Anthroposaurus
Can other Animals be as Intelligent as Humans?
Abstract
Contents Updated: Wednesday, December 15, 1999
Naught may endure save mutability.
Genes and Explosive Evolution
There have been conflicting views about how easily intelligence evolves. The age old view supported by religious dogmata was that man is unique in all of creation and therefore intelligence is very rare indeed. In contrast, not many years ago a curious equation was bandied about which purported to prove that we are surrounded by life wherever we look in the universe. A proportion of this is bound to become intelligent and so intelligence exists in every direction you look into space.
The view expounded here is that intelligence corresponds with certain troughs in the evolutionary hyperspace, lakes in the evolutionary landscape. They might be very difficult to get to, perhaps via a small number of tortuous narrow valleys, but any species that finds itself evolving into one such valley is likely, sooner or later, to develop intelligence. Intelligence could be unique at the present time, if only man has so far reached one of the lakes, but in principle other species could get there.
H—J Jerison has introduced the idea of the EQ, the encephalisation quotient. The EQ takes the ratio of the brain weight to the body weight of an animal, and relates it to the average such ratio for a group of comparable animals.
An EQ of 1 means that the animal’s brain weight to body weight ratio is typical of the group of comparable animals. If its EQ were bigger than 1, it would have a greater weight of brain than an animal typical of its size in the comparison group.
EQ is not the same as IQ. Intelligence depends upon other factors besides the relative mass of the brain, such as the speed of transmission of nerve impulses and their shape. But EQ does indicate potential for IQ: the brain power is there if the evolution of the animal is able to find ways of using it. It is a useful proxy for intelligence.
EQ depends upon the ecological niche occupied by the animal. The three dimensional environment of squirrels give them a higher EQ than their rodent relatives, the rats. Insect eating monkeys have a higher EQ than their fruit eating cousins and the latter, in turn, have a higher EQ than leaf eating monkeys. Animals surrounded by food, the leaf eaters, need little brain power to seek it. The fruit eaters have to hunt for their food and need intelligence to find it. Insect eaters have to develop intelligent strategies to capture their prey which itself has the sense to try to escape. In general carnivores have a higher EQ than the herbivores upon which they prey.
For fossil animals fairly reliable estimates of EQ can be made from cranial casts and the size of the whole skeleton. They show that brain size tends to get bigger over time in accordance with Marsh’s Law. There are well established explanations for this.
One is that intelligence of response is one aspect of the competition between the predator and its prey. Another is sexual selection. This particularly can give rise to exponential—explosive—evolution via positive feedback loops! Consider the two mechanisms in turn.
Other things being equal, a marginally more intelligent predator will be more successful than its dimmer peers in capturing its prey. The prey caught will be those that are marginally less intelligent than their peers. In the fullness of time, the results in the populations of predator and prey are that intelligence will increase: the predator’s through the animal passing on its characteristic intelligence more successfully; the prey’s because the less intelligent were less likely to pass on their lack of intelligence. Later generations of herbivores and carnivores are both more intelligent. There is still a balance of power but at a slightly higher level.
An evolutionary arms race is taking place with intelligence the superpower weapon. Predator and prey both finish up with a stronger armory but the balance of power is maintained. Of course intelligence need not be the only weapon. Similar arms races occur in respect of other weapons.
An obvious example is provided by tyrannosaurus rex and the ceratopsians both evolving in response to the other as each improved its weaponry. One developed more and more elaborate defences, heavy bony neck frills and long horns, while the other developed more and more sophisticated jaws and teeth for attack. Both also developed quite large brains by popular standards for dinosaurs.
Thus a predator-prey arms race should result in selection for increasing intelligence in both predator and prey and one might expect technological levels of intelligence to emerge quite naturally, even commonly.
That the tendency is there is unequivocal but that high intelligence develops commonly might not be true. The answer again lies in the phrase, “other things being equal”. They are not equal. And often they interfere with the competitive progress described above. At the extreme one could not imagine two separate intelligent species evolving in mutual contact. Whichever was the more advanced would rapidly eliminate the other. It seems this happened in the evolution of mankind... possibly several times.
Nevertheless, there is a tendency towards selection for intelligence in all predator-prey interactions. Any such tendency, once established, can be powerfully reinforced by sexual selection.
An organism has to reproduce as individuals before it can survive as a species. If an individual is highly successful but fails to reproduce, its successful characteristics cannot be passed on. Selection is not selection merely to survive but selection to reproduce.
It is survival until reproduction that is necessary for the continuation of the species. Darwin’s dictum would be better expressed as “reproduction of the fittest” rather than “survival of the fittest”.
Reproduction has its own necessities. Creatures must first find suitable mates. Then they must be preferred by their intended mates above other competing members of the species. This element of choice of mate is where sexual selection comes in.
Usually it is the female that does the selecting. Why? Dawkins invites us to think of the whole cycle of courtship and mating as a game played each mating season. Impregnation puts the females out of the game because she has to concentrate on giving birth, but not so for the male. He can stay in for another round.
