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Power, Sex, Suicide: Mitochondria and the Meaning of Life
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Book Club 2012 > March 2012: Power, Sex, Suicide: Mitochondria

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message 1: by Betsy, co-mod (last edited Mar 02, 2012 10:08PM) (new) - rated it 4 stars

Betsy | 1740 comments Mod
Since we had a tie for the February Book Club read, we already have selection for March. You can use this thread for discussions about Power, Sex, Suicide: Mitochondria and the Meaning of Life. Let us know what you think.


message 2: by Betsy, co-mod (new) - rated it 4 stars

Betsy | 1740 comments Mod
Has anyone read this book yet? What did you think? I'm about 10% into it. It's interesting, and very accessible to the lay reader, so far.


Tasha I had to go through chapters 4 and 5 twice to make sure I got it, but other than that I agree it is understandable. I'VE LEARNED SO MANY NEW THINGS!!!


message 4: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments I am around 22% (Chapter 4), and agree that it is very interesting and I am learning a LOT! Betsy, I think you will find the next stretch to be more complicated; like Tasha I have had to re-read some of the passages, and I haven't even gotten to the protons yet. But I am really impressed with the story and the logic, and the writing is very good.


message 5: by Charise (last edited Mar 10, 2012 02:38AM) (new) - rated it 3 stars

Charise | 54 comments Betsy wrote: "Has anyone read this book yet? What did you think? I'm about 10% into it. It's interesting, and very accessible to the lay reader, so far."

I am also about 1% in - -just started yesterday - -so far I have also learned quite a bit. I remember the first time I had ever heard of mitochondria and became enamoured with this tiny organism - it was a prominent part of the fiction novel A Swiftly Tilting Planet. What an amazing organelle is mitochondria.


message 6: by Betsy, co-mod (new) - rated it 4 stars

Betsy | 1740 comments Mod
I remember first hearing about mitochondria in a TV show about human genetic ancestry, and how they were able to trace early migrations based on genetics. I've been fascinated by them every since.


message 7: by Steve (last edited Mar 11, 2012 10:45AM) (new) - rated it 4 stars

Steve Van Slyke (steve_van_slyke) | 378 comments I'm a little over half way through and so far one of major take-aways for me is the author's description of the “chasm” between bacteria and eukaryotes, how if the tape of life were somehow rewound and played again that it is highly unlikely that all of the improbable steps that led to the endosymbiotic development of eukaryotes from the union of an archaea and a bacteria would repeat.

Based on that it made me think about the Drake Equation, which is used as a tool to foster discussion about the number of intelligent life-forms with the ability and desire to communicate with other, similar forms of life might exist on other planets in our galaxy. Using the standard values for the variables in the equation, the answer comes out to be 10.

However, given what Lane tells in this book, the value for the variable f-sub-i (probability that intelligent life will evolve once basic forms of life have established a foothold), should be something much smaller than the .01 that the standard equation uses. Even if we only add one more zero after the decimal that would change the answer to 1 vs. 10; i.e. the likelihood is that there is only one other form of intelligent life in the Milky Way Galaxy, and even that is probably optimistic. If, like me, you've tended to go along with the optimists like Drake and Carl Sagan, this comes as a bit of a jolt. But once recovered I think of just how amazing it is that we are here on this planet discussing such questions. If the author is correct, then we are as he says, not necessarily alone but probably quite lonely. Fascinating.


message 8: by Tasha (last edited Mar 12, 2012 07:21AM) (new) - rated it 5 stars

Tasha Steve wrote: "I'm a little over half way through and so far one of major take-aways for me is the author's description of the “chasm” between bacteria and eukaryotes, how if the tape of life were somehow rewound..."

This book has made me think a lot about that as well. There have been so many planets found in our galaxy so far, and so many galaxies, that I almost took it for a given that life exists somewhere else. And it still probably does, but maybe only bacterial.


message 9: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments I have some catching up to do after a hectic family weekend; around 30% into the book now. I am very interested in comments by Steve and Tasha about the relevance of this book to the incidence of intelligent life on other planets. Hopefully I can add something useful to their discussion soon.

I have finished the ‘full metal jacket’ and ‘life itself’ sections on how the earliest common-ancestor cells may have originated - with iron-sulphur ‘membranes’ and microscopic bubbles in the volcanic seeps. A truly amazing story, and he convinced me that it is quite likely to be true.

I want to point out that the author is stepping very methodically through the research that produced these amazing new concepts. It may seem tedious to go through it, but he wants to show how the ideas evolved, and I find his discussion very illuminating. He gives an authentic feel for the competing (and often contentious) schools of thought, and the rise and fall of particular concepts for the production of energy and origins of life. I am assuming that he continues in this mode for the other questions that come later.

There are several other aspects of this book that I really appreciate. One is that he has made every effort to tell the story in a clear and accessible way. This is especially impressive because the book is extremely ambitious. It is centered on mitochondria, but he is really considering the history and origins of all early life forms.

