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The Cooperative Gene: How Mendel's Demon Explains the Evolution of Complex Beings

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Our view of life is usually pretty limited. Seeing trees, the family dog, winging birds, ourselves, we forget, if we ever knew, that complex life forms are in the historical and numerical minority. Even after 3 thousand million years, single-celled animals have the longest duration and largest population. Globs of material with a string of molecules, which we call "bacteria" were and are the most common form of life. Mark Ridley traces how those simple creatures underwent a radical change. They became restructured in a revolutionary step that would enable highly complex life to exist and evolve. Part of that revolution was the development of the most absurd concept in life's long history - sex. Gregor Mendel investigated the passing on of traits by counting peas. Ridley introduces an avatar, "Mendel's Demon" to explain how sex regulates what is passed on in us.

In this superbly written account, Ridley clearly explains the advantage sex has in the evolution of life. He uses the children's game of Chinese Whispers [called Gossip in my childhood] to explain how evolution operates. In Gossip [forgive the chauvinism], a group of children whisper a message from one to another. Record the original message "when the tiger comes, freeze." Compare it with the version expressed by the final child. There will certainly be changes. In almost all occurrences, the errors are in misunderstood whole words, not just letters - "freeze" becomes "wheeze." The "words" of life are our genes. Acting as instructions to forming a new individual, the message must be clear enough to build the organism. That organism must survive to produce another. Sex provides ways of assessing the message to assure its validity before generating an offspring.

Ridley goes on to discuss how complex life forms emerged. The most important steps were the protecting of DNA in a cell nucleus and the addition of mitochondria. Mitochondria are the energy modules of cells - chloroplasts in plants probably being the best known. Their joining the nuclear cell provided a trade-off. Mitochondria were given a place to live, paying rent by transferring much of their DNA to the cell's nuclear version. Once these two changes had been achieved, sex evolved with mechanisms to overcome the problems of DNA playing Gossip. Ridley shows how the processes surrounding sex overcome the mistakes that inevitably occur in the copying process. Gross errors don't survive - indeed they rarely achieve the development level of a fetus. The apparent dichotomy here is that while reducing errors may mean conserving an organism's traits, it may also reduce the diversity necessary to survive in a changing environment. The balance is delicate, as the fact that 99.9 per cent of all species having gone extinct over time testifies.

Ridley sensibly brings each detailed description of the cell's processes back to how it relates to humans. This ploy is highly successful in making the book readable and focussed. It also builds a framework for the concluding chapters. After his thorough analysis of the procedures of reproduction and evolution, Ridley goes on to some highly speculative notions about the future. He notes that our species carries more genetic errors across generations than any other species. Could this error rate lead to what he calls "mutational meltdown"? Possibly, but not likely. Having speculated on conditions of life on alien worlds, he uses those ideas to suggest future scenarios to prevent that "meltdown." That bugaboo of today's society, cloning, Ridley dismisses as too vulnerable to natural selection. Instead, he sees gradually improving methods in using genes for therapy, organ replacement or repair, possibly even a drastic change in gender identity.

Ridley's almost anecdotal style makes this overview of a complex topic an absorbing read. Reaching from deep history to a plausible future he covers much ground. His imagery retains your attention and he carefully builds your knowledge as you follow his lead. He's also careful with his science. No assertions are put forward without good foundation, and where the evidence is lacking or slim, he cautions us about coming to conclusions. The balance is so carefully maintained that this book might be considered a call for research in particular areas. Formidable and challenging, this is a delightful book for countless reasons. Intriguing questions, bold but realistic speculation, sound science vividly presented. A rich treasure, this book will be valuable until all Ridley's questions are resolved.

Note to those who have found the title a problem, be aware that this book was originally published as: Mendel's Demon: Gene Justice and the Complexity of Life. Why the title was revised for U.S. publication remains elusive.