The mating game consists of a first round where the most desirable females select the most desirable males as a mates. The less desirable females are not immediately successful because they also are on the look out for very desirable partners. They delay their choice hoping for a desirable mate but tend not to be chosen while there are some of the best females still around. Having secured a desirable mate, the desirable females become pregnant and drop out of the game for the rest of this season.
The desirable males are then free to rejoin the less desirable males not yet selected by the less desirable females who are still delaying their choice. Of course, while the most desirable males were courting some of the less desirable males and females will have tired of looking for perfection and will have also paired off. The females remaining are not so desirable but the most desirable males returning to the mating game will again have their pick of them. The desirable males play the field.
The net effect of this is that some of the other males do not get mates because the most desirable ones have had several goes and each time a female is eliminated from the game. The least desirable males do not breed. Males are selected for their desirability, whatever it is. The obvious advantage to a male of being desirable is that he can impregnate several of the females thus passing on his genes and his particular brand of desirability. The males that fail to attract a mate do not pass on their genes.
On the other hand females have little need to evolve obviously desirable traits. They only have one turn and even the “undesirable” ones will be in demand by desirable males when all the more attractive females are pregnant. The females then are normally the sex that does the choosing, needing not to be unusually desirable as long as they are not repugnant.
The males benefit by being desirable in some way. Whatever is desirable about them will tend to be enhanced by sexual selection because those that are insufficiently endowed with it have no offspring.
Many characteristics or qualities of individuals within a species, such as height in humans, do not depend upon the interaction of only one gene with the environment but upon many acting together. These are called polygenes. Female preference is a characteristic controlled by a polygene. So also is the set of male features that the female finds rather alluring. The main point of such features are that they are continuous rather than having discrete values.
Consider a male hairy chest. Woman tend to find hairy chests, to a greater or lesser degree, attractive or repugnant. Chests themselves can, of course, be, to a greater or lesser extent, hairy. Some women may have genes giving them a preference for chests which are to a degree hairy while others may be endowed with a preference for the more smooth chested males. If, for some reason, the preference for smooth chests became dominant then the most hairy chested men would find it difficult to find a mate.
In the story of the aquatic ape, hydrodynamics determined that smoothness would be advantageous to a swimming primate. The smoother apes would tend to survive and once sexual selection started favoring smoothness then smoothness would prevail even without the influence of the water.
You may protest, “what is to stop women being perverse enough to prefer hairy chested men even though smooth men are in the majority?”.
The answer is smooth men have the genes for smoothness, plainly enough, but they also have the genes for preferring smoothness. These will be passed on to their daughters who will tend to select smooth chested men as mates!
“But why?” you may persist. “Surely a smooth chested man could have the genes for the preference of hairy chests which he would pass on to his daughters.”
He could. But is he likely to? The answer is no. A smooth man is more likely to attract a woman who prefers smoothness and a hairy chested man is more likely to attract a woman who prefers hairiness.
I am hairy chested like my father. It is more likely—in so far as hairiness was a factor at all in my mother’s choice of partner (assume for the sake of this argument that it was)—that my mother preferred hairy chests. It follows that the genes I inherit from my mother are likely to be those for female preference for hairy chests. My daughters will be likely to inherit my mother’s preference for hairiness through me or my wife’s preference for hairiness (again assuming that my hairiness was influential in my wife’s choice of mate).
You can see that hairiness and the preference for hairiness tend to link together through sexual selection. In a species which is predominantly smooth we can be sure that the majority of women prefer smoothness. This linkage of genes is called linkage disequilibrium.
When genes are in equilibrium in a population, no particular pairings of genes are favored and the distribution of features is even.
The interesting thing about linkage disequilibrium is that it can form a positive feedback cycle leading to explosive evolution. In the case of smoothness, it could lead to such a selection against hairiness that in a very short period in evolutionary terms, men became smooth—“other things being equal”. That all men are not smooth shows that we are dealing with a gene complex and there are other factors. Perhaps hairy men are more dominant and some females forgive the less-than-ideal hairiness to associate with a dominant male.
Or many other things! Sexual selection and the linkage disequilibrium it causes have led to bizarre effects like the elaborate displays of the birds of paradise, or the helmets and crests of the hadrosaurs.
Human males have the largest penis of all the great apes though some of the apes have much larger bodies. Sexual selection with positive feedback associated with the human change to an upright posture could have been the reason.
A positive feedback loop leading to explosive evolution simply requires sexual selection for a particular feature more exaggerated than the average, and the development of a linkage disequilibrium. The degree of exaggeration controls the rate of evolution with slow evolution accompanying a slight exaggeration and rapid evolution accompanying a large exaggeration.
Imagine, for the sake of illustration, how the large penis of the naked ape might have developed according to this hypothesis. Ignore cultural influences because culture, including religion and indeed clothing, had not arisen when this selection was initially taking place.
