The early evolutionists

kw: book reviews, nonfiction, evolution, evolutionary theory, short biographies, history of science

The fundamental divide between the facts of evolution and the theory of evolution has been at the root of both the scientific and theological debates about "transformation of species" for centuries. In Charles Darwin's correspondence he once referred to "us transformationists", using the word derived from ancient speculations about species change. As Rebecca Stott brings out in Darwin's Ghosts: The Secret History of Evolution, some early attacks upon On the Origin of Species were accusations of plagiarism!

Poor Darwin was assailed from all sides. The religious censured him for impiety (as many still do), and most scientists either decried his theory of natural selection or denied his priority. Claimants to priority put forward by various "correspondents" included Aristotle, nearly 2,200 years earlier, and Jahiz of Basra "only" 1,000 years before Darwin's publication. As Professor Stott shows, these first two at least are bogus claims. Anything that either man may have written about mutability of species served only as a foil to clear statements on their eternal fixity. Aristotle in particular may have been curious about the apparent ambiguity of sponges, but seems to have concluded that they were rather peculiar plants. It was not until the 1820s that the motile larvae of sponges were observed, giving the first clue to their animal nature.

However, numbers of earlier students of natural history did speculate about species change. Such speculations were based on observations that the boundaries of "kinds" were not as fixed as one might like. Certain hybrids were known, for example, some sterile and others not. In the 16^th to the early 19^th Centuries, however, just to speculate in print could get you in serious trouble with the theocratic governments of Europe. There were notions that all species might have somehow been derived from a "primordial filament". Those who published such views were at great risk.

Prior to Jean-Baptiste Lamarck in 1800, though, nobody put forward a theoretical explanation for a mechanism of species change. His theory is called "Inheritance of Acquired Characteristics", and the best-known example is the giraffe, which is imagined to have arisen as ancestral forms stretched their necks to reach the leaves of trees; those which could stretch the best passed on longer necks to their descendants. Charles Lyell effectively demolished this view before Darwin had developed his own theory.

As the mini-biographies in Darwin's Ghosts show, those who published "transformationist" views prior to 1840—including Erasmus Darwin—and thus risked censure, persecution and death, laid the groundwork for Darwin to publish Origin and survive with his skin intact. The only person who clearly enunciated a theory of Natural Selection, independently of Darwin, was Alfred Wallace. The gentlemanly way both Darwin and Wallace and the scientists Darwin consulted handled the priority question is a highlight of scientific history.

The priority question arose only because the theocratic risk had induced Darwin to spend some twenty years gathering added examples and refining his arguments, so there would be no refuting his theory (so greatly did he underestimate the persistence of Pharisaical creationists!). Had he published his theory soon after he had confirmed it, Wallace would likely have known about it, and possibly had the book in hand during his expeditions in the Malay Archipelago. Think what a different route his collecting activities might have taken were he searching for further confirmation of the theory! However, his independent derivation of Natural Selection, based on Malthusian theory for both him and Darwin, strengthened Darwin's supporters when the debates heated up in the decades after 1860.

The debates continue, sad to say. While proponents of Judaism don't seem to care much, both Christian and Muslim apologists decry all aspects of evolutionary theory, from the great spans of time it needs to the notion that human dignity is denigrated (We're apes, folks. Get used to it). Now that millions of fossils and their stratigraphic relations have shown that extinction and evolution are factual, many are forced by the evidence to admit that "life has changed through time", which is how evolution is defined. But the Theory of evolution! Now, that's where the Shinola "hits the fan". The Theory is Natural Selection. Its outline is simple:

• Most individuals of all species die young and thus do not reproduce.
• There is variation among the members of any species.
• Certain variations tend to help an individual survive and reproduce, while others tend to hinder or prevent survival and reproduction.
• There is a mechanism that leads to increased variation within a species, nowadays called mutation.
• Over long periods of time, variations that promote survival and reproduction increase, even as others decrease.

All this together is also called Descent with Modification, a term Darwin first used. By contrast, in the prior theory, Lamarckian evolution,  modification precedes descent.

The matter of mutation was unknown to Darwin and his contemporaries. So was the digital nature of inheritance. When I was young, "mutation" in popular culture was thought to be some sudden, monumental change, such as the radioactive spider biting Peter Parker to turn him into Spider Man. Actual mutations are tiny, tiny variations in DNA. Every one of us contains between 50 and 100 such mutations that make each person genetically different from being exact replicas of the parental mix that produced the egg and sperm that fused to form the embryo that became him or her. Even "identical" twins are different in this way. Most mutations have no effect. Of the very few that do, some cause the embryo to die very early, some lead to birth defects or other debilities, while a few may be beneficial. These last are most likely to help us or our descendants survive better.

