“KINDS”

“KINDS”

The Bible (probably an English translation, like the King James’) uses the word “kind,” as in Noah took two of each kind into the Ark. At least this is the English translation of a Hebrew word and Creationists have used this word as some sort of synonym for species. Creationists claim that God1 created each kind of organism and each is fixed and immutable. One kind does not evolve into another kind, this seems to be the closest to a definition that you can get. Some Creationists have accepted that some evolution does (or did) occur. They will accept that a small bit of change can occur (something like what evolutionists call microevolution) within a “kind” so that each kind may more perfectly fit its environment. God, or the Designer, has permitted this variability for the benefit of His/Its creation.

However, one kind still cannot evolve into a different kind (what some evolutionists think of as macroevolution). This is where things get confusing, Creationists never clearly define “kind,” beyond one kind cannot evolve into another kind. This is unlike scientists who do try to define “species” and are constantly discussing it, and use it fairly consistently. You cannot test their claim that “kinds” do not evolve into another kind because they do not define the term or use it in a consistent manner from which one can construct a definition. The only consistent thing seems to be that humans are one “kind” and apes are another.

“Kind” does seem to be used as a synonym for species and a kind can evolve enough to be called a subspecies. But if you start discussing real life examples (e.g. Darwin’s finches, lions and tigers, horses and zebras) maybe “kind” is not species but genus which can change enough to be a new species within a the genus. The genus Equus evolved into Equus caballus, E. burchelli, E. zebra, and E. asinus, etc.). Or maybe it is a family like the Felidae, the cat family. Felines include at least 37 species in four genera.2

Kind is used in a relative way: relative to how much evolutionary change has to be accepted, the “kind” expands or contracts so that no matter how much change there is it is only within the confines of a “kind,” never one “kind” evolving into another “kind.” With the proviso I mentioned above that apes are always a different kind than humans, who are always a separate “kind” from all other organisms. Even if the “kind” is a family level (i.e. cats/Felidae) and includes as much or more difference as in the Ponginae family—the apes—gibbons, siamangs, orangutans, gorillas, bonobo, chimpanzees, and (to some scientists) man. Others prefer to put the orangutans, gorillas, bonobo, and chimpanzees, in Homininae, with man. And of course. there all those fossil species.  Kind is used in a rather amorphous way that prevents it being of any use, except to avoid being pinned to a single concept that is indefensible without admitting to there being evolution.

1 Intelligent Design proponents and Creation Scientists claims that a “designer” created each kind. But “designer” is a linguistic subterfuge to avoid be called a religion based theory. But make no mistake they are talking about God: a Christian, Biblical God.

2 Felis—the small cats: wild cats, domestic cat, lynx, bobcat, puma, caracul, etc.; Neofilis—the clouded leopard; Panthera—the big cats: snow leopard, tiger, leopard, lion, and jaguar; and Acinonyx—the cheetah. Then there are the extinct cats: the saber-tooth Smilodon, Machairodus , Homotherium Megantereon, etc.

GEOLOGIC TIMESCALE

GEOLOGIC TIMESCALE

 

It should be noted that neither Cuvier or Smith was an evolutionist, and the and the principles of relative dating do not require evolutionary theory as part of the framework.                                          —Bruce MacFadden 1992:123

When geologists and paleontologists talk about the age or time of fossils or rock formations, they use words use words like Pliocene, Upper Pleistocene, Devonian or Jurassic.  This can be really annoying.  I mean what is a Pliocene?  Jurassic has something to do with dinosaurs (actually T. rex was Cretaceous). That is unless you are like me. These words have a meaning to me, like how long ago and for how long of a time.  Pliocene and Pleistocene are periods of time the geologists and paleontologists use. If you understand something of the meaning this blog will be more understandable to you. So we need to talk about how geologists and paleontologists measure time and name it. Geologists use two different time scales:  relative and absolute.  I am going to discuss relative time here.  Absolute time, and how it is determined, will be the subject of another post.

We measure time by clock and calendar. Minutes and hours make up days and days form weeks, months and years. We’re all familiar with this system and generally number our years based on the date of the birth of Jesus (the A.D., anno Domini, and B.C., before Christ, that are sometimes used with the year number). But there are other ways of numbering years. The Muslims use the date of the Hegira (July 16 622) as the year one. Other cultures have used other methods, e.g. the years since the accession of king, emperor, or pharaoh. There has been a trend to recognize the Christian bias of the common numbering system and use C.E. (Common Era) and B.C.E. (Before the Common Era).

Whichever year numbering system is used, they only work for events we have a record of and can determine how many calendar years have elapsed between them and now. (The calculation of the year Jesus was born was wrong so the Christian calendar is off by several years). Even at that, records may be inexact and no precise determination can be made. Then we have “dates” for events like: “in the 11th century B.C.” or “sometime before 960 A.D.” For prehistory (by definition before the written record) we have no way of measuring time by consulting a clock or calendar. We must use other means of determining time.

Whether you are aware of it or not, you use two forms of time: absolute and relative. An absolute date is one like your birth date or the Battle of Hastings on Saturday October 14, 1066 A.D. (or C.E. if you prefer). The Magna Carta was signed after the Norman Conquest because the date of the signing is after 1066, and if you look up the date (June 15, 1215) you can figure out just how many years elapsed between the two events (149 years). An absolute date can be considered as a date fixed in time at a precise point. It is possible to determine how many years (or minutes or hours if the time is figures that precisely) have passed since the event occurred.

