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Wednesday, April 06, 2016 - 02:00 AM

(Photo Credit: Tom VanNortwick/Flickr)

There’s a black hole in the middle of the history of life: how did we go from tiny bags of chemicals to the vast menagerie of creatures we see around us? 

Today, we explore one of the most underrated mysteries of all time, and present one possible answer that takes us from an unexpected houseguest to a tiny bolt of lightning to every critter you hold dear. It’s the story of one cosmic oops moment that changed the game of life forever.  

Production help from Matt Kielty and Annie McEwen. Reporting help from Latif Nasser. Special thanks to Eric Steinbrook, Scott Dawson, Ahna Skop & Rachel Whittaker


Nick Lane and Ed Yong


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Comments [77]

Miriam English from Australia

So good!! I LOVE listening to Radiolab. You guys tickle all the science bits in my mind while entertaining. I already knew most of the data in this episode but what made me especially love this one is the way you put it in perspective. Wonderful, wonderful work. Thank you.

I notice many people have suggested you follow up on a talk about chloroplasts. That is another truly fascinating story, particularly when you include the incremental steps of extracting progressively more energy from light.

Heheh :) A few people have taken you to task for your throwaway line that only one creature has developed consciousness. I'm gratified to see so many people who are not caught up in a human-centered view of the world. The word "conscious" is confusingly used to mean two quite different things: 1) being awake, attentive, feeling here and feeling emotions, and 2) having a mind that watches itself.

There are plenty of experiments that show pretty-much all fairly complex animal life that has a central nervous system has the former. In truth all you need do is to watch animals for a while and you can see they have complicated inner lives. For example watch a cute little jumping spider develop plans and strategies for hunting its prey and you can see it isn't just a little mindless robot, and I'm not just anthropomorphising here. There are, of course, animals with nervous systems that it's difficult to believe have any feeling of being, such as jellyfish and sponges -- creatures with a distributed nervous system. Consciousness (in this immediate awareness form) would appear to require a centralised brain, and would seem to be an evolutionary "trick" to enable more computing to be accomplished with less machinery.

Having a mind that watches itself is apparently far less common. There are elegant experiments that show a number of other big-brained animals have this ability: elephants, dolphins, crows, parrots, some (perhaps all) dogs. I'm willing to bet pigs have it too (they're smarter than dogs).

I've never understood why people even want to confine aspects of our lives to humanity. Awareness, self-awareness, tool use, war, charity, even the non-existent soul have all been claimed for humans only and all have been shown to be qualities shared with other animals -- except the soul; it's easy to prove the soul doesn't exist.

So, love your show, guys. Keep it up! My heartfelt gratitude to you.

Sep. 28 2016 05:38 PM
Sweethome Teacup from Portland Oregon

Mystery number 3????? WRONG! There is not just one animal that exhibits consciousness and self awareness. Dolphins, whales, chimpanzees, trees, fungi... Perhaps even the cells that bonded did so due to an intelligence that we ignorant humans cannot perceive. The ego of the human species it what blinds us to the interconnectedness of all things.

Sep. 14 2016 06:53 PM
Annette Olson from Seattle

When I heard this podcast, I knew I wanted to assign it to the students in my marine algae short course. Over the ten years of teaching the algae section of Oregon State's Marine Biology field course, only a few students have really been interested in knowing this story.

But there's more! The next major event in the history of life (to seaweed lover) was the origin of chloroplasts--the acquisition of a photosynthetic endosymbiont by a eukaryote. Again, this was a single event, but the history of chloroplasts turns out to be a LOT more complex than that of the mitochondrion.

Please let me know if you ever make a similar episode on chloroplasts--I'll assign it to my students, as well!

Jul. 29 2016 04:29 PM

Hi Radiolab! I just graduated from University of Wisconsin- Madison and there is a wonderful professor there, David Baum, who just published a very interesting "update" on Margulis's endosymbiosis theory. It not only explains origins of eukaryotic cells, but also the formation of many other internal cellular structures!
Here is the link:
I talked to him about the podcast and it sounded like he would be happy to talk more about it if you wanted to do an update podcast. He has also worked with Lynn Margulis and has many insights on her theory as well!
Thanks for a great show!

Jul. 23 2016 01:34 PM
Mark from St Louis

If you really want to know "si from ny" you would take the time to read the ten pages here:

Joe Schmoe would profit from that as well.

Jul. 11 2016 01:27 AM
si from ny

can someone tell me how the "bags of chemicals" came into being?

Jul. 04 2016 10:29 AM
Joseph Schmoe from Europe

Mark. I didn't say it wasn't difficult, or a religious inevitability, as the straw-man you put up suggests. I meant that given the size of microbes, and therefore their rate of interaction in a given area, multiplied by the area in which they exist (practically everywhere on earth) multiplied by billions of years, even a minuscule likelihood becomes a high probability.

