The Meaning of Life

The word, not the phenomenon – that’s a story for another blog. Carl Zimmer has an article at Txchnologist on the ongoing disagreements of how to scientifically define life. It seems intuitive that we know what life is – it’s… you know… living stuff. The reality is much less settled:

When NASA says it wants to find out if Mars was ever suitable for life, they use a very circumscribed version of the word. They are looking for signs of liquid water, which all living things on Earth need. They are looking for organic carbon, which life on Earth produces and, in some cases, can feed on to survive. In other words, they’re looking on Mars for the sorts of conditions that support life on Earth.

But there’s no good reason to assume that all life has to be like the life we’re familiar with. In 2007, a board of scientists appointed by the National Academies of Science decided they couldn’t rule out the possibility that life might be able to exist without water or carbon. If such weird life on Mars exists, Curiosity will probably miss it.

Defining life poses a challenge that’s downright philosophical. There’s no ambiguity in looking for water, because we have a clear definition of it. That definition is the same whether you’re on Earth, on Mars, or in intergalactic space. It is the same whether you’re dealing with water as ice, liquid, or vapor. But there is no definition of life that’s universally agreed upon. When Portland State University biologist Radu Popa was working on a book about defining life, he decided to count up all the definitions that scientists have published in books and scientific journals. Some scientists define life as something capable of metabolism. Others make the capacity to evolve the key distinction. Popa gave up counting after about 300 definitions…

[Edward Trifanov, biologist at the University of Haifa] analyzed the linguistic structure of 150 definitions of life, grouping similar words into categories. He found that he could sum up what they all have in common in three words. Life, Trifonov declares, is simply self-reproduction with variations…

A number of the scientists who responded to Trifonov felt that his definition was missing one key feature or another, such as metabolism, a cell, or information. Eugene Koonin, a biologist at the National Center for Biotechnology Information, thinks that Trifonov’s definition is missing error correction. He argues that “self-reproduction with variation” is redundant, since the laws of thermodynamics ensure that error-free replication is impossible. “The problem is the exact opposite,” Koonin observes: if life replicates with too many errors, it stops replicating. He offers up an alternative: life requires “replications with an error rate below the sustainability threshold.”

Jack Szostak, a Nobel-prize winning Harvard biologist, simply rejects the search for any definition of life. “Attempts to define life are irrelevant to scientific efforts to understand the origin of life,” he writes…

It’s conceivable that Mars has Earth-like life, either because one planet infected the other, or because chemistry became biology along the same path on both of them. In either case, Curiosity may be able to do some good science when it arrives at Mars this summer. But if it’s something fundamentally different, even the most sophisticated machines may not be able to help us until we come to a decision about what we’re looking for in the first place.

I have to agree with Szostak; the definition of life is, at least from science’s perspective, irrelevant. However, there is a standard set of criteria used by biology, as far as I learned in school and Wikipedia has to say:

• Homeostasis: Regulation of the internal environment to maintain a constant state; for example, electrolyte concentration or sweating to reduce temperature.
• Organization: Being structurally composed of one or more cells, which are the basic units of life.
• Metabolism: Transformation of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
• Growth: Maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
• Adaptation: The ability to change over a period of time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism’s heredity as well as the composition of metabolized substances, and external factors present.
• Response to stimuli: A response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is often expressed by motion, for example, the leaves of a plant turning toward the sun (phototropism) and by chemotaxis.
• Reproduction: The ability to produce new individual organisms, either asexually from a single parent organism, or sexually from two parent organisms.

Seems like pretty basic, inclusive criteria. Homeostasis is a word you don’t hear often, but it’s important; it’s basically what keeps organisms being themselves. It’s an organism’s negative feedback mechanisms, always adjusting to changes and trying to keep its state in the ideal place – ideal temperature, ideal CO2 level, ideal blood sugar, anything and everything. Also note that viruses aren’t considered to meet this definition of life; they can’t reproduce themselves per se, they’re not composed of cells, and they don’t grow, as far as I’m aware. 