In a later edition of Origin, Darwin was persuaded to add a Historical Sketch, to outline the ideas of his predecessors. This Sketch is included as the last chapter of Darwin's Ghosts. So what is the secret of this Secret History? That Darwin and Wallace really did produce an entirely original theory. Natural Selection has been called the most successful scientific theory (proponents of quantum electrodynamics or the general theory of relativity notwithstanding). It has been said that without Natural Selection, none of biology makes any sense, but with it, everything does.

For me, the book placed a solid stamp on the originality of the theory of Natural Selection. Those who accused Darwin of plagiarism were mistaken. No theory of descent with modification preceded Darwin and Wallace. No substantial variant theory has stood the test of time. Subscripts such as "punctuated equilibrium" add details that explain the effect of sudden shifts of environment, for example, without changing the essential nature of Darwinism.

Getting Darwin wrong

kw: book reviews, nonfiction, evolutionary theory, polemics

I can just hear all the biologists and paleontologists saying, "For pity's sake, don't publish that! We've got trouble enough in the trenches against the Creationists!!" But no, they just had to do it: Enter What Darwin Got Wrong by Jerry Fodor and Massimo Piattelli-Palmarini. To jump to the chase, the statement that is sure to get everyone's attention is their conclusion, that "there isn't any theory of evolution."

So what did Darwin get so wrong? It wasn't proposing that evolution is happening and that new species are produced from existing ones. It wasn't even his lyrical descriptions of the spreading diversity of living things, as exemplified, for example, by the finches that had "obviously" radiated from a founder population that came to the Galapagos Islands not too many thousands of years ago. Rather, it was his proposal of a mechanism for evolutionary change and innovation, for which he proposed the name natural selection, as somehow analogous to the artificial, human-directed selection that has produced many dog breeds from the primordial wolf, many pigeon breeds from the rock dove, and many breeds of cattle from the aurochs.

There genuinely is a serious problem with this analogy: artificial selection is mindful, but natural selection is mindless. In fact, to be a viable theory of evolutionary change, it is required to be so mindless that it is very, very hard for us mindful creatures to imagine it. We mostly don't. Instead of doing the hard cognitive work to discern the natural history sequence that may have led to a particular hummingbird species, for example, most writers produce "just-so stories" filled with intentional language. The hummingbird's ability to nearly stop its heart overnight when it can't feed is typically described as a reaction to the bird's "need" to conserve energy. I have yet to see a depiction that begins with a pre-hummingbird, which was probably larger and had plenty of energy to survive the night, a description that shows how, by various stages, as a population of nectar-feeding opportunists became one of nectar specialists, the entire physiology of the birds changed, one part of which being the development of a more variable metabolism.

Generalists becoming specialists. Is such specialization some kind of natural law? It is sometimes stated as such, as though it were as infallible as the law of gravity. But this kind of language sounds like there is some mind directing things behind the scenes. Perhaps Darwin did not make his argument sufficiently clear. He proposed an entirely mindless process, which nevertheless produced a result (many, many results) that we, with our pattern-detecting and -generating minds, think of as "progress".

I could go very long here, and I gathered a lot of quotes from the book, with some intention to take up the cudgels on behalf of natural selection. I think the theory of natural selection is quite valid, but I have to agree with this book's authors that Darwinists and Neo-Darwinists are guilty of a great deal of sloppy thinking. So I will do my best to keep this short, and merely present a few points worth considering. For a longer discussion of related points, see my posts of July 13, July 15, and July 17.

First and foremost, if a creature is alive, it is taking advantage of a flow of energy from some source to some sink. Most life on earth lives courtesy of Solar energy, but some lives instead on energy released from Earth processes, or stored chemical energy left over from the formation of Earth. For simplicity, I'll consider some animal in the food chain that begins with plants that photosynthesize Solar energy and ends with the decomposition of the animal, or its predator, by fungi and bacteria. The requirements for this animal's sustenance are: something to eat; sufficient water, either for it to drink or such that it won't desiccate (maybe it lives in water); a range of temperature in which its proteins work right; a low enough population of predators that it can live a while; and safe places to hide when predators are around. But this animal was born, and if its species is to continue to exist, there are a few more requirements: other members of the species (or the population) sufficiently close by that it can find a mate (we're assuming a sexual species here) and a level of stability in its environment that is tolerable, during this animal's productive and reproductive life span. There may be requirements I haven't thought of, but this is a sufficient set to make the point.

That collection of requirements describes what is often called the "niche" for a species. This is useful shorthand, but we must use care to avoid circular language. Creatures tend to create the niches in which we find them. There is no pre-existing niche that yawns expectantly until just the right critter comes along. Consider rabbits and Australia.