...but just to be (apparently) more controversial, organisms work together all the time. So yes, I think it is an inevitability that eventually two organisms become so close that human definitions of what constitutes a species consider those two organisms as one.

Jun. 29 2016 03:24 AM
Mark from St Louis

From the posts here, I see that the myth of Lynn Margulis as science hero is far more important the reality of her as a working scientist.

"Joseph Schmoe" has literally no idea how difficult it was for two organisms to work together well enough to be considered a chimeric individual organism but he is confident about his religious statement that it is inevitable.

Jun. 12 2016 09:19 PM
indianagoldenbrown from Dillon, CO

No mention of Lynn Margulis? How about a follow-up with her work!

Jun. 11 2016 01:08 AM
Joseph Schmoe from Europe

"We can say that because we are black"
Terrible comment. Losing interest in Radiolab by the day.

And Lynn Margulis first proposed this many years ago.
Also its not as highly probably as it seems. If there is a mass of microbes constantly bumping into each other for 2 billion years, eventually it will happen.
Probabilities don't mean much in the face of large numbers.

Jun. 08 2016 05:39 AM
Lindsey from Vancouver

Any body read about Monocercomonoides published in Current Biology? Chinchilla guts! Who knew!?

Jun. 06 2016 05:53 PM
Mark from St Louis

As I've pointed out in a previous comment here, Lynn Margulis was not the first one to propose endosymbiosis, much less the other parts of the discussion. She was the foremost advocate of mainstreaming endosymbiosis, aided by advances in technology that provided necessary evidence.

May. 23 2016 02:09 PM

I'm a little disappointed that we have an entire episode dedicated to this discussion and yet the episode fails to mention the name of the person who first proposed the theory. It's particularly disappointing considering that the person in question is a woman, Lynn Margulis.

May. 18 2016 05:30 PM
reinaldo franqui

I LOVED this espisode! Im a scientist, so Ive been taught a lot a bout the mitochondria but this is such an awesome way to tell its story!

May. 11 2016 04:11 PM
Mark from St Louis

Dipper Pines is illustrating why not bothering to do the research so you can be sarcastic makes for poor science commentary.

Richard Wrangham's Catching Fire is not about monkeys but trying to explain what fueled the radical change between Homo Habilis and Homo Erectus. Homo Erectus was the first real proto human, significantly taller than Habilis, with bigger brains, but smaller guts and surface area of teeth.

May. 11 2016 01:01 AM
Dipper Pines

I think there was a flaw reasoning of the last theory, because that would mean that we could feed a monkey cooked meat and it would eventually become sentient.

May. 08 2016 10:05 PM
Mark from St Louis

I'm repeating from two previous posts here but since most people seem to read only the topmost posts.....

Anybody who wants a ten page primer on how life manages its energy usage and how fundamental that was to its development should read this:

Oft_ of US makes the same mistake as others here of bringing up chloroplasts so I repeat my answer:

There are only two documented cases of a bacterium living inside another. There are not documented cases involving archaea. Eukaryotes have many documented cases but they've got so much energy to burn that amoeba can create protein on demand to 'flow' and gobble up stuff. It is not surprising that after eukaryotes already existed that a group managed to acquire the set of tame cyanobacteria we call chloroplasts.

Fred from Berkeley makes the common mistake of conflating the origin of multi-cellular life with that of the complex cell itself. Given key aspects of the sexual reproduction of single complex cells, multicellularity was inevitable and has happened on multiple occasions, but it is an effect of the origin of a cell with mitochondria not a cause.

When Nick Lane speaks of that being a fluke or freak accident, he is overstating the case to work against the common view that the complex cell is inevitable. There is absolutely no evidence that it is inevitable. The square-cube law has kept bacteria and archaea small since their origin. All complex life shares a single origin even though there are ecological niches open for a second attempt. That is more compatible with an event requiring exact circumstances than inevitability.

May. 07 2016 02:23 PM

Why did this have to a short? Oh I know, Jad is tired of science. Wah wah.

May. 05 2016 04:57 PM

More stories like this please! Fascinating.

May. 04 2016 09:40 AM
John from US

Hey Radiolab,

This is more like it.

Cut down on the dramatic (and manipulative) sound effects and music and you'll have a better than average show.

Thank you for forsaking ice cream trucks and K-pop this time around. Keep it up.

May. 02 2016 09:46 AM
Oft_ from US

That was pretty enjoyable, it's always nice to wonder about how complex life developed. I haven't read through all the comments, but what about chloroplasts? These have their own DNA, and I believe were taken up in a process like that of mitochondria. So I don't think you can say the merger of the mitochondria and the other cell was an astronomically improbably event. Like they say about life, if you only see it once, you're not sure. If you can detect it more than once, it no longer appears to be a nearly insurmountable barrier.

