Since popularization of Darwin's theory there have been two broad approaches to the complex issue of evolution and human behavior. The first is to concentrate on modern behavior, elucidating a theory on its own grounds with only passing references to evolution. Freudianism or behaviorism used this approach, which was successful to an extent that whatever the merits of the behavior theories at least they would not be undermined by any shift or doubts in evolutionary theory itself. The second approach is to begin with evolution and try to explain human behavior directly by evolutionary science. In most opinions this approach has been perennially unsuccessful. It has not only failed to provide convincing explanations of human behavior, but raised concerns over the viability of evolutionary theory itself, that it could spawn such misguided offshoots.

In this book the approach is more circumspect. Firstly, the theory of behavior, that humans are psychologically motivated to maximize their options is plausible on its own. It provides a fresh perspective on human behavior while inferring nothing about general evolution apart from inquiring why such a motive might evolve. Next, the theory of how humans specifically evolved also avoids major controversy. We already know from the fossil record how humans evolved in broad terms. We just need a better theory of details such as why humans lost body hair, why language evolved, or how humans evolved a large brain. The Theory of Options explains how questions like this can be more easily answered if we assume that humans were evolving along a pathway in which fit moves were those that maximized the options of behavior. The theory does not insist that humans evolved because of this, or that if they did, this alone explains human motivation. It is just a hypothesis for testing against other ideas.

Yet why did humans evolve?

Why say, did intelligent life evolve on Earth when it did, not an eon earlier or later? Why did not a dinosaur descendent evolve into an intelligent creature, or a marsupial? Why is there only one intelligent species? There are many close kin species of other primates but all near-kin human species were wiped out, so why was this? Is it a rule that that on a planet that evolves intelligent life there can only be one intelligent species? If humans did evolve along a pathway that maximized options of behavior why was it this pathway, and not another path? Or why did humans evolve first by rapid biological evolution then stop evolving, and transform evolution and adaptation outside of biology? Or if it is fit to evolve large brains why do not other creatures evolve this way? Steven Gould or most biologists today tell us that we should not ask these questions. To ask implies there is something unique to human evolution whereas the modern view is that human evolution is a trivial, insignificant evolutionary event. But this only raises other questions: 'Why do they think that?' or 'What in evolutionary theory tells them that human evolution is not significant?'

This chapter will outline a new model of evolution different from orthodox theory that can better answers such questions. Only we must warn the reader of the trap, not of suggesting a new model of evolution, but of inferring anything about intelligent life having seen it only on one planet. The new model will suggest that given sufficient time abundant life will proceed almost inexorably towards a saturated state. Once this state is reached, if evolution continues intelligent life will evolve, not precisely in a human form, but it will maximize options and move further adaptation outside of biology. This is a reasonable inference about life on Earth because large animal life had been steadily evolving increased intelligence, versatile behavior and higher rates of adaptation well before humans came. We also imagine, and it is quite reasonable, that if in the future humans discover life on other planets, even if not intelligent life, we could make inferences if intelligent life had a chance to evolve there. This would be based on trends that we saw leading to intelligent life on Earth. Just that we could not say of two competing models of evolution that one model is correct merely because it predicts evolution of intelligent life. Any model could be disastrously wrong on this point, because of billions of planets in the universe that might evolve life we only know as a fact that intelligence emerged on just one. If anything, current indications are that it is very difficult to get the right combination of factors that allow long term, stable development of life.

Also, to those not familiar with evolutionary theory the new model will not appear that different from the orthodox one, in ways that are easy to understand. (Cynics will add that it is not different from orthodox theory in ways that anybody can understand!) But there are differences, some radical. A prominent departure in the new theory is that organisms increase complexity against a loss of genome fitness. This does not mean each reproductively successful individual is not fit as a phenotype, or each fit individual does not pass on unique DNA. But over a lineage of change in which complexity increases from a simpler ancestral individual into a complex, modern descendent, genome fitness falls. Yet, all theories concur that organisms will try to avoid loss of fitness. This means effectively that organisms will try to avoid evolving vastly increased complexity, although how this need translates as motive or impulse to individuals, if at all, is subject to much debate. The paradigm breaker of the new theory though is that even if higher forms evolve inexorably, from a genome fitness perspective they try to avoid it. Organisms try to stay simple and only evolve complexity when other pressures, sometimes acting on a vast scale over the biota of life force them to do so.