Relative time is not a date or time interval that is known with exactitude. Before, after, long ago, recently, or short time before are terms that may be used to describe when an event occurred or how much time has elapsed relative to some other event of date. The Magna Carta was signed after the Norman Conquest. A long time elapsed between the building of the pyramids and the landing on the moon; and Columbus rediscovered the Americas between the two events. Relative time does not use calendar dates. Without knowing when William the Conqueror invaded England or when King John signed the Magna Carta we can determine the chronological sequence of the two events simply by knowing that King John was a descendant of William the Conqueror. Anything King John did must be later in time than anything William did. However we don’t know how long after,even if we know how many generations are between the two (William was the great-grandfather of John). You can estimate how much time might have elapsed between the two, but you won’t know exactly how much time or be sure how accurate the estimate is. We use relative time a lot, as in: “it was late last summer before Labor Day.”

If you looked at the rocks, particularly if they formed a cliff, you would notice the the rocks at the bottom had to have been present before the rocks above were deposited and therefore the lower rocks had to be older.passage of time. The sequence of rocks represented the passage of time, just how much time they had no idea.   Some thought that each strata of rock was the result of a single depositional event, say a flood, and might represent a few days or months. Others thought that the strata represented continuous small-scale deposition over hundreds, thousands, or tens of thousands of years.

When they examined the fossils contained in the rocks they discovered the fossils of animals, mostly unknown in the present world. Using the sequence of fossils, “index fossils,” and the stratigraphic sequence of rocks, geologists were able to correlate rocks across Europe and eventually most of the world. Without knowing how old a rock was or how long it took to deposit the rock (how much time the thickness of the rock represented) they could say that one rock strata in one place was the same age as, older than, or younger than the rock strata in another place. The rock units represented an interval of time and they could determine the relative age of the units.

As the science of geology developed in the last half of the 18th century and early 19th century, geologists developed a time scale.  People realized that the same type of rocks did not always underlie the soil at the surface every where. different rocks were often exposed in different places.  One of the first attempts to explain why there were different rocks and why they changed depending on their location in the rock column was based on the story of Genesis in the Christian Bible.  It was proposed that the rocks had settled out of the primordial ocean, probably on the third day when God created dry land.  The hypothesis was that the rocks had been deposited in the order of their density, heavy rock like basalt and granite had been first, followed by others such as limestone, sandstone, shale, etc.  This scheme did not last long as it became obvious that in places sandstone and shales were inter-bedded in multiple repeating sequences.  The rock types which should have been deposited all over the earth at the same time, in the same sequence, were in fact in deposited in different order in different places.  In France, there was even an area where basalt, which should have been at the bottom of all the rocks, was on top and even looked like it had flowed across the land and even filled existing river valleys. The rock strata indicated that the rocks had formed and been deposited in some other fashion.

Several schemes were developed to organize the rock sequences and the time the represented, so that geologists could hold intelligent discussions that didn’t bog down over describing time in cumbersome terms (e.g. Formation X is about as old as Formation Q and both are older, really, really older than Formation J but not as old as Formation Z). Stratigraphic sequences, chosen from areas where they were well defined and with distinctive fossils, were used as “type formations” to represent a specific time interval. Most of these were given a name generally based on a Latinized name for the region or former inhabitants of the area: the Cambrian from Cambria, the Latin name for Wales,  Devonian for Devonshire, England, Silurian for the Siluries, an ancient Celtic tribe, or Permian for the Perm Mountains in Russia. So, now all you needed to say was that Formation X was early Devonian and everyone could figure out how old it was relative to all the other formations.GSA Geologic Time Scale

The largest geologic time unit is the Era, Eras are divided into Periods, and Periods into Epochs. There four Eras. The Eras are divided into from two (the Cenozoic Era) to five Periods (the Paleozoic Era). The Periods are the commonly used time units except in the Cenozoic Era where the Epochs (seven) are the commonly used time units.  Almost all fossils of mammals occurred within the Cenozoic, so much so that it is also called the Age of Mammals. The appearance of humans occurred in the Cenozoic, actually very near the end and extending into the following Quaternary and Holocene.

Attempts were made to estimate how much time was actually represented by the rocks and how old they were. Figures of 10, 15, or 50 million years were put forth. But it wasn’t until the discovery of radioactivity and radioisotopes that the guess work was replaced by more concrete data and absolute dates could be calculated for the relative time units. I will discuss some aspects of radioisotope dating in a further post on absolute dating methods, but for now, all that matters here is that the radioisotope dates confirmed the sequences determined by both the stratagraphic position and fossil correlations.

Because fossils were used to correlate rock units and to determine the relative age of the units, only those rock units that contained fossils could be dated. The age of non-fossiliferous rocks could only be estimated based on what fossiliferous rocks they were above, below, or between. Underneath all the fossiliferous rocks were entire stratigraphic sequences of rocks which had no fossils because they were believed to have been deposited before there was life on earth (at least before there were life forms with hard parts that would fossilize). These strata (often known as basement rocks) represented an unknown amount of time and, it was believed, vast amount of time (since the Cambrian rocks that overlaid these basement rocks were believed to be the oldest rocks fossiliferous rocks, the rocks below them were called Precambrian).

You may have noticed, although more likely you didn’t, that I have never mentioned the word “evolution ” or “evolved.”  Nothing that I have talked about here requires that there be evolution and as mentioned in the epigraph at the beginning of this post, the early practitioners of relative dating did not believe in evolution.  In fact, relative dating does not even require that fossils be the petrified remains of once living organisms (animal or plant). Only that most fossils have restricted range in time.  They appear in some rocks for a time, disappear, being replaced by other fossils and do not reappear again. I qualified this statement to say most fossils because there are some organisms that have appeared in the fossil record, then disappeared, only to be discovered alive and well.  The coelacanth fish is an example.  These organisms are often called “living fossil.”  The horseshoe crab is another.