May. 01 2016 12:17 AM
Travis from Maine

Anyone else make the connection between lightning-generating mitochondria and the Star Wars reference that Jedi measure their power with how many midichlorians are present in someone? Cool idea, that the power generated by midichlorians theoretically powers how much Force Power you might have, and mitochondria give a lightning-bolt-level boost to their hosts. I know, fiction vs fact, but it's a fun idea to run with!

Apr. 29 2016 05:05 PM
Patrick Campbell from Northridge, CA

First time commenter and religous listener (as in I try to listen as soon as a new episode is out, but no shrines or thinking Jad Abumrad and Robert Krulwich are supreme beings).

With that said, I am graduating next month the a BA in biology, and I know the difference between laymen "theory" and a scientific Theory. I am not here to debate anything nor shoot down the topics brought up in the episode. I just want to expand, or investigate, the idea mentioned at time 20:29 that there is no impetus in the universit for complexity.

I've been trying to understand how complexity has evolved myself, and what I've come to, what has been the answer that clicked, was entropy.

We know entropy as pertaining to the second law of thermodynamics, specifically that the universe is always tending toward disorder. For a refresher, this means solutes disperse down their concentration gradient, water diffuses to where it is less abundant, gases expand until they are at the maximum distance away from itself, etc.

However, I postulate that entropy is the ultimate driver of complexity. This is kinda Biology 101 when looking at endergonic and exergonic paired reactions in an organism, and the subsequent heat lost to the system through inefficiency (entropy dictates that too). Beyond this molecular level, however, we have to think about how an element in the ground on the African continent can be incorporated into the body of a complex organism and then released into the atmosphere in a tragic plane accident. Or, how about the logical extreme, where we humans ourselves become interstellar, and our complexity, inherent in our physical bodies through evolution as well as through our technological innovation, increases the galactic entropy?

I cannot think that there is nothing in nature that dictates the formation of entropy, because the very example of our spreading our space junk along with hitch-hiking terran microbes (assuming contamination), and the combustion of fuels to do so, inherently increases entropy in the system, which, as the second law states, the universe is always headed toward.

Apr. 29 2016 04:39 PM
Frantz from Montreal

What is going on out there?
Radiolab is not what it used to be anymore.
Lacking interesting subjects?
Crispr part 2 would be great, but lately it's been out of breath.
Please regroup and create wonders again


Apr. 28 2016 11:56 AM
Fred from Berkeley CA

I found an interesting, and relevant, post today that mentions "Throughout the history of life on Earth, multicellular life evolved from single cells numerous times, but explaining how this happened is one of the major evolutionary puzzles of our time. " As one of the previous commenters explains, "if you roll dice for 2 billion years, lots can happen". In fact this did, multiple times. So positing that this event is somehow unique to life on Earth, one of countless planets with life, becomes a little less convincing. After all it happened here more than once.

Apr. 25 2016 04:25 PM
Rin Tenebaum from Galway

Any thoughts on what the next "energy canyon" might be?

Apr. 25 2016 06:55 AM
Dan-Thanh Ton-That from Rome

I was also extremely disappointed in the declaration that humans are the only conscious animals. Other animals show self-awareness, complex emotions, ability to plan into the future, ability to lie, etc. These are all abilities we once assumed were exclusively human. To say that we are the only conscious animal is not only presumptuous, but also wrong.

Apr. 23 2016 04:04 PM
Christopher Berry from Berkeley

Very disappointed that a science-oriented podcast said that humans are the only "conscious" species. We are not. It is widely accepted that nonhuman animals, at least in our phylum, are sentient and experience consciousness in a similar way that we do. The word I think you are looking for is sapient, i.e. capable of civilization. We are the only one of those. We are not the only sentient or conscious species though.

Apr. 23 2016 03:32 PM

Thanks Mark for bringing up chloroplasts! The story totally ignores chloroplasts, which have their own genomes and are related to cyanobacteria! This happened after the mitochondria incorporation, but still very important to plant life as we know it.

Plus, the natural history of chloroplast containing dinoflagellates is a pretty interesting story.

Apr. 22 2016 08:13 PM

A fascinating, but too short, subject sandwiched between Robert Krulwich wasting our time while he pretends to be a lot funnier than he is, and two unfunny "comedians" obsessed with race and someone named Michael Fastbender. (Who the hell is Michael Fastbender?) Just imagine a couple of white comedians giving that routine, or replacing every instance of "white" with "black," and vice versa. Your show would be yanked by NPR in an instant for being racist.

If you don't have enough material to fill an entire episode with real content, then just keep the episode short, or play multiple minutes of ads for Mailchip or something. Don't waste my time with racist trash.

Apr. 22 2016 11:15 AM
Chris from CA Desert

Certains mysteries, especially the one who created life and what it's purpose and meaning is, might as well remain as such forever.

If humanity would understand how to create life on a planet, they would certainly attempt doing it and inadvertently create irreversible chaos and havoc.

Btw, I can find answers for these mysteries in plain everyday sight since I have been a kid : Random chaos with no particular higher purpose or meaning whatsoever than what we can experience and for some of us attempt to understand.
Everything else seems to thrive in people's minds and imagination only, primarily based on primal fears.