There were no rabbits in Australia until some well-meaning humans brought a number of breeding pairs there in 1859. The conditions over a large part of the continent are ideal for rabbits. Accounts abound of the awful consequences of their spread there, to the point that two million could be killed yearly and have no noticeable effect on the population. Was there a niche for rabbits, awaiting their arrival? No, there were other grazing animals that had been making full use of the native plants. Their populations waned as rabbits spread. Though this is natural selection in action, no new species have so far been produced, though a few may have gone extinct. In time, perhaps the local predators will get better at hunting rabbits, and a new species of marsupial rabbit hound may arise. Unless, of course, humans find an appropriate rabbit disease with which to eliminate them.

Let us consider a longer span of time into the future, say 100,000 years. That is a lot of rabbit generations. If Australia still has rabbits, it is likely that a few species of more specialist rabbits will have evolved. Some might eat mostly grassy plants and their seeds (as the rabbit in my yard does); some may eat more woody fare; some may get better at swimming and eat marsh plants, though they'll have to watch out for crocs. Why is this? When an environment is "too rich", as Australia is, in rabbit terms, the development of specialist species is favored because the total of their populations exceeds the population of a more generalist species that is less efficient at metabolizing a wider range of foods.

This, by the way, is the kind of prediction that natural selection allows us to make. It is no empty theory, as our two philosophers would have us believe. Theories have two principal uses: to explain what we see, and to predict what might happen as a consequence. Some theories, such as Newton's theory of gravity, or Einstein's general theory of relativity, are sufficiently exact that they can be used to make very exacting predictions of such things as the dissipation rates of globular clusters of stars, or of the position of the planets and their moons for many centuries into the future.

The theories of natural history, and most particularly evolution's theory, natural selection, deal with much more complex systems, and their predictions are correspondingly less precise. Natural history and paleontology show us that mammal species tend to survive for between one and four million years, before either evolving into new species or going extinct. However, we know of mammal species that are quite a bit older than four million years, and we are finding out how easy it is to drive even young, thriving species to extinction by hunting or habitat destruction. So the "one to four million years" species lifetime is no more than a historical range, and cannot be taken as a natural law. But it allows us to say that, were we to invent a time machine and jump twenty million years into the future, very few of today's species of mammals would still be in existence, and while a similar total number of mammal species would likely be found (unless humans are still around and have really messed things up), most of them would be just one or two million years old.

Finally, I must agree with the authors in decrying the tendency of many to say that natural history can produce anything. They ask, "Will pigs fly?" and they answer, only if their weight, musculature, and number of limbs change (they also posit feathers, but bats fly without feathers). Let's see, reduce the weight so wings don't have to be 747-sized; instead of adding limbs, reconfigure the front limbs; change the forelimb and forehoof into some kind of flying surface...well, I can see the direction this is going, and that "niche" is already filled, with the flying foxes, the large tropical fruit bats.

But the point I'll make, enlarging one the authors make, is that natural selection has to work with the changes that mutations can produce from already-living creatures. You can't have a hand without an arm (well, you can, if your mother took Thalidomide during pregnancy, but it isn't a very useful hand). It seems that natural selection hasn't deviated from the humerus-ulna-radius scheme for arm bones of mammals and birds, but the number of "finger" bones has varied. Some humans have six fingers, and I know one man with no thumbs, just five fingers on each hand. Equids have one "finger" in each foot. While it can be thought of, to have an extra bone accompany the humerus in the upper arm, the present arrangement is "good enough" and has never been improved upon.

The authors do not propose a new theory of evolutionary mechanisms. They say there isn't one, and simply propose that we stick to descriptive natural history. I think a point or two that I have made, in an elementary way perhaps, show that natural selection is a useful theory. It gives us language with which to describe how populations change through time. It accompanies the fact of evolution and provides explanatory power. It is easy to misuse, and Drs. Fodor and Piattelli-Palmarini have done us good service to point out the many ways it has been misused. But let us not discard the theory just because it has been misused. We don't discard our hammers, just because a hammer is occasionally used as a murder weapon.

Adapted for what?

kw: observations, evolutionary theory

I am part way through a difficult book, and reading it spins off ideas every which way. The current chapter makes much of the concept of "selection-for", in the sense that physical traits manifest a direction imposed on natural selection so as to make a creature optimally adapted to its environmental niche. The notion of selection-for is advanced as a weakness of Darwinian (or Neo-Darwinist) evolutionary theory.

