interested in publishing it. Amazingly, Miescher did not believe nucleic acid had anything to do with heredity! He preferred to see nucleic acid as a storage for phosphorus! This sort of stories make what was only the name of an author into a real person.

Another example is the famous Thomas Hunt Morgan, who at first was unimpressed by Mendelian genetics and chromosomes, but "in 1915 he publicly purged himself of his earlier sins in The Mechanism of Mendelian Heredity". It is travelling back in time. Lessons to learn when reading the scientific journals of today. 
The most amazing aspect of the history of DNA is that researchers investigating DNA had no clue that DNA equals heredity.

DNA is by far the most beautiful, oldest and most informative molecule in the universe and Gareth Williams made it even more interesting. Such a molecule deserves another book. Williams wrote a friendly introduction into the history of that molecule. The merit of Williams' book is that he is not only telling the hard scientific facts, but also the personal and conceptual struggles of the scientists involved in such a way that one is intrigued and wants to know more. 

update 10 July: small text edits.




  1. Tetra-nucleotide hypothesis is very shortly discussed in The Eight Day of Creation, but a whole chapter is dedicated to the Tetranucleotide hypothesis in Portugal and Cohen; and in Olby. But I must have forgotten it completely.
  2. Portugal and Cohen in A Centry of DNA wrote "Thus, in 1938, Levene and Schmidt were able to measure  the molecular weight of native DNA at between 200,000 and 1 million. (88). And: Levene "proposed a linear combination of nucleotides with the correct internucleotide linkage." (p.89).
  3. The publication of Takahashi is in the list publication of GW, but he does not include the Takahashi figure in his book.
  4. However the wikipedia figure must be a modern reconstruction of Takahashi figure. This must be because in F.H. Portugal, J.S. Cohen (1979) figure 4.10 shows the tetranucleotide in a different form, and the bases are indicated with 'pu' (purine) and 'py' (pyrimidine) and not with A, C, T, G.
  5. Williams informs me that "Levene never dreamed up a cyclic structure" (personal communication 17 June 2019). I had formed the view that Levene was dogmatic about the tetranucleotide and therefore obstructed the progress of science.
  6. After I wrote that, I found in Olby The Path to the Double Helix: "The number of Bausteine which can take part in the formation of the proteins is about as large as the number of letters in the alphabet."  which was written by Kossel in 1911. So, the alphabet was used as a metaphor for information in proteins. Maybe this was not a general view? But there seems to be no conceptual barrier viewing DNA as a carrier of information.
  7. The tetranucleotide hypothesis and especially the single-stranded DNA hypothesis prevented Chargaff to correctly interpret his own data. He did not try a double-stranded structure. Apparently, that is a huge leap.
  8. Maurice Wilkins (2003) The Third Man of the Double Helix, wrote no more than one sentence about Phoebus Levene: " ... analytical chemist Phoebus Levene, who had argued for decades that DNA could not be gene material because it only contained four bases, which would, he claimed, make it far too simple a compound to contain genetic information." (p.152). That is really disappointing. What a terrible thing to say about the man who discovered the D-ribose sugar and the nucleotides and nucleosides in DNA! Even worse: Wilkins wrote Levene had a negative influence on Chargaff!
  9. In Francis Crick (1988) What Mad Pursuit, "Phoebus Levene, the leading expert on nucleic acid in the 1930s, had proposed that they had a regular repeating structure [the so-called tetranucleotide hypothesis]. This hardly suggested that they could easily carry genetic information. (p33-34). But it is highly unfair to condemn Levene after 1953! What is needed the data available at his time. And therefore actual publications of that time should be investigated.
  10. James D. Watson (1982) The Double Helix. Penguin Books. Nothing about the history of DNA research! DNA has no history!
  11. Single-stranded DNA does not occur in bacteria, plants and animals, but there exist single-stranded DNA virusses. RNA is single-stranded.
  12. Levene said in 1916 about nuclei acids (DNA): "“They are indispensable for life, but carry no individuality, no specificity, and it may be just to accept the conclusion of the biologist that they do not determine species specificity, nor are they carriers of the Mendelian characters” (source). This is probably a far more serious error than publishing a wrong model of DNA. [added 21 Jun 2019 ]
  13. This what Andreas Wagner said in an interview: "Failure is key to success, and it should be embraced as a necessary part of the creative process. “If we are honest with ourselves, we understand that we are failing more often than we are succeeding, and that is a very Darwinian concept,” ..." source [ added 22 Jun 2019 ]
  14. See: Human genome in wikipedia. The smallest human chromosome is chromosome #21, the biggest is #1. The total length of the human genome is over 3 billion base pairs. [ added 10 Jul 2019 ]


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