Tuesday, June 29, 2021

Science is a universal human skill

 kw: book reviews, nonfiction, science, citizen science

On August 21, 2017, a total solar eclipse crossed the middle of the United States. For those who couldn't travel to the path of totality, a partial eclipse could be seen throughout the country. I was to work at the Delaware Museum of Natural History that day, and the amount of the Sun to be hidden was about 80%, so it was a significant event. At the Museum, we announced and advertised a public Eclipse Day, with a number of telescopes and other devices prepared for the public to join in.

Here we see U.S. Senator Chris Coons looking through binoculars fitted with special filters so he could see the Sun directly and safely. He was one of hundreds of people who came to join the event.

We showed people how to make a "pinhole" with their hand, or by making a small hole in a piece of paper or cardboard, so they could see the shape of the sun projected onto the ground as the Moon crossed in front of it.

People most enjoyed the four telescopes that we set up for projecting the solar image onto screens, as seen in this photo. My own "stovepipe" telescope is in the foreground. Only a little of the Sun was covered at this point. Just behind it a volunteer is adjusting another telescope to move the image back to the center of the screen. The other two telescopes are hidden by the crowd. The picture below was taken near maximum eclipse.

This event shows that people in general are fascinated by nature and natural events. Yet about 9 people in 10 would say, "I am bad at science." That is because they don't know what science is. They don't realize that our life is built around science. The way we learn to interact with people, beginning in infancy, is by observing how others react to us, and by trying different things to see what the reaction will be, and learning to do what gets the reactions we want. Growing up, we learn how to walk around without getting hurt (too much), how to throw a ball, and a great many other skills, by this ordinary process: observe, experiment, categorize, and predict.

What people actually mean is, they are bad at some of the things "professional scientists" do, such as making formal (and often costly) experiments, or publishing articles. If we broaden "publishing" to include gossip and giving advice, though, and also consider how diligent we are to learn things that really interest us, we are all scientists. It's time we acknowledge the fact.

You may have heard the term "citizen science." Perhaps you have stumbled across one of its manifestations, such as Galaxy Zoo, SETI@home, or the Great Sunflower Project (I'll explain what they are in a moment). Equally likely, you may know nothing of these things yet. In either case, a new book should prove quite a treat!

The Field Guide to Citizen Science: How You Can Contribute to Scientific Research and Make a Difference, by Darlene Cavalier, Catherine Hoffman, and Caren Cooper, introduces just the tip of the iceberg of the immense field citizen science has become. For several years I have participated in a number of projects through the Zooniverse interface, which currently includes 78 active projects, all performed online. I got started at Zooniverse through the Galaxy Zoo, for which I viewed galaxy images from the Hubble Space Telescope and reported their shape and other characteristics. Over time I participated in 36 projects, from counting penguins to transcribing labels. The Field Guide introduces the much broader scope of projects of all kinds, about 1,600 of them, available through SciStarter, which was founded by Ms Cavalier.

The bulk of the book describes more than 40 projects. Some are carried out online (including some of the Zooniverse projects); some are done in the home or yard (such as Great Sunflower, for which you plant sunflower seeds and, once they grow up and flower, count the types of bees that visit them); for some you venture out in nature; some are done by day, some by night; and for some you need to get equipment such as a trail camera or a kit the project supplies. The authors also have suggestions for introducing citizen science into schools, libraries and other public venues, such as the eclipse event I described above.

I have to put in a plug for museums: are you a collector? Maybe you collect things that would interest a museum. I work with the seashell (mollusk) collection at the Delaware museum, and I have noticed that more than half the museum's holdings of 2 million shells in more than a quarter-million "lots" (groups of shells of one species collected at one place and time) were donated by private collectors, either during their lifetime as active collaborators, or they were willed to the museum. Whatever museums exist near you, do find out what kinds of items they are interested in receiving for their collections. If you collect seashells, for example, even if you just pick up "a few pretties" every time you go to the shore, it is worthwhile to have a conversation with a curator of mollusks, to find out what kind of data to collect along with the shells, so if/when you later donate them, they will be useful to the museum and researchers that use the collections for scientific purposes. Museums don't hold collections "just so they'll have them", but so historical and ecological study can be done. Not only do I occasionally take in shells I have collected, a month ago I found a recently dead opossum. After making sure it was actually dead, not just fooling, I put it in a bag and drove it right to the museum, where the curator put it in a freezer (all new animal specimens are put through a freeze-thaw-refreeze routine to kill parasites and their eggs).