 

 

THE TAUNG CHILD: AN IMPLICATION OF ITS AGE

THE TAUNG CHILD:

AN IMPLICATION OF ITS AGE

By Patrick Light

I spend much time outdoors, not as much time as I would like to spend, and maybe not as much time as some people think I do, but still, more time than most people do. On several occasions I have looked at the equipment I carry with me, what little I sometimes need to live comfortably enough in the woods, and I have thought how little it is that we actually need. How simple it can be to satisfy our basic needs. I have also realized how bound we are to these things, how necessary these things and the knowledge of their manufacture and use are for human survival. This is the difference between us and the other living organisms on this earth.

Several years ago, I listened one day, as an excited gradu­ate student told nearly everyone who would listen about an article he had read. The article explained that recent studies had shown the Taung skull to be that of a three year old child, not that of a six year old child as it is usually considered to be. The original estimate that it was six years old is based on the dental development of the skull compared to standard human development rates. The study mentioned in the article had determined, by microscopic examination of its teeth, that the Taung child was three years of age at the time of its death. It is possible to determine the actual time required for various teeth to form and grow by counting lines formed in the teeth (the perikymata). The article’s conclusion was that the Taung child (and by inference all of the australopithecines) had physically developed, matured, at a much faster rate than do modern humans. The rate of development was, in fact, identical to that of the apes.

The graduate student was quite excited and, it seem to me, disturbed, about the “pongid pattern” of growth and development exhibited by the Taung skull. I have never been quite sure what the graduate student had found so exciting or disturbing. He may have feared that, because of this pongid pattern of growth, the australopithecines would be removed from the evolutionary line leading to Homo sapiens, like poor old Ramapithecus. The idea being that if they developed like pongids, then they must be pongids and not hominids.

I did not find the information particularly exciting, or disturbing. The australopithecines did not have a large brain, so why should they be expected to have an extended, a slower, more human, pattern of growth and development? That the bipedal Taung child was only three years old, but developmentally equal to a human child at six years, further demonstrates the mosaic nature of evolution. It was only later, primarily while writing my thesis, that the full implication of this pongid pattern of growth became apparent to me.

The old concept of the Great Chain of Being still affects how we reconstruct evolutionary scenarios, how we visualize evolution. The concept is based on the obsolete idea that each organism, living and extinct, occupies a point along a single line leading from the most primitive to the most advanced, just like links in a chain. Progression from one species to another is gradual and even, where large gaps exist between living species, the “missing links” are species that are now extinct. In a sense, the metaphor is an accurate description. Each living individual, each of the species can trace an unbroken chain of ancestors back across billions of years to a primordial organism that was the first living organism.

The problem with this concept of a chain develops when a gap needs to be filled in. What did that missing link look like? If the gap is small and there is only one link missing, one inter­mediate step, the missing organism is reconstructed with charac­teristics halfway between the two known species. If the gap is a large one and there is more than one link, the reconstructed species show a shift from primitive to advanced characters proportional to the species position between the two known species. If the reconstructed species is 1/4th of the way from the primitive to the advanced species, its traits are 3/4ths primitive and 1/4th advanced. If it is half way, it is one half primitive and one half advanced. A species 7/8ths of the way toward the advanced species, is 7/8ths advanced and 1/8th primi­tive. This does not mean that 7/8ths of the traits are advanced, but that each trait is 7/8ths of the way toward the advanced state. You can see the results of this, using apes and humans as an example, in the older reconstructions of Neanderthal Man. Since he lies somewhere between the apes and modern man, he is an amalgam of characters both ape and human. In more recent ver­sions, he is placed still closer to being human, but still not quite so. He is slightly stooped, intellectually dull, and not fully capable of articulate speech. The australopithecines, are even closer to the apes and therefore were originally thought of as being almost apes. It has taken much evidence and even more argument to change this view. According to the Great Chain of Being Concept, they should have been only slightly bipedal, slightly tool-using, slightly large brained, slightly hairless and slightly articulate. But they are not, and now, we have gone to almost the opposite extreme. Some recent reconstructions make them into hairy, little humans, culturally and linguistically primitive to be sure, but, nonetheless, very human.

The Great Chain of Being was based on the concept of unili­neal evolution. The apes were not modern species that had evolved from some distant common ancestor with man, but they were that ancestor from which man evolved. They had not changed, had not evolved further, only man had. It was even a fashion for a time to place the various cultures and races of man along the chain, in positions ranging from just slightly above the apes, through various grades of primitive to civilized. Even though the unilineal concept of evolution has been replaced by a multi­lineal “tree of life” concept, the Great Chain of Being concept still affects many of our ideas about evolution.

Earlier I mentioned that, lately, we have gone almost to the opposite extreme in our reconstructions of the lifestyles of the australopithecines. The reconstructions make them are very human, more human, I believe, than the evidence warrants.

Apparently, all the australopithecines matured at a rate equal to the apes. This reduces the amount time available for the brain to grow and for the individual to learn. On the face of it, any reconstruction of australopithecine life that is much different from the apes, that postulates much dependence on tools, on an extended and dependent childhood is probably inac­curate. An australopithecine child was what we would call “extremely precocious.” This is not to say that they were exactly like apes. They were doing something different. They were using their brains in a way that the apes weren’t. Neurolo­gical changes were taking place in the brain, it was being reorganized. This reorganization would eventually make it possible for at least one population of australopithecines to become something else.

What I find most interesting is that there is evidence that Homo habilis had the same rate of development as the australopi­thecines. At first glance, that does not seem sensible. Homo habilis was larger brained than the australopithecines and used tools, even made tools. It would seem therefore, that they should have been developing at a slower rate than the australopi­thecines, much slower, more like Homo sapiens. Yet, I will venture to argue, it is reasonable, even to be expected.