This illustrates a profound misunderstanding of natural selection. Darwin invoked artificial selection, which has produced hundreds of breeds from a few species of wild stock (such as Dobermans, Mastiffs and Pekingese from wolves), and used it as the basis for his introduction of natural selection. The problem is, one is purposeful, the other purposeless. So Darwin, if he leaned too hard on this analogy, as many say he did, left himself open to criticism. The core concept is this: artificial selection is purposeful, driven by conscious entities, and is indeed a series of selections for variations in traits that are desired by those entities; natural selection is selection against variations in traits that are less advantageous to the reproduction or existence of creatures as they cope with their environment.

The heart is used as an example. Two characteristics we might point out are that it pumps blood, and that it makes "lub-dub" sounds. Extreme adaptationism is held up as a straw man who says that both characteristics must have been selected for, because they both exist. I don't know anybody who believes the heart sounds were selected for explicitly. Natural selection is not influenced by possible futures; it cannot have "known", half a billion years ago, that one day doctors would listen to heart sounds to discern the health of their patients! The sounds are a side effect of the heart's action, just as the slapping sounds of your feet on the pavement are side effects of running or walking.

As a matter of fact, I suspect that loud heart sounds were selected against, because they'd make an animal more easily detected by a predator with good hearing. The present level of heart sound is a compromise between the energy needed to circulate blood and the risk of a predator hearing it happening. Perhaps this is why, though fight-or-flight terror causes the heart to race and get louder, total shock makes its beat weak, fluttery and almost silent.

A key point I have very rarely seen addressed, which is so far not mentioned in the book either (I'm halfway through), is that every creature is a work in progress. Evolution isn't finished with us yet. A few items in human evolution that I can think of off the cuff:

• Wisdom teeth. Many people have a mouth too small for them to fit, and have them removed (at least in the developed world; in poor places they just eat poorly and cry a lot). And some people are born with three or fewer, or even none. So if there were no dentists, never fear. In 50,000 years few people will have wisdom teeth anyway.
• Lower back pain. The back has been changing for the 2-3 million years that hominids and humans have walked upright. It is still changing. People 50,000-100,000 years from now will have a very different posture than we do, and there won't be any more chiropractors.
• The appendix. It serves an immune function in most mammals, but primates have a more efficient immune system and it is not needed. Its tendency to become infected, if there were no antibiotics or surgeons, would lead to its gradual elimination. As it is, however, future monkeys and apes are likely to have no appendices, but humans still will.

Selection happens all the time. When an environment has been stable for a long time, the creatures are well adapted to it and to each other, but still some more, some less. Creatures in a stable environment display a narrow range of variation. Let instability come in, and the resulting stresses will increase the variation in all the species, because of variable responses to stress that were masked when stress was low. The death rate will increase as larger numbers of creatures succumb; those that die were well enough adapted before, but closer to the edge than most. Now they are "unfit" for the changed environment and get culled. Meanwhile, generation after generation, mutations at every level continue to introduce new variations, some of which survive and reproduce better than others, leading to genetic drift "toward" adaptation to the new environment.

Introduction of a species into a relatively empty environment leads to adaptive radiation, like that seen for Darwin's finches. At one time, there were no birds on the Galapagos Islands. At some point a breeding colony of finches was established. There was variation in this population, and the plethora of kinds of food available led to variation in the finches. But it worked like this: pre-existing variations in the strength of the beak made some finches prefer grass seeds, while others could eat tougher seeds. Perhaps at first there was so much "easy food" that they all ate that. But of course the population outgrew the easy food source. The birds that could survive on the different foods gradually became several species, each adapted to a diet different from the others.

There were side effects to this. The finches that needed the strongest beaks, which were of course the thickest beaks, became physically larger. It takes a bigger body to support the heavier, larger skull needed to energize a real nutcracker of a beak. Larger body size wasn't "selected for" all by itself. It was part of the package needed to exploit the largest and hardest seeds.

It can be said that life is the ultimate energy filter. Energy from the Sun mostly just radiates to the edge of the Universe. Some strikes the Earth, energizing its biosphere. Left to itself, the Earth would absorb the radiation and re-radiate it at a longer wavelength, mostly to the edge of the Universe. But Earth is not a passive, vacuum-immersed globe. It has an atmosphere full of greenhouse gases such as water (by far the most efficient one). Just the presence of this wet atmosphere changes the energy flow, shifting the temperature of Earth's surface to a new equilibrium, some 30°C warmer on average, but with a much smaller total variation, compared to the vacuum-wrapt moon.

Then life gets involved. Chlorophyll converts some of the light energy into electric charges, enough to promote a chemical reaction that converts oxygen and carbon dioxide into carbohydrate. It incidentally reduces the planet's temperature a couple of degrees in the process. Chlorophyll-bearing plants, algae and cyanobacteria are eaten by animals (and protists and certain bacteria). And, of course, animals eat all of the above, up to top predators that are typically eaten only by scavengers and "decomposers" when they die of elderly infirmities.