The title of this book is clearly a reference to Richard Dawkins' famous "The Selfish Gene." One of the most amazing develpments in evolutionary and developmental biology in the past couple of decades is that evolution is just as much about cooperation as it is about competition. In particular, several authors, including Maynard Smith and Szathmary, Michod, and Keller (see his Princton U Press collection) have analyzed the development of multicellular organisms in a conflict/cooperation framework. The result is quite unfavorable to Dawkins' approach.
This book mentions the problem, but disposes of it so rapidly that virtually nothing of interest can possibly get through to the reader. Rather, this book is about the problem of replication error in copying dna. Ridley argues that the level of complexity of organisms is limited by their ability to sustain highly accurate copying, and that humans are about at the limit of this ability.
This is a interesting argument, but to my mind it isn't earth-shattering and it doesn't require a whole book to tell. Of course, you will learn a lot of biology in the telling (if you didn't know it already), and Ridley is a very good writer.
Ridley flirts with eugenics in the policy section of the book, lamenting that modern wealth, technology, and medicine allows lots of defective genes to proliferate in society, but he does not recommend doing anything about it---such as forcing people to abort imperfect fetuses. He argues that cloning shouldn't replace sexual reproduction because, whatever the value of sexual reproduction (Ridley is agnostic, but favor Kondrashov's model), it's clearly valuable. But we don't need a book or copying accuracy of dna to tell us that.
In sum, nothing monumental here, but very nice if you want to learn a little about how modern biologists think, and what they think about.

I don't know if Mark and Matt Ridley are brothers, but they should be. Each is English, has a doctorate, and writes in an engaging and literate way about evolution. Matt seems more interested in what is called "evolutionary psychology", discussing social issues in the light of our evolved traits. Mark is more the scientist, pursuing the fundamental questions of life. This book is about such a question: why did complex life evolve at all?

At first that might not seem like much of a question. The hard part, after all, is to get "simple" life -- a bacterium. After that, given enough time and the creative power of DNA mutations, complex life is more or less inevitable. Right?

Actually, from the evidence it seems that simple cellular life evolved rather quickly -- within a few hundred million years at most -- after it was possible for any life -- that is, after the planet had cooled down and water was mostly liquid. Yet, after that it may have taken two billion years for the eukaryotic cell to arise. That is such a large part of the total amount of time life has been on the planet that it is very possible that the eukaryotic cell might never evolve at all if the history of life were rerun.

And, according to Mark Ridley complex life -- multicellular life -- only arose because the genetic mechanisms invented by the eukaryotic cell allowed it. Complex life is complex because it has lots of parts, and requires lots of DNA, which must be duplicated from generation to generation. Copying errors turn out to be a limiting factor once you get to billions and billions of "letters" in your genome, even with the various enzymatic mechanisms for checking and correcting DNA copies (invented by bacteria billions of years ago and never improved upon). For bacteria, 99% of their offspring are perfect genetically, since their DNA is short enough that errors are unlikely. For us, we're lucky to get one or two perfect gametes in a hundred. So how in the world can we go on, generation after generation without degrading like a much-xeroxed document?

In a word, sex. This is really the crux and subject of the book: sex, gender, and the peculiarities of meiosis are there to overcome the daunting problem of copying error and allow beings with lots more DNA than a bacterium to quite faithfully reproduce themselves generation after generation. Even without any steamy scenes sex and gender are fascinating, and Ridley's explanation of why we have them (sex and gender are not the same thing) is convincing and entertaining. But I will say no more about that. You will just have to read the book, which I recommend, with some reservations.

I like Mark Ridley's writing. His sentences are graceful and laced with wit and learning. Where he falls down, though, is in the explanations, or justifications, for the material he introduces. The ideas of copying error and how it plays out in different organisms was new to me, as were the arguments justifying sex, gender, and the peculiarities of meiosis. On the way to them there were also various subsidiary conclusions, and in few cases were his explanations terribly coherent. At least part of this book had its genesis in lectures, and it shows. There are small inconsistencies: he refers to the new result of 30,000 genes in a human, for example, and later casually throws in the older presumption of 100,000, no doubt in a section lifted from an earlier talk and never corrected. But more annoyingly, his basic style of argument is what an old math professor of mine called "hand-waving". This is where you talk fast and plausably to skate over difficult points rather than using logic. Lectures to a lay audience tend to be mostly gee-whiz facts, jokes, and hand-waving arguments. Ridley is not that casual here, but still induced a kind of mental whiplash by discussing in excessive detail rather obvious points, and then making a sudden jump across an intellectual chasm to a daring conclusion, then blandly continuing.

In conclusion, I would recommend the book for its very interesting subject matter and breezy style. But I would add that you might find yourself wishing for a bit more rigor. Or not.

Mark Ridley has two major themes in this book, the appearance of what he calls complexity, and the role of what he calls gender. I use this awkward repetition of words because what Ridley calls complexity is not what students of complexity call complexity, and what he calls gender is not what linguists call gender. Unfortunately he is not very precise with his definitions in either case. Indeed, in the case of complexity he recognizes his vagueness explicitly: "Complexity is an ill-defined term ... I am as puzzled as anyone by what exactly I mean when I say it." One may hope for something a bit clearer than that, but one will be disappointed. Most of the time what he seems to mean by claiming that humans are complex and bacteria are not is that a human is an organism with numerous kinds of cell, most of which have nuclei, whereas a bacterium is just a single cell with no nucleus. It is reasonable to ask what conditions allowed multi-cellular nucleated organisms to appear, but less reasonable to claim that bacteria are not complex.