He stresses the central importance of proton pumping for all respiration, whether in mitochondria, chloroplasts, or bacteria. This common mechanism is consistent with the idea that all three forms of respiration may have developed from a common ancestor. He shows that fermentation requires at least a dozen enzymes, and is likely too complex to have served as the first and therefore only means of providing energy. In addition, different enzymes are used for fermentation in archaea and bacteria, and some of them appear (from DNA analysis) to be quite unrelated. So, it is unlikely that fermentation was the earliest mode of energy production, or that it was inherited from the hypothesized common ancestor (LUCA).

Coming back to respiration, he shows how the reservoir of protons created by pumping is absolutely critical for making ATP. The reservoir is itself crucially dependent on a non-leaky membrane to serve as a ‘dam’. The process halts if the membrane breaks or the proton pumping stops. But he makes the critical point that the membranes of bacteria and archaea today have very little in common, beyond the fact that both are composed of lipids. So, a different sort of membrane was likely present in the common ancestor.

He then builds the case that the earliest version of this membrane was likely based on sulphur/iron compounds, radically different from the lipid-based membranes found in all cells today. And he makes that seemingly absurd idea plausible by showing that 1) bubbles in volcanic seeps have membrane-like sulphur/iron compounds associated with them; 2) such ‘membranes’ can and do maintain proton gradients, and sunlight can power them; and 3) with the ‘simple’ insertion of an ATPase in the membrane, these systems could begin to capture the energy potential in the gradient, and thus support other biological functions.

Inserting the ATPase is of course not simple, but it is very much simpler than building a complete electron chain or fermentation sequence as other models would seem to require. The flow of the logic here is just amazing, from what I can see.

All of these threads are woven into a very engaging narrative. You really have to work at it to understand all of the findings he is throwing out there – a real mountain of ideas. But he is giving you a chance to see how some accepted models fell because of fatal weaknesses, and how other models that were initially ridiculed turned out to be correct. If you take the time to follow his logic, these are fascinating stories.

Two more quick points to finish this comment. One, I know that there are members of this group who are far more expert than I on the cell/molecular biology of these pathways and their evolution. I hope that I am getting the author’s narrative approximately the way he intended it. But please (anyone!) correct me when I get something wrong, and/or add comments about important points that I have left out.

And two, Lane makes it very clear that this is all work in progress, and the story will develop and may change as new findings come in. That is the process of science, and he is doing an excellent job of depicting it here.


Steve Van Slyke (steve_van_slyke) | 378 comments Jim said: I have finished the ‘full metal jacket’ and ‘life itself’ sections on how the earliest common-ancestor cells may have originated - with iron-sulphur ‘membranes’ and microscopic bubbles in the volcanic seeps. A truly amazing story, and he convinced me that it is quite likely to be true.

Anyone interested in more details on the competing origin-of-life theories (of which the above is a prime contender), should check out Robert Hazen's Genesis: The Scientific Quest for Life's Origins. This was a fascinating and very accessible read. I would happily read it again if it is ever selected for book-of-the-month.


Steve Van Slyke (steve_van_slyke) | 378 comments Jim said: You really have to work at it to understand all of the findings he is throwing out there...

For me that is a gross understatement, particularly in the case of the section on bioenergetics and proton transfer. I definitely should have paid more attention in Chemistry class!


message 12: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments Steve wrote: "...check out Robert Hazen's Genesis: The Scientific Quest for Life's Origins. This was a fascinating and very accessible read."

Great suggestion, Steve! I got the Kindle sample and will definitely look into it.

Steve wrote: "I definitely should have paid more attention in Chemistry class! "

Me too! Guilty, guilty, guilty...


Tasha Steve, thank you for the recommendation, if it's not chosen for a group read in the near future I will have to read it on the side.

I agree with Jim. Lane goes through all the theories step by step and makes very convincing arguments. There is a pattern to the book. He starts with earlier popular theories and explains them in a way that makes them sound complete, then he explains the problems with them and gives a more complete theory.

I'm really enjoying this read.It's challenging,but rewarding.


David Rubenstein | 916 comments Mod
I just finished this book. It is excellent, and I recommend it highly to anybody who has a strong interest in biology. It's not an easy book to read, but it is so jam-packed with awesome information and--well, it reads almost like a detective story. It's great to read books about science by expert scientists who are also good writers. Here is my review


Tasha David wrote: "I just finished this book. It is excellent, and I recommend it highly to anybody who has a strong interest in biology. It's not an easy book to read, but it is so jam-packed with awesome informat..."

That is an interesting take, the detective story. That is not a connection I would have made myself, but I see it now. A detective story with disappearing evidence. I like detective stories.


message 16: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments Wonderful comments, Tasha, David and Steve.. I will chip in when I have made more progress on the book.


message 17: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments I have (finally) neared the halfway point in the book after a busy week. I would like to go back to the discussion points by Steve and Tasha (messages 7 and 8) about the likelihood of intelligent life evolving on other planets.