Carl Zimmer posted a response to his article from an evolutionary biologist named David Hillis that I found interesting and insightful:

Like all historical entities (including other biological taxa), it is only sensible to “define” Life ostensively (by pointing to it, noting when and where it began, and following its lineages from there) rather than intensionally (using a list of characteristics). This applies to the taxon we call Life (hence capitalized, as a formal name). You could define a class concept called life (not a formal taxon), but then that concept would clearly differ from person to person (whereas it is much less problematic to note examples of the taxon Life). So, I’d say that I can point to and circumscribe Life, and that it the appropriate way to “define” any biological taxon. A list of its unique characteristics is then a diagnosis, rather than a definition. So, I’d argue that any intensional definition of Life is illogical (does not recognize the nature of Life), no matter how many words are used.

Defining Life (the taxon) is like defining other particular historical entities. We don’t “define” Carl Zimmer or the United States of America by listing out their attributes. Instead, we point to their origin and history. The same should be true for Life. If we ever discover a Life2, we’ll have a new origin and history to point to…

So that is another way of looking at it that I had never heard before, and it seems like the reasonable way to think about life. I don’t know if we’ll find any revolutionary kind of life in my lifetime, but if we do it’ll be pretty interesting to see different fields struggle with the implications. I hopefully will not be too worried about that – I’ll just want to pick its brains.

What Casual Climate Science Deniers Don’t Understand About Science

I’m really averse to writing about the political controversy around climate science because it’s beaten to death in every kind of media already, and there are plenty of blogs revolving around it. Without it, though, I might not have started this blog in the first place, since that and the political controversy over evolution are the biggest symptoms of a society that doesn’t know enough about science.

You may have heard about what the media gleefully called “Climategate 2.0”, a release of more stolen emails from climate scientists. Here’s Scientific American and LiveScience discussing the leak, and Life’s Little Mysteries addressing the scientific complaints against anthropogenic climate change. 

In my opinion, the controversies over evolution and climate science stem largely from a sheer lack of understanding of how science works. As I see it there are a few main misunderstandings:

1) Nothing is 100% certain. Deniers demand 100% certainty in scientists’ claims, which is literally impossible. There is always room for error and misinterpretation, in every kind of science. Scientists know this and so they tend to talk about their findings cautiously. This doesn’t translate well in the public sphere; we’re used to people in everyday life making certain claims, especially when those claims are relevant to politics. What kind of politician would say “My plan is to do this, because such-and-such is probably the problem with our economy, and such-and-such will probably help”? That would be honest, but it wouldn’t sell, and that politician’s dishonest opponent would come off much more convincingly.

This creates a conflict when science is dragged kicking and screaming into politics. There’s pressure to put things into certain terms – it’s technically bad science, but good politics. From what little I’ve seen excerpted from the hacked emails, it looks like this is what these scientists are discussing – how to remain scientifically accurate while trying to get across an important public message. Does glossing over the science in this way make them liars or frauds? No, it makes them roughly as inaccurate as everyone else in the public sphere. It’s regrettable that science has to be dumbed down for public presentation, but the dumbing down is obviously not a conspiracy. 

2) There will always be internal disagreement between scientists on smaller issues. Deniers will point out any and every sign of disagreement between scientists when it comes to climate science or evolution, and use this to claim that the science isn’t settled. There will probably always be differing hypotheses when it comes to the details of the matter, but that has no bearing on whether the field as a whole is valid. There’s tons of uncertainty in climate science, and personally I don’t like it at all when bold predictions about 100 years into the future are made, because it seems obvious that those predictions are so error-prone as to be meaningless. However, there’s negligible uncertainty when it comes to the facts of the Earth gradually warming over the last century, and the human release of greenhouse gasses as a significant contributing factor.

Do we know how all of this will pan out? No, not at all. I summarized a New Scientist article earlier showing just how little we know about the magnitude of the problem. This kind of subtlety can be confusing to the public – if we don’t know, then why should we take such dramatic and costly steps to respond? Science doesn’t work strictly by knowing though, as should be clear by the fact that nothing is 100% certain. Everything is a matter of probability. If curbing greenhouse gas release is very likely to be beneficial, then it makes sense to do it, whether or not we can know for sure – which we really can’t, ever. Doing nothing is making an active choice to act on the much less probable future scenario, which doesn’t make any sense. 