The other term that is crucial for the book, but is ill-defined, is gender. Ridley uses it to distinguish sex -- the idea that an individual is the result of mixing the genetic information from two different parents -- from the idea that the two parents are different from one another, coming from two (or more) classes such that the members of the same class cannot breed with one another. Unfortunately he not only neglects to explain in so many words that this is what he means by gender, he also forgets from time to time to maintain the distinction, referring, for example, to "single-sex changing rooms" when he means, in his terms, single-gender changing rooms.

To this point I have concentrated on the more negative aspects of the book, probably excessively, because there is a large amount of interesting discussion in it as well. Ridley has a lot to say about the dangers of conflict between the different genetic components of a multi-cellular organism: conflict between nuclear and mitochondrial genes, between nuclear genes from the two different parents, between the mitochondria from different parents, and so on. He argues that avoiding and defusing potentially disastrous effects of such conflicts explains what would otherwise seem absurdly complicated and wasteful ways of doing things. Most organisms exclude the mitochondria of one parent from entering the egg when it is fertilized, but the few exceptions illustrate what can happen if they are not excluded. In mice, for example, the paternal mitochondria do enter the egg, "like missionaries walking into a cannibal feast", whereupon they are promptly destroyed. Even in humans some paternal mitochondria are able to escape the strip search of the sperm cell when it enters the egg, but they too are destroyed. Yet mitochondria are expensive to produce, and potentially valuable, so why wantonly waste them? Avoiding even more wasteful wars with the maternal mitochondra appears to be the reason.

Ridley explains that most of the apparent complications in reproduction are necessary for effective policing of the system so that it remains fair, to give genes on the two chromosomes in each pair exactly the same chance of getting into the fertilized egg. What is the point, for example, of doubling the total number of chromosomes as the first step in halving the number? Multiplying by two and then dividing by four seems an absurdly complicated way of dividing by two, but it appears to be necessary as a way of preventing cheating. Humans, incidentally, are far more at risk from trisomies like Down's syndrome than animals like rabbits that breed at much younger ages, and the risk increases with the mother's age. Ridley argues that this is related to the fact that a mother's eggs are all made at the time of her own birth, not being used until as much as forty years later. He suggests that this long period gives cheating genes the time to "learn" how to subvert the process of discarding three of the four copies of each chromosome that occurs at fertilization, so as to increase the chance of survival of a chromosome that carries a cheating gene.

The book concludes with a discussion of the future of human breeding, including the question of whether cloning is likely to be feasible (yes, almost certainly) and desirable. All of the reasons why sexual reproduction exists in the first place imply that without it errors in the genome would accumulate in an uncontrolled way and extinction would follow. This would suggest that cloning will almost inevitably produce offspring weaker and less viable than the mothers of whom they are supposedly the clones.

The Cooperative Gene: How Mendel's Demon Explains the Evolution of Complex Beings written by Mark Ridley who is one of today's leading evolutionary thinkers. This is a well-written book that brings to the reader an intellectual treat.

"The Cooperative Gene" give us clues as to why and how complex life came about. It was by natural selection by ingenious solutions to copying errors and uncooperative genes. The author explains everything in a distinctive style that is very cleve... indeed.

This book is geerd to a person with a scientic background as it delves into biology, biochemistry, and cell biology, but it isn't out of reach of a well read lay person. The author's wit and intelligence comes through and he seems to get the reader involved so you're not lost. I was pleasantly intrigued by the author's historical grounding of this book and the up to date relevance. From the initial wobbly, replicating molecules, through microbes, worms and flies till we get to mankind, the author reveals how life evolved on earth.

Natural selection encouragess genes that look out for themselves, while delfish genes that could easily evolve to sabotage the development of complex life forms. Ther author painstakenly explains the difference between a selfish and a cooperative gene. As well as giving the reader his definition of Gregor Mendel's fundamental laws of inheritance... Mendel's Demon, thus, we find out about the origins of sex, gender, and cloning.

The DNA in a human being is 6600 Million letters long and codes for about thirty thousand genes. In contrast, the DNA of a bacterium is two or three million letters long and codes for two or three thousand genes. You see where coding for a human being can bring on more mistakes. Mendelian inheritance controls how genes are inherited in complex life. It combines sex, reproduction, and the probabilistic rather than certain inheritance of genes.