The early hominids, whether by the aquatic route or the savannah route, had begun to walk upright. They had accordingly begun to adapt to copulating face-to-face. The change was not easy. Females did not find it very satisfactory in most instances because their sexual organs were still oriented rearwards. Males with longer penises could effect face-to-face intercourse more successfully.
Suppose that the average early hominid had a penis similar to a chimpanzee’s but our female ancestors had more sexual satisfaction from those few males having larger penises. Males with larger penises would tend to be sexually selected, would be more successful in reproducing and would have more offspring. In time, the whole population of males would tend to have larger penises and, through linkage disequilibrium, would carry genes for the preference for larger penises among females. At the same time the females would tend to prefer males with larger penises and would carry the unexpressed genes for large penises.
What is happening is that the two sets of genes (for large penises and for the preference for large penises) are selecting each other using the size of the penis as a signal. A female chooses a male with a large penis because his large penis advertises the fact that he carries genes for the preference for a large penis. The female is choosing a male who has the same or related polygene to her own.
So, after some evolutionary time penises will be larger. The preference for large penises will also be stronger. This may even be the case though the average penis length has now become sufficient to satisfy the female when copulating in the newly adopted face-to-face position.
The cycle apparently could continue locked in its positive feedback loop with ultimately bizarre consequences. In reality, of course, the feedback loop is broken and an equilibrium established when the environmental disadvantages of the feedback begin to outweigh the advantages of further response to sexual selection. For the birds of paradise and the hadrosaurs the equilibrium was sufficiently tilted to the sexually selected side that exotic features were the result, despite their apparent disadvantages for survival.
It might be interesting to know whether penises are still tending to get bigger—perhaps 30 per cent of human females still do not get adequate satisfaction from orthodox sex, suggesting that we have still not fully adapted to face-to-face copulation—but it might not be so easy to test.
It is more acceptable to test tail feathers on birds.
Malte Anderson, a Swedish ethologist cut off the end of the tail feathers of some male Kenyan long-tailed widow birds. The trimmed-off ends he stuck with superglue to the ends of the tails of other birds. Thus some of the male birds had artificially long tails and some had artificially short tails. There were also controls that had had their tails cut off then stuck on again (to test whether the operation itself had any effect), and some untouched birds.
The males with the artificially long tails attracted four times as many females as the artificially short tailed birds. This proves that sexual selection is still propelling the birds towards longer tail lengths, although in practice a maximum has been reached. Longer tails render the male more liable to predation and failure to breed. But Anderson did not check whether the longer tailed birds survived less well than their short tailed rivals as the theory would predict.
So, sexual selection is one way of developing a grossly enlarged feature.
Does the overdeveloped tail of a widow bird remind you of the human brain? In the sense that the human brain is another grossly overdeveloped organ and might have been produced by the effects of sexual selection, perhaps it should.
Assuming that nerve connexions, the synapses, in the brain work like the elements of a computer and correspond to one of two states, on or off, then the brain, which has a hundred million million synapses, has two to the power of a hundred million states, a number greater than the number of elementary particles in the universe. It is capable, in this computer analogy, of storing and processing immense amounts of information.
Not only that, the brain also arranges its synapses into tiny microcircuits that increase still further the total number of possible states of the brain and add to the efficiency of processing information. The human brain has prodigious amounts of memory and the potential for even higher performance.
Besides this huge amount of brain capacity, there is the split brain. In most animals both parts do the same things but, in humans, they have begun to specialize in various ways. We are developing two brains working in parallel on different types of problem.
Our brains have apparently overshot their optimum size. Like a computer with four megabytes of memory but which is only able to address 640 kilobytes, they have incorporated excess capacity and, at present, most of it is redundant. But sooner or later a mutation will arise that is able to make use of all that power. One need not expect subsequent evolutionary change to be slow.
Evolution often uses redundancy. Redundant parts of an organism are found new uses by evolution. Fish taking to the land no longer needed their swim-bladder, an air sac that kept the fish buoyant in the water. The swim bladder was redundant but found an excellent new use as a rudimentary lung.
Higher organisms often have large amounts of apparently redundant DNA (called introns) between the coding sequences that contain the instructions for the growth of the organism. The introns contain bits of DNA with odd properties. Some are mobile, acting as though they are hitching a ride on the main sequence of the DNA molecule but cannot make up their mind where to sit. Some are “decayed” genes, no longer functional but subject to mutation. Others seem to be immune to mutation.
There are repetitive sequences apparently made by bits of the code that are conceited, duplicating themselves at random places in the introns and even from one chromosome to another. Genetic information is increased commonly by a mutation causing part of the genetic code to double. The redundant excess part is then able gradually to take on a new role.
The introns seem to be one place where mutation and role adaptation can occur with ease. They are just the place to look for the causes of fast evolution of new species.
Even ordinary evolution by selection of the fittest can be extraordinarily fast. There are examples of new characteristics evolving observably such as the growth of resistance to antibiotics in bacteria, the resistance of insects to DDT and the resistance of rats and mice to warfarin rat poison. In each case resistant strains were selected in only a few generations, taking only a few years.