3) Science is not an opaque, elite clubhouse. The fact that e-mails from a small group of scientists are being used to smear an entire field betrays a profound misunderstanding of, everything. Science is a global pursuit. Even if these fantasies about these emails being incriminating were true, it would have virtually no implications for climate science, since different groups of scientists have independently come to the same conclusions anyway. Individual scientists can’t just make things up or conspire with impunity. They’re accountable to everyone – anyone can debunk their claims, and if they’re caught forging data or being incredibly dishonest in any way, it’ll probably mean the end of their careers. Science is not like politics – you can’t just lie and move on. If you’re a bad scientist, you’re done, for the rest of your life. There’s no way one particular group of scientists would just decide to make enormous lies about something that’s being investigated all over the world. 

I think the faster-than-light neutrino story is a great example for understanding science better in this context. Were the CERN scientists shunned for going against the overwhelmingly dominant consensus theory? No, quite the opposite. Is there a possibility that the theory of relativity is incomplete? Yes, anyone will admit to that. Does that mean we should ignore all of the findings brought to us by assuming that relativity was completely correct for the last hundred years? No, that would be ridiculous. 

In sum: even the best of theories can be challenged, even the best of theories can be incomplete, but it makes sense to act on what information we have even if it’s not perfect (which, again, it never will be). This alone should be enough to finally move past this political misunderstanding.

All of that being said, another reason why I’m averse to writing about topics like this is because I get the impression that facts and reason are not what’s driving the discussion. I have no idea what will convince most deniers to jump on the modernity bandwagon and trust the global institution of science, but it’s probably not posts like this. 

“Science can answer moral questions”

Here’s a TED talk in which Sam Harris argues that we don’t need to rely on conjecture or appeals to authority to find moral truths – we just need to look at the science. According to Wikipedia, “Sam Harris is an American author, philosopher, and neuroscientist, as well as the co-founder and current CEO of Project Reason.”

Unfortunately, I disagree with him, and I hope it’s obvious why I think he’s wrong. He immediately equates morality with human well-being, explains that through neuroscience and psychology we can measure well-being, and therefore through neuroscience and psychology we can dictate morality. If only it were that simple.

Not everyone equates morality with human well-being – in fact, I’d argue that few, if any, people do. There are at least two obvious alternatives to maximizing human well-being as the objective of morality – obeying a higher authority, or respecting human rights that appear self-evident. If someone finds a certain right to be self-evident and inviolable, for example, then whether or not it’s best for human well-being is absolutely irrelevant. One might assume that science could tell us how to maximize human well-being given the limitation of respecting human rights, but in any case that won’t result in everyone being able to agree on what’s moral or not. 

Sam Harris can claim that these alternative systems of values are wrong, but there’s simply no scientific basis for that, or for any system of values. He can use science to explain how best to get what we want, but not what to want – just like the chocolate or vanilla comparison he used, wrongly. 

This post of mine definitely seems to stray hard from science to philosophy, but I think it’s important to recognize the boundaries of what science can tell us. I think Sam Harris seriously misunderstands or misrepresents this. Science remains what it’s always been – our best tool for surviving and thriving – but how and if we use it is still up to us. 

“What Do Organisms Mean?”

Finally we’re on to part 3/3 of this New Atlantis series I’ve been reading over the past two days (part 1, part 2), roughly about whether the mechanics of life are quantifiable; whether physics can fully explain biology. The series took a slide from scientific and agreeable to me to philosophical and disagreeable to me, but I stuck through it in the search of something convincing.

This third essay, “What Do Organisms Mean?”, basically expands on the arguments presented in the second one, and I feel the same way about them – his arguments are very god of the gaps-like, and he seems to give scientists’ pathetic fallacy significance that it doesn’t have.

A main thing that confuses me about his arguments is that he insists that he is not arguing for a non-material life force, while saying that physics cannot explain biology because there’s some greater organizing force at work in organisms. He addresses this discrepancy below; for context, his general argument is that there’s some sort of meaning inherent in living organisms, some overarching goal or thought process not encapsulated in its physical composition.