All in all, this book was rather captivating to me, the narrative wasn't overbearing and it easily readable, but you have to have a scientific origin to get the most out this book.

We are "complex life".
Is our complexity limited by the rate of DNA copying error?
Simple life reproduces and evolves much faster than complex life.
Time measured by physics and fossils versus time measured by DNA changes.
Life existed 3500 mya (million years before present)
but fossils only go back a mere 550 mya.
It took a long time for complex life to evolve.
Live complexity hits its ceiling when the DNA message
is so long that a mistake happens every time it is copied.
For each organism, the important issue is that one or more of its
many offspring must be correctly copied.
Human beings seem to make about 200 copying mistakes in each child!
Most of this error is irrelevant (in junk DNA?).
The harmful mutation rate per generation is about 2-20.
Shocking! We are in the paradoxical zone.
RNA is more fragile. Because of their copy error rates,
RNA viruses could not evolve to be much bigger than they already are.
Bacteria use DNA as we do so they can be much bigger.
Base C is the main culprit; it tends to mutate to base U.
Mukai's experiment. Kondrashev's theory.
Is the paradox explained by sex?
Sexual selection tends to group good genes with good and bad with bad.
[Only good with good survive? (under prehistoric conditions)].
This was the place to mention the genetic advantages of female infidelity
but he didn't.

Complex life is at odds with internal gene competition.
Here, I the reviewer am not convinced of one of the author's major claims,
"The deep nature of maleness is to eject organelles from reproductive cells;
the deep nature of femaleness is to keep them."
I recall the "neutral theory" of evolution,
that many genetic changes make no difference to fitness.
It's like the "null space" in algebra.
A wide variety of models may have equal fitness.
He hasn't convinced me that organelle competition is destructive.

Page 184 explains the double division in meiosis as
a mechanism for limiting gene competition.
I don't understand this point yet but
I intend to return to the book many times in the future until I do.

The books ends with a chapter on The Human Condition and one on A Complex Future.
Although he enjoys a tongue-in-cheek discussion of sex of angels,
the book does not focus as sharply as it should on the fearsome question
that it should: How fast will our species will decline if we
are all good citizens and have our alloted 2.3 children?

Ridley's book is a rare combination : a popular book by a professional biologist with novel, important and well-founded ideas. Unfortunately he does not quite succeed in convincing me, even though I started out with a similar outlook. But there's a lot to enjoy, admire and learn from nevertheless: Ridley knows his stuff, has a lively and amusing style, and thinks clearly.
His central idea is that sexual reproduction allows the evolution of much larger genomes, encoding much more complex organisms, than asexual reproduction, because it allows Darwinian evolution to continue even when the single-base copying error rate is much larger than the reciprocal of the genome length. Evolution is thought to be possible if organisms reproduce only asexually if they copy the nucleotide bases comprising their DNA with an error rate less than the reciprocal of the DNA length - a result which was first clearly stated by Manfred Eigen. As Ridley explains, this is because mistakes will accumulate over many generations unless at least half the offspring have error-free DNA. There is an important, thought probably quantitatively minor caveat: the mistakes must be deleterious (and the extent to which they are deleterious affects the error threshold above which Darwinian evolution fails). Obviously, this idea is not easy to convey, even though it makes intuitive sense, and unsurprisingly Ridley does not quite succeed in explaining it. But it's such an important idea, and Ridley does quite well, that I have to give him a high grade - an A-. I feel he could have shown one of Eigen's classic graphs, even if it would require some hand-holding.
He does not really address the dependence of this issue on the rate of environmental change, though he hints at it. In an unchanging environment, one expects the mutation rate to be minimized, perhaps to the level that is physically attainable. Indeed, prokaryotes seem to operate in this regime (possibly because they reproduce rapidly, so their environment appears to change slowly).
He then points out that complex organisms do not seem to conform to this theory, and he (correctly in my view) surmises that this is precisely why they are complex: they have astonishingly large genomes, and yet copy their DNA no more accurately than the asexually reproducing prokaryotes. He then suggests that complex organisms can do this (i.e. defy Eigen) because they reproduce sexually. Indeed, he argues that the life that is familiar to us, and in some ways "real life", is only possible because of sex. In a nut-shell, sex IS life! I think this idea is correct, but it is rather surprising, and Ridley does not quite convince.
It's well known (except fortunately by creationists) that it's very difficult to explain how sex persists despite its twofold cost. Ridley believes (again I think correctly) that there is a huge, outweighing, advantage to sex: it allows an apparently impossibly high mutation rate because it greatly increases the power of natural selection. In particular, he favors Kondrashov's idea that sex allows one to more efficiently remove deleterious mutations, because it brings them together in the same, sacrificial, offspring genome. To make this idea work, one has to assume that bad mutations interact synergistically, and one probably also has to assume that the environment is changing rapidly in time and/or space (an aspect that Ridley does not address well). Ridley mentions fleetingly Hamilton's parasite sex theory, and disappointingly doesn't explain why he does not like it, or why it is not just a special case of the Kondrashov theory (i.e. the environment changes rapidly because parasites rapidly co-evolve, a la Red Queen). I believe there is no clear consensus amongst biologists on these important issues, and Ridley does not quite convey the complexities and confusions of these debates - perhaps wisely. But nevertheless I wish he had tackled them more head-on.
The next part of the book is very good, and here he seems much more at home. In particular his account of the difficulty of preventing selfish genes from subverting the new opportunities offered by Mendelian sex is superb. But while fascinating this is not really the nub of the matter.
In summary, this is one of the best accounts anywhere of crucial aspects of Darwinian evolution that are often concealed by the experts (perhaps because they do not want to admit that the whole structure is surprisingly rickety). I believe that despite appearances the structure is indeed sound, but even this admirable book does not provide completely convincing evidence.