Lane has done his usual thorough job of putting the story together. I would like to discuss some particulars, but first I want to restate what I think is his core argument. As usual, I will appreciate other thoughts, corrections, additions.

1) Life in a generic ‘bacterial’ form is very robust, and can survive almost anywhere in the crust or atmosphere of the earth.
2) The evolution of life from simple compounds was very ‘difficult’, but still highly likely given the intermediates of RNA replication and other steps that he discusses.
3) So overall, we should expect to find comparable ‘bacterial’ forms of life on numerous other planets.
4) But formation of the first eukaryote was an extremely unlikely event, for many reasons that he discusses.
5) And only eukaryotes offer a gateway to more complex organisms, let alone intelligent beings.
6) Thus, the incidence of intelligent beings may be exceedingly rare, even possibly unique to Earth.

This argument certainly hangs together for me, but I think it has some weak spots - very specific assumptions that may not hold on other planets, or even on this one if the tape of life were replayed. I just want to sketch out my thoughts for now, and maybe bring in some details in further discussion.

Consider the ‘bottleneck’ at point 4 above. Lane makes a compelling case for the near-miraculous nature of the convergence event that led to the first eukaryotic cell. And he makes a strong case that if the merger hadn’t happened the way it did, it probably wouldn’t have happened at all.

But I think that the latter statement is open to question. The following quote puts more emphasis on point 1:

“Self-sufficient (autotrophic) bacteria live in countless numbers in the ‘deep-hot biosphere’, buried up to several miles deep in the rocks of the earth’s crust... Other bacteria survive radiation at the genetically crippling doses found in outer space, and thrive in nuclear power stations or sterilized tins of meat. Still others flourish in the dry valleys of Antarctica, or freeze for millions of years in the Siberian permafrost, or tolerate acid baths and alkaline lakes strong enough to dissolve rubber boots. It is hard to imagine that such tough bacteria would fail to survive on Mars if seeded there...”

So bacteria can live nearly anywhere, in zones that entail extreme selection pressures and a lot of mutations from radiation, etc. As Lane discusses, in certain cases they can also live without cell walls and develop internal support structures (cytoskeleton). Very importantly, they actively tailor their genomes to fit prevailing conditions, and exchange genes through a variety of mechanisms. They can also live in symbiotic near-neighbor relationships.

Taken together, these traits create a huge catalogue of mechanisms for possible adaptations. To my mind, that raises the probability that some alternative series of chance events could lead to a eukaryotic cell. This cell might have different components and a different mechanism for energy production (not proton pumping), but be functionally equivalent in the sense that it escaped the bottleneck and provided a gateway to higher complexity.

Lane emphasizes very strongly that this alternative eukaryotic cell did not happen (so far as we know now), even in the billions of years that it might have. This is certainly important evidence, but he seems to take it as a prima facie case that it could not happen in any other way. But I would argue that this position, while reasonable, is not especially compelling after considering the range of alternatives that appear to be available.

I don’t know the equations, but it seems clear to me that natural selection would produce a wider range of improbable events if it operates on a larger number of random variants. That is why point 1 is so important, because the number of random variants that are generated by such diversity is simply staggering. If a highly improbable event hasn’t happened in 3 billion years, it could still happen tomorrow, or a billion years from now, or in the different geochemistry of a different planet, and so on.

There are other points to consider, but I want to push this much out there and see what other members think about it. I have not read the Hazen book that Steve mentioned, so it would be good to consider points of view expressed in that and other sources on these issues.


message 18: by David (last edited Mar 16, 2012 08:54PM) (new) - rated it 5 stars

David Rubenstein | 916 comments Mod
Jim wrote: "I have (finally) neared the halfway point in the book after a busy week. I would like to go back to the discussion points by Steve and Tasha (messages 7 and 8) about the likelihood of intelligent l..."

Jim, I think you have summarized the early part of the book correctly. I had always thought, that if there is a "bottleneck", then it would have been the original generation of life. I was surprised by Lane's idea that the bottleneck was actually the evolution of the eukaryote cell. Like you, I wonder about how unlikely this evolution really is. After all, if it happened on earth (at least once), how unlikely can it be?


message 19: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments Thanks very much, David, and I am glad to see the confirmation of my summary points.

Like you, I had never thought of the first eukaryote cell as a bigger bottleneck than the origin of life itself. Lane may very well be correct about this, and I love the way he summarizes all of the more recent evidence (to date of publication). He also states most of the assumptions that I am questioning here, so he certainly is aware of the issues.

But the mass of detail, and the repetition of his major conclusions (which is helpful overall), had the effect of making his story seem inevitable. As I read more, I started thinking about other possibilities. Changing any of the assumptions - the proton pumping for energy generation, for example - could drastically loosen the constraints that make up the 'bottleneck'.