The accusation of vitalism seems inevitably to arise whenever someone points to the being of the organism as a maker of meaning. This is owing to a legacy of dualism that makes it almost impossible for people today to imagine idea, meaning, and thought as anything other than ghostly epiphenomena within human skulls. So the suggestion that ideas and meaning are “out there” in the world of cells and organisms immediately provokes the assumption that one is really talking about some special sort of physical causation rather than about a content of thought intrinsic to organic phenomena…

But ideas, meanings, and thoughts are not material things, and they are not forces. Nor need they be to have their place in the world. After all, when we discover ideal mathematical relationships “governing” phenomena, we do not worry about how mathematical concepts can knock billiard balls around. If we did, we would have made our equations into occult or vital causes. But instead we simply recognize that, whatever else we might say about them, physical processes exhibit a conceptual or thought-like character. And so, too: the meanings that give expression to the because of reason do not knock biomolecules around, but — like mathematical relations — are discovered in the patterns we see. The thought-relations we discover in the world, whether in the mathematical demonstrations of the physicist or the various living forms of the biologist, need to be genuinely and faithfully and reproducibly observed, but must not be turned into mystical forces.

From this I think I can succinctly state where I disagree with him: he claims that “physical processes exhibit a conceptual or thought-like character,” instead of recognizing that we assign conceptual or thought-like character to physical processes. To borrow my analogy from my previous post on this series, a protein that we call a master regulator isn’t analogous to a boss at work intrinsically; there’s nothing intrinsic about it that indicates that it relays orders or interprets feedback. That’s a purely human invention meant to explain a physical phenomenon through analogy, because we assign agency to things left, right and center.

Our unavoidable tendency to assign agency led people to create pantheons of gods in the past to explain the conscious motivations of nature, and leads us to anthropomorphize molecules now. The difference is that at this point we consciously acknowledge this fallacy, and embrace it as a part of human perception, not as part of reality. I think the author’s error is in failing to separate this feature of perception from the objective reality it tries to describe.

I think I’ve said about as much as I can about this series of essays; they are long and a bit dense, but I hope you’ll take a look at them too, to challenge how you think about biology and reality. I can’t capture all of it, but I’ll quote some of the meaty parts of this third essay below: 

Is a Whole Organism More Than the Sum of Its Parts?

Here is the second part of the essay series I started looking at yesterday, about the complexity of living things and ultimately pointing towards an argument for a new type of scientific explanation for life. The article is called The Unbearable Wholeness of Beings, and unfortunately it started being disagreeable to me from the get-go. If you’re interested in the idea that there may be more to life than chemical processes – whether in agreement, disagreement or uncertainty – you should check it out. 

(Update: here is my post on the third essay.)

This post is much longer than the norm – I had the “yelling at the TV” effect where I couldn’t help but disagree as I was reading along, so I thought I’d share my opinions along the way.

Animals and plants are a long way from rocks and clouds, and also from automobiles and computers. The need to point this out today is one of the startling aspects of the current scientific landscape. It is true that the concept of “vitalism” has been problematic in the history of biology, but no less so than “mechanism.” The two problems are in fact devilishly intertwined. We will never get straight about vitalism if we do not also get straight about mechanism. And until we sort through the associated confusions, we have little hope of meaningful conversation about many of the perplexities vexing biologists today…

Here, then, is my question: Are you and I machines? Are we analyzable without remainder into a collection of mechanisms whose operation can be fully explained by the causal operation of physical and chemical laws, starting from the parts and proceeding to the whole? It might seem so, judging from the insistent testimony of those whose work is to understand life.

The article goes on again into the depths of cell biology. The last article explained these complexities to show that the field of biology is not what it used to be, and that scientists have discovered that things are not as easily explained as they once thought. This article unfortunately seems to be making similar points but to the end of making a lower-level “god of the gaps” argument – not for religion, but for an explanation of life that doesn’t conform to modern science. 

The fact that I called it a god of the gaps argument shows chiefly what I think is wrong with it; it criticizes conventional explanations without offering any evidence for an alternative, and assumes that a current failure to fully comprehend something indicates a permanent failure. 

The author makes a few arguments, of which I’ll only excerpt a morsel:

“Science and Religion Do Mix”

From Rice University: A study finds that only 15% of scientists at major research universities say that science and religion are always in conflict. Does this counter the popular view of academic scientists as non- or even anti-religious? I don’t think so, but I’ll explain why below.

Throughout history, science and religion have appeared as being in perpetual conflict, but a new study by Rice University suggests that only a minority of scientists at major research universities see religion and science as requiring distinct boundaries.