Every schoolchild will know of industrial melanism in the peppered moth. A rare dark variety of the moth began to outnumber the common speckled variety because of industrial pollution. Normally the speckled variety was adequately camouflaged on clean lichen-covered tree bark but pollution killed the lichen and blackened the bark making the speckled variety conspicuous. Natural selection was effected by foraging birds. The dark mutant found the blackened bark excellent camouflage and the birds missed them.
The house sparrow, introduced into North America in the middle of the 19th century has evolved into several distinct subspecies in only about 110 generations. Some plant species have separated in only 50-100 generations. Experimenters with fruit flies claim to have shown speciation to occur in only 12 generations.
Lake Nabugabo became separated from Lake Victoria by a sand bar only 4000 years ago. Today the sand bar is still only three km across yet it has enabled five species of haplochromis to evolve. They are amongst the newest species we know and illustrate how quickly speciation can occur even in vertebrates when a population gets isolated.
Closely related species are nearly identical in the protein coding parts of their DNA but differ enormously in the repetitive sequences in the introns. G—A Dover proposed that it is the differences in the apparently functionless repetitive sequences that determine the species. When these satellite sequences differ two animals cannot successfully mate. They, at best, produce sterile hybrids like the mule.
The satellite sequences can change very rapidly compared with the stability of the protein coding sequences. They copy themselves rapidly to random locations, even in other chromosomes, thus providing a means of rapid speciation. There is, in humans, a repetitive sequence amounting to three per cent of all DNA. By changing this sequence in a newly fertilized egg it might be possible to produce a different species of human being almost overnight.
Though the repetitive sequences seem to be functionless, could they express themselves somehow at the macro level, perhaps in a way that could only be sensed by others with the same sequence? Could they account for forms of rapid speciation? Are these mechanisms adequate to account for profound changes like advanced intelligence?
In gradual evolution there are always countervailing factors. Can any form of gradual evolution lead to really revolutionary new physiological structures? The human brain seems to have three levels of structure, each one overlaying the previous one. What led to the adding of a new and apparently superior part to the brain on two occasions?
Some biologists have always felt that there were problems in the Darwinian view of evolution by accumulation of small changes even allowing for isolation and rapid evolution. How, for example, could it account for the major divisions in taxonomy such as that between reptiles and mammals? There seem to be too many fundamental differences between such groups of creatures. How could all these vital distinguishing features have evolved simultaneously?
One solution that has always been controversial, and still is, is saltation. Saltation is macromutation—major changes occur in a single mutation not via the accumulation of many small changes (called micromutation).
The argument against saltation is that large changes in physiology caused by mutation must be harmful because they amount to a gross deformity. The chances that a deformity on this scale would be beneficial to a creature are considered to be vanishingly small.
R.A.Fisher used the analogy of a microscope to show that macromutations cannot lead to viable changes. Imagine a microscope almost in focus. The focus is the evolutionary equilibrium state and the microscope is nearly at it. Suppose a tiny small random movement of the microscope adjustment were made to represent a micromutational change. The microscope barrel can only move inwards or outwards so there is a 50 per cent probability that the change will improve the focussing and a 50 per cent probability that it will make it worse. Eventually, through accumulating such small mutations, the microscope could become fully focussed.
What though if the random change to the adjustment were large? Moving the barrel in the wrong direction would obviously worsen the focus; but moving in the correct direction would also worsen the focus, because a macromutation, a large change, would considerably overshoot it.
A random mutation could be in the right direction and exactly the size needed to drop the microscope into focus, but this is so unlikely compared with all the other possibilities that it can be safely ignored. In practice a random large change cannot improve the focus of the instrument.
The alert reader will notice that this analogy is a terrible example of evolution. Evolution is not random in its overall effect precisely because natural selection tends to eliminate the bad variations. The microscope would tend to become focussed because the micromutations away from the focus would die out leaving those that were tending towards the focus. The macromutations would die out anyway because they must always be further from the focus.
What, now, if this microscope had two foci? If, for example, it had two eyepieces which were themselves not equally adjusted so that when one was in focus, the other was not, and vice versa. Now there are two chances of getting a focus, one with each eye. If the microscope were adjusted close to one focus, the micromutational argument of Fisher would still apply, but what of the macromutational argument. There must be a chance that a random macromutation would put the other eyepiece into better focus than it was—perhaps, even put it into better focus than the instrument had before. In this case a macromutation could improve the overall focus of the instrument. Though it is still unlikely, it is more likely than before.
How does this translate into arguments about evolution? In the analogy of a multidimensional evolutionary space, a hyperspace, stable forms correspond to depressions in the landscape. The flow of evolution can be imagined as the flow of a river down the valleys of this landscape into a depression, forming a lake corresponding to a stable species or a developed feature.
Translating the microscope analogy into the landscape analogy, we find a lake at the microscope focus, the species equilibrium position, but on either side of it we are moving uphill away from the focus. The uplands are bleak. Individuals here are badly adapted, the result of mutation: species here are badly adapted, the result of a changed environment. Finding themselves there they had better quickly head downhill towards the lake—the focus of the microscope in Fisher’s analogy—by evolving rapidly or die. Death is, of course, extinction for the species or the effect of a disastrous mutation on an individual.