Apr. 18 2016 04:21 PM

"this is my Rosa Parks moment. And you why I can say that is because I am not black."
Do you have to bring race into everything? This sjw routine has been beaten into the ground. Just shut up and do your silly little show.

Apr. 18 2016 02:16 PM
Mike Holland

Cruelwich has infected Jad with his preciousness-of-life ideas: Stop trying to say life on earth is somehow precious... such a religious crutch to the reality of the power of evolutionary math.

Here is a recent finding which should help you better interpret your own show.(can you tell I'm still pissed you copped out and let the Sewage Industry basically spoon feed you your own show about sewage sludge, awhile back).

"These bacteria are tinier than any we've studied to date; they fit through filters with holes that are only 0.1 microns in size. And their genomes reflect that, as they are about five times smaller than E. coli's. They lack genes for basic metabolic processes, like making amino acids, DNA and RNA nucleotides, respiration, and the Krebs cycle, used to generate energy from food. The researchers infer that they must be symbionts with a partner supplying all of their required materials."

Tree of life shows that trees are a rarity

Apr. 17 2016 12:39 PM
Mark from St Louis

To the people wanting to have a serious discussion of a non supernatural origin of life, please read this first:

It will address most of your issues, though the answers won't be in the same depth as the author's last two books. I can't remember if this episode made perfectly clear that the new hypotheses make simple cells an emergent property of wet rocky planets with carbon dioxide. My main problem is that in their eagerness to push back on the unwarranted belief that the complex cell is inevitable they oversold its improbability, making it seem like a miracle.

On that note, the suggestion of Signature of a Cell is not helpful since it is an intelligent design book and does not belong in a discussion of science.

No argument positing the existence of a creator or designer is of any use whatsoever since it always ignores that the creator or designer is far more improbable than anything serious scientists propose. Intellectual honesty is not the strong suit of cdesign proponentsists.

On a similar note, panspermia is no solution since it simply moves the location of the abiogenesis off planet. It was only proposed since there didn't seem to be time for abiogenesis to occur in a primordial soup. Fortunately, alkaline hydrothermal vents are far, far more dynamic than a chemically inert soup.

As for those who keep conflating the idea of endosymbiosis among prokaryotes with that involving extant eukaryotes I repeat the following paragraph from my previous post:

There are only two documented cases of a bacterium living inside another. There are not documented cases involving archaea. Eukaryotes have many documented cases but they've got so much energy to burn that amoeba can create protein on demand to 'flow' and gobble up stuff. It is not surprising that after eukaryotes already existed that a group managed to acquire the set of tame cyanobacteria we call chloroplasts.

Apr. 15 2016 09:10 PM
Benjo_San from Oregon

Did anyone immediately think of the word "snarf" when the endosymbiosis schtick came up?
Highly technical term, offered to me in my upper division phycology course at Humboldt State.
Use: in the early times, one single cell organism senses another to be of value. It then Snarfs the other one, who is brought kicking and screaming into the vacuole of the first. However, by some process, it is not eaten, but rather, incorporated.

Snarfing, its a thing.

Apr. 14 2016 08:05 PM
Old White Guy from Manhattan

Great episode on mitochondria, the creatures within!

And then we got to all the unfunny "riffing" from those two new WNYC Podcast hosts...

As an uncool old white guy, I know that I am extremely appreciative of living in a time when I can see almost every day in the media some negative comment about my supposed demographic.

"Who dis?" - That's some really sophisticated, transcendent comedy there.

Apr. 14 2016 06:13 PM
Gwendolyn from Utah

I made a comic about this 2 years ago for an exhibit on mitochondria for the Science Museum of Virginia! How cool to have this story pop up again.

Apr. 14 2016 06:01 PM
Eric from NV

0:01 - 24:00 I'm very happy about Radiolab getting back to actual science podcasts. I'm referring to the previous, piss-poor "Debatable" episode. Thank you for having an informative portion of your show again, the reason I loved it in the first place.

And then after 24:00....
"All it takes is for two black guys to do something to make it cool." and
"White ladies; Sarah, Jenny, do not go jogging at dawn! mmm'kay, girl!"

Since you got so much flack for racist stuff on your last episode, you're now placing it on another but airing portions on RL? WTF? I mean, if you want to just have black racists from "black lives" on all day then do it and quit trying to hide it in "comedy."

Apr. 13 2016 01:58 PM
Nick from Omaha

What about chloroplasts? What about this guy?

What about plastids in general? This has happened quite a bit in history. Not saying it's common, but endosymbionts are at least not so miraculous that such an act has only happened once. it was pretty great that it happened with a mitochondria, though.

Apr. 13 2016 12:38 PM
Jerry from Oregon

Everyone should read the book The Signature in the Cell.