Sherwood Washburn has said: “Changes in behavior occurs before changes in morphology.” The changes in the pelvis, the knee, and in the position of the foramen magnum did not occur to allow the hominid to walk bipedally. The changes occurred because of the bipedal behavior of the hominid. In Homo habilis, the behavior was changing, they were using tools more often, they were becoming dependent on tools, on culture (or symboling, if you prefer) for their survival. They were making behavioral changes, changes permitted by their present morphology. The changes created selective pressure for morphologic changes that improved the organism’s capacity for the new behavior. These morphologic changes allowed for further behavioral changes, which led to further morphologic adaptation, a self-reinforcing cycle. Homo habilis had embarked on a new adaptive trend, one different from the australopithecines, and one that had tremendous poten­tial. Each little shift toward greater ability to symbol gave such immense advantage over other populations that the selective pressure for those adaptations was great. Homo habilis didn’t have a chance. Homo habilis barely shows up in the fossil record before being replaced by descendent, Homo erectus, the culture-bearing animal.

The australopithecines lived like pongids, they were a little more intelligent, a little more capable of problem-solving than the apes. Homo habilis had begun to make changes in their behavior, they were tool-users and tool-makers. They were becoming dependent on culture, on the ability to symbol. The morphologic changes that distinguish man from ape were beginning to appear. However, it is with Homo erectus that the morphologic changes occur with full force. Homo sapiens is just the final polishing to these morphologic changes.

I am not surprised that the australopithecines and Homo habilis matured as rapidly as do the apes. They were only beginning to make those behavioral changes that would lead to Homo sapiens. The changes in morphology related to the extended childhood that is the hallmark of cultural man, would occur afterward, in Homo erectus.

REFERENCES

Beynon, A. D., and B. A. Wood

1987 Patterns and Rates of Enamel Growth in the Molar Teeth of Early Hominids. Nature 326:493-496.

Bromage, Timothy G.

1987 The Biological and Chronological Maturation of Early Hominids. Journal of Human Evolution 16:257-272.

Bromage, Timothy G., and M. Christopher Dean

1985 Re-evaluation of the Age at Death of Immature Fossil Hominids. Nature 317:525-527.

Brower, Bruce

1987 Hominid Headway. Science News 132:408-409.

Conroy, Glenn C., and Michael W. Vannier

1987 Dental Development of the Taung Skull from Computerized Tomography. Nature 329:625-627.

Smith, B. Holly

1986 Dental Development in Australopithecus and Early Homo. Nature 323:327-330.

Tobias, P. V.

1974 The Taung Skull Revisited. Natural History 83(10)38- 43.

HOW THE GIRAFFE GOT ITS NECK

HOW THE GIRAFFE GOT ITS NECK

The idea of evolution was around long before Darwin,1The Origin of Species, or when he started thinking about the “species problem,” it was around before he was born.  What Darwin contributed wasn’t that evolution happened but that it was caused by natural selection. Before Darwin, one of the postulated mechanisms for evolution was the “inheritance of acquired characteristics.” This is often called Lamarckian evolution after Jean Baptiste de Lamarck (1744-1829), a prominent supporter and defender of the concept.

According to the theory, physical characteristics acquired during life by an organism can be passed on to its offspring. By using or not using a body part,2 thus modifying it, the change would accumulate over generations leading to the evolution of a new species.

The classic example is the long neck of giraffes. The original ancestor of giraffes was a short-necked animal, probably similar to the living okapi, which fed on the leaves and twigs of trees. According to Lamarck, these proto-giraffes would stretch their necks in trying to reach the leaves higher up in the trees. Over the course of their individual lives this would cause their necks to become slightly longer. Their offspring would be born with this slightly longer neck. They, in turn, would also stretch their necks slightly trying to reach even higher leaves. Repeated over a number of generations the short-necked proto-giraffes would evolve into the long-necked giraffe we see today.

Darwin would have explained the evolution of the giraffe’s long neck as an example of how natural selection working on a population with variable traits can create a different organism, adapted for a different econiche.

Within the population of short-necked proto-giraffes there were some with necks longer than average, also some with necks shorter than average. Also there was a similar variation in the length of the legs and body size (leg and neck length are in proportion to body size and also absolutely longer in proportion). Perhaps the traits were related and perhaps not. The individuals who were longer necked, those longer legged, and those who were bigger than the average had an advantage eating leaves from trees. They could reach leaves that the others couldn’t. They could eat the same leaves that the other could reach and leaves the other’s couldn’t. In times of drought or anything else that reduced the numbers of leaves on the trees (including large numbers of proto-giraffes), those who could feed on the higher leaves could obtain more food. They were more likely, on average, to be better nourished and to survive famine conditions. The shorter-necked proto-giraffes were less likely to either survive or produce healthy offspring who stood a good chance of surviving. Gould (Bully for Brontosaurus 1991:166) ) discusses this example and mentions that perhaps the long neck was not an adaptation for feeding but a selective advantage in sexual competition. Giraffes fight among themselves slamming their heads and necks against each other. Whether this fighting is for sexual competition or social dominance (which can also have sexual advantages), I don’t know. A giraffe with longer and heavier neck would presumably have an advantage. “Knowing” the way evolution works, longer necks could have been selected for both because they were advantageous for feeding and for inter-specific competition.

Over generations the average neck length, leg length, and body size would increase. These three characteristics, if not already caused by related genes, would increasingly tend to occur together(co-evolution of genes). That is, any proto-giraffe with all three traits would generally do better than one with only one of the traits.