The great variety of projects offered through SciStarter will have something, probably several somethings, for anyone with any sort of interest. I created a SciStarter account to see how it compares with Zooniverse. Prior to today, I have participated in 36 Zooniverse projects (and made nearly 20,000 classifications), I also have the iNaturalist app on my phone (but it's early days, I have only "collected" 55 observations), and I recently got the Cicada Safari app to use whenever Brood X erupts in my neighborhood (none so far).

When I set up a SciStarter account, I found that in my profile I could link its dashboard to the accounts I have with Zooniverse and iNaturalist. In the Field Guide I found a few projects I may try out, including Fe-BARQ ("Fe" for "feline": describe your pet cat's personality) and Foldit (a kind of game to investigate how a protein molucule folds). In the past I've run the SETI@home "screen saver", which actually works one's computer flat-out, analyzing signals from space in hopes of finding intelligent life elsewhere; I may do so again.

In the Project Finder I entered a few key terms: my state; "animals"; and checked off project types "at home", "on a hike", and "exclusively online". The project types are inclusive, not combined. SciStarter suggested 54 projects. That was just a test. I can go back later and select one or more to try.

Science depends on data. When citizens collect or help sort and categorize data, it helps professional scientists. It can also introduce us to new friends we meet through the projects, friends with common interests. It is worthwhile to get this book and keep it on hand.

Friday, June 25, 2021

Mechanisms of evolutionary saltation

 kw: book reviews, nonfiction, evolution, development, evo-devo, dna, molecular biology

It took Stephen Jay Gould twenty years to write The Structure of Evolutionary Theory. It will take me longer than that to read it. I bought a copy when it was released in 2002, and I am only one-third of the way through it. I intend to read it all.

You may know that Dr. Gould is one originator of the hypothesis of Punctuated Equilibrium: fossils show that species tend to persist almost unchanged for periods of a million years to tens of millions of years, and then undergo rapid change, during which new species arise quickly. His book discusses this matter, and much more, in a historical context. I probably haven't come to the "good bits" yet. But others have, and scientists continue to discover new aspects of genetics and evolution, so I read widely in the field.

A stellar new volume is Some Assembly Required: Decoding Four Billion Years of Life, from Ancient Fossils to DNA, by Neil Shubin, a researcher and professor of Organismal Biology and Anatomy. His book outlines certain events in the history of evolutionary thought and genetic discovery, with an emphasis on a seminal thought expressed by one of his mentors, "Things didn't start when you think they did."

For example, he discusses wings and flight. Flight arose at least four times, in insects, pterosaurs (reptiles), bats (mammals), and birds. In each case, wings didn't appear all at once, but we find that earlier tissues and structures with different functions were co-opted to become wings, in a rather short time span. Furthermore, by digging into the genetics of wing development, he and others have found that the precursors to wings have similar origins in these very different types of animals. I can't do justice to an explanation of this. The book's discussion is brief yet illuminating. Bottom line: structures that could later become wings were developed long ago, for other purposes, and only millions of years later did the new function of "catching air" arise, requiring comparatively modest further development.

Another example every school child of my generation learned (do they still?): lungs developed from flotation bladders in fish. Whether the bladder developed a connection to the mouth by accident or for another reason, once that occurred, the already-existing practice many fish had of gulping air when the oxygen supply in the water was low, when combined with a new place to put that air, allowed these fish to survive better. Also, fins in some fish species were modified with "lobes", and these precursors of legs were used to move along the bottom of a lake or stream. "Walking" in this way keeps the animal below the worst of currents that it wants to move against; only later were the "legs" used to move onto and across the land, and eventually they were strengthened into legs strong enough to support amphibian bodies.

The pace of evolutionary development was very slow long ago, but has been accelerated over time with various developments. The first living things were like bacteria, or perhaps their cousins, the archaea. These together are called prokaryotes ("before the nucleus"): a prokaryote cell's DNA is a loosely-wound loop that runs throughout the interior of the cell. After a half billion years of gradual proliferation, some prokaryotes developed photosynthesis. Before that all life was chemosynthetic, using processes such as robbing sulfur from metal sulfides for energy. There are several kinds of photosynthesis; only one, initially, used CO2 and water to produce sugar, with oxygen (O2) as a waste product. Today's cyanobacteria (also called blue-green algae) are descended from O2-producing bacteria that arose about 3,500 million years ago.