Only explaining why the same pressures that force organisms to seek fitness over a small scale might over a large scale force some organisms to evolve against a loss of fitness is not easy. It is like trying to explain why the wind is sometimes soft and other times strong, or why the same piece of metal can be magnetized in one instance, but demagnetized in another. Similar forces of mutation, selection, adaptation and renewal act on organisms all the time. But mostly these forces act in countervailing ways so that their net effect on species is slight, or it adapts them by minor refinement. Yet, at other times these same forces align so that their net effect is to drive the evolution of some organisms very far in one direction. The new theory concerns how forces acting randomly or unaligned in some instances, form aligned, focused, directional effects at other times.

Again, none of the new theory is easy to explain, or even visualize. The wind blows steadily across an ocean and the sea tries to move in the direction of the wind. But though both are fluid, a large mass of water is harder to move in one direction than a mass of air. So, near the surface it is easier for water to bob up and down than move in one direction. This creates an energy wave, which travels for hundreds of miles. Near a coast the sea becomes shallow, so now it is easier to mover water than sand, and the waves start to break. The steady movement of air on the open sea is producing movement of water that slowly shapes a coastline hundreds of miles away.

The action of wind on water would not be easy to visualize if we had not seen it. Even then, how many people realize that waves form because it is easier to move wind than water? Yet we do not picture evolution as easily as we observe ocean waves. We only observe via the fossil record that new species evolve relatively suddenly then persist unchanged for long periods. We also observe, or think we do, that genes mutate at steady rates, and natural selection brings constant change. We observe DNA in isolation and conclude that DNA is easy to change. So, any change in DNA at a steady rate should produce a change in evolution at steady rate. Very small changes in evolution do occur steadily for small changes of DNA, which reinforces our convictions of how the process must work over larger scales. But over the scale of an ocean to a droplet, or a hurricane to a puff of breath, evolution does not act the same way, and this is very puzzling.

The new theory proposes that large evolutionary effects such as step changes in the fossil record or loss of genome fitness as organisms evolve complexity also arise because steady forces push against properties of life that are easier to alter than others. At the beginning and end processes of evolution we can see this clearly. In the innate universe, which existed first, chemical changes are easier to enact than formation of new elements. Air is easier to move than water, or sand easier to change than rock. In highly evolved life, we see that behavior is easier to adapt than instinct, or psychology is easier to change than biology. We also see, if we look closely, that large animal life has evolved in ways that make biology easier to adapt. It is easier to adapt a warm-blooded, furry creature to climate change than a cold-blooded, scaly one. It is easier to adapt a hand to a change of food gathering than a claw. It is easier over the course of evolution to adapt a limb, once evolved, as a hand, foot, leg, flipper or wing, than evolve the limb design the first time. It becomes easier as life develops for small changes of DNA to produce large changes of morphology, an effect know as the evolution of evolvablity, and this is well observed.

Only while the innate properties of the universe and the developed phenotypic traits of life appear grouped as easy or hard to alter, life on Earth is encoded by DNA, or some by RNA. These codes in isolation appear easy to alter, so it is difficult to visualize how traits encoded in DNA could be hard-to-alter sufficient to cause large step patterns to evolution. The earlier chapter on Easy and Hard Changes explained with examples from both life and computers, why codes, which appear in isolation as easy-to-alter, can be hard-to-alter in reality. All codes, DNA, RNA, or computer codes do not evolve independently of how the universe physically exists, but reflect its extant properties. If a stable cell wall material is hard to evolve, but cell diameter can be varied easily, DNA evolved to encode those realties. DNA and RNA codes correlate this. Genes that evolved early in life to express its fundamental, unchanging properties, are short, prokaryote-like, stable genes with low (above 10^-8) mutation rates and high, for some RNA often 100% conservation. Intermediate genes that express complex, later evolving traits are longer, more eukaryote-like, easier to change with intermediate (10^-6 to 10^-8) mutation rates, corresponding to the time in generations for new classes, orders and species to evolve. Finally, very long or non-genetic DNA alters easily as the genetic personality of modern organisms, but does not change the fundamental structures of life. We also have shorter viral or parasitic code that alters rapidly, but it too represents life's easy-to-alter modern attributes rather than its fundamental structures. So, though a cannon of modern faith is that all traits expressed by DNA can change easily and in any direction, this is just a paradigm that people cling to. But it is only an emotional, not a scientific objection to the new theory that once any trait is encoded in DNA it could never ipso facto be hard-to-alter.