The microscope with two foci is a landscape with two valleys separated by a hill. A macromutation, a large jump from the edge of the lake in one valley could land you in, or close to, the lake in the other valley. If the other valley were deeper and steeper (representing a highly specialized species), merely landing on the other side of the watershed might lead to rapid evolution to the new species—the flow down the steep hillside would be rapid. The mutants, though ill adapted, must become rapidly fitter by micromutational (Darwinian) selection or perish anyway.
Far from macromutation being always unsuccessful in a multidimensional space, there are rare occasions when it is successful and provides the sudden jump that the fossil record needs to explain the distinctions between major groups of organisms like families.
Richard Dawkins argues:
Virtually all the mutations studied in genetics laboratories—which are pretty macro because otherwise geneticists wouldn’t notice them—are deleterious to the animals possessing them.
Since he says “virtually all”, the implication is that some macro mutations studied in the laboratory are beneficial, or at least neutral, to the animal possessing them.
Even if the “virtually” were erased, one is entitled to ask how an evolutionist could imagine that, however many experiments were carried out in laboratories, the vastness of the range of nature’s experiments could be reproduced. Even accelerated evolution usually depends upon passages of many millennia, impossible to simulate in a laboratory. This is especially true of saltation precisely because beneficial macromutations are, as all agree, rare.
But Dawkins readily accepts that the type of mutation he refers to as “the stretched DC8 macromutation” is not unusually rare. Like the DC8 aeroplane lengthened by adding a new section of hull, mutations of this sort would put a complete additional segment into a millipede, extra ribs into a snake or an extra digit to a human hand.
According to Dawkins these are really micromutations. Although they are major changes for the complete organism, they are only small changes to the genetic instructions.
If you were to write a computer program to print five asterisks in a row you could write a program to print one asterisk then put the program into a loop telling the computer to repeat the instruction five times. If you found that six asterisks had actually appeared you would not think that the complete set of instructions to print another asterisk had miraculously been duplicated. You would realize there was one small error—you had mistyped six for five in your program which had then looped six times not five.
Dawkins says that disposes of saltation—when it occurs it is not a macromutation at all. But it actually justifies it. It makes macromutation at the whole organism level more likely, depending as it does on only a micromutation at the level of the program, the genetic code.
Small changes in genes that are subtly linked together to influence a complex of apparently unrelated features can have profound changes on the organism. The environment effects natural selection on the whole organism not on the genes themselves, so it is the macro effects that matter in the selection process.
Some micromutations can simply be the re-expression of a previously unexpressed gene or group of genes. The interesting aspect of this effect is that it can cause apparent violations of Dollo’s Law in that features which have apparently disappeared can reappear.
When a macro feature is lost during evolution it does not follow that its genetic blueprint has gone, simply that it has switched off. The complete genetic blueprint is never fully expressed in advanced animals. The inoperative bit of genetic code will be lost eventually. Mutation will lead to reprogramming of the redundant piece, although that might be millions of years later.
A feature which has disappeared has done so for a reason. It is unlikely that conditions would turn again in its favor before the underlying code had been altered—thus upholding Dollo’s Law. But, though usually so, it need not always be true and lost features can reappear, albeit rarely. If the section of genetic code remains intact, it can occasionally be expressed by accident causing atavisms or throwbacks. If the throwback happened to be again of value to the organism, it could again be selected.
Atavisms, as one would expect, mainly look bizarre and are not of any benefit—quite the opposite. Three toed horses are not particularly uncommon, the extra toes not being a crippling deformity, but whales with rear limbs are more unusual. Both represent throwbacks of tens of millions of years of evolution.
No birds today have teeth but experiments have shown that birds are capable of growing them given the right conditions. Surgical manipulation in a chicken’s foetus can induce structures to grow that normally would not. The genetic instructions for their growth must be present even though they are not usually expressed.
Furthermore, the growth of some structures induces the growth of others. The fibula in a chicken normally has atrophied to a splinter. Yet if it is encouraged to grow until it reaches the ankle, lo and behold, ankle bones, that normally do not grow at all in a chicken, appear.
The hoatzin chick is, in some respects, a throwback to the archaeopteryx. It has the three grasping claws on its forelimbs seen in the archaeopteryx but not present in other birds including the hoatzin’s near relatives. They recede in the adult form. Evolution seems to have partly revived an otherwise discarded plan by bringing it out of genetic storage because for one odd bird it has proved advantageous. The hoatzin chick can cling to reeds, roots and branches above the marshes where it lives.
The apparent loss of the wishbone or collar bones in dinosaurs seemed to preclude them as ancestors of the birds. Consequently Heilmann in 1925 proposed that primitive reptiles called pseudosuchians were the ancestors of both birds and dinosaurs. Birds retained the wishbone but dinosaurs, in the main, lost it. What renders this theory untenable is that the archaeopteryx with its wishbone is so uncannily like some dinosaurs without it. Possibly some of the bird branch and some of the dinosaur branch evolved in parallel, having split from the pseudosuchians.