As you say, the original generation of life may have been a tighter bottleneck, since (among other things) you have to go through RNA or some other intermediate before you can use a DNA code. Not an easy problem, that is for sure.

It is all fun to think about, and amazing how much progress has been made on these questions.


Tasha Lane seems to argue that the evolution of the eukaryote is less likely than the origin of life. In fact if I remember correctly, he explicitly states this. They both seem to have happened only once on this planet.

Jim, you make a good point. Just because this is the only example of complex life we have doesn't mean it's the only way to do it. I may have had a failure of imagination. I should never underestimate nature.


message 21: by Ali (new)

Ali (doublehelix88) I see that mitochondria makes the center focus of this book as I can tell from the comments above. As a biology major student, I can say that mitochondria is my favorite part of the cell, or as we call it, "organelle". It's the source of energy that supplements the cell with power. Definitely reading this book.


message 22: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments Tasha wrote: " Just because this is the only example of complex life we have doesn't mean it's the only way to do it. I may have had a failure of imagination. I should never underestimate nature."

Thanks very much for the comments, Tasha, and I doubt that there was any failure of imagination on your part. This book gives you so many things to think about, and is so persuasive in its conclusions, that it is very tempting to just absorb his message and move on.

Lane's view may very well apply both to our planet and many others. If it does, there are strong predictions that can be made, and these may be testable in our own solar system - on Mars, for example.

Lane would predict (I think) that
1) 'bacterial' life forms should be found very frequently on planets that satisfy minimal constraints for size, temperature range, radiation exposure, etc. - so long as they have water, preferably in the liquid form.
2) eukaryotic cells with 'mitochondrial' power plants will be extremely rare by comparison with bacterial forms.
3) complex/intelligent life forms will never be found without a wide variety of eukaryotes and an ascending ramp of complexity.

My point above was basically that we may (someday) find eukaryotes, or their functional equivalents, that do not have mitochondria. But these would have some other method of producing energy (most likely symbiotic and within the cell as mitochondria are). Or, we may find eukaryotes on many planets that do have mitochondria, an indication that the merger event was not as 'near-miraculous' as Lane argues in the book.

Intelligent life forms might or might not evolve in such cases, but we might not recognize them even if they slithered past!


Tasha All great points Jim. It would be nice to have a larger sample size. One just isn't enough.


message 24: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments Tasha wrote: "All great points Jim. It would be nice to have a larger sample size. One just isn't enough."

Exactly! In the current economic/science funding climate, Mars may have to do for the next data point on predictions 1 and 2 above. However, a lot of bad science fiction movies would suggest that we might get a positive test on prediction 3 as well!


Ali, we are definitely talking mitochondria here, as you say, and I hope you enjoy the book.


Steve Van Slyke (steve_van_slyke) | 378 comments Jim said: I have not read the Hazen book that Steve mentioned, so it would be good to consider points of view expressed in that and other sources on these issues.

Genesis: The Scientific Quest for Life's Origins deals little if at all with the development of eukaryotic life, so I doubt it would shed much if any light on the question of how probable that event was.

Excellent, and thought provoking critical analysis of Lane's line of reasoning, Jim.

Given that bacteria and archaea arose almost as soon as the earth had cooled from its molten state, almost instantly in geologic time, it would seem that the probability of similar forms of life on other planets is high. On the other hand, since it took another two billion years for something more complex, the eukaryotic cell, to evolve that it is clear that the probability of that type of event is much lower.

It seems the question we're asking is: Does it just take two billion years for the soup to simmer before you get something more complex? In other words, if the soup is cooking on lots of worlds do you eventually get something like eukaryotes after a few billion years? Or, as Lane suggests, can you cook forever and rarely get the set of circumstances that causes two elements in the soup to join forces to make something completely different?


message 26: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments Steve wrote: " Does it just take two billion years for the soup to simmer before you get something more complex? In other words, if the soup is cooking on lots of worlds do you eventually get something like eukaryotes after a few billion years? Or, as Lane suggests, can you cook forever and rarely get the set of circumstances that causes two elements in the soup to join forces to make something completely different?"

Those are all excellent points, Steve, and I really like the way you summarized the question under discussion. Let me see if I can add a little perspective to the questions as you asked them. I will start by highlighting a point that I left out before.

In the primordial soup, before there were any viable, reproductive cells, there was also no competition for scarce resources. Such resources as were there were probably quite abundant. So the very first reproductively viable cell, regardless of its internal machinery, would have had an open planet to allow for near-unlimited reproduction.

Contrast that scenario with the one facing the first ‘attempted’ eukaryote. Now there is a huge amount of competition, and resource limitations are very likely to be a limiting factor. As Lane points out, under these conditions the first eukaryote must be as reproductively fit as the competition that surrounds it. That is a very tough problem to solve, and as such it is very unlikely to be solved.

So how long does the soup need to simmer before you get a eukaryote that is reproductively fit? I think that the time-tested bacterial competition is a good reason to agree with Lane’s argument - that the soup may never produce a eukaryote that can ‘hit the ground running’ and multiply, then evolve toward more complexity.