“When it comes to questions about the meaning of life, ways of understanding reality, origins of Earth and how life developed on it, many have seen religion and science as being at odds and even in irreconcilable conflict,” said Rice sociologist Elaine Howard Ecklund. But a majority of scientists interviewed by Ecklund and colleagues viewed both religion and science as “valid avenues of knowledge” that can bring broader understanding to important questions, she said.

They interviewed a scientifically selected sample of 275 participants, pulled from a survey of 2,198 tenured and tenure-track faculty in the natural and social sciences at 21 elite U.S. research universities. Only 15 percent of those surveyed view religion and science as always in conflict. Another 15 percent say the two are never in conflict, and 70 percent believe religion and science are only sometimes in conflict. Approximately half of the original survey population expressed some form of religious identity, whereas the other half did not.

“Much of the public believes that as science becomes more prominent, secularization increases and religion decreases,” Ecklund said. “Findings like these among elite scientists, who many individuals believe are most likely to be secular in their beliefs, definitely call into question ideas about the relationship between secularization and science.”

The reason I wanted to post this article is because I thought it would be a surprising find, and would conflict with my assumptions, but unfortunately I don’t think it does that. The headline proclaims “Only 15% of scientists… see religion and science always in conflict.” Considering another 70% saw them as “sometimes” in conflict, why not “Only 15% of scientists don’t see religion and science in conflict”?

Also, the fact that they didn’t separate out the natural scientists from the social scientists is telling. I don’t know much about social sciences, but I can’t think of why studying politics or economics would come into direct conflict with religion. My guess is that the percentage of natural scientists who thought that religion and science weren’t in conflict was probably much lower than 15% – confirming the stereotype that the author claims to be refuting. 

I found this article via Science Daily, who probably put it best: they modified the title from “Science and religion do mix” to “Science and religion do mix?” Very sneaky, SD. 

“Why There’s No Such Thing as North and South”

This article from Degrees of Freedom points out that people often take certain man-made conventions for granted as actual, physical realities, using the example of north and south, and the right-hand rule (which, if you’re like me, you may vaguely remember from high school physics – here‘s a teacher’s explanation of it, here are videos showing it with respect to a magnetic field (around a wire) and magnetic force). 

The human mind often confuses familiarity with understanding.

You’ve learned the basics of a field. You’ve memorized the rules and used them so many times they have become second nature, or “common sense”–which means that you have stopped asking yourself why they should be true. And now it’s often harder for you to learn a new concept than it would be if you were to start from tabula rasa.

… In EM class, students learn that an electric current generates a magnetic field. That field swirls around the space surrounding the wire similar to how the pattern of wind velocity in a hurricane wraps itself around the eye of the storm. To remember which way the field goes, students are taught something called the right-hand rule.

… Then someone comes along and claims that electromagnetism has nothing to do with handedness after all. You listen to their words but all the while your brain keeps blocking them out and instead visualizing the picture of the magnetic field around a wire. How could it ever be, your inner voice keeps repeating, that the theory of the right hand rule cannot tell left from right?

The reason is simple: the idea that the magnetic field itself points in a well-defined direction–the idea that there is a north and a south–is purely a convention.

… But is the orientation of the magnetic field really arbitrary? After all, doesn’t a bar magnet point in a definite direction? In fact, one way to define the magnetic field is by observing its effects on bar magnets, in particular on a compass. You place the compass at a point in space and you take note of which way the “N” points. If you walk your compass around the electric wire the S->N direction is always that of the magnetic field, as defined by the right-hand rule.

There is one small problem, though. Our very definition of magnetic north is itself a convention. It would not be any easier to explain to an alien what we mean by north than it would be to explain our concept right-handed.

We are accustomed to looking at maps in which north is up and south is down (although the North Pole of maps does not quite coincide with the North Magnetic Pole, which complicates things a bit). Maps point north perhaps because they were invented by people in the Northern Hemisphere, who may have found it convenient because they used the North Star for navigation. If you look at the North Star while holding up a map in front of you, it helps to be able to read the labels on the map without having to tilt your head. According to some, the tradition of putting north up and south down dates back to Ptolemy.