But the anatomy of archaeopteryx and its dinosaur twins is so close except for the wishbone that convergence seems less likely than that the collar bone reappeared as a throwback in species that had lost it. If atavism is caused by failed suppressor genes then even though dinosaurs like deinonychus had lost their wishbones, the genetic information for wishbone production still existed and could be recalled. In archaeopteryx, it proved advantageous to do so. Powerful flight muscles anchored to the revived wishbones were essential to flight and the evolution of birds.
Having found itself with a new, or revived, macro-feature, the mutant organism, whether it be bird or bacterium, finds itself in a new evolutionary channel possibly leading to an undiscovered Shangri-La in the evolutionary landscape. With its novel characteristics, the mutant can evolve rapidly and, ultimately, disperse into the niches available to it.
In the evolutionary landscape lakes are stasis and torrents tumbling down steep hillsides are rapid evolution. Both are understandable in the ways outlined above, so, long periods of little change and short periods of rapid change can be explained provided that the conditions are suitable for each.
But could evolution be yet more highly directed? Could the development of the embryo be an initial mutational filter, a preselector especially valuable in selecting viable saltational changes?
Embryos spontaneously abort if a macromutation is unsuitable for embryological development. Subject to micromutations only, the embryo will survive until birth because small changes will not normally affect its viability. But macromutations very often are not viable for survival of the embryo. The windpipe might be missing or the heart punctured. The brain might be large but the neck too weak to support it, and so on. Development of the embryo is a filter for macromutations. Rejects are spontaneously aborted stopping the parent from wasting time and effort on unviable offspring.
Hence the only macromutations that see the light of day are those that permit survival of the embryo until birth. Many, if not most, of those will also die, but successful embryological development is the first stage of natural selection.
Evolution might be a vector quantity, having direction as well as magnitude. A species in stasis and subject to no particular selection pressure experiences mutations in all directions in evolutionary space and most are neutral or selected against. But once evolution towards a new equilibrium position begins to occur, mutations in one direction can be favored by selection—evolution can therefore be a vector quantity in evolutionary space complete with its own momentum.
Not all genetic mutations are equally likely. Mutation can be itself controlled to some extent by a gene. That is not to say that all mutations are thus controlled, random mutations will still occur, but a gene could tag another gene or mixture of genes for change when appropriate. Such a gene could control the extent to which a group of genes mutate thus effectively providing a mechanism for macromutation in the right conditions. It is a gene having mutagenic properties leading to saltation, a saltatory gene, a saltagen.
In stable conditions the saltagen, which itself mutates readily, would be switched off. Obviously it would have no effect on evolution. If it switched on, since the species is in stasis, the mutations would tend to be unfavorable and selected against.
If conditions changed, and the saltagen switched on some mutations would be favored and selected. The saltatory quantum would be one, one gene at a time would mutate, it would be in its x1 quantum state. In a subsequent generation it could mutate to the x2 state, triggering other genes to mutate or single genes to mutate more. In the offspring of those which survive, the saltagen would mutate again, perhaps to a x4 state, inducing more mutations in the main sequence genes which it influences. Further mutations to x8 etc could occur as long as the gene was transmitted to a successful later generation.
What are the conditions for activation of the saltagen? The environment must have changed sharply (in geological terms) so that the species is unstable in it. It is ill-fitted to the conditions in some way. The saltatory gene determines how much mutation occurs in the genes which it controls. As long as the next generation survives, the saltagens it carries will also survive and be able to switch to higher states. Each higher state will cause larger amounts of genetic change. Eventually it will cause macromutation of the organism.
Obviously a stage will be reached when the saltagen’s mutational steps and the scale of genetic change are so large that the mutations induced are all damaging. Selection or embryonic preselection will then tend to eliminate the individuals with the highest level of saltagen and the escalating process will go into reverse eventually switching off the saltatory gene when stasis is again reached.
The gene then only switches on randomly, to test the environment, so to speak. This process allows a faster approach towards the evolutionary solution. It also might go some way towards accommodating the "creative evolution" of Bergson and Shaw, generally frowned upon by orthodox evolutionists.
“All very fanciful”, I hear sceptics say, “but where is the evidence?”
Professor John Fincham of Edinburgh University, Scotland writes:
The spontaneous mutation frequency of an organism is to a large extent controlled by its own genotype.
In other words organisms mutate at rates controlled by their own genes. Precisely. The saltagen controls the mutational rate.
We know organisms have genes called antimutator genes which provide mechanisms to repair DNA chains that have replicated wrongly. These DNA repair and mutation avoidance mechanisms work thus: the faulty bit of DNA is tagged by some suitable chemical sidechain, specific chemicals called enzymes seek out the tag, cut out the faulty part and replace it with the correct piece.