The example of a giraffe3 evolving a longer neck either by stretching its neck to reach higher leaves in a tree, or long-necked giraffes surviving better because they could reach higher leaves than other animals is repeated in many books to demonstrate the difference between Lamarck’s Evolution by the Inheritance of Acquired Characteristics and Darwin’s Evolution by Natural Selection. It is often believed that either Lamarck used the giraffe to demonstrate his theory or Darwin used it show how his theory was different. I have an old biology textbook that calls it “the classic example (though now rather hackneyed).”S.J. Gould (Bully for Brontosaurus 1991:166) believes that this comes from “a few lines of speculation” that Lamarck wrote. And it was about the giraffe’s legs (and he was wrong. A giraffe’s front legs are not longer than the rear). Darwin used the giraffe’s tail and its use as a fly swatter. Further, as Gould notes, there is no evidence that the giraffe’s long neck is an adaptation to eat leaves on the tops of trees. The fact that male giraffes fight by swinging their necks against their opponents, “necking,” and the winner is usually the taller giraffe makes one wonder. But I digress. That wasn’t why I brought up the subject of giraffes and their necks.

I have come across an illustration using this example. It is a series of four drawings of a giraffe standing next to a tree. In the first drawing the giraffe has a short neck which gets progressively longer until in the fourth drawing it is as long as the present day’s giraffe. What really got my attention is that the rest of the body didn’t change. The legs on the short-necked giraffe were just as long as those on the long-necked giraffe and the back had the same sloping line.

The evolution of the long neck on a giraffe involved more, much more, than a simple lengthening of the neck. There were many other changes involved, changes that had to proceed in some sort of coordination with the longer neck. Just how do random mutations coordinate themselves? Must they all happen in one fell swoop?

The neck of the giraffe is quite a bit longer than yours or mine, but for all its length it still has the same number vertebrae (seven) as our necks do. The length is achieved by making the body of each vertebra longer in relation to its diameter. Ours are sort of short, squat and round. The giraffe’s vertebra are long, round cylinders. However that is only a small part of the changes involved in increasing the length go the neck (or maybe the height of the head above the ground).

The greater the distance the head is above the heart the harder the heart has to pump to get enough blood to that head, and then you have the weight of a large volume of venous blood coming back down that same neck to the heart. And the reverse when the head is just about as far below the heart when it is lowered to take a drink of water. A head that might have to be very suddenly and quickly raised to allow the giraffe to escape an ambush at the waterhole by a lion.

A giraffe does have high blood pressure, nearly twice that of us, and a very large heart. The lower part of the carotid artery is very elastic. It expands when the heart pushes a mass of blood into it and then contracts helping to push that pulse of blood further up. The jugular is thick-walled so it doesn’t expand under the weight of the descending blood and it has numerous valves to prevent a reverse flow of blood when the head is lowered. The reta mirabile around the brain has a “bypass” from the carotid to the vertebral artery (for the neck muscles). There is no connection of the vertebral artery to the reta mirabile. This prevents congestion in the fine blood vessels of the reta mirabile by the overflowing of the vertebral artery when the head is lowered. The reta mirabile is also elastic and will absorb some increase of blood when the head is lowered and hold it momentarily when the head is raised. This prevents giddiness. (Unlike one author4 who implies that the reta mirabile is a “special pressure-reducing mechanism . . . provided” solely for that reason and is only in giraffe, it serves other functions and is a basic part of mammalian anatomy.)

A giraffe’s heart beats very fast, especially for an animal of its size. The veins and arteries of the legs are buried in a long, bony furrow, this prevents their swelling and the skin is very tight, not very elastic, and thick (just like support hosiery). So it acts as a”g-suit” to counter the pressure of the blood.

Taylor also points out how a human breathing through an eight foot tube would die because he would never inhale new air, he would simply re-breathe the same air over and over. He says this problem is “intractable” and leaves us to wonder if giraffes don’t breathe.

Giraffes have very large lungs to actually move enough air to get oxygenated air to the lungs. Even so a large part of the inhaled air remains in the trachea and is not used, wasted. The blood has a large number of small red corpuscles, that take up more oxygen very quickly and giraffes have a slow the rate of respiration to more thoroughly use the inhaled air.

The steeply sloping back of the giraffe is not because its front legs are so much longer than the back legs, as so many have believed (including some who should have known better like Lamarck). The front and rear legs are nearly the same length and the spine is nearly level, parallel to the ground. The shoulders of a giraffe are not as high as you might think, the steep slope of the back is due to the very tall spines on the thoracic vertebrae. These spines provide greater surface for the attachment of the enlarged neck muscles and, like the tall pillars of a suspension bridge, a better angle for those muscles to move and support the neck.

So how did all these different adaptations (and more) occur together, in a coordinated system? If evolution is random they can’t have occurred together.

A number of people don’t believe in evolution because they do not comprehend how it can occur, others deny it is true because they say it cannot occur. Others think that there had to be some Intelligent Designer (God) directing the whole thing. The purpose of the following scenario is to present a way, a plausible but not necessarily the way, a short-necked animal (similar to the okapi) could have evolved into a long-necked giraffe with all the different adaptations they have that form an integrated system that works together without being caused by Divine Intervention, direction, or an implausible sequence of random mutations occurring simultaneously.

This is a “thought experiment”and we need to choose a stating point because you need to begin somewhere. We will start with a proximal beginning, the ultimate starting point is with The Big Bang, or whatever was the beginning of the Universe. However this would make things unmanageable, or at least really long. To make things manageable and more to the point we will begin much closer to the point of what we want to illustrate. This is similar to starting a story in the middle and there is already a number of factors (previous history) that already exist and constrain the future. Keeping things manageable is also why we tend to deal with a single gene (or trait). One of the points behind this thought experiment is to show how many genes can appear to cooperate and evolve in unison.

We start with three givens:

1) An animal similar to the okapi (Okapi johnstoni). The okapi is chosen because it is the closest relative to the giraffe and it is similar to known fossil ancestors of the giraffe. It does have a neck that is somewhat elongated and a short body. They currently live in dense forests of the Congo. In the scenario a population of these animals is expanding their range into the more open woodlands.