If we agree with Lane’s position, then two points are really striking to me. First, Genesis: The Scientific Quest for Life's Origins and any other book on the origins of life will certainly need to take this bottleneck into account. As Steve and Tasha said, we may indeed be lonely - unless we grow really fond of bacteria.

On the other hand, (I think) we are still left with all of the alternative avenues to complexity that I talked about before - understanding that most of my reasoning was speculative and based on possibilities, not data. For any avenue to complexity, the competition factor probably needs to be reduced in a particular niche, and that seems likely given the number of niches.

So my scenario would be that the soup needs to simmer in a lot of isolated compartments, as a multitude of mixtures, some having limited bacterial competitors and abundant resources. These compartments need enough stability over time to support a lot of mutations, and other variants that could produce the magic union of two cells that is required in Lane’s model.

This is the sort of scenario that could be modeled on a computer using statistical tools. There are a lot of free parameters that would need to be filled in by explicit assumptions. I have no idea what the models would predict, but my gut feeling is that the chances are reasonably good for a functional equivalent of eukaryotic cells to exist on many other planets. As Tasha said, we need a larger sample size. I think that more testing within our solar system may help a great deal to firm up the free parameters - for example, whether viable complex cells exist but with different energy-producing mechanisms, a different nuclear envelope, and so on.

But with that said, let me throw a spanner in the works with another striking concept from Lane’s book. The astonishing resilience and adaptability of bacteria give them a bulletproof quality that may guarantee a high level of competition in every sample of soup. That would reduce the chances of any more complex cell taking hold. Moreover, bacteria behave with a form of cooperativity, especially in their gene-exchange mechanisms, that creates a kind of superorganism - one that can lose any component without damage to the whole. Most eukaryotic cells and organisms, for all their complexity and abundant mitochondrial energy supply, simply can’t take similar losses - of brain, liver, or lungs as examples - and survive. In other words, bacteria are relatively simple as single cells, but extremely complex as an ecosystem.

I would like to expand on the latter idea in a day or two. Please jump in, anyone, with your thoughts, corrections, etc.


message 27: by Riku (new) - rated it 4 stars

Riku Sayuj (sayuj) So many chance accidents has to happen for complex life to evolve... has anyone worked out the probabilities? what if that number turns out to be bigger than what our universe can allow?

I am sorry if this is an out of context question, but Jim keps tempting me about this discussion.


Angus Mcfarlane | 71 comments Riku, to continue your aside.... It seems to me improbable events can happen quite frequently. Looking at local rainfall records (Australia) there have been a number of months where the rainfall volumes are 1 in 10000 yr events, this unless than 200 yrs of records. If I've interpreted this correctly (correction welcome by the way), could the rise of life in the universe then be less probable than the number of planets, yet found on a number of them?


Steve Van Slyke (steve_van_slyke) | 378 comments We've drifted away from the star of the book (mitochondria) but it has been an interesting discussion nonetheless.

Jim said: As Tasha said, we need a larger sample size. I think that more testing within our solar system may help a great deal to firm up the free parameters...

Agree completely. Thus it is a great shame that the proposed 2013 budget for NASA reduces the budget for planetary exploration in favor of, as one example, the SLS or Space Launch System, also known as the Senate Launch System and Rocket-to-Nowhere, because of its parochial pork-barrell raison d'etre.

Thus it will be longer before we can sample the waters beneath the ice of Europa and Enceladus to see if anything might be hanging around possible volcanic vents.


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Jim (Neurprof58) | 129 comments Riku wrote: "So many chance accidents has to happen for complex life to evolve... has anyone worked out the probabilities? what if that number turns out to be bigger than what our universe can allow?"

Welcome to the discussion, Riku! On your first question, Steve mentioned the Drake equation as an estimate for intelligent life-forms elsewhere, and Genesis: The Scientific Quest for Life's Origins for competing theories on the earliest events.

My feeling at this point is that it will be very difficult to get a good estimate of the probabilities without more data. As Steve mentioned in his last message, it appears that the US will not be a lead investigator in that quest, at least not in the current political climate...

On the second question about a too-high number, a scenario that comes to mind is that too many intelligent life-forms might start terraforming in too many places and screw up the balance of mass and energy, with catastrophic results. A pretty scary but intriguing thought (if that was the thrust of your question).

I guess some pretty disruptive things could happen at the level of individual planets too, but the orthodox notion (I think) is that this planet will spin along in terms of entropy, conservation of mass, etc. with only minor effects from biological activity. In other words, biology changes the flow of events and energy, but not the ultimate thermodynamic outcome. I think that's what I was taught...

I have a different train of thought that goes more like this: what if the intelligent life-forms that do develop are intrinsically self-destructive, and their high-energy mitochondria are a big part of the problem because they lead to wasteful use of resources, aggressive (consuming) behavior, and the like?