This is another great and endlessly enjoyable work by Mark Ridley.

Just to eliminate any confusion, I want to reiterate what an earlier reviewer pointed out; the title of this book is "Mendel's Demon: Gene Justice and the Complexity of Life". The American edition of the book was published with an altered title, creating the absurd impression that this book is somehow a challenge to the landmark work "The Selfish Gene" by Richard Dawkins. Some misleading reviews printed here reflect that this silliness actualy worked as a marketing tool aimed at simpletons.

Mark Ridley was an undergraduate student of Richard Dawkins at the University of Oxford and is now a colleague of his there. Throughout Dawkins' work (ie. the preface to "The Extended Phenotype") he has lauded Ridley's brilliance, and he did so again in his review of this book.

Anyone who is confused by the name change (a routine by American publishers that plays havoc with citations) ought not to be confused about the book's implied content; it is a fascinating read about fascinating topics, not a "challenge" to something that Mark Ridley hasn't the faintest desire to attack.

We are "complex life".
Is our complexity limited by the rate of DNA copying error?
Simple life reproduces and evolves much faster than complex life.
Time measured by physics and fossils versus time measured by DNA changes.
Life existed 3500 mya (million years before present)
but fossils only go back a mere 550 mya.
It took a long time for complex life to evolve.
Live complexity hits its ceiling when the DNA message
is so long that a mistake happens every time it is copied.
For each organism, the important issue is that one or more of its
many offspring must be correctly copied.
Human beings seem to make about 200 copying mistakes in each child!
Most of this error is in junk DNA.
The harmful mutation rate per generation is about 2-20.
Shocking! We are in the paradoxical zone.
RNA is more fragile. Because of their copy error rates,
RNA viruses could not evolve to be much bigger than they already are.
Bacteria use DNA as we do so they can be much bigger.
Base C is the main culprit; it tends to mutate to base U.
Mukai's experiment. Kondrashev's theory.
Is the paradox explained by sex?
Sexual selection tends to group good genes with good and bad with bad.
[Only good with good survive? (under prehistoric conditions)].

Complex life is at odds with internal gene competition.
Here, I the reviewer am not convinced of one of the author's major claims,
"The deep nature of maleness is to eject organelles from reproductive cells;
the deep nature of femaleness is to keep them."
I recall the "neutral theory" of evolution,
that many genetic changes make no difference to fitness.
It's like the "null space" in algebra.
A wide variety of models may have equal fitness.
He hasn't convinced me that organelle competition is destructive.

Page 184 explains the double division in meiosis as
a mechanism for limiting gene competition.
I don't understand this point yet.
I intend to return to the book many times in the future until I do.

The books ends with a chapter on The Human Condition and one on A Complex Future.
Although he enjoys a tongue-in-cheek discussion of sex of angels,
I was disappointed that he did not attend everyday matters such as
the genetic advantages of female infidelity.

Evolutionary history is considered in Mark Ridley's Cooperative Gene, a superbly presented and insightful survey of the evolution of complex beings and genetic influences. Among the unusual contentions here: gender may be an evolutionary fluke, our mutation rate is higher than a living system can have, and being single is one of the biggest risk factors in human life. And there's more! Riveting.