Rather than altercate over DNA and hard-to-alter traits, we should try to understand how easy and hard to enact changes effect the unfolding of life. Again, there are no novel forces. Forces which push steadily are mutation, selection, adaptation and renewal, but these forces channel with different energies depending on the ease or resistance to change that they encounter. Resistance to change must be measured as a cost. There can be several ways to measure this, such as increase in metabolism, energy or food gathering cost, or physical difficulty to accommodate new change. The large human brain, say, bore a high cost of change both in its large energy need to sustain it and the pain and complication it brings to the birth process. It also bore other indirect costs to do with complex creatures, and the difficulty of one individual among equally complex and intelligent rivals passing on large amounts of unique DNA.

Another way to estimate cost is by the complexity of change, and we can crudely relate this to how humans build devices. If one builds an airplane from existing technology the cost of change is not so high, and we often build very good airplanes by slightly altering the shape of the wing or streamlining the body. But if the only way to build an airplane is by developing new materials or technology it is a high cost of change, especially if critical technologies must all work together the first time. In life too new materials and technologies, rather than altering the shape or function of an existing design bear a high evolutionary cost to evolve. We can estimate the cost from the fossil and phylogenic record. Attributes that evolved once only, that are monophyletic, took a long time or required unique circumstances to evolve, are hard-to-enact changes. Changes that occur relatively quickly among many types in a variety of situations would only bear a small cost to change, even if, like the eye that evolved forty times, it is not clear why the cost was so low.

The new model teaches that nature will adapt low cost changes first. Only when it is forced, when all the easy, low cost changes have been consumed, will nature adapt high cost, hard-to-alter changes in concentrated efforts. This produces the step changes. The step is not the radiation following a flowering of the altered type, but the build-up preceding it. The radiation of mammals 65 myrs ago looks in the fossil record like a step change, and in the rapid evolution of mammal orders such as carnivores or primates, it was. But mammals were able to radiate rapidly because the high cost changes had been paid for in the previous 140 myrs when mammals accumulated novelties such as body fur, placenta, or four-chambered heart. We presume too that the Cambrian Explosion within 15 myrs was the result of a prior accumulation that might have begun with the evolution of sex, half a billion years earlier.

So, in the new model it is not that selection and mutation do not act all the time. Just that mutations can be both "selected for" or "selected against". In stable ranges existing organisms tend to be already optimal, so only very favorable mutations improve adaptability, and these are rare. But once organisms are pushed into marginal niches they must drastically alter type anyway. Mutations will not be so much selected for, but mildly mutated types can survive as well as non-mutated types in a novel range where previous adaptability no longer counts. The survival of the mutated types is crucial for large-scale evolution. We say 'two wrongs do not make a right', but in evolution if a non-advantageous mutation can survive long enough it might join a second, third, or multiple mutations over time, which eventually expresses a useful new trait. Major genetic changes seem to work by this method of paralogous evolution rather than by the single allele mutations of neo-Darwinism. Over time new traits can evolve whose total complexity might not have had the opportunity to accumulate in a stable niche, where fitness margins were too tight.

Although the mechanism is different to his, here we agree with Steven Gould at least about the possibilities of change. It will take more than alterations in a few allele frequencies to change a dinosaur into a bird, or a reptile into a mammal. It will take massive directional selection over millions of generations to make these types of changes remotely credible as to how they occurred.

2.5.3 The Cost of Change

In orthodox theory the fitness landscape is a series of mountains, or peaks. Species try to 'ascend' the peaks, to always end 'higher' than they were before. Favorable mutations will push an individual slightly up the peak. The new theory has peaks too but only as small rises on larger plateaus. The paradigm is reversed because the simplest most reproductively fecund organisms like bacteria occupy the highest plateaus. Only a limited number of organisms can occupy a plateau, so population pressure eventually "pushes" some organisms off the plateaus into a fitness decline. The organisms on the decline throw up new mutations (literally, there is evidence that they mutate faster) searching out the adaptation that will arrest the decline and establish a stable plateau, at the least distance of fall. But declines can be large. Birds evolved for 60 myrs before they stabilized and radiated. Mammals evolved from mammal-like reptiles in 100 myrs, but from full reptilian ancestor it was 240 myrs. There were minor plateaus and radiations in that time, but apart from radiation of placentals, a recent event, the mammal type did not stabilize into full radiation until 65 myrs ago. For the evolution of prokaryotic into eukaryotic life a monophyletic search for a new fitness plateau continued for a billion years.