At first, all the excess oxygen was used up by oxidizing sulfides into oxides and sulfates. This slowed down after another billion years, and oxygen began accumulating into the atmosphere. From 2,500 million to 1,500 million years ago, during the "boring billion", O2 slowly increased to about 2%. Then things began to change more rapidly. About that time, or perhaps a few hundred million years earlier, more complex cells developed. The DNA was encapsulated inside its own membrane, and at least two events of engulfment happened. Most probably the first "guests" invited into a larger cell (or they were invaders that were subdued and enslaved) were cyanobacteria, which were put to work turning air into sugar, while being kept safe inside the cell. Now they are called chloroplasts. Almost immediately, the second event was the capture of certain small, energy-efficient bacteria that probably looked a lot like E. coli. These became mitochondria. These larger, compound types of cell are called eukaryotes ("good nucleus"). A discussion of this process on pp 195-6 seems to imply that plants have chloroplasts but not mitochondria; not so, they have both. They need both!

Single-celled eukaryotes are still with us, most familiarly in the form of protozoa such as Amoeba and Paramecium. Some time before 1,000 million years ago, molecular mechanisms that were being used to attach to a substrate or to food particles before "swallowing" them, were re-purposed to allow cells to cling together. In the book a lovely discussion of choanoflagellates discusses how this works. The earliest multi-cellular creatures, whether they were proto-plants (with chloroplasts) or proto-animals, had a variety of shapes, but mostly looked quilt-like or mat-like. Some time around 600 million years ago an organizing principle arose. To introduce it, we must look into segmentation.

The prototype of segmented animals is the earthworm. You can see the segments, a lot of them. We vertebrates are segmented also. Our spine expresses the segmentation. Not all animals are segmented; in fact most phyla are not, but all have some kind of body plan. The Homeobox, or HOX, genes are controllers of body plan development. Every animal species has them. The HOX genes are organizers, and represent a kind of meta-control. The simple idea that we have "a gene" for this or that is a big distortion. Even in a simple animal such as a 1mm nematode, there are HOX genes that make the difference between front and rear and so forth. The more complicated sets of HOX genes found in more complex animals arose from reduplication.

Reduplication is a big theme in genetics. The added sets of HOX genes we need are an example. Mutation isn't a matter of creating a new, complex function out of whole cloth. It proceeds by various errors of copying, which will usually just kill the animal, but occasionally are at least mostly harmless, and over time, the odd bit can gain a new function. The most common mutations are single-point changes, such as from an A to a G in the genetic code. But whole segments can be duplicated, particularly during the "crossover" that occurs during the production of eggs and sperm. If an extra set of HOX genes is produced, one set can go its merry way, controlling the body's development, while the other set is modified and can lead to an extra function or body part or even whole section. Again, this isn't usually good for the animal, but it can be.

Segmentation arose by reduplication. In some cases, many identical segments were produced (earthworm). In others, the segments became specialized. The HOX genes control all this. The illustration, from this article at Socratic.org, compares the HOM genes (as they are called for insects) with the multiple sets of HOX genes in humans and mice. The segmentation of the insect's body is emphasized in the drawing.

It may seem strange that we share this organizing principle with fruit flies, mice and everything else. From an evolutionary perspective, it makes sense. The system works, and we can see that it works, for it has produced millions of species of animal.

Now to the matter of saltation, as in this review's title. Saltation is a dirty word to most evolutionists. It has come to mean things like a rabbit suddenly "evolving" into a dog or a horse. That's ludicrous.

In a proper sense, saltation means "jumping", and the concept (if not the term) had to be coped with once Barbara McClintock discovered jumping genes in corn. They have since been found in every species, and certain kinds of them form much of the "junk DNA" found between the genes in our genome. But others have been put to use, and HOX may be an example.

Just by the way, there's a lot less "junk" in our DNA than early reports claimed. Just 2% of it codes for proteins. An additional 2% (perhaps much more) consists of regulatory sequences that control when and how the genes make those proteins, a further 8-10% consists of deactivated viruses, which form a "library" of stuff gathered from everywhere, that can be re-purposed. Some is apparently second- and third-level regulatory stuff. About 2/3 is "palindromic repeats" (such as AATTGCACGTTAA) that consist of head-to-toe copies of "stuff", which at the moment, is at least useful for landmarks used by CRISPER/CAS gene editing.

All these things, and many more discussed in the book, are mechanisms for more rapid evolutionary change, compared to waiting for single-letter mutations to accumulate. Even over millions of years, that process is dreadfully slow. The beauty of these mechanisms, still being discovered, is that they allow big changes to occur without disaster.