Apr. 13 2016 12:34 PM
Sloppy from Stockholm

Like some others have said, the "consciousness" bit made me distracted. Not only was it confused and misused but not at all necessary for this piece. All it served to do, mentioning consciousness, was to make me very skeptical of anything being said afterwards.
This theory is cool, which is to say "interesting". Not sure it was clear how it could have only happened once. I'm not sure if I enjoy or am annoyed by the fact that this will and has inflamed the Creationists versus the Fluke-ists leaving the rest of us like King Arthur's crew in The Holy Grail screaming "RUN AWAY!!!" ;)

Apr. 13 2016 10:36 AM
Shilla Nassi

apropos of this topic, a very interesting article in nature microbiology, re-examining the genetic relationships among the various branches of the tree of life, discussed in the atlantic monthly online:


Apr. 12 2016 10:47 PM
Jason from Texas

I wouldn't go as far as Adam and call you obtuse, but even as someone with a genetics degree and a medical doctorate, the extreme randomness that it discussed seems to be a blazing neon sign that shouts Creator. The almost mathematically impossible chances of the formation of eukaryotic organisms is crazy enough, but for those same organisms to evolve over a relatively short period of time into sentient beings is a little too random for me!

Apr. 12 2016 10:05 PM
Adam from North Carolina

In listening to your episode, I was astounded by the obtuseness in your lack of mention of the possibility of a creator throughout. You have 3 mysteries in this episode that all point back to the biggest mystery which you failed to allude to. That mystery is: what caused the creation of atoms/molecules/matter/universe (aka the big bang) to begin with?

Answering that metaphysical question is the priori problem and helps to solve the rest of these mysteries. Clarity of these 3 mysteries begins with clarity in that ultimate mystery.

Apr. 12 2016 09:00 PM
Will from New York

Terrific episode. Please follow up with a second to expand on some of the facts from the episode and address some of the comments posted here.

However, I was very turned off by the commercials for that couple of women with a new show and their racist commentary. They made two comments about how they could do things because they are black - implying that other races can't or shouldn't. I'm sure those in charge at Radiolab decided it was okay because they are black. We will never have equality as long as races are given different standards. They should have been called out for their racist remarks.

Apr. 12 2016 08:36 PM

FYI: A recent paper in the journal Nature about some of the details as found from a reddit link.

Apr. 12 2016 02:16 AM
Andrew from Sacramento, CA

Great episode, but there are a couple of issues I want to address.
First, the emphatic assertions of improbability are somewhat misleading. Endosymbiosis successfully starting at any one opportunity is unlikely, but that's not terribly useful to say that because there were an insane number of opportunities and a huge advantage to the first organisms that manage it. It only needs to work once, because that first success has essentially won the metabolic jackpot, and another endosymbiosis event wasn't really necessary or even favored.
Second, the commenters positing this evolutionary step as a miracle or being compatible with a creator have got two huge problems. The biggest issue is that instead of addressing how life arose, you're simply pushing that explanation back onto an even harder question; where did the creator of life come from? It's an uninformative answer, because it substitutes the first question with a less soluble question.
Only slightly less problematic is the assertion that we can't prove it didn't happen. We can't prove there isn't a teapot orbiting Pluto, but that doesn't mean we can assume its existence. You can't prove it didn't happen is a scientifically useless statement. Trying to insert unscientific premises into scientific efforts is rather pointless (unless your goal is to give researchers like myself a headache).

Apr. 11 2016 09:49 PM
Craig from Minneapolis

"Cellmates" was an interesting podcast, but it greatly overstates the "simplicity" of prokaryotic life and marginalizes their role in setting the table for the evolution of eukaryotes and metazoans. If eukaryotes rule diversity of form (one basic cell and metabolic type is responsible for all the life we see), prokaryotes have ownership of diversity of metabolism. If energy can be extracted from the environment, chances are prokaryotes have evolved a strategy to do so, even if it required complex partnerships between genetically unrelated organisms.

One of the central premises of your podcast is correct: there needed to be an excess of energy for “complexity” to arise. Life on Earth evolved in an anaerobic world regularly struck by meteorites. Before “complex life” had a chance, the bombardment had to end and photosynthesis evolve. Anaerobic photosynthesis led to oxygenic photosynthesis, which essentially terraformed the planet. An atmosphere filled with oxygen and allowed life (like us) that is reliant on aerobic respiration to evolve and prosper.

Evolution is random, but never understate the power of randomness when it is given millions and billions of years to act. If energy can be extracted from an environment, there’s a good chance that life will find a way to do so.