Consider an early Earth, with lots of energy flow but little life, yet. The environment seems poor, but is actually rich for the creatures that exist. There is more energy available than they can make use of. Easy sources are used first. The population grows until all of the easiest source is taken. Those creatures that, because of chance variation, can exploit less easy sources, gradually become new species. Over time, at any trophic level, this leads to broad, rich niches becoming narrower and narrower, and species multiplying. This picture is complicated by all the side products of these burgeoning species, which provide energy to creatures that could not have existed before (lots of these become parasites).

No matter where you start looking at the situation, whether today, or during the age of dinosaurs, or a billion or two billion years ago, the central fact is that this is a situation of profound disequilibrium. If all humans were to leave the Galapagos Islands, and keep it quarantined for a million years (we should exist so long), there would then be more finch species than there are today, each zealously exploiting a narrow niche defined by food source. There would also be more species of most kinds of the creatures there, perhaps even of the giant tortoises.

Every one of those species would be a work in progress: well adapted to its niche, seemingly optimally so. But look beneath the surface. Finch species A's population is expanding, putting pressure on Finch species B, which doesn't quite eat the same sort of seed, but there is some overlap of food source. Over time, Finch species B could change, maybe just a little, so it can better withstand the competition from A…or it faces extinction. More likely, a sub-population from either A or B may begin to specialize on the "overlap" food source, and eventually lead to a new species, muscling out both A and B from it, until both of them quit using it (At that point, A and B may have become new species, replacing their former selves; there's more going on than just food preferences here).

Well, I've come far afield with this selection-for rant. This is the take-away. Every species is a work in progress, no environment is totally stable, and tomorrow will be different from today. Natural selection is our name for the differential death rate between variations that can either more easily or less easily take advantage of the resources provided by the present environment. Its partner, mutation, requires a rant of its own (Oh, goody! Now I have a subject for tomorrow or the next day).

Chronoclines

kw: evolutionary theory

A cline is a gradual variation in something. For example, the thermocline is a change of temperature in the ocean, and is used specifically to refer to a range of depth in which the temperature change occurs at a greater rate, or in a reverse direction, than in most of the ocean.

A chronocline is a change over time, a change of some measurable character. For example, the average life span in America had changed from about 35 to more than 70, in the past 200 years. Much of this change occurred in the 20^th Century, because of improved public health and the development of effective antibiotics. One could call the past 100 years a cline in American life span.

In evolutionary theory, clines are an important concept. The factors that underlie evolutionary change are

• There is variation within a species and new variations arise continually through mutation,
  
• Some varieties leave more offspring than others, and
  
• Most individuals die without leaving offspring.

Only for humans and for some domestic animals do a majority of the members of a species leave offspring. With the three factors listed above, we would expect that a species will be either well adapted to its environment, or that the mix of varieties will change over a few generations to improve a mismatch. For example, if the average climatic temperature falls by a few degrees (the beginning of an ice age, perhaps), we might expect that the fur of mice or lemmings will get thicker and the animals will tend to get fatter in the Fall (or the animals may die out in that area if the change is too great for them to adapt).

Looked at another way, in any population of mice, some individuals have thicker fur than others due to natural variation. In a stable environment, the "average" amount of fur is the best, and large variations tend to get weeded out. Nonetheless, there is some natural range. Now, suppose we have that drop in temperature. Previously, the mice with the thickest fur were a little more poorly adapted than the "average" mouse. Now, they find themselves with an advantage. They survive winter better, and are the ones leaving the most offspring. Within a few generations, there is a new average, and those whose fur matches the former average are now somewhat disfavored.

If temperature changes gradually over many generations of mice, we might find that, when the environment stabilizes, the range of fur thickness is completely different from what it was earlier. The cline in temperature was followed by a cline in fur (and other characteristics, no doubt). Now, were you to compare a group of mice collected "today" with a group collected before the temperature changed, you might think they are a different species. But if groups of mice were collected from every generation, a gradual change would be seen.

Now, suppose we are talking about mouse fossils, and all this happened thousands or millions of years ago. Fossils are poor samples of the biodiversity of an area. But if we get enough samples, it is sometimes possible to trace variations like that described. However, fur doesn't fossilize except very, very rarely. Bones and shells fossilize, so things that affect the shapes of bones or shells are what we have to work with.

Disclaimer, this is a made-up example, for simplicity. It is based on a real example described by one of my geology professors.

This cliff is like many limestone cliffs, with various layers that weather differently. The limestone in the middle has a more resistant layer above, and a less resistant layer below, so we get an overhang. Within the middle layer, there is also a gradual change in the amount of silt and clay from bottom to top.