The Earth would seem quite full of many species, were there only a few tens of thousands of them. It is astonishing that there are millions! I work in the "shell room" of a museum, and every time I open a cabinet I see something new, just among the mollusks! That room contains specimens for more than 20,000 species...of seashell! Nearly 100,000 are known. It seems that life, having figured out how to spin out new kinds of creatures, is still ramping up. While we may be driving thousands of species to extinction, it is likely that new species are arising even faster. If we attain wisdom enough to let nature alone and "live lightly", we may see even more variety in the multiplicity of life in the future.

Thursday, June 17, 2021

The biosphere has used five of its lives

kw: book reviews, nonfiction, geology, geologic history, earth history, mass extinctions

Beginning Geology students have to learn a plethora of new terms, including the geologic ages: Pre-Cambrian, Cambrian, Ordovician, Silurian, Devonian, Carboniferous (in the US, divided into Mississippian and Pennsylvanian), Permian, Triassic, Jurassic, Cretaceous, Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, and Recent. I remember learning a letter-mnemonic for Cambrian through Recent: COSDMPP-TJC-PEOMPPR. Over time we learned that each such age has characteristics that differ from the others, including different prevalent rock types and different fossils.

Later on we learned that the significant differences from age to age are a result of great revolutions in the kinds of living things, and the transitions are marked by large increases in the rate of extinction. Further, five of these are called "the Big 5" and "the Great Extinctions". Here is a summary of these as shown in a poster prepared by Bud Charles, in use by many web sites that discuss "the Big 5"

The "Death Rate" reported in the diagram is the number of species that were driven to extinction. The percent of the biosphere that was destroyed is a much harder quantity to determine, and I have not found any published estimates. Considering the certain damage to each species that survived any of these events (or periods; some "events" took a million years or more to unfold), it is likely that the actual reduction in the "living biosphere" was 90% or greater for each of these, and may have exceeded 99% for the biggest, the end-Permian mass extinction.

The recent book The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth's Past Mass Extinctions, by Peter Brannen, is a very well-written travelogue through the geologic ages, focusing in some detail on the processes of each of the Big 5. The photo plates show scenery of the existing geology resulting from them. It would have been very beneficial to have a chart such as that above, with even more detail, because more is known now (in 2017, the date of publication), compared to just a few years earlier when the poster was produced.

It would also be useful to have a visual of where these fit in time, such as this diagram from an article in the Washington Post, reproduced here at a small size as allowed by copyright law.

The section on the right labeled "Tertiary" includes all the ages from Paleocene to Recent. The dips and wiggles show how extinctions less severe than the Big 5 have played a part in the transition from each age to the next. Also, the little dip in the middle of the Carboniferous represents a significant change in plant life that accompanied a lesser extinction event, which marks the divide between the Mississippian and Pennsylvanian ages as recognized in the US.

In this diagram, the metric is "number of families", rather than number of species. Look particularly at the end-Permian, where the number of families has dropped by about half, as compared to the number of species, which, as noted above, dropped by 95% to only 5% of its former value. The taxonomic Family is two levels broader than the Species, so if even a single species in a family survived, that is a surviving family. Nonetheless, the end-Permian event is clearly the most severe.

The kinds of things that nature can throw at Earth and its biosphere are described clearly in the book. In many cases, the primary causes may differ, but the critical factor is a great change in global temperature. In the chart above, "rapid global cooling" is mentioned twice, and "rapid global warming" is mentioned twice. In the case of the end-Cretaceous event, it is likely that almost instant world-wide broiling occurred, followed by decades or centuries of "impact winter".

Three of the Big 5 were caused, at least in part, by the eruption of flood basalts, a tame term for the sudden release of 100,000-1 million (or more) cubic miles of lava. Even the end-Cretaceous event, which destroyed all the dinosaurs (except a few that became birds) plus the flying and aquatic reptiles, which "everyone knows" was caused by an asteroid crash 65 million years ago, coincided with the eruption of the Deccan Traps ("Trap" is another word for flood basalt), in India. Enough is known about the Deccan Traps to calculate that if the lava had been evenly spread over the Continental US, it would have been 600 feet deep. That makes the scale of the Yellowstone "supervolcano" a cap pistol by comparison. As big as that was, the Siberian Traps that we think were the primary cause of the end-Permian extinction, 251 million years ago, were as much as ten times larger. The third flood basalt event left remnants in New Jersey (the Palisades) and around the East Coast of the US at the end of the Triassic about 200 million years ago. It was smaller than the Deccan event, but big enough to rate as one of the Big 5.