A gene observed in the gut bacterium, E coli, is called Treffers Gene. Normally it acts as an antimutator gene, but it too is subject to mutation. When it mutates its effectiveness in suppressing mutations in other genes decreases, making the rate of mutation of these genes rise a hundred times.
Here we have a gene which, when mutated causes other genes to mutate more. A saltagen?
Another mechanism operates while the DNA chain is replicating. DNA polymerase, an enzyme that has the function of building the DNA polymer, checks the chain as it is being built. It “proof reads” each copy of the genetic code. If the last monomer it added matches the DNA template, the unraveled DNA strand from the previous generation, then a new monomer is added. If it does not match, the DNA polymerase cuts the previous monomer away and replaces it with a correct one.
But certain mutations affect the DNA polymerase itself, rendering it not such a good “proof reader”. The result? More mutations of the genes during their construction!
Many DNA sequences have more than one function. They can be read more than once with different results. My milkman sees a message by my doorstep saying, “No milk today” with a pointer that can be directed at the word “No” or the word “milk”. If it points to the “No”, I get no milk but if it points to the “milk”, I get milk. The code “No milk today” does not alter but the outcome depends on where the message starts.
That illustrates one way that one stretch of DNA can be read differently. Another way would be to read it in a different order, akin to reading the word “STAR” (forwards) or “RATS” (backwards).
The way in which the bit of code is read is determined by a previous bit of code. Errors in these instructions can have profound effects on the meaning of a genetic sequence and thence on the macro features of an organism.
An example is the pseudogene for production of globin, a protein, in humans. Pseudogenes are “decayed” genes. The pseudogene for globin is all but identical to active genes for globin production but have mutated in their initiation codon, the piece of DNA coding sequence saying where the message starts, and also in other parts of the code. In short, the mechanism for reading the gene no longer operates.
It seems a piece of DNA containing the active globin gene mutated by doubling then one of the bits fell out of use, remaining only as redundant code.
What causes plagues? I am not digressing. The answer provides an interesting example of the effect of a copying error and switching off a gene.
Hans Wolf-Watz of the University of Umea in Sweden and his team have looked at the DNA sequences of the plague bacterium, Yersinia. Normally this bacterium is not very virulent, but occasionally a copying error occurs in which one letter of the code is lost thus scrambling a whole coding sequence. The function of that part of the code is not known but the effect of the error gives a clue—the mutant bacterium is deadly. The piece of code helps the host to defend itself against the bacterium.
Why should it do that? Simply because by not doing, it kills off its hosts rapidly leaving it with nowhere to live—it too dies. With the bit of protective code active the host is likely to survive and the bacterium with it. The protective sequence is in a part of the code that has a high mutation rate so deadly mutants are thrown up quite often, but plague epidemics are not very frequent. The reason is that the virulent form of Yersinia normally kills its host before it has had time to be transmitted to another. Only in overcrowded and unsanitary conditions is it able to spread from one host to another before the hapless host is done in.
The rapidly mutating piece of code looks as though it switches on occasionally to test the environment. If it is suitable—conditions are overcrowded and unsanitary—the virulent bacterium spreads rapidly but otherwise it dies out for awhile until reborn by a replicating error. A gene which switches on to test the environment—just like a saltagen!
Even more relevant may be a phenomenon called “replicating instability” which, unlike the examples just mentioned, seems to be a positive effect rather than a negative one, although it is not yet understood. It seems to allow a “propensity to mutate” to transmit through an indefinite number of replications before, for some reason, it manifests itself. Isn’t that another gene that is switched off until the conditions are right?
Earlier we speculated about an incest gene. If there were such a thing it could, once it had turned on, remain switched on so that it actually provided the distinguishing feature of the new species. Linked to some physical characteristic it would be recognizable by all others possessing the gene, drawing them inexorably into mutual reproduction.
As more creatures were born with the gene, it would cease to cause incest because others not in the immediate family would also carry the gene. It will have become a breeding preference distinguishing two populations and eventually leading to speciation.
Alternatively, perhaps like the saltagen, it turns on under environmental pressure for change—in other words when there is a need for rapid evolution. This could have been true of certain apes in the last ten million years or so, judging by the successive waves of hominids appearing until the Cro-Magnon variety, only a few tens of thousands of years ago. Either way it can permit speciation when it might not be expected and therefore speed up evolution.
Jane van Lawick Goodall has noted that chimpanzees and other primates show no sexual interest in their mothers. Yet men seem obsessed by the Oedipal complex. That man carries the incest gene unlike his primate cousins might be the key distinction between them. Have we evolved rapidly because we are the Oedipal ape?
“Impressive testimony to the existence of a fast-acting mechanism” for creating extra bits of DNA sequence, according to Fincham, is the behavior of cells cultivated in the drug methotrexate. An excess of this drug, which inhibits one of the cell’s enzymes, in the environment causes the cells to develop enormously lengthened chromosomes carrying multiple repeats of the DNA segment for production of the enzyme. In response to the intense selection pressure of the harmful drug, the cell repeatedly mutated by doubling the satellite sequence containing the code it needed to manufacture the enzyme under attack.
