The Resurrection of Darwin's Pangenesis theory?

©http://darwin-online.org.uk

Is Darwin's long forgotten and discredited theory of Pangenesis resurrected from the dead? A publication in Nature Reviews Molecular Cell Biology [1] suggests his theory is at least partly true and was the inspiration for a number of scientists after Darwin.

What is Pangenesis? Darwin published his Pangenesis theory in volume 2 of The Variation of Animals and Plants under Domestication (1868). According to the authors the Pangenesis theory proposed a mechanism for the flow of hereditary information between cells and between generations.
Strinkingly, this definition merges two completely different phenomena in one concept: cell-to-cell communication and the transmission of genetic information from parent to child. Next, the authors claim that "emerging evidence of cell-to-cell communication urges the reconsideration of this 150-year-old theory."

More precisely, the Pangenesis theory says (according to the authors) that in addition to cell division as a means of transferring information, every cell emits numerous gemmules. They travel through the body and unite with other somatic cells and germ cells. So, it appears that both parts of the theory cannot be separated. It is a complex theory. Darwin knew this.

Additionally, and importantly, gemmules can be modified by the environment. If those modified gemmules end up in germ cells, and are transmitted to the next generation, it is called 'Lamarckian inheritance'. The consensus in the biological community is that Lamarckian inheritance is not possible and should be rejected.

What is the new evidence according to the authors? They point to extracellular vesicles such as exosomes [2] which transport information in the form of RNA and proteins between cells, including germ cells. In particular small RNAs have been found in sperm. They are the carriers of acquired phenotypes such as diet-induced metabolic disorders and mental stress phenotypes. This is an extra-chromosomal type of inheritance. There is no integration in DNA. The authors propose that also circulating cell-free DNA and mobile RNAs could be viewed as instances of Darwin's pangenes. If these factors are indeed inherited, they seem to me a form of transient inheritance.

The transmission of exosomes is not the same as Transgenerational epigenetic inheritance because transgenerational epigenetic inheritance is the transmission of epigenetic markers of DNA or histones. Those markers are inherited together with chromosomal DNA and follow therefore a Mendelian pattern.
However, the authors also include epigenetic inheritance as evidence for Darwin's Pangenesis theory. This is confusing because these markers are not transmitted in exosomes. Exosomes carry small pieces of RNA and proteins and not whole genomes with epigenetic markings attached. Epigenetic markers cannot be transmitted as free floating individual molecules. They could not be viewed as modern incarnations of Darwin's gemmules. And gemmules are at the heart of Pangenesis. Therefore, I do not consider epigenetic markers an evidence in favour of Darwin's Pangenesis. In a more general sense, epigenetic markers could be  evidence for the rather vague idea of inheritance of acquired characteristics. But one should be careful to distinguish those different meanings.

I think it is a little far-fetched to interpret Darwin's gemmules in cellular or molecular terms as the authors do [5]. Darwin did sometimes use the word 'cells', but he certainly could not think in molecular terms. Furthermore, in my view his Pangenesis theory tries to unite too many different phenomena in one theory: ordinary heredity, the inheritance of acquired characteristics, recessiveness, causes of variation, and more.
I think it is confusing that the authors of the Nature article lump together chromosomal inheritance -which equals the complete genome of an organism- with modifications of that DNA, or a few small RNA molecules. The difference in the amount of information can easily be a million fold. Human sex cells contain three billion DNA base pairs. That is huge compared with what could be present for example in exosomes. Furthermore, chromosomal DNA is necessary to create a new organism (plant, animal) and inherited epigenetic modifications are mostly facultative additions.

The well-known role of histone methylation in animal development [3] has nothing to do with inherited epigenetic modifications, since those tissue-specific embellishments are necessarily newly created in the embryo. One cannot inherit tissue-specific instructions through one sperm and egg cell.

The authors downplay the fundamental difference of Darwin's theory of heredity with the current theory. Heredity means for Darwin the aggregation of the gemmules produced by all somatic cells. For Darwin gemmules are not an addition to the main mechanism, they are the main mechanism of heredity. We now know that this is completely wrong [4]. Furthermore, I think the authors do not present an overwhelming amount of new evidence to justify the resurrection of Darwin's Pangenesis theory.