Still, extended periods of monophyletic fitness decline, where a narrow lineage accumulates complexity through strong selection directionality is nature's way of being efficient. When traits are at low cost to evolve there is no build-up of pressure for massive change. Only when existing phylogenies become saturated will new, hard-to-alter traits accumulate. Like with human R&D, this requires a concentrated effort. In evolution, change comes at a cost. Life is fragile. It takes huge effort to move life further from thermodynamic equilibrium. Thousands of different species scattered all over the face of the globe cannot suddenly all discover it would be fit to evolve feathers, placenta, or a large brain. The cost for so much wasted effort would be huge. Instead, of the billions of individuals forming the biota of the planet at any point in life each will try to adapt at the very minimum cost of change. A pterosaur will not attempt to evolve feathers if it can fly slightly faster than its rival via a thinner wing. A dinosaur will not evolve a four-chamber heart if it all it needs to run slightly faster is a longer leg. Just that over the entire biota of life, eventually all the easy changes; bigger, longer, sharper or faster become consumed. Only when there are no easy, low cost fitness changes left, some peripheral population, in a peripheral niche, bears a grim alternative to extinction by paying the fitness cost of radical change.

Only to speak of the fitness cost of change makes another break, very radical, from orthodox theory. As explained there are many ways to measure the cost of change; by increased metabolic rate, complexity, or the historic frequency or rarity of a type of change. But the best way to measure change is how nature does it, by measuring the change of DNA from one generation to the next. If an organism is perfectly adapted to its environment there is no need to alter DNA. If a slight alteration of an easily variable attribute like length or shape could better adapt the organism, only the DNA expressing those attributes, but not the basic DNA need be altered. So, a balance must be struck between allowing small changes when required but not willy-nilly mutations that would be costly and disruptive. That balance has been refined over billions of years of selection by the attributes of DNA. DNA does not mutate at the same rate, but DNA expressing various functions mutates at rates appropriate to evolutionary needs. DNA or RNA crucial to life barely alters, or does so at very slow above 10^-8 rates. Genes that must alter occasionally mutate at average 10^-5 to 10^-7 rates, while DNA that expresses the genetic personality of individuals, changes every gamete.

We are not sure exactly how parts of DNA 'know' the optimum rate at which they should mutate. If anything, we try to avoid the question by pretending that DNA mutates at the same rate. But the new model proposes that DNA fills a 'spectrum' of possible rates of alteration, analogous to the famed exclusion principle in physics. If we assume that DNA tries to mutate the least possible, there will only be one spot on the spectrum that can occupy a prime position of minimum alteration. This will go to genes that evolved early in life, and express homologies crucial to all life. Then as life evolves genes jostle to move further along the spectrum. They try to move away from the loose end, where DNA alters every gamete, and closer to the fixed end, where genes barely mutate a single bp over the history of life. And if this model sounds strange it makes sense. In neo-Darwinism single genes pass or fail at each reproduction, but this is only true for unique DNA. Most genes occupy a spectrum of probabilities of passing on in any generation. The new model can better express this, although it only applies to large-scale gene flow.

The new model can also better explain the genome fitness loss. The genome is the entire spectrum in any one individual, including its slow and fast mutating elements. Generally, individuals will try to pass on as much of their spectrum as they can, which might exist as a subjective compulsion like sexual urge to the individual, but also as an objective measure to the scientist of how successful the design of any genome was. Only genes within the spectrum have "selfish gene" interest too. Unique DNA and the individual as a phenotype both want the whole spectrum to pass on. But highly conserved genes will pass on anyway as a probability, whether the individual in which they happen to be transiently resident reproduces or not. When we say that genome fitness falls as organisms evolve greater complexity it is only the frequently altering DNA that looses fitness. Here, the variable part of the DNA spectrum is forced to alter to the new requirements. Highly conserved genes are more likely to gain fitness as types accumulate homologous traits. It is like with sex. 50% of easily altered DNA fails to pass on during sexual reproduction. But early evolved, highly conserved genes, those around when sex evolved, pass on anyway. Plus they gain fitness from sex because they spread into more variety and types.

We suspect then that though genomes loose fitness as types accumulate complexity, certain genes gain fitness. We see this in the evolution of higher animals. To evolve from a reptile to a mammal must have extracted a huge fitness cost. Reptile DNA was altered or deleted, litter sizes went down, metabolic rate went up, and the complex genome of a mammal is harder