But there is a perfect symmetry between the north and south magnetic pole of the Earth. Nothing moves preferentially from south to north–or from north to south–except in our imagination. Auroras don’t happen any differently at the South Magnetic Pole than they do at the North Magnetic Pole. An alien arriving at Earth would certainly be able to measure the geomagnetic field, but from that he could never guess which way we have conventionally decided to point the arrow on our compasses.

While the fact that North and South are arbitrarily defined is an interesting thing to think about, this article is more interesting to me because it brings up the idea that there are some things that we just take for granted that aren’t based on reality. I would’ve liked if the author had had some more examples, because I’m sure there are other big ones – but maybe he doesn’t realize them either?

The Complexity of Life’s Building Blocks

I just discovered a site called The New Atlantis: A Journal of Technology and Society. It features in-depth, apparently very articulate essays on science and society, which seem pretty awesome to me, although they are certainly on the long side. A recent article called “What Do Organisms Mean?” caught my eye – it seems to be a discussion of materialism, that will inevitably go into the question of what makes life “alive” – I must read it! 

It’s the third essay in a series though, so I faithfully started at the beginning, with “Getting Over the Code Delusion” (Update: my takes on the second and third essays). It discusses how the formerly popular assumption that DNA sequence determined everything about life has been changing as science delves into epigenetics (can’t seem to get away from that topic!) and the mind-boggling complexity of DNA’s structure.

… The most striking thing about the genomic revolution is that the revolution never happened. Yes, it’s been an era of the most amazing technical achievement, marked by an overwhelming flood of new data. It’s true that we are gaining, even if largely by trial and error, certain manipulative powers. But our understanding of the integrity and unified functioning of the living cell has, if anything, been more obscured than illumined by the torrent of data…

The human body is not a mere implication of clean logical code in abstract conceptual space, but rather a play of complexly shaped and intricately interacting physical substances and forces. Yet the four genetic letters, in the researcher’s mind, became curiously detached from their material matrix. In many scientific discussions it hardly would have mattered whether the letters of the “Book of Life” represented nucleotide bases or completely different molecular combinations. All that counted were certain logical correspondences between code and protein together with a few bits of regulatory logic, all buttressed by the massive weight of an unsupported assumption: somehow, by neatly executing an immaculate, computer-like DNA logic, the organism would fulfill its destiny as a living creature. The details could be worked out later.

… The central truth arising from genetic research today is that the hope of finding an adequate explanation of life in terms of inanimate, molecular-level machinery was misconceived. Just as we witness the distinctive character of life when we observe the organism as a whole, so, too, we encounter that same living character when we analyze the organism down to the level of molecules and genes. One by one every seemingly reliable and predictable “molecular mechanism” has been caught deviating from its “program” and submitting instead to the fluid life of its larger context. And chief among the deviants is that supposed First Cause, the gene itself. We are progressing into a post-genomic era — the new era of epigenetics.

The essay quickly becomes a rather detailed description of just how insanely complex DNA is, and the factors that determine how it’s read. I think it’s accessible to anyone with a basic biology background but it does get pretty heavy. If you want to feel like a genetics boss, you should dive in; a few minutes’ reading will teach you a lot, and maybe give you a good dose of humility about the organized insanity that’s going on in our cells. 

Based on this article, and Wikipedia’s description of The New Atlantis as “traditionalist conservative,” I can’t help but feel that I’ll disagree with the last essay’s conclusion – I assume, that there is something inherently unquantifiable, or supernatural, about life – but it promises to be an interesting and informative read in any case, so I’ll go on to part 2 tomorrow.

Edit: Further research has shown that the author has this to say about this series of essays:

They are attempts to describe our reigning (and mostly unconscious) cognitive habits, the limitations of conventional science, and the redirections required for a new, qualitative science. By virtue of its qualitative character, such a science will be holistic and irreducibly ethical (or unethical).

So… now I’m pretty confident that I’m going to disagree with whatever it is he concludes. But that makes it more interesting, doesn’t it? We’ll see how this goes over the next couple of days. (Update: check out my posts on the second and third essays in the series.)

Linking Average National IQ and Infectious Disease

Christopher Eppig at Scientific American writes about his search for the factors that determine average national IQ. This is a topic that’s apparently been studied quite a bit, and Eppig explains that the cumulative evidence points towards rates of infectious disease as a determining factor. 