Having said all that, I still think that the chapter about Pangenesis in The Variation of Animals and Plants under Domestication deserves a fresh study. It should be interesting to investigate how Darwin thought about the material basis of heredity without knowledge of Mendelian inheritance, chromosomes and DNA. I think it is interesting despite the fact that Darwin had a profound Lamarckian view of heredity. Darwin collected an enormous amount of data and his theory of Pangenesis was designed to explain them all. And as usual he discussed objections to his theory. I expect that reading Darwin will learn us a lot about his struggle with those objections, and how he tried to create a synthesis of the knowledge of his time, just as he did with his theory of evolution. Undeniably, it is one and the same person who created the theory of evolution and the Pangenesis theory.

Notes

1. Yongsheng Liu, Qi Chen (2018) 150 years of Darwin’s theory of intercellular flow of hereditary information, Nature Reviews Molecular Cell Biology volume 19, pages 749–750 2018.
2. Do not confuse 'exosomes' with 'exomes' because 'exome' refers to the part of the genome that codes for proteins in contrast to 'introns' which are eliminated from a gene before being translated in to a protein.
3. Ashwini Jambhekar, Abhinav Dhall, Yang Shi (2019) Roles and regulation of histone methylation in animal development, Nature Reviews Molecular Cell Biology volume 20, pages 625–641 (2019)
4. One of the main problems with gemmules (pangenes) as the mechanism of heredity is: if gemmules are continuously produced by all body cells and spread through the body, what mechanism guarantees that exactly the right amount and types of the gemmules, not too many, not too few of the same kind are collected in the germ cells (egg, sperm)? Imagine many copies of 20.000 free floating genes through the whole body! Total chaos! We now know that the function of chromosomes and cell division is to ensure that the daughter cells get the right amount of genes. I do not know whether Darwin was aware of that problem. [ 9 Oct 2019 ]
5. Darwin knows about cells: "Virchow, the great supporter of the cellular theory" but the theory was not well established at the time. [ 9 Oct 2019 ]

Further Reading

• Charles Darwin (1868) THE VARIATION OF ANIMALS AND PLANTS UNDER DOMESTICATION, CHAPTER XXVII. PROVISIONAL HYPOTHESIS OF PANGENESIS.
• Yongsheng Liu, Xiuju Li (2014) Has Darwin's Pangenesis Been Rediscovered? BioScience, Volume 64, Issue 11, November 2014, Pages 1037–1041 (free access) (this paper presents a lot of evidence supporting Darwin's Pangenesis theory - according to the authors)
• Yongsheng Liu (2019) Darwin and Nature’s 150th anniversary, Correspondence 1 October 2019, Nature 574, 36 (2019) (free access)

Test van ObsIdentify algoritme voor automatische identificatie van dieren en planten

laatste update: 13 okt 2019  

Soorten identificeren is nog nooit zo makkelijk, zo snel en zo leuk geweest. Er zit als het ware 24 uur, 7 dagen per week een deskundige op ieder gebied voor je klaar die je binnen een seconde antwoord geeft op je vraag: welke soort is dit? 
Ik heb het over software die tegenwoordig zit ingebouwd in waarnming.nl.
ObsIdentify is beeldherkennings software. Beeldherkenning in het algemeen is software met als doel patronen in data te herkennen. ObsIdentify neemt sinds kort een centrale positie in bij waarneming.nl. Je kunt je foto's uploaden en binnen een seconde heb je antwoord.

Ik heb vroeger gewerkt met beeldherkenningssoftware (image recognition) en was daarom nieuwsgierig naar de prestaties van het programma. Hoe goed is het? Ik wilde het testen en kijken hoe makkelijk je het kunt misleiden. De resultaten zijn indrukwekkend. Het programma is in staat om foto's met 100% zekerheid op soort te brengen. Wanneer ObsIdentify een soort herkent met 100% zekerheid dan is het ook goed. Tenminste, tot nu toe, wat ik gezien heb. OK, het kan niet alles, maar wat hij kan doet hij goed en razendsnel. Ik geef een paar voorbeelden van de Atalanta.