Apr. 11 2016 10:11 AM

Years ago, Steve Martin quipped that there were only two steps to NOT paying taxes on $1,000,000. It went something like this:
First, make a million dollars.
Then, remember these two words: I forgot.
It is absurd to say that the first life form was simple. It wasn't. This is especially so when, at the end of the 'cast, it is stated that there has been no change in the simplest cell over the last 2x10^9 or so years. The simplest cell we know of is highly complex. Imagine thousands of New York Cities shrunk and placed on a pinhead.
Now, here's a quote about abiogenesis from Paul Davies. He says, "It has been estimated that, left to its own devices, a concentrated solution of amino acids would need a volume of fluid the size of the observable universe, to go against the thermodynamic tide, and create a single small polypeptide spontaneously. Clearly, random molecular shuffling is of little use when the arrow of directionality points the wrong way."
During the 8th minute we hear about requisite complexities in transitioning from a small to a larger organism. Then it's made pretty much into a matter of energy. I don't think energy is the solution to the problem any more than sticks of dynamite beneath heaps of bricks are a solution to house-building.

Apr. 11 2016 05:49 AM
JJ from Seattle

Now you should do a show about chloroplasts, the other "endosymbiont." Fascinating. (I just reserved Nick Lane's book at the library by the way.)

Apr. 10 2016 11:06 PM

I wanted to agree with commenters Ethan Fischer and Ullrich Fischer. As a Philosopher, Robert's narrow description of consciousness had me distracted for minutes afterward, so that I had to keep rewinding the show to relisten. Not only do we customarily ascribe some degree of consciousness to animate beings, but many animals have demonstrated self-consciousness through the limited means we've thus far found to test it. We should try not to let our natural biases for our own species obstruct our views.

I also felt, like Ullrich, that the episode seemed a bit skewed or insufficiently considered. Robert was so enthusiastic - which I don't begrudge so long as alternatives are considered - that I came away with the feeling he was trying to push a narrative that would favor a divine inception of life on Earth without explicitly saying so. I was not convinced by the end of the story that this was a singular event merely because it was the only instance that we may presently be aware of. The prevalence of parasites seems to suggest that this kind of thing is rather common, unfortunately killing the host species more often than not.

Thanks for your excellent work. Your consistently high standards are what produces intelligent audiences and highlights these occasional foibles or oversights.

Apr. 10 2016 04:23 PM
Joseph Simone from MONROE NY


Apr. 10 2016 11:31 AM
Steve from Idaho

I'm sorry, but the idea that a creator/scientist God gave the nudge that "solved" the three mysteries is just as valid a hypothesis as any other, absent any evidence to the contrary.

Apr. 09 2016 09:05 PM
Del from Oregon

Great episode! Really interesting. However I agree with Jon from Chicago. The comedy podcast that was plugged in the second part of the show didn't at all appeal to me.

Apr. 09 2016 06:49 PM
Mark from St Louis

Margulis wasn't even the first to propose endosymbiosis. Schimper, Mereschkowsky, Wallin, Ris and others made important if overlooked contributions. She was the first to make it stick, to make it impossible to ignore, aided by advancements in technology that could lead to some conclusive evidence. On the other hand, she didn't even know at the start that two different types of prokaryotes involved because Woese was just starting the experiments that revealed the distantly related archaea hiding in plain sight among the bacteria. That's how science works. Different people discover things and the best verify those discoveries and say "If that's so....".

There are only two documented cases of a bacterium living inside another. There are not documented cases involving archaea. Eukaryotes have many documented cases but they've got so much energy to burn that amoeba can create protein on demand to 'flow' and gobble up stuff. It is not surprising that after eukaryotes already existed that a group managed to acquire the set of tame cyanobacteria we call chloroplasts.

As for how vital energy management is and how life on Earth did it though chemiosmosis, you might want to read this short article:

Apr. 09 2016 09:46 AM

What is the track that begins at 7:07? Is it stock? Or was it sound designed for the show? I want to groove to that marimba in my daily life.

Apr. 08 2016 11:26 AM
Leah Smith

I was dismayed when, at about 6 minutes in, you guys conflate the term "theory" with "hypothesis." It's so important that the public understands the difference! This lack of understanding is why many creationists feel justified to scoff at the theory of evolution, as if "theory" means "guess" (which is actually more or less what hypothesis means), when in reality, a theory, in scientific parlance, is a well-supported body of facts connected by common ideas.

Apr. 08 2016 10:14 AM
Ethan Fischer

You guys confuse consciousness with self-consciousness and then say we are the only known species to have it. So many things wrong with this.

Otherwise an enjoyable podcast as always!

Apr. 08 2016 04:35 AM
Dillan Mohottige from Orlando, FL

This topic has already been done on Radiolab. Why are they redoing topics?
The bar needs to be kept high.

Apr. 07 2016 11:55 PM
Ullrich Fischer from Canada (Wet Coast)

Interesting talk on cellmates. I don't think mitochondria and chloroplasts are that unlikely. There are numerous events where one micro-organism gets inside another and survives. In most cases, it winds up killing the host, but not always, that's how almost all internal symbiots probably got started in multicellular organisms... like the nitrogen fixing bugs in legumes and the gut biomes in mammals. It could have happened only twice in the history of single-celled life on Earth, but it also could have happened many times but all the other organisms to which it happened might have gone extinct in the meantime leaving only our ancestors to eventually develop multicellular life. I don't think we know enough about the probabilities involved yet to make any reasonable guesses about how unlikely multicellular life is in the universe at large.