If you were to collect fossils from the three spots at the ends of the arrows, you might find shells such as those shown. Ideally, you'd collect a few dozen shells at each level so you could study variation within each population. Then, that population with 19 ribs might be seen to vary between 16 and 22 ribs, though 80% of the shells collected have either 18, 19, or 20.

Side note: the next ten times you eat an orange, first count the segments. Clementines (Mandarin oranges), for example, have an average of 11 segments, but the range, in my experience, is from 8 to 13.

Now, if you stop with three collections, you might conclude that these shells represent three species of Pecten (scallop). However, what do you think you'll find if you collect at two more points, one above the middle and one below; or if you collect a dozen shells at each foot of height up this layer (perhaps twenty collections)?

If this represents a cline, you'd find that the average would vary along a trend. Then instead of three species, there would actually be one clinal species, a chronocline. Now, the question to ask is, how common is such a situation? It is actually rather rare, for two principal reasons. Firstly, it is rare to have a continuous exposure of fossil-bearing rock that encompasses a slow, gradual change in environment. Secondly, what looks like a climate-cline may really represent the sideways shift of an environmental boundary area.

For example, if one beach is mainly sandy and down the beach a mile you have mainly mud, somewhere in the middle there will be a mixed sediment. If a growing delta gradually mixes in one sediment, a vertical section in the middle will appear to be clinal, and in a sense it is. But the shells found in the sediment will probably not form a chronocline. Instead, one kind of shell is best adapted to sand, and another to mud. If mud encroaches, you'll get gradual invasion of the second kind of shell, while the first kind retreats to sandy areas. For a chronocline to form, you need a change of environment that is widespread enough that the critters don't have anywhere to go, and it must be slow enough that the population can shift. Even then, a population will tend to remain stable until a large proportion of its members are overstressed by the change. The smaller a population is, the more rapidly it can generate new varieties and the more quickly favorable new varieties can take over.

To summarize: a chronocline illustrates how one species might gradually change into another, but it is rather arbitrary where to put the boundary. Environments and fossil formation seldom "cooperate" so as to leave a clinal series of fossils. A cline is one set of evidence that evolutionary change is driven by natural selection.

Green means everything

kw: book reviews, nonfiction, evolutionary theory, plants

In 1980 Plate Tectonic theory was sufficiently established to be accepted dogma (as it still is) but new enough that great uncertainties surrounded nearly every major hypothesis. One entire course was devoted to studying when plate motions began and how plate tectonics might have evolved through time. As I recall, the fact that radioactive heating of the earth was six times greater than now, some four billion years ago, was never mentioned.

However, it is a smaller incident that comes to mind today. In a follow-on course I happened to remark that the existence of life, that is the actions of the biosphere, must have had a great effect on the rates of weathering and sedimentation, and may have actually multiplied the rate at which the continents accumulated. The professor objected to this point strongly, and the debate led, over time, to my receiving a B in the course rather than my customary A. This was but one of two Geology courses for which I did not receive the top mark while in graduate school.

As it happens, for more than half the history of life on earth, the biosphere has consisted primarily of bacteria. But by two billion years ago (and perhaps still at one billion), though the oceans were bluish-green with cyanobacteria, the visible color of Earth's continents was still the grayish brown of completely inorganic soils. How things have changed!

Algae of many colors must have brightened up coastal margins, but it was only with the evolution of true plants that living beings came ashore and began to colonize the land. The green-on-blue look of Earth today, shown here in a GOES-8 image from NASA, illustrates that more than 95% of the biomass is now plant life. In The Emerald Planet: How Plants Changed Earth's History author David Beerling explains the part plant life has played, primarily over the past half billion years, and argues for a greater understanding of plants as one of the great driving forces of planetary evolution.

Plants harvest sunlight and so form the basis of all non-bacterial life on earth. So imagine a planet without them, and perforce, without any animals either. Oh, there are perhaps stromatolites in the ocean shallows, and similar bacterial mats in pools and streams of fresh water. But the land surface is no different from that of Mars: brown or reddish-brown, sandy and dusty, or gritty-muddy on a rainy day (as Mars's land would be if it would ever rain there). The cloudiness of the skies might be quite different...I can't say just how. But there would be probably ten to twenty times as much carbon dioxide in the atmosphere, and at most one-third of the oxygen seen today. This bacterial world would be much, much different.

However, I would make one change to the book's title: ...How Plants Determined Earth's History. This is not too strong an expression. For most of the past half billion years, particularly since the evolution of leaves about 450 million years ago, plants have covered much of the land, greatly increasing weathering rates with organic acids, yet holding soils so that bulk erosion rates decreased even as chemical erosion increased.