One study found that newborn humans spend close to 90 percent of their calories on building and running their brains. (Even as adults, our brains consume as much as a quarter of our energy.) If, during childhood, when the brain is being built, some unexpected energy cost comes along, the brain will suffer. Infectious disease is a factor that may rob large amounts of energy away from a developing brain.

I was a bit hesitant about linking to this article because a) it’s written by the grad student who conducted this research, although I leave it to Scientific American to ensure that he’s being honest and accurate, and b) not once in the article does he question IQ as an objectively meaningful measure of intelligence. That’s a huge elephant in the room that I’m really surprised he did not address, and it definitely detracts from the article.

Nevertheless, this is an interesting theory that may not have been the most obvious explanation (I doubt I would’ve thought of it), so I put it out here for you to mull over. Mull away.

On the Other Hand… Epigenetic Changes May Have Less Effect On Evolution Than We Think

I love this: I posted a TED talk about the potent future of genetic sequencing in medicine, then posted an article about the importance of epigenetic changes in a model plant, and made an offhanded comment about how that reined in my enthusiasm about the TED talk. Now Science Daily brings us an article from researchers who’ve monitored epigenetic changes in that same model plant over the course of several generations, and found that while the epigenome changes rapidly, those changes don’t necessarily stick – so they’re not necessarily an important factor in evolution, or at least not as important as that last article would’ve had you believe. 

Why do I love this? Because, in a sense, it’s science at its best: constantly re-evaluating and self-correcting. Clearly Science Daily had no problem juxtaposing these articles within a few days of each other, because it’s not its agenda to push one view or another (as far as we can tell, anyway); just to advertise the truth, or rather the closest thing we have to it.

I also love it for my own educational value, because suddenly I was like “Wait – I just swallowed that last article uncritically. Now I feel kind of silly.” The thing is, individual scientific findings are rarely interesting on their own – they’re interesting in terms of the implications and applications, which is why any of these articles will probably have less to say about the actual study conducted than about what the researcher thinks this means for the future. And this latter part, unfortunately, will always be conjecture. We’ll just have to absorb and move along with the actual findings, and try not to get too attached to the hypothetical implications 🙂

Onwards: I briefly explained epigenetics in the last post on the topic, but here’s Science Daily’s superior background briefing, and more about the study:

Jean-Baptiste Lamarck would have been delighted: geneticists no longer dismiss out of hand his belief that acquired traits can be passed on to offspring. When Darwin published his book on evolution, Lamarck’s theory of transformation went onto the ash heap of history. But in the last decade, we have learned that the environment can after all leave traces in the genomes of animals and plants, in form of so-called epigenetic modifications…

Using Arabidopsis, the workhorse of modern plant genetics, the researchers determined how often and where in the genome epigenetic modifications occur — and how often they disappear again. They found that epigenetic changes are many orders of magnitude more frequent than conventional DNA mutations, but also often short lived. They are therefore probably much less important for long-term evolution than previously thought.

A team led by Detlef Weigel, director of the Department for Molecular Biology, focused on one of the most important epigenetic marks, methylation of DNA. Tiny chemical building blocks, methyl groups, are thereby attached to individual letters of the DNA, mostly to cytosines. The genetic information itself in form of the four different letters or nucleotides that make up the genetic code remains unchanged in this process…

“Our experiments show that methylation changes are often reversible.” In other words: New epimutations are often not maintained over the long term. “Only when selection wins out over reversion can these epimutations affect evolution,” says Hagmann. A new epimutation thus must have a strong evolutionary advantage so that it can become established before being lost again. Because reverse mutations do not necessarily happen in the next generation, it is still possible that epigenetic differences contribute to inheritance of traits between parents and their children or grandparents and their grandchildren…

What makes epigenetics interesting for human health is the fact that some epigenetic changes can be triggered by external factors. There is evidence that nutrition or the bond between children and their parents can leave traces in the genome that can be passed on to the next generation. The limited stability of DNA methylation implies, however, that such differences do not necessarily last forever, which is probably not a bad idea because a famine might not last forever. It also means that altered DNA methylation often cannot become subject to natural selection.

I wonder if epigenetics will ever take as prominent a role in students’ education as genetics? I don’t think I ever heard of an “epigenetics class” in university… Quick, to the future!