2) A selective advantage to these animals of a longer neck. This advantage need not be the ability to eat leaves off the tops of trees. After all, maybe giraffes eat the leaves off the tops of tress because that is where their heads are (and maybe they aren’t taller because most trees are not). Maybe males battle between themselves for dominance by “necking” and a longer neck is part of being successful and being dominant leads to greater reproductive success. To a point, the exact reason for the selective advantage doesn’t matter, only that longer necks are part of it.

3) That there be variation between individuals and that it be inheritable. There must be some variation between the individuals o the species and that some of this variation (e.g. neck length, length of leg, size of lungs, heart rate, elasticity of the skin, etc.) be due to genetic, and inheritable, differences. This can be the presence or absence of a particular gene or genes, or the traits that are caused by multiple genes, the percentage of particular genes. Say “tallness” is due to the ratio of “tall” alleles to “short” alleles, the more “tall” alleles an individual has in its genotype, the taller it can grow. Potentially a population can contain quite a lot of variation. There are some 800 breeds of dogs in existence. Most of these breeds are of recent origin. Even the oldest breeds are not much more than 10,000 years old. It does not seem very likely that all the “new” traits that distinguish the various breeds are the result of recent gene mutations. A very large part of the variation within and between the breeds was present in the original canine populations. Man has simply identified various traits and by interbreeding the selected dogs (artificial selection), concentrated the alleles so that the chosen traits breed true and consistently. Although once the genetic variation in a gene pool is exhausted, new variation can only arise through mutation.

At the risk of being accused of making up a “Just-so Story” or, worse yet, of having a plausible scenario taken as factual, I want to give here a scenario of how it might be possible for a number of adaptations to evolve, forming a “coordinated” system. It is not intended to be an accurate account of giraffe evolution or even intended to be how it really did happen. Rather, the scenario is only meant to be plausible, to be a demonstration of a way it could have happened, an analogy to the how it did occur and an answer to critics’ claims that evolution cannot work by “natural” means. Evolution and natural selection can function in a natural way without miraculous of extremely improbable events.

Mostly we construct scenarios as if only one gene at a time is evolving. This scenario deals with multiple traits and genes.

So, beginning with an okapi-like animal, an even-toed ungulate living in the forests of Africa and expanding out into more open woodlands that, for whatever reason, is under selective pressure for a longer neck. Males gain greater access to females by defeating their rivals in head-slamming contests is an adequate selective pressure. In the male social structure dominance is achieved by physical contests between the males and part of the outcome between two males is based on which one is taller. The higher a male ranks in the social hierarchy the greater his access to females and the greater the likelihood of him successfully passing on his genes.

Every population of living sexually reproducing organisms contains an amount of variation (unless they are clones) in its gene pool. Some traits/characters will be closely “fixed,” others will be more variable in their expression. Humans have two hands, each hand has four fingers with three joints and one thumb with two joints. The vast majority any way, so many that two hands with four fingers and a thumb on each is “normal.” I knew a man with two little fingers (one growing off the side of the other) on his right hand (and two little toes his right foot) and someone born with a thumb and only two fingers on each hand (I presume the feet were similar but do not know for certain). Others area born with abnormally long and thin fingers (arachnodactyly) and some with two fingers joined together (syndactyly). These variations are known but generally rather rare. Humans vary in adult height. There is no single height for an adult that nearly everyone reaches that can be considered normal in the same way that two hands is normal. There is a range of variation in adult height and if it is plotted on a Cartesian graph (adult height on one axis and number of individuals on the other axis) the distribution will form something like the standard bell curve. Most individuals will be close the average with fewer and fewer individuals toward the extreme ends of the curve. There may be 7 foot humans but they are very rare, rarer than 6 foot 4 inch humans who are rarer then 6 footers who are much more common but not as common as 5’4″, 5’6″, or 5’8″ humans. Height is due to the effects of both multiple genes and the environment. There is no single gene5 that controls how tall you grow. Height is determined by how fast you grow, how much of the energy resources consumed are committed to growth, how long the body grows, etc. Some alleles will increase the body’s ability to grow taller and others will reduce the body’s ability to grow. We can call these alleles “tall” genes and “short” genes if you remember that they probably have other effects than just on height and that the amount and quality of food consumed and at what stage of growth also determine stature. You might have the genes to potentially grow to seven feet but if you do not get enough food when you are growing you will never reach your potential. Humans shorter than the average have more than the average number of genes that act to keep adult stature short. Humans taller than the average have more than the average number of genes that act to increase growth. If those persons at one end of the curve (the tails) do not contribute their mix of genes (for whatever reason) to the next generation, the proportion of those genes that contribute to that extreme condition will decrease in the gene pool. This will shift the average toward the other end. This is what natural selection is about. It doesn’t even require a total failure to pass on those genes, only a reduction. If those people are one percent of the population but their offspring form just less than one percent of the next generation, the gene pool will slowly lose those alleles.

In a population of proto-giraffes the situation is similar. In the gene pool of these proto-giraffes there are a number of genes/alleles that influence neck length, each proto-giraffe has in its own genetic makeup these genes in a particular mix and therefore a neck of a certain length. I am not saying that the neck length could be one foot, two foot, or seven or eight feet. The variation need be only inches. There is also variation in the length of the legs, the thickness of the skull, size of the heart, elasticity of the veins and arteries, tightness of the skin, etc. A male proto-giraffe may have a neck of average length but a skull that is thicker than average. Because the head is heavier he can deal heavier blows (and the thicker skull can better withstand the impact) to his opponents and achieve a higher status than other average-neck-length-males. He has a combination of genes for short and long neck (they average out to medium) and genes for a thicker skull (more genes for a thick skull than thin). He mates with one of more females with their own combination of genes for short and long necks and thin or thick skulls. Their offspring gets genes from both. The mother is more likely to have had a slightly-longer-necked-than average father and so the offspring is more likely to have a longer neck genes and thicker skull genes than others of its generation. This combination of slightly longer neck and heavier skull is more advantageous then either alone. The proportion of these genes in the population’s gene pool begins to increase. Not only does the proportion of them increase but the proportion of them occurring in the same individual increases. Necks get longer and skulls get heavier throughout the population. Now even longer necks and heavier skulls are favored. A gene pool can contain a very large amount of variation. The gene pool of proto-giraffes may already contain enough variation in the population of six foot high animals to grow one (with all long-necked genes) that is 18 feet tall. That is conceivably possible, however it is not necessary.