Hopefully, both concepts are full of it, and everything will work out for the best.

Angus wrote: It seems to me improbable events can happen quite frequently. Looking at local rainfall records (Australia) there have been a number of months where the rainfall volumes are 1 in 10000 yr events, this unless than 200 yrs of records. If I've interpreted this correctly (correction welcome by the way), could the rise of life in the universe then be less probable than the number of planets, yet found on a number of them?

I agree completely with what you are saying, Angus. 'Rare' events are not so rare after all, certainly on the scale of an entire planet. And each rare event provides an opportunity - a niche - for complex processes to combine in such a way that natural selection can pick a viable winner, if there is one.

On this point, Lane sounds very confident that all life forms on earth share the same genetic code (DNA->amino acid). But we need to understand that our sample is still small, compared to the millions of distinct organisms (species) that exist on the planet. We should not be shocked if a headline appears in the news one day, something like "New Form of Life Discovered in Volcanic Formation".

Steve wrote: Thus it will be longer before we can sample the waters beneath the ice of Europa and Enceladus to see if anything might be hanging around possible volcanic vents.

Now I am seriously bummed. And just when I was getting to the heavy lifting on my tax returns!


aPriL does feral sometimes  (cheshirescratch) | 280 comments Sorry if I seem the lame-brained, but I'm a creature of literary appreciation. I love science despite my lack of innate resources,so I hope everyone can put up with me, now and in the future. I'm a recent member and this is my first club read. This book is great. It is filling in a lot of gaps in my general science education. Even New Scientist Magazine hasn't filled in these a facts and speculations, before. I've read the previous comments about life hopefully being out there (me, too, hoping, that is), even if all we learn is that a microbe or two lives under Jovian moon seas. Unlike scientists, I have to admit I'd be as excited too if the microbes are planted there by our explorations, but grow wildly. Heresy, I know, but still! Also, do I understand this correctly - our cells are SPLITTING atoms? Routinely using proton flow to generate electricity? REALLY? REALLY?


Steve Van Slyke (steve_van_slyke) | 378 comments Welcome April, the more the merrier.


Tasha @ April
Yes, but removing an electron from an atom (e.g. rubbing a balloon against your hair) is not the same thing as fission (splitting an atomic nucleus). A hydrogen atom is one proton and one electron. Still, the proton pump is amazing.


message 34: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments Great explanation, Tasha! And April, let me add my welcome to those of Steve and Tasha. I love your enthusiasm!

I am still trying to sort out the theories on cell death (apoptosis), origins of sexual reproduction, and (especially) the putative roles of mitochondria in the evolution of both. I am still in a muddle about quite a few of the points, and would WELCOME comments from others about their understanding of Lane's presentation.

I hope to have something coherent to post tomorrow.


aPriL does feral sometimes  (cheshirescratch) | 280 comments So, the original parasite/proto-mitochondria kills the host cell because that cell is creating the means for energy worse and worse. It leaves for a better host cell. However, now it performs the function of signaling cell death in order to have the chance of passing on its genes? Or it's kind of a leftover knee jerk reaction from when it was more independent? At least that's how it read to this Dickens fan, Jim. Also, by adding mitochondria to the cell, the benefit of it was similar to adding 1,000 calories a day to a starving man's diet, which boosted energy levels to a point which made saving unused genes and the strengthening effects (by repair) of mixing sperm and egg genes more beneficial than too costly? Lastly, the cure for old age is piling in excessive mitochondria to reduce free radicals, especially during resting? Since I haven't scampered for a hidey hole in awhile, and resting is my everyday life, I hate to imagine the state of my electron buildup, (positive or negative). I suspect, Jim, this isn't too helpful, but it certainly is my thinking on finishing this book.


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Jim (Neurprof58) | 129 comments April the Cheshire Meow wrote: "So, the original parasite/proto-mitochondria kills the host cell because that cell is creating the means for energy worse and worse. It leaves for a better host cell. However, now it performs the..."

Wow, April!! I think I may have to call in air support for this mission...

I am still working through some of the sections you describe, but let me see what I can do to shed a little light on a few of the points. A lot of what you are saying is basically (I think) correct. But, as my adviser used to say, let’s back up a step.

A central question in the book is why any cell would give up its autonomy, and freedom to replicate, under the principles of natural selection. For example, how can we explain programmed cell death? How does any cell let itself be harnessed by the organism, instead of multiplying like cancer cells do? And how can mitochondria just sit inside a cell and make ATP, instead of multiplying by letting their DNA replicate as much as possible? There are lots of questions like those in the last half of the book.

But to answer any of those questions, you need to know at what level selection really operates. Is it the Selfish Gene of Richard Dawkins? Or is it the individual cell, with or without its mitochondria (and are they independent selection units)? Or is it the multicellular organism, as one might assume for sexual reproduction?

Lane talks a lot about these issues, and goes back and forth over the possible answers. And the bottom line is, it’s complicated, and it varies with the situation. And the specific answers for the individual situations are the answers to your questions, and those above.