Carbon dioxide has been successively drawn down, though not at a steady rate. Rates of volcanism are a primary driver of CO₂ production, and particularly during the Carboniferous and Permian, this fertilizing gas was produced at much greater rates than at present. In addition, plant remains were being incorporated into sediments at unprecedented rates, which led on the one hand to the Coal Measures, and on the other to a much greater level of Oxygen in the atmosphere, and thus to a higher atmospheric pressure.

Various studies have confirmed that oxygen, which today forms one-fifth of the air, was greater than one-third some 300 million years ago. The nitrogen amount was the same, so this thicker, energy-rich air supported an age of gigantic insects, such as the three-foot wing span dragonfly Meganeura. A gigantic mass extinction episode 250 million years ago nearly eliminated the biosphere, and put an end to the era of big bugs.

200 million years later, the continents were differently configured, and various factors combined to add "extra" greenhouse gases such as nitrous oxide and ozone to the lower atmosphere, multiplying the effect of a rising amount of carbon dioxide. This "Eocene optimum" (optimum for who? I wonder) produced alligators in arctic and antarctic areas, and tropical forests that, paradoxically, had to survive months-long winter darkness, but not winter cold. The average temperature of the planet was 18°C greater than today, primarily because of greater polar warmth.

Finally, the evolution of C₄ grasses, which use a more effective type of photosynthesis, led eight million years ago to the spread of savannas in place of dry land forests, and into some semi-arid areas that could not be forested. The author does not mention this, but I wonder if the spread of savannas led to certain chimp-like apes finding it beneficial to stand upright, so they could see over the grasses. Chimps today live in the forest, where there aren't tall grasses to overtop; they would gain little advantage by standing up. Is Grass a parent of Humanity?

And a final question: Is the current series of Ice Ages fundamentally a result of the great draw-down of carbon dioxide that began eight million years ago, and if so, will it continue until the Sun heats up enough to overcome it? Our "global warming" fears ought to center not on the gases we emit, but on the Sun on which we depend.

So whattaya get for being nice?

kw: book reviews, nonfiction, evolutionary theory, altruism

"...for scarcely for a righteous man will anyone die, though perhaps for a good man someone would even dare to die." (Romans 5:7)

Would you die for another? Have you ever taken a risk for another's sake? Why would anyone in a right mind do so?

Altruism is defined a number of ways. To some, it means taking a risk, even risking death, for no apparent return or recompense. To others, it means working to benefit others at some cost to oneself, though in a social setting where "what goes around comes around." To others it is being good when you don't have to.

I've worked as a lifeguard. There is nothing like saving a life...what a rush! But, wait a minute!! Where does that rush come from? It's a chemical reaction in my brain, which means there are genes that produce proteins that give me this towering feeling when I do something heroic. Why would such genes ever evolve? What's in it for them?

What, indeed? It doesn't take much looking to find that most animals—at least the warm-blooded ones we can sort of understand—engage in caring behaviors, not only with family members and other kin, but with unrelated acquaintances. Caring for kin one can understand; it helps more of those carrying at least some genes that match yours have successful offspring. And, the social environment tends to help all members toward reproductive success.

But in social insects, we find the majority of members of species such as bees and ants perform all the grunt work for their colonies, with no hope of reproducing. How could such species evolve in the first place?

Darwin puzzled over this, and proposed only partial answers. Many, many others have done so since, and today we actually have a mathematical theory, part of which is expressed as "I'd die for two brothers or eight cousins." This reflects the fact that your siblings each contain half the same genes you have, and that a cousin shares one-eighth of them.

The 150-year saga of the theory of genetic altruism is ably presented in The Altruism Equation: Seven Scientists Search for the Origins of Goodness by Lee Alan Dugatkin, a Biology professor in Louisville.

The author focused his investigation on the four primary British evolutionary scientists—Charles Darwin, Thomas Huxley, J.B.S. Haldane, and W.D. Hamilton—, two Americans—Warder Allee and George Price—, and the Russian prince Petr Kropotkin.

Darwin made a strong case for altruism, and behavioral tendencies in general, being just as subject to natural selection as any other traits, though he frankly didn't know quite how to prove the point. Little did he know how long it would take.

Huxley and Kropotkin were exact opposites in viewpoint, largely because of their own formative experiences. Huxley, raised in crowded poverty, in a violent milieu, promoted "Nature red in tooth and claw", using the metaphor of gladitorial combat for the struggle for resources. Kropotkin, raised with more privilege, but experiencing Siberian living for many years, saw cooperation on every side, and promoted "mutual aid" as the way members of most species gained a greater share of resources; for him, the struggle was against the environment, not against one's fellows.