The neck would lengthen and as it does so the need would arise for the means of getting the blood to the head, dealing with the added pressure, stronger muscles, adequate surface to anchor those muscles, and what we may call the side effects of an elevated head—the longer trachea, the great difference between the raised head and the lowered head, etc.

All the differences between an okapi and a giraffe that make the giraffe’s longer neck and elevated head possible had to have either already existed in the gene pool of the proto-giraffe or “appeared” (by mutation) in it as the proto-giraffe evolved into the giraffe. There is a limit to how long the neck can grow and the legs lengthen (remember it is not the length of the neck but the height of the skull above the ground that really matters) before all these ancillary/supporting changes also need to exist.

With longer necks and legs being more advantageous to the population, the average length of the necks and legs would increase until some point where the gene pool’s supply of long neck/leg genes is either exhausted of the taller giraffes begin to have problems with inadequate oxygen in their lings, low blood pressure, weak necks, swollen ankles, etc. The selective pressure for longer necks still exists, a longer-necked male giraffe would still be at an advantage over shorter-necked males if he had the stamina to run long enough and fast enough to escape his predators, if in swinging his neck up from drinking he didn’t pass out, if his circulatory system didn’t keep losing blood to seepage in his lower extremities. All these and other “ifs” had to be coordinated6. The available variation in the genes of the length of the neck might be the limiting factor, but it might be the ability of the heart, or lung capacity, the height of the neural spines, the elasticity of the arteries/veins. All these factors are involved and the gene pool does not contain some variation involved with these. These form limiting factors, once the variation was exhausted, further selective pressure would have little effect except to maintain the change. Little effect until a mutation in any one of these genes permitted further increase until another limiting factor took effect. Then again things would halt until another advantageous mutation occurred. Evolution is not a gradual, smoothly continuous process, it will go in “fits and starts.” It can be gradual and smooth if all the needed genetic variation is already contained in the gene pool. If it isn’t, change has to await a useful mutation. Changes hits the end of available, stops, a useful mutation occurs, change resumes, uses of the new variability, stops, time passes, a useful mutation occurs, change resumes. ad infinitum. Faster, slower, irregularly, first a change in one thing, then something different. All the changes working over time (as long as the selective pressure remains) toward an end, that in looking back, appears to have been a coordinated and directed evolution to a predetermined goal. We believe (some of us anyway) that giraffes are as tall as they can be, evolution/natural selection has reached its “goal” with a 14 or 15 foot giraffe and stopped. It may be that an even longer neck is of no advantage any more in establishing dominance. Perhaps with a longer neck, a giraffe’s head would be above all the trees and there is not enough to eat. Maybe giraffes have reached the absolute physical limits for a mammal. Human basketball players can not get much taller. Our bones cannot withstand the stresses incurred by being taller, heavier, and active. Just maybe giraffes are as tall as they can get until an advantageous mutation occurs that permits them to exceed the current limits. Time will tell. Evolution hasn’t stopped.

Proto-giraffes were not trying to evolve into something new. No species is trying to evolve into a new species. Every organism is simply (well nothing is ever simple) struggling to be the species it is, just a little better than the others or, at least, no worse. By trying to maintain the status quo change happens. Evolution creates a new species.

When Darwin proposed his theory one of the problems with it that he recognized, was how a “favorable variation” (his term) could spread through a species. No one understood how “heredity” worked. It was apparent to people that children showed some traits of their parents. Others were aware that it was possible to breed animals for certain characteristics by selecting animals with the characteristics you wanted and breeding them (artificial selection). There was no knowledge of genetics or the principles of heredity.

Darwin had talked to various breeders, even doing some pigeon breeding himself. He had seen what humans had done to change various species and knew how they had done it. He had seen with his own eyes that species were changeable, variation normally existed between individuals of a species, and this variation was inheritable and by selective breeding certain traits could be emphasized.

Darwin’s critics pointed out that if a new trait, or favorable variation of an existing trait, appeared in one individual, that individual would have to mate with another who did not have the new trait. The new trait or variation would have to blend with the existing trait and it would effectively disappear. A proto-giraffe with a slightly longer neck would mate with one with an average neck, their offspring would mate have necks with a length in between that of their slightly longer-necked parent and the average-necked parent, so they argued. The offspring in turn would mate with average-necked proto-giraffe, resulting in offspring with necks even closer to average. Should any of these mate with a shorter-than-average-necked proto-giraffe the offspring would have average or even below average-length necks. Darwin had no effective answer to this, no one did. He could only say that he had seen breeds of animals developed by humans in which certain traits had been emphasized. Somehow it was possible for a new trait or favorable variation to increase in a population, become “fixed,” and bring about a significant alteration in the entire population.

1“Lamarck . . . is the real founder of this Theory of Descent . . . and it is a mistake to attribute its origin to Darwin. Lamarck was the first to formulate the scientific theory of the natural origin of all organisms, including man, and at the same time to . . .[infer] from this theory . . . the descent of man from the mammal most clearly resembling man—the Ape.” Ernst Haeckel 1897:84-85.

2Laamarckism seems to require behavior. Plants have no behavior so how do they evolve?