This is hardly random mutation. “Impressive testimony” indeed.
Fincham sums up thus:
These mechanisms are themselves subject to mutation and natural selection and the spontaneous mutation frequencies which we find in natural populations of organisms of all kinds are adaptive. They presumably represent a compromise between short-term need to replicate already well adapted DNA sequences with sufficient precision and the longer term advantage of variability.
The mutation rate per gene is only one per million replications but, because a lot of genes are needed to define an organism, that makes mutation quite likely in the whole DNA sequence. Large organisms average about one mutation in ten replications many of which, we have noted, are harmful and most of those that are not are neutral. This may be near the acceptable limit for human DNA. More complex DNA would mutate too often making reproduction unreliable. Hence beyond this level of complexity, evolution favors the storage of information in the brain rather than in the genes.
By comparing the amount of information estimated to be in the genes of different types of animal with the amount of information estimated to be in their brains, Carl Sagan deduces that “somewhere in the steamy jungles of the Carboniferous Period” animals emerged with more information in their brains than in their genes. This estimate is quite imperfect because the information is imprecise and the figures cover a large range requiring logarithmic relationships which exaggerate errors. But, though the date of the crossover is inexact, the notion seems valid.
Since the crossover point, whenever it was, brains have increasingly dominated genes. This suggests there might be a threshold beyond which evolutionary pressure builds up to develop brain rather than extend the complexity of the DNA. Some dinosaurs, having passed the threshold, might have built up an evolutionary head of steam for intelligence.
Evolution is faster for birds and mammals than for the cold blooded amphibians, fish and reptiles. At the annual meeting of the British Association for the Advancement of Science in 1988 Allan Wilson, of the University of California at Berkeley, proposed that animals with larger EQs evolve faster than less brainy relatives. Wilson believes the increase in brain size accounts for their difference in evolutionary speeds. If true then one can expect an explosive evolution of the brain by positive feedback.
To measure evolutionary differences, Wilson took 20,000 bone measurements from 400 species of vertebrates. From these results he created an index of how different the shape of the body was for any two vertebrate species. Closely related species like the coal tit and the blue tit had an index of 3 whereas the differences between an eagle and a sparrow were reflected in their index of 25. Combining this index with the date of separation of species using the molecular clock allowed Wilson to plot evolutionary change against time.
He found that evolution is speeding up. His explanation is that brains drive evolution:
As brains became bigger and bigger they became the predominant cause of the pressure to evolve.
More intelligent species are more willing to try new forms of behavior and that gives more scope for selection to operate. When a group of animals have learnt a new behavior then evolution will change their physical attributes the better to take advantage of the new behavior. Animals evolve more quickly when their brains are advanced enough to allow them to modify their behavior. The creature’s body then evolves along the lines best suited to the new behavior pattern.
Because the brain is both one of the physical attributes subject to evolution and a factor controlling the rate of that evolution, a chain reaction occurs by positive feedback. The result is exponential growth—growth which is at an ever increasing rate. Wilson believes that innovation and imitation among our hominid ancestors provided selective pressure for physical changes including greater brain size.
Those lineages with larger brains evolve more and more quickly, and eventually you get a species which is so intelligent that cultural evolution takes over entirely from genetic evolution.
science writer, Nicholas Schoon relates that our ape like ancestors of the past few million years…
…have undergone one of the fastest rates of evolution on record. The brain almost trebled in size, the larynx, tongue and lips changed as speech developed, the thumb and fingers altered so that we could manipulate tools with precision, and walking on two legs was perfected.
According to Wilson, it is inevitable that overwhelmingly intelligent species should dominate the planet. If humans were to die out another mammal or a bird, would replace us.
Since exponential growth is steady continuous growth but at an ever increasing rate, for a very long period both size and growth rate are so small that changes can hardly be noticed, but eventually the growth rate seems to take off, as if it had passed a threshold.
This is just what we see in the growth of intelligence. It is as if, in our evolutionary hyperspace, intelligence is a lake at the bottom of a trough with steeper slopes the closer the approach to the surface of the lake. You slip down the slope gathering momentum until you tumble over the edge. Any creature getting to the edge will find itself precipitated into the Sea of Knowledge.
There are conflicting views about how easily intelligence evolves. Some say it is rare yet I argue that species are accelerating towards ever higher intelligence.
The conflict is explained by the hazards of getting to where the slope starts perceptibly to incline towards the sea of knowledge. There are many other comfortable troughs that species can settle in before it gets to the edge, just as a golfer might find it difficult to get on to the green without getting trapped in a bunker—and this is not a par five hole: it has countless dog legs and bunkers on the way.
The many species that have existed on earth without developing intelligence couldn’t get out of the bunkers. So far, not many have got to the green, the equivalent in the golfing analogy to the sea of our landscape analogy.
What is clear is that, given certain attributes, intelligence seems bound to evolve—and quickly. Some dinosaurs seem to have had those attributes and could have developed rapidly, just as we have.