Apr. 07 2016 09:40 PM
Peter from Cambridge, MA

Episode was a enjoyable and accessible description of the probable origin of modern multi-cellular life (something I've never seen/heard before, I might add). Thanks for the episode. Some questions:

Aren't intracellular bacterial parasites pretty common in modern eukaryotes? Is it that hard to imagine a prokaryotic intracellular parasite that invaded our proto-eukaryote?

Also, as other commenters have mentioned -- what about plastids (such as chloroplasts)?

Apr. 07 2016 07:34 PM
Steve from Canada

I think a discussion of the entropy theory of life would have improved this episode. Entropy increases with time, and more complex life increases the entropy of its surroundings more than simple life. This becomes a selection force that favours more complex forms of life. This is a relatively recent theory that is being developed by Jeremy England, a physicist at MIT:

Apr. 07 2016 05:48 PM
Oren from North Carolina

Roz and Charles are on to something, and it would be great if Radiolab could explore it further. Lynn Margulis was one of the most heterodox and fascinating thinkers in modern evolutionary biology, largely because she showed that some of the most significant biological transformations occurred not via organisms evolving new traits to better fit their environments (as the modern evolutionary synthesis of genetics and natural selection would expect them too), but rather by involuting those environments into themselves. Don't get me wrong, I was really glad to hear you guys discussing this oft-ignored theory, but the reason why it's so important (and which you might have noted) is that this suggests natural selection and genetics are not the whole story of biological change, and its makes that criticism from within biology (as opposed to the kinds of extra-biological, creationist and psuedo-scientific criticisms that, I at least, find less convincing). Margulis work, and the ideas you discussed, show that biology has still yet to fully theorize itself. That's a big deal and it needs to be discussed further, both within biology and without.
You might try talking to biologists like Richard Lewontin (who's done a lot of work that tries to think past the modern synthesis of genetics and natural selection) or the team of researchers that are advancing work on "niche construction," who theorise along lines very similar to Margulis. There's a lot of really fascinating, if slightly against-the-grain research being done in these areas that would make for great future shows.

Apr. 07 2016 04:10 PM
Jon from Chicago

Interesting episode. The first half. The second half seemed like your producers forced you plug this new show and say it would appeal to us. I understand the give and take of fiscal requirements vs. creative freedom, but I'm somewhat confused by Jad saying that he thought his audience would find this comedy show interesting if we like Radiolab. I don't want to speak for others, but as a very dedicated audience member, I feel like you guys just get me. You know what works. You even speak for me when Jad and Robert go back and forth speaking in the voice of the listener, which is awesome. Radiolab to me is all about curiosity, making you think, shining a light on things, surprising you spiritually, intellectually and morally through moments of spoken word, sound and silence. This comedy show you are plugging started out with singling out races as the butt of jokes and didn't seem funny at all to me. I found some of the jokes insulting and none of it was anything I haven't heard elsewhere on mainstream TV that I avoid like the plague. It came across to me as low brow and predictable. Radiolab has introduced me to many new radio shows that I love like the Moth, Planet Money, etc. But this one was a big fail in my book as it didn't appeal to me at all. No offense is intended by my comments. I know there are people out there who love this sort of thing. But I seriously doubt they listen to Radiolab.

Apr. 07 2016 02:59 PM
Liz from Chicago

Can someone link me to the podcasts of the comedian ladies at the end?

Apr. 07 2016 11:59 AM
Roz from Vermont

I'm so glad to read Charles from Israel's comment because that is exactly what I wanted to say, so I'll say it again. Lynn Margulis developed this theory years ago. I first learned about her in a book by Fritof Capra, "The Web of Life", in which he says, "The most striking evidence for evolution through symbiosis is presented by the so-called mitochrondia, the "powerhouses" inside most nucleated cells." He goes on to quote Margulis. One theory is that the earth was covered with blue-green algae at the time producing too much oxygen, so the mitochondria went inside. Voila - breath! Margulis'1998 book, Symbiotic Planet has been sitting on my shelf a long time, so thanks for the podcast, which has inspired me to actually read it. I didn't realize she had been married to Sagan. I love RadioLab but you could have done better with this one. Thanks anyway.

Apr. 07 2016 09:32 AM
Richard from Dublin


You say this "sad state of humans, who are so good at creating,designing, and organizing and yet find it unreasonable to attribute the complexity of design in the universe to a creator"

I think you'll find there have been near infinite attempts by people to attribute creation to near infinite different creators. There are thousands of forgotten gods and creation myths that we know about, and who knows how many more before the advent of any knowledge we can remember. I find it amazing that people who are so good at making up nonsense, think they must have a divine insight.