3 Gerenuks and ditabags also have necks that are, in proportion to the size of their bodies, longer than is “normal” for antelopes and/or gazelles. In Swahili gerenuks are called swala twiga, the impala giraffe. I have personally seen gerenuks feeding in tall bushes by standing almost straight up on their hind feet (resting their front feet on the limbs) to reach leaves nearly twice their height.

4 Gordon R. Taylor in The Great Evolution Mystery 1983:157.

5 Okay there are a few genes that can “overwhelm” all the other genes affecting height. There are several forms of dwarfism that are genetic and Abraham Lincoln probably suffered from Marfan’s syndrome, one the effects of which is his tall and gangly appearance. However height in the general population is due to multiple genes.

4 Coordination does not imply or require a “Coordinator” any more than design requires a “Designer.”

 

THE NATURE OF SCIENTIFIC EVIDENCE

THE NATURE OF SCIENTIFIC EVIDENCE

It may be truth, but it is not evidence.
—Thomas H. Huxley

Several years ago I saw part of a documentary on extra-sensory perception (ESP) in animals. One of the cases put forward as evidence was one in where a dog had been responsible for rescuing a drowning person. According to the dramatization of the event. the victim, who was mute and possibly confined to a wheelchair (in any event could not swim), had fallen into a river. The river was flowing fast and noisily at the time. As the victim struggled in the river, unable to cry out for help being mute, they were swept downstream and around a bend or two. Now downstream was another human (I do not remember the sex of either this person or the victim). This person had been walking along the river with their dog and had turned and headed back to their car. Having gotten some little distance from the river, the dog turned and went back to the victim’s rescue. I do not remember whether the dog actually rescued the victim or drew its owner’s attention to the victim, who then effected the rescue. I remember something about the dog’s excited barking at something in the water getting the owner’s attention.

The gist of the argument is that the river was noisy so the dog could not hear the splashing of the struggling victim over the river noise, the human victim was mute and couldn’t call for help, and the dog was walking away from the river and couldn’t see the victim or the river. The dog’s owner neither heard nor saw anything so the dog could not have either. The victim, being mute, was unable to call out, however due to the  extraordinary peril of the situation, sent out psychic cries for help that the dog picked up. If you believe in ESP this is evidence for its existence. But is it “scientific” evidence? No, it isn’t. Now I am not saying that ESP doesn’t exist. It may exist and ESP may have been involved in this instance. But this is not “scientific” proof of ESP. There are other explanations, explanations that don’t involve ESP, that have to be ruled out first. When an anecdote “supports” what you believe we tend not to examine it closely, these are precisely the ones that need to be closely examined.

Sherlock Holmes is reputed to have said that after you have ruled out all other explanations whatever is left, no matter how improbable, must be the truth. This is a good working method and the scientific method in a nutshell. By experimentation (controlling variables, changing only one thing at a time) you can rule out possible answers and what is left is probably the correct answer.

The anecdote related above doesn’t rule all other possible solutions. Contrary to your opinion it does not rule out the dog having heard or seen the victim struggling in the water. We have the dog’s owner statement that the dog could not have heard or seen anything. That’s based on the owner’s perception, nobody asked the dog. (Of course nobody asked the dog, we don’t know how to ask the question or probably understand the answer.) What the owner recalls seeing, hearing, not seeing, or not hearing is irrelevant to what the dog may have or not have seen or heard. Anyone who has used or heard (actually you do not hear) a dog whistle knows that a dog’s hearing exceeds the range of a human’s. Also a dog’s visual field is wider than a human’s. Their eye’s field of view extends further to the side and back of a than a human’s. Perhaps the dog saw something out of the corner of its eye. Because the owner didn’t see anything doesn’t mean the dog didn’t.

There is one further factor to be considered. Based on my personal observations, and what I have been told, and observed, most humans are not very aware of the world around themselves. Their senses may function very well but a lot of what their senses pick up never reaches the conscious level of the brain. I may have a very low opinion of the awareness of humans of their surroundings. However, based on the frequency with which I drive up behind people sauntering down the middle of the parking lot blissfully unaware that I am behind them. They always have such a surprised look on their faces when after 5 or 10 seconds they look back and see my truck. Humans who live in cities and/or suburbia seem to have lost at least some of that “situational awareness” we must have had long ago. Some still have and I believe, so do domesticated dogs and cats.

Nothing was offered in the documentary as evidence that the dog could not have seen or heard anything, nothing but that its owner was not aware of anything. I have spent a number of nights camped along creeks or rivers. I know that there is a rhythm, a pattern to the noise flowing water makes. Each piece of river has its own rhythm, depending on the configuration of the river bed and the amount of water in it. I have heard, among that pattern, the added sound of a deer stepping into the water. It is quite possible that the dog heard the different noise of the human victim struggling in the water. This possible explanation was not ruled out. Further, the possibility that the dog had looked back was not ruled out. There are at least two non-ESP explanations that have not been excluded. ESP may have been involved but this is not, scientifically, evidence for it.

Anecdotal evidence is usually not scientific evidence, the variables are not controlled. It may however point to interesting research topics. Hunters, explorers, and others in Africa occasionally reported incidents of elephants moving leisurely along in one direction, pausing as if listening to something, then heading off in a different direction. Following the elephants (best done at a discrete distance) they were seen to meet another herd of elephants coming toward them. There other similar cases where elephants seemed to be aware of the presence of other elephants miles away, who they were, and what they were up to. Hunters had known for years that a contented elephant’s stomach rumbled. If it stopped you were in for trouble. (The “rumble” isn’t stomach noises and is under conscious control.) Eventually it was discovered (by Katy Paine, etc.) that they were in fact communicating by subsonic vibrations transmitted through the ground (and felt through their feet) and through the air.

While anecdotal evidence may not be considered suitable evidence to support a hypothesis, when a categorical statement is made (such as: all swans are white), anecdotal evidence may be legitimate evidence against it (such as: I have seen black swans in Australia).