700x700 pixels	Resultaat: "ObsIdentify is helaas niet zeker: de eerste voorspelling Atalanta Vanessa atalanta (76.2%). Probeer de foto bij te snijden." Een close-up. Een vreemd resultaat: je denkt: hoe meer details hoe beter, de foto is groter (700x700) dan de volgende. Maar zo werkt het kennelijk niet.
275x215 pixels	Resultaat: "ObsIdentify voorspelt Atalanta Vanessa atalanta met zekerheid 99.0%" Vreemd resultaat: de determinatie is goed, maar foto heeft dezelfde uitsnede als vorige, maar foto heeft veel kleinere afmetingen! Dus: kleiner is beter?
275x225 pixels	Resultaat:  "ObsIdentify voorspelt Atalanta Vanessa atalanta met zekerheid 100.0%" Complete vlinder in beeld en 100% zekerheid: dat is wat je verwacht van een goed programma. Gezien het kleine foto formaat is het zelfs een knappe prestatie!
133x104 pixels	Resultaat:" ObsIdentify voorspelt Atalanta Vanessa atalanta met zekerheid 99.9%". Knap resultaat gezien het zeer kleine formaat! Het standaard formaat is 2988 x 5312 pixels!
120x94 pixels	Resultaat: "ObsIdentify is helaas niet zeker: de eerste voorspelling Ichneumon sarcitorius (32.7%)." Nog kleiner formaat en gaat  volkomen de mist in: een sluipwesp! De ondergrens is bereikt.
100x78 pixels	Resultaat: "ObsIdentify is helaas niet zeker: de eerste voorspelling Bonte beer Callimorpha dominula (18.9%)." Nog kleiner formaat: een totaal andere vlinder! Fascinerend!
275x225 1x blur	Onscherpte test uitgaande van foto die 100% zekerheid opleverde: "ObsIdentify voorspelt Atalanta Vanessa atalanta met zekerheid 99.8%" Goed resultaat. Je foto's hoeven dus niet scherp te zijn!
275x225 2x blur	Onverwacht resultaat: "ObsIdentify is helaas niet zeker: de eerste voorspelling Nephrotoma crocata (24.7%). Probeer de foto bij te snijden." Nog een beetje vager en ObsIdentify gaat volkomen de mist in: de voorgestelde soort is een langpootmug. Lijkt er totaal niet op. Voor het menselijk oog is het verschil met de vorige afbeelding niet zo groot. Interessant is dat 1 van de 4 onzekere voorspellingen de Atalanta is!
275x225 black-white	Resultaat: "ObsIdentify voorspelt Atalanta Vanessa atalanta met zekerheid 96.1%". Kleur is helemaal niet nodig om een Atalanta te herkennen!
275x225 foute kleuren (hue-180)	"ObsIdentify voorspelt Grote weerschijnvlinder Apatura iris met zekerheid 98.9%". Grote weerschijnvlinder Het ontbreken van kleur is geen probleem, maar foute kleuren zijn fataal! Het pratroon telt niet meer mee. Desondanks grote misplaatste zekerheid: 98.9%!
275x225 foute kleuren	Resultaat: "ObsIdentify voorspelt Atalanta Vanessa atalanta met zekerheid 100.0%"  Ondanks foute kleur goede voorspelling met 100% zekerheid! Misschien omdat er geen soortgelijke vlinder met geel bestaat?
275x225 stippen toegevoegd!	Resultaat: "ObsIdentify voorspelt Atalanta Vanessa atalanta met zekerheid 100.0%" Dit gaat wel erg ver: een fantasie Atalanta wordt met 100% zekerheid herkend alsof er geen stippen waren toegevoegd! Hoe kan dat? Bestaan er varianten met stippen?
275x225 sterke RGB noise toegevoegd	Resultaat: "ObsIdentify is helaas niet zeker: de eerste voorspelling Atalanta Vanessa atalanta (66.6%). Probeer de foto bij te snijden." ObsIdentify kan redelijk veel ruis verdragen. Wordt het té erg, dan wordt hij/zij onzeker, maar blijft desondanks het correct resultaat geven.
275x225 hogere scherpte GIMP90	Resultaat: "ObsIdentify is helaas niet zeker: de eerste voorspelling Atalanta Vanessa atalanta (86.4%). Probeer de foto bij te snijden". Als je de scherpte kunstmatig verhoogt (GIMP:90) begint O. onzeker te worden, maar blijft Atalanta voorspellen.
275x225 scherpte GIMP95	Resultaat: "ObsIdentify voorspelt Atalanta Vanessa atalanta met zekerheid 97.0%" Extreme 'scherpte': voor het menselijk oog ziet deze Atalanta er beschadigd uit, maar O. vindt hem véél duidelijker dan de vorige (GIMP90) die er voor ons juist weer normaal uitziet. Bij de maximale 'scherpte' GIMP99 voorspelt O.: Zigzagbeukenmineermot Stigmella tityrella (38.5%) met als alternatief zelfs het Oorzwammetje!
275x225 met golfjes vervormd	Resultaat: ObsIdentify is helaas niet zeker: de eerste voorspelling Geelbuikschildpad Trachemys scripta scripta (67.2%). Probeer de foto bij te snijden.   Met deze golfjes is de Atalanta voor ons nog wel enigzins te herkennen, maar wij zouden er nooit een schildpad van maken! En dan nog wel met 67% zekerheid. Snapt O niet het verschil tussen vlinder en schilpad?
275x225 GIMP-oilify	Resultaat: "ObsIdentify voorspelt Atalanta Vanessa atalanta met zekerheid 100.0%"  Een sterk geschematiseerde Atalanta waarin alle fijne details zijn verdwenen, zijn ideaal voor O. Ga je nog verder met schematiseren dan ziet O de Open-breedbandhuismoeder die geen witte vlekken heeft.