"2 billion years is indeed a long time, but why should 2 billion years lead so far in one direction (advanced organized life) and not another direction (entropy)?"
You fail to recognise that life is an agent of entropy, whenever we digest food, the energy we get is not lossless, we are basically a living fire, and propagating life increases entropy. .
The idea life escapes entropy is just short sighted, when we burn fuel entropy is increased, but it requires a spark or ignition, an external supply of energy to get started but once it does it can keep going on it's own. Life is just a fire that's been burning for billions of years

Apr. 07 2016 04:37 AM
Joseph from San Antonio

I appreciate the fact that the author mentioned that there is no law or tendency or mandate that advanced life form appears. In fact, there is quite the opposite law in physics called the second law of thermodynamics that all systems drift further and further into entropy. 2 billion years is indeed a long time, but why should 2 billion years lead so far in one direction (advanced organized life) and not another direction (entropy)? Even the interviewee commented on how ridiculous our situation is; he told us not to expect it in other worlds.

In all other situations, when we encounter events of unbelievable odds, we are comfortable saying that those events are not random. When we see rocks spelling out HELP, we would never say that it is the random action of tides. Why is this situation any different?

The evidence provided for the endosymbiotic theory (that mitochondria share genes with bacteria) is interesting but by no means conclusive. Could you not make the same argument that an intelligent designer would reuse the same gene in two different places? You don't even need a designer. For example, you could have a bacterial resistance gene, such as the beta lactamase gene, that is present in one bacteria species. It can then conjugate and transfer this gene to another bacteria, which is now resistant to beta lactams. As a result, there is a transfer of genes without the hocus pocus of cells "colliding" into each other or "falling" into one another.

Since there is no way to test either hypothesis (the designer or the endosymbioic hypothesis), there is no way to prove either hypothesis. In my opinion, that's what makes this type of biological cosmology more philosophy than science. In conclusion

Apr. 07 2016 01:02 AM
Mike K from NYC

If you roll dice for 2 BILLION years no matter how unlikely any one outcome is, it becomes a lot less unlikely. Don't act like it was so impossible. Also, assuming it only happened once. If it only happens every few billion years per planet maybe the second time happened last week. Who knows?

Apr. 06 2016 07:16 PM
Freddie Kelly from New York

I love the human touch to your podcast as a whole! But this episode is a prime example of the sad state of humans, who are so good at creating,designing, and organizing and yet find it unreasonable to attribute the complexity of design in the universe to a creator. Often times the thought of a creator being the answers to mankind origin, for some, seems like an anticlimactic conclusion. But when has having the answer to your question been a bad thing. Especially if you've spent your wheels dealing in the realms of uncertainties. Isn't it exhausting constantly hearing that a bunch of scenarios with an infinitesimal chance of happening, didn't just occurre once but millions of times. And then just poof hear we are. (Seems a bit childish). That thought seems less scientific then the idea of there being an actual intelligent creator. Just a thought :) Love you guys

Apr. 06 2016 05:39 PM

The fact that plant cells have both mitochondria and chloroplasts suggests that this event occured mire than once with the latter happening later.

Apr. 06 2016 05:10 PM
Kenny from Brazil

Zach: Yeah, they exagerated a lot the improbability of mithocondria, but I think its just to make the storytelling better and mysterious.

Apr. 06 2016 01:13 PM
Kenny from Brazil

Irreducible complexity is a pretty bad argument, every species and system that the ID people claims irreducible complexity show up that have a simpler form in the life tree. Pretty good episode, with the recent news of the simpler life form created in lab, we will understand life more.

Apr. 06 2016 12:50 PM
Jared Fowler from Southern California

I'm glad this subject was brought up since our origin is important. I also found it fascinating that they could mention so much the "irreducible complexity" of life and not realize it (see Michael Behe Ph.D.). The entire podcast seems to silently be saying, "Miracle, Miracle, Miracle", but without ever using the word. Instead they use words like "impossible" and never" and throw untestable numbers out like "2 billion and maybe more". This seems more speculative than based on empirical data (especially if our experiments show "impossible" and "never"). Let's just use the word everyone is scared to use: Miracle.

Apr. 06 2016 12:18 PM
Zach from Santa Barbara, CA, USA

I feel like they have overstated the improbability of mitochondria. What really struck out to me as wrong was the repeated mention of this only happening once in the history of earth. What about chlorophyll? Chlorophyll was thought to start as an independent cell and be absorbed by a eukaryotic cell. Chlorophyll like mitochondria have their own DNA. I was really surprised this wasn't even touched on.

Apr. 06 2016 11:35 AM

Amazing episode! Feels like its been forever since you did a sciency episode. More of this please!

Apr. 06 2016 11:30 AM
Charles Hurwitz from Israel

The theory described in the podcast was actually propose about 50 years ago by Lynn Margulis ( Also known as Carl Sagan's ex-wife.

Apr. 06 2016 05:40 AM

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