Haldane, Allee, and Price each added their piece to a mathematics of the tendency to help others, but it was left to Hamilton to develop the theory in full form. Now it is a commonplace that any of us shares almost exactly half of the genes of each parent, the same proportion with each sibling. Half-siblings share only a quarter, and so on...at least in "outbred" populations. I'll consider inbreeding in a moment.

The basic equation is very simple: if c is the cost of an action, b is the benefit that accrues from it, and r the relatedness one has with the object of the (beneficial) action, then whenever br>c, the action is more likely to be performed. If there is a gene (or a gene complex) for altruism, this equation shows how it takes care of its own survival.

For example, it may be that swimming in icy water to save a sibling entails a risk of 1/10 that you will instead lose your life. The cost is 0.1. The benefit for a successful rescue is 1.0 to the rescued sibling. The relatedness is 0.5, because half of your genes will be preserved because of the life you save. Thus br=0.5, which is greater than 0.1. Should the risk (icier water, a longer swim, fast current) cause the cost to approach 0.5, you are more likely to have second thoughts.

The math required to actually determine r can be quite complex, particularly in inbred populations. For example, I have an ancestor who was born on Nantucket Island, then left for North Carolina in the 1700s. He was of the sixth generation from the founders. Nantucket was founded as a Quaker colony by ten families in the 1620s. A generation later, a few more families came, and their parents (in the Old Country) were of the same generation as the ten founding families.

This ancestor of mine, named Joe, had 2 parents, 4 grandparents, and so on, back to 32 ancestors of the founding generation. Of course, ten couples only provides twenty ancestors. As it turned out, he was descended from only seven of the founding families, or fourteen in that generation. He was also descended, in the fifth generation back, from three couples of the later comers, or six couples from the Old Country in the founding generation, for a total of 14+12 = 26 unique ancestors. Thus among his ancestors were a few sets of cousins who married.

As it happens, his parents were third cousins, his father's parents were second cousins, and one of his mother's ancestor-couples were first cousins. I haven't gone through the math, mainly because I haven't looked at Hamilton's work in detail to figure out how he would do it. But, I'd guess that, if 32 unique, unrelated ancestors produces a relatedness among two siblings of 0.5, then 26 ought to boost that to about 0.6. Thus, inbred populations will have larger r factors, and should exhibit increased altruism.

This is exactly what we see, in humans and animals both. At its most extreme among mammals, a naked mole rat is found to share 0.8 or more genes with any random colony mate, which is greater than the 0.75 found among the sterile workers in social insect species. So it is no surprise that these mammals have a social life more reminiscent of ants than of other mammals.

Well, all of these are fun facts. There is another side, thought, that the book scarcely mentions. Altruism toward strangers cannot be of the same source as kin-based altruism. Herewith, my own thoughts:

In old Western movies, we see everyone is really polite, because everyone is armed, and frequently, quick to take offense. Lack of niceness is likely to be answered with hot lead. Today, the situation is the same in many inner cities, but even in the suburbs, the chance that a random person who takes offense might take a poke at you is a pretty good reason to be at least polite, and better, helpful if requested.

Secondly, what goes around comes around. Those who are known for helpfulness are more often helped by others, even those less disposed to be helpful.

And thirdly, there must be some gene complex that produces variable amounts of altruistic-toward-strangers behavior, to account for the rush I felt whenever I saved someone's life or health. Some people have more—and thus are more likely to work in a "helping profession" like medicine, nursing, or the ministry. Others have less, and among these we find variously unpleasant people, the jerks we dread, for example, or the perennial moochers, and of course career criminals and psychopaths.

Just as the offspring of two tall parents are likely to be tall, but vary a lot in height anyway, the offspring of two "good" (or two "bad") parents may be similarly disposed, but will vary from one to another. A case in point, my own family:

First, height: Father 6 feet, mother, 5'6" (tallish). Four sons: 6 feet, 6'2", 5'8", 5'9" (not in birth order).

Second, "goodness": Both parents from ardently Christian families, raised to be helpful folks, and they really are. Four sons: all tend to be helpful, but they vary quite a lot (I will go no further...).

I suspect there is thus another factor in Hamilton's equation, call it t, for the tendency to be helpful. It ranges from zero to infinity. Then if tbr>c, an altruistic action is likely to be carried out, otherwise, unlikely. Where t is around 1.0, the "hamiltonian" situation ensues. Real jerks have t less than 0.5, while others have t of 2 or 3 or greater, so that "everyone is like a brother." Considering that r is never really zero (we're all descended from Noah, way back when!...or from a small pool of early humans), we all have at least a little tendency to help just about everyone.

And that's a good thing.