Now here is a key insight - the structure of the DNA molecule is perfect for self-replication - a single strand has the exact physical/chemical structure needed to make a complementary strand. So, the DNA is the selection unit, right? Because any DNA strand that can copy itself, and make more copies from the copies, is a winner. The rest are all losers. That was the Dawkins idea about the selfish gene.

The problem for the gene is that it needs a package - membrane, enzymes, power supply, etc. - to support the copying process. And the packages have to multiply, so the process can continue. So the cell provides the package, and usually the cell is the unit of selection. At least, I think that’s where Lane ends up.

And mitochondria add a lot of calories to speed these processes up, as you say. But as you said, the earliest partnerships between host cells and mitochondria must have been fragile, because the mitochondria were still capable of independent reproduction and might just go that route. But over time and through selection, the partnership matured, and the mitochondria stayed put. As that happened they no longer needed all those genes for independence, and they gradually transferred most of their genes to the cell nucleus.

Now, how and why do mitochondria cause cell death? Well, I am still a bit muddled about the why part of that. But the how is easier - when things go wrong in the cell, the electron chain and proton pumping no longer work efficiently, and free radicals are created by the oxygen at the end of the chain. Since the electrons are not coming down the chain as they should, the oxygen starts grabbing electrons from other molecules, creates free radicals, and that is bad for business in the cell. In my understanding, the free radicals start the death spiral for the cell. I hope I got this right.

The question that was never really resolved, in my mind, is what do the mitochondria gain by killing the host cell, i.e. why do they do it? And the answer that I got (I think) was that they don’t gain anything in that cell - they are just vulnerable to cell damage because the electron chain and proton pumping no longer work properly, and the energy supply grinds to a halt, and the free radicals, caspases, etc. chew up the mitochondria along with the rest of the cell. But the organism as a whole gains because it doesn’t have to feed damaged cells, and so the mitochondria (and other DNA) in other cells get to replicate.

So let me leave it there for tonight, and maybe others can cover the points about sperm and eggs, and aging, before I get back to them. I am still mulling over details of the logic for sexual reproduction, and 2 genders in most cases but more in a few others. I am reading now about the human lineage studies, and haven’t gotten to the aging section yet.

I put most of this together from my recollection of the book, so PLEASE correct any errors I made. Anyone.

April, it is a pleasure to discuss these issues with you and the group, and I hope I have added a bit of clarity to a few of them. I will (hopefully) be back tomorrow with more. Thanks for the comments and questions, and give my regards to Dickens!


Tasha If I understood correctly, and I probably didn't, the sex and suicide parts are linked. When the cells were independent organisms, the burst of free radicals signalled cell damage. This damage could be corrected by combining with another cell. So the burst of free radicals was a request to mingle genes (sex). Later when the cells lived as a colony it became a signal for cell death.

April, this is off topic, but I read A Tale of Two Cities for the first time last month, and I loved it. I'm trying to give Dickens a second chance after he was ruined for me in middle school.


message 39: by Eric (new) - rated it 5 stars

Eric Bingham | 72 comments OK, I have 2 questions that I was hoping someone could answer. I apologize if they've alrady been answered somewhere else in this thread. First, I've heard the common belief that arterial blood is red and veinous (deoxyngenated) blood is blue. I've alway been told, and all the respectable internet sites I can find indicate, that this is a myth. I know there are 2 colors, but I've heard them referred to as bright red (arterial) and dark red (veinous). Lane says that veinous blood has a "purple" color. Is "purple" a way of mixing the "dark red" and the "blue" idea? My second question is that Lane says that the process of photosynthesis produces ATP. I've never heard that before, and he didn't really elaborate on it, (at least not as far as I've read, but I'm only on page 80, so maybe he does later in the book.) Does photosynthesis really produce ATP, or am I misinterpreting what he is saying?


aPriL does feral sometimes  (cheshirescratch) | 280 comments Eric, I think I remember he says all living things make ATP, which surprised me too. Also the purple blood thing made me go ?????? Too. Fresh blood depleted of oxygen looks darker than fresh oxygen-full blood, but as far as I know, since I'm was a simple office worker type, I've never seen or read of purple blood, only seen weird blue blood from crabs and gross yellow/green gunk (which may or not be blood) sometimes from insects. Wow. This is an interesting sideways jaunt I'm taking, isn't it? But I also wondered about that color reference. Any surgeons here?


message 41: by Steve (last edited Mar 27, 2012 11:19AM) (new) - rated it 4 stars

Steve Van Slyke (steve_van_slyke) | 378 comments Jim said: So let me leave it there for tonight, and maybe others can cover the points about sperm and eggs, and ageing...