Dagpauwoog

Dagpauwoog (zwart-wit)

Laten we nog eens een Dagpauwoog in zwart-wit testen. Het ontbreken van kleur is fataal bij de dagpauwoog want zwart-wit geeft: "ObsIdentify is helaas niet zeker: de eerste voorspelling Oranje luzernevlinder Colias crocea (40.3%)."   De voorgestelde vlinder lijkt er totaal niet op!

Tot slot nog een vogeltje:

"ObsIdentify voorspelt Gele Kwikstaart Motacilla flava met zekerheid 93.1%".
Niet slecht! De rest van de foto's wordt niet met enige zekerheid herkent. Het loont de moeite om meerdere foto's te proberen.

Conclusie: ObsIdentify (het blijft een lelijke naam!) is een bijzonder nuttig hulpmiddel voor de beginnende vogel-, vlinder-, en libellenliefhebber. Het helpt je altijd flink op weg en meestal is de determinatie goed zodra het programma zelf aangeeft zeker te zijn (>95%). Uitzonderingen zijn gemanipuleerde foto's. Dat kleur niet zo belangrijk is blijkt ook uit de disclaimer: "De software kijkt voornamelijk naar structuur en patronen niet zozeer naar kleuren". Voor een Atalanta is kleur niet nodig, maar bij de Dagpauwoog is het ontbreken van kleur fataal. Grappig is dat ObsIdentify moeite heeft met dieren met een goede schutkleur! Dat is de uitdaging voor de toekomst. Enige onscherpte vormt geen probleem, maar te veel onscherpte is fataal.
Eigenlijk zijn de papieren veldgidsen overbodig geworden. Vervelend, want ik had juist de nieuwste veldgids nachtvlinders gekocht! Mooi boek, daar niet van, maar de foto's staan ook op waarneming.nl . Aanbevolen programma! De natuurliefhebber is in een nieuw tijdperk beland. Het tijdperk van Artificial Intelligence (AI).

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?

Conclusion

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.)

Postscript

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???

Postscript

20 Sep 2019
I found a review of the book in The New Statesman 27 February 2019 in which the author is disappointed about the conclusions Frans de Waal has drawn from his knowledge about animal emotions:

"It is when the author turns to the implications of all this that his reflections are weakest. His best suggestions include a rather self-serving point that zoos are important repositories for dwindling mammal genes and that supermarkets could carry barcodes on meat products that triggered smartphone images of the living conditions for the dead animals on sale."

Notes

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.