What can cause volcanism on such a scale? Generally speaking, the splitting of a continent will fill the bill. Prior to about 1966, the continents were thought to be stable and immobile, and all kinds of wild ideas were in vogue at various times to explain the origin of mountains. Plate tectonics was "discovered" in the early 1960's, after being proposed in 1912 by Alfred Wegener, and just when I began to study geology in earnest (1970), this new paradigm changed everything. It was an exciting time to study geology. One offshoot was the study of supercontinents. They seem to form periodically.

The mid-Atlantic Ridge is pushing that ocean's coasts apart at a rate of 2.5 cm/yr., which amounts to 25 km per million years. The Atlantic Ocean's width varies from under 5,000 km to 6,000 km or so, which implies that the breakup of a supercontinent that once included Africa, Europe, and the Americas adjacent to one another along a "seam", occurred beginning about 250 million years ago, and was completed after 200 million years ago. That 250 million-years-ago figure is suspicious. Another "seam" appears to have ruptured at the same time thousands of miles away, and apparently it was the more "active". That would be the source of the Siberian Traps. The 200-million-years-ago figure, relevant to the Equatorial Atlantic, would point the finger at the end-Triassic event that covered much of the eastern US with lava. I think that is enough to make the point.

The mid-Atlantic Ridge isn't the fastest. The Pacific Plate is presently being absorbed under Asia at a rate of 8 cm/yr or 80 km/million years. Other plates are moving in other directions, with Africa as an apparent pole of stability. Other plates and their continents show evidence of passing over hot spots in the mantle, such as the one that produced the Hawaiian Islands and the Emperor seamounts, the one currently under Reunion Island, and the one that produced Yellowstone and a chain of calderas stretching at least as far as Idaho. Africa doesn't seem to have any hot spot traces, but it is apparently beginning to rift apart near its eastern margin, in the beginnings of another cycle of continental splitting. 

The crust of the Earth undergoes cycles of continental mash-up into supercontinents, followed by fragmentation. Note that we are in an era of partial fragmentation; Asia occupies about 2/3 of all the continental area of the Earth, and is likely to gather the rest of the continents into one after another 100 million years or so. The Pacific Ocean is shrinking at a rate of about 80 km/million years, so it won't last forever!

Considering this, I wondered if the breakup of earlier supercontinents might be implicated in other big extinctions. Here is a list, summarized from several articles and other documents. Note that Pangaea spans the end-Permian and end-Triassic extinctions. I find it curious that Pannotia came together just after the Deccan Traps erupted, so perhaps continental construction is as effective as continental splitting at producing biosphere-threatening volcanism.

The earlier supercontinents occurred before the Cambrian, which means before easily-found fossils. They could not have been involved in the Big 5. But there were earlier mass extinctions; they are hard to detect, because only bacteria (and archaea) lived then. I suspect a number of Precambrian great extinctions happened. Numerous Precambrian geology specialists are busily working on it.

Atmospheric chemistry is a different driver of extinction. It may be that the biggest mass extinction of all occurred when oxygen began to accumulate in the atmosphere. Photosynthesis began about 3.5 billion years ago. There are several types of photosynthesis, and at first, only one, called "C3", found today in algae and most plants, produced oxygen directly. Other types, such as that used by green sulfur bacteria and purple sulfur bacteria, have other chemical results. For a billion years, none of the oxygen made it to the atmosphere. It was all consumed oxidizing iron and its sulfides, and other reduced materials, forming the great "red beds" and other oxide ore accumulations, for example. About 2.5 billion years ago, most reduced materials had been oxidized, and oxygen began to enter the atmosphere.

We can see from this chart, found in Wikimedia Commons, that a low level of oxygen, in the 3%-5% range, prevailed for more than a billion years, and it seems life kind of stagnated once it got used to that. This era is called the "boring billion." The upward inflection shown here at about 900 million years ago probably occurred a little earlier, maybe at 1.1 billion years. The red and green lines are limits proposed by various workers; the red line is the more probable.

Animals and plants apparently evolved just about a billion years ago, with a metabolism fueled by increasingly abundant oxygen. The big uptick occurred during the Permian, when oxygen probably exceeded 30%, compared to 20% today.

The other significant gas is carbon dioxide, CO2. This is one of numerous diagrams showing the level of CO2 over the past 600 million years. In The Ends of the World it is stated that the primary mechanism for absorbing CO2 is weathering of basaltic rock. However, it is slow, taking place on a scale of 100,000 to a million years. Based on this chart, one would expect that fresh basalt was made available in the mid-Cambrian, all during the Ordovician and Silurian ages, and in the early Carboniferous. That doesn't seem so. Rather, in particular for the Carboniferous age, the huge expansion of forests that produced nearly all the coal in the world occurred. I'll leave it at that because this is a side point.

Apparently, the dip in life's diversity in the mid-Carboniferous that I mentioned earlier happened when CO2 was drawn down to modern levels (between 200-400 ppm), at which point trees, which rely on C3 photosynthesis, have a hard time growing rapidly. At the far right, the CO2 drawdown that trended during the Tertiary (Paleocene until the present) was apparently a result of new types of green photosynthesis, called CAM and C4. Grasses, the main sort of C4 organism, and their relatives are very happy with 200 ppm of CO2 or less, while trees are happiest when CO2 is in the 1,000 ppm range. Experiments with rice plants have found that rice grows best when CO2 is 2,000 ppm.

The author makes much of the gyrations of CO2 that occurred in the past. While he is right in general, he tends to be alarmist. I almost added "polemics" to my labels for this review, but I decided not to. The book may get a little polemical, but it is much more than that, and contains a great amount of interesting and useful information about the worlds that preceded us, particularly how different each one was from what we live in now. For example, we are accustomed to reefs based on hard corals that host mollusks and fishes of many kinds. Permian reef backbones were masses of brachiopods and mollusks, with corals scattered among them, hosting more ammonites than fishes. Cambrian reefs were even more weird, made of piled-up animals that looked like individual coral polyps, lots of brachiopods (they look like cockles, but with much lower metabolism), and the main swimming things were trilobites and nautiloids, which look like straightened out ammonites (both resemble squids with big shells).

I was particularly interested in the analysis of one person cited, who said we are nowhere near a sixth great extinction. He has the numbers to prove it. So it is a little early to call the past century or two the beginning of the Anthropocene age. But we would do well to be wary. The greenhouse effect is real, and it is pretty certain that we are contributing to it. Whether it will lead to catastrophe or instead ameliorate the next ice age is yet to be seen.

How much can we heat the planet if we continue to burn petroleum and coal? As a teen I reproduced the calculations of Arrhenius, the one who first publicized the CO2-induced greenhouse effect. Later, using differential-albedo modeling (such as how sunlight heats something that absorbs visible light better than infrared, or vice versa), I verified something I read: "If we push CO2 so much that we 'close' the 'window' of its absorption bands in the infrared, the maximum warming would be 4°C". Statements about 9°C and even 12°C are not realistic, nor mathematically possible. Now, four degrees is significant. Will it melt Antarctica? Probably not.

We are also not going to push CO2 into the tens of thousands of ppm range, just by burning fossil fuels. Some look at the oxygen in the atmosphere as being entirely "carbon debt". That 20% is 200,000 ppm. CO2 weighs 37.5% more than oxygen does. If we could really extract (and burn) that much carbon from oil and coal fields, the actual mass of the atmosphere would increase 7.5%, and this new, heavier atmosphere would be 25.5% CO2, or 255,000 ppm. We would all have died from anoxia long before that point. But the total extractable carbon in the crust is only a fraction of this, a few percent. Most of the carbon from decaying "stuff" was carried into ocean trenches and is deep in the mantle, perhaps making gigatons of diamonds!

I have a quibble of a different nature: on page 189 it is stated that the asteroid that did in the dinosaurs "put a hole in the ground 20 miles deep—deep enough...to puncture the earth's mantle...". This should state "puncture to the earth's mantle", which begins around 20 miles down, and extends 1,800 miles deep.

On a happier note, the author cites Mark Richards as proposing that the asteroid impact actually triggered the formation of the Deccan Traps. A more modest level of flood vulcanism had begun before the impact, but it took off right at that time. I suggested this to one of my geology professors some 40 years ago, and he was very skeptical. At that time the "impact theory" was accepted, but the location of the crater in Yucatan wasn't yet known. I suggested a possible impact antipodal to India, somewhere in the South Pacific, perhaps 1,200 miles southwest of the Galapagos Islands. Dr. Richards does say that an antipodal arrangement would yield the best "focusing" of the seismic disturbance caused by an impact, but since the asteroid's impact was like a magnitude 11 or 12 earthquake, such focusing was not needed to trigger an ongoing eruption into a mega-event, releasing its pent-up lava over a much shorter interval.

Another significant theme is that all of the Big 5 mass extinctions were multi-factor "perfect storm" sorts of things, with the end-Permian event being the "most perfect". I'll leave that for readers to discover as they enjoy this readable and informative book.

Friday, June 04, 2021

Linear thinking in a non-linear world

 kw: book reviews, nonfiction, prediction, forecasting, disciplines

My colleague at work had a poster: "Life is uncertain. Eat dessert first." We hate uncertainty, which is why we want to find out what is going to happen. We hate lack of control, which is why we try to control the future. Unfortunately, the future is unknowable and beyond our control. We aren't even very good at self-control. How could we hope to control a world composed of billions of others who are just as uncontrollable as ourselves?

What do you see here? Suppose this represents the general state of someone's health, projected over a long lifetime. Where is its end? If this shows the life of someone who is "fated" to live 85 years, they had a near-death experience around age 35.

Sliding toward the bottom of that valley—was it an illness, an accident?—, it may seem like the end is near and that good health is irretrievable. But, hey, things get a little better almost immediately, and later, a lot better. But that's not where these data came from.

Suppose instead it represents some factor of the economy. Is this part of a bigger picture? What comes after, and what came before? Did you notice that the end of the diagram is close to the level of the beginning, though a little bit lower? There are a couple of big, sustained "UPs", and a couple of big, sustained "DOWNs". In the middle of one of those sustained runs, whether up or down if you had to bet on the future of the rest of the diagram, how would you bet? Would you have any idea what the value would be at any point on this chart?

As a matter of fact, this is a financial chart, and adding the axes shows more context:

This is the Google Finance chart of the weekly closing price for Apple, Inc (AAPL), from 1/1/2021 to date (6/3/2021). It looks pretty dramatic! But check the left axis: the low for the year, in early March, was 116, the high in late January was 143, and the June 3 closing was 123.5 (pretty close to the average for the period of 128.6). If you knew just those figures, you could make a "bet with sideboards" that, for the short term, the stock price would be within ±11%. A final chart will show a little more context:

I downloaded the YTD historical data and charted it in Excel. When a stock price chart includes a zero, it looks less dramatic. From this perspective, this stock has been "flat" for five months.

How long will it stay "flat"? I couldn't hazard a guess. Do this: pick a time frame, such as a year, or five years, or (being more canny) the Midterm Election in late 2022 or the Presidential Election in 2024, and call that "the end of AAPL flatness." Write it down (or put a memo in your phone's calendar). Check it on that date and see if AAPL is still flat, or if it entered a period of serious gyration.

Now think about possible "black swans", such as someone buying Apple, or a competing product blowing the iPhone out of the market, or more globally, a new war, a recession, or a suddenly booming economy and the Dow Jones goes to 100,000. I don't have any idea how possible any of these things are, but if the possibility of any of them is more than a few percent, it would call any prediction about this stock or any other into serious question.

Consider this. The moment-by-moment price of a stock is influenced partly by the market as a whole, made up of investors that represent only a couple % of the population, and partly by the emotions of investors in that particular stock, which number a few dozen to a few hundred people. Wouldn't you expect that predicting the outcome of larger questions might be even harder? A year or five years from now, what will be the health of the economy of the nation or of many nations; what is the likelihood of war between two rival nations; or what of the effects of offshoring or onshoring a major segment of the work force? All of these depend on the decisions of thousands to millions of people!

About two months ago I reviewed a book about forecasting and "superforecasters", the kind of people who are better at making predictions that are at least a little more accurate than guesses. The author of that book referred to another, Future Babble: Why Expert Predictions are Next to Worthless, and You Can Do Better, by Dan Gardner. I spent the past two weeks reading this book, with some care. I think it best to begin with a few statements that caught my eye:

On Behavioral Economics, "In the 1950s, Solomon Asch, Richard Crutchfield, and other psychologists conducted … experiments that revealed an unmistakable tendency to abandon our own judgments in the face of a group consensus—even when the consensus is blatantly wrong. …three-quarters of test subjects did this at least once." (p. 99 in Chapter 4)

On "predicting 'more of the same' ", "…[such] predictions are more likely to be right when current trends continue and least likely to be right when there is a drastic change. That's most unfortunate, because when the road is straight, anyone can see where it is going. It's the curves and corners that cause crashes. …predictions are most likely to be right when they are least needed and least likely to be right when they are essential." (p. 105 in Chapter 4)

On Chaos, or the unexpected influence of small differences, "Like most of what's interesting in life, weather is subject to chaos and all sorts of nonlinear weirdness that limits how far we can peer into the future. Those limits will never be eliminated." (p. 105 in Chapter 8)

The first item above refers to "groupthink", which led to the disastrous Bay of Pigs "invasion" of Cuba early in the Kennedy administration, and to the under-planning of a tragic rescue attempt in Iran during the Carter administration. Do note the successful rescue operation in 1979, of two EDS employees being held in Iran, an operation ordered and sponsored by H. Ross Perot: his decision, carried out under the command of one experienced "hired gun". No groupthink.

Allied to this is the need for certainty, which means the most confident (and loud) voice typically carries the day. But turn the last phrase of the around: one-fourth of the experimental subjects did not succumb to groupthink. Their voice may not have prevailed to "turn" the others (who were all confederates of the experimenters), but they did not give up their view. In the terminology used by Gardner, they were probably "foxes", as in the proverb, "The fox knows many things, but the hedgehog knows one important thing." As one might expect, the hedgehog's "important thing" may or may not be correct, but when it is wrong, the hedgehog will not change his mind. Foxes are more flexible. They are willing to consider whether their thinking is wrong. Using the same analogy, the "superforecasters" I wrote about in April are foxes.

Let us consider the idée fixe, or fixed idea: an idea or desire that occupies one's mind, often to the point of obsession. This is the hedgehog's specialty. It takes work to break free from an obsession, but successful forecasters are willing to do the work, and the extra work to gather knowledge from numerous sources (the fox's "many things"). However, foxes have a hard time getting through to the public, which prefers the certainty of hedgehogs, no matter what their track record (which is uniformly abysmal except for the occasional lucky guess).

I recall that the root word for "fool" in the book of Proverbs is "self confident". It is used about 70 times. Not only are hedgehogs such fools, so are all those who listen to them uncritically.

For the second quote, I'd call it self-evident, but we all have "hindsight bias", which is its basis. There is a road I sometimes take to work. It goes over a rather steep hill. Just at the top, the road jogs just a little to the right, which means if you aren't paying close attention, you will suddenly be halfway into the other lane. A great place for head-on collisions. It would be better if the roadway on either side of the hill were curvy, forcing drivers to pay better attention. Even better if the highway department tore out fifty feet on either side of the crest and smoothed that transition.

Life doesn't usually provide smooth transitions. Look again at the stock charts above. Any two points more than a tenth of an inch apart would seem to have nearly no relationship to each other. In a few cases, a tenth of an inch is enough for a rather dramatic swing. The basic rule of thumb we need to guide us is, "The more confident an expert sounds, the less we should trust the prediction." Let me repeat that:

The more confident an expert sounds,
the less we should trust the prediction.

As fun as it would be to belabor the third quote, about Chaos, I'll forbear. I realize that only the "choir" would take such a word, and everyone else would ignore it. Instead let's realize that Chaos is a manifestation of Nonlinearity. We have linear minds. From many years as a working mathematician, I know how hard it is to think nonlinearly. It isn't natural to us. Even when we know something is cyclical, like the march of the seasons each year, the day-to-day variations of sunlight, clouds, rain and high or low temperature are tough to predict. The best weather forecasting computers do OK for a day or two. After that all bets are off.

Mark Twain wrote about a period of around 100 years in which the Mississippi River's length was reduced by dozens of miles, because a few long, loopy bends in the riverbed were cut off when the river flooded and cut shortcuts. He said that if the trend continued, in another couple of centuries St. Louis would be practically a coastal town on the Gulf of Mexico, and that millions of years ago the river must have been sticking out over the Gulf "like a fishing rod." 

We know that is illogical, and we laugh at it. But we neglect to consider that seemingly regular trends don't persist. Any measure we might look at is more like the stock chart above, with ups and downs that nobody could predict. Over the entire five months charted, the stock price went from 129.4 to 123.5. That's about a 5.5% reduction. But there were a couple of spots in there where a day trader could have gained 10% or more in a week's time, and a couple of others where a day trader would have had to ride out a 10% loss.

I apologize if I keep returning to the stock market as an example. It is an area I'm familiar with. It is seldom referred to in Future Babble. The author's interest is in the way we react to predictions and the way we almost always forget that they very rarely pan out. Most pundits are so wrong so frequently, it is amazing that anybody buys their books. So I'll end with a prediction: 

The pundits and "experts" who are the best at sounding confident will get rich on the gullibility of a public that craves certainty where there is none to be had.