I found the ageing part fascinating. I was curious if (hoping?) Lane might tell us there was a silver bullet right around the corner that could put us all in the same league as birds and bats, living to a very ripe old age with none of the typical diseases that now plague us in our "golden" years. I was amazed to learn that an albatross can live to be 150 years old and that rather than succumb to a disease that it is likely that their muscles and reflexes atrophy to the point that they die as a result of crash landings.

I spent hours on watch in the Navy watching albatrosses following the ship, never flapping their wings once, simply riding the wind. Now they are even more incredible.


aPriL does feral sometimes  (cheshirescratch) | 280 comments That whole slow metabolisms outlive fast metabolisms with the exception of birds was pretty interesting. Albatrosses are great lifestyle stories, too, if I remember right. They can fly for months?


message 43: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments Tasha wrote: "If I understood correctly, and I probably didn't, the sex and suicide parts are linked. When the cells were independent organisms, the burst of free radicals signalled cell damage. This damage be corrected by combining with another cell. So the burst of free radicals was a request to mingle genes (sex). Later when the cells lived as a colony it became a signal for cell death."

Another great explanation, Tasha! Now it all seems clear to me, and I see why I was confused when I read this section.

I didn't understand the evolutionary sequence, beginning with single cells that fused in response to damage (free radicals) and could then repair their genes. This process continued in more complex organisms as fusion of gametes (e.g. sperm and egg). It also diverged to become the cell death pathway for somatic (non-gamete) cells, as Tasha explained.


message 44: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments Eric wrote: "First, I've heard the common belief that arterial blood is red and veinous (deoxyngenated) blood is blue. I've alway been told, and all the respectable internet sites I can find indicate, that this is a myth. I know there are 2 colors, but I've heard them referred to as bright red (arterial) and dark red (veinous). Lane says that veinous blood has a "purple" color."

Looks like dark red is correct for the venous blood itself, as explained here:

http://en.wikipedia.org/wiki/Venous_b...

Here is a quote from the article:

"Venous blood is not blue as it is often depicted in many medical diagrams. Veins often look blue when seen through the skin, but this is due to Rayleigh scattering – venous blood itself is actually a dark red color (but looks purple through the opaque skin)."


You will need one of the physicists to explain Rayleigh scattering - something to do with diffraction of the light rays.

Eric wrote: "Does photosynthesis really produce ATP, or am I misinterpreting what he is saying?"

Photosynthesis does produce ATP, and the process is complicated but has similarities to what mitochondria do, as explained here:

http://answers.yahoo.com/question/ind...

There is a diagram of the two systems here:
http://en.wikipedia.org/wiki/Electron...

As a general note, I wouldn't take Wikipedia as the last word on anything important. But it is almost always a very good place to start, and if it has cited journal references (at the bottom) you can be pretty confident about the information. For serious research, you would want to go and read the cited references, and dig from there.


message 45: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments Steve wrote: "I found the ageing part fascinating. I was curious if (hoping?) Lane might tell us there was a silver bullet right around the corner that could put us all in the same league as birds and bats, living to a very ripe old age with none of the typical diseases that now plague us in our "golden" years."

Steve, I am being a real turtle this month on the reading - just too many moving parts at the moment. I hope to get to the ageing section in a day or two, but I am still reading about mitochondrial gene recombination and the Eve hypothesis.

However, if Tasha has the time to share some more wisdom with us, we might get the rest of the book covered in the next day or two. Maybe if we asked really nicely? (this goes for anyone of course...)


message 46: by Tasha (last edited Mar 27, 2012 08:03PM) (new) - rated it 5 stars

Tasha I actually had some foggy moments in the ageing chapters. I think I got the overall idea, but I am not quite as comfortable with that part. It ties the power and suicide parts together well. And the very last chapter is a concise summary, which was nice.


aPriL does feral sometimes  (cheshirescratch) | 280 comments Yes, please Tasha! I kid a lot but I love learning. It's why I joined. This book was truly amazing.


message 48: by Jim (new) - rated it 4 stars

Jim (Neurprof58) | 129 comments Foggy moments are just a sign that you are paying attention in this book, Tasha! I need that last chapter to pull it all together for me...

I won't push you... too hard... maybe tomorrow?? I will try too.


message 49: by John (new)

John Waterman (writerjohn) | 37 comments Jim:

The secret to why cells do the things they do is explained by evolution and natural selection. As complicated as it all seems, it was all accomplished one step at a time over the 4.6 billion years since the earth formed out of swirling chaos. The living things that survived, and are thus here for us to analyze today, are the ones that weren't killed off by random unsuccessful mutations in their DNA. Note that we don't see any living examples of extinct species or their cells. The successful mutations are the ones that survived and propagated into modern times. The zillions of rejected errors are gone for good, and leave no evidence behind.

Later, John.


message 50: by Eric (new) - rated it 5 stars

Eric Bingham | 72 comments Jim wrote: "Eric wrote: "First, I've heard the common belief that arterial blood is red and veinous (deoxyngenated) blood is blue. I've alway been told, and all the respectable internet sites I can find indica..."

Thanks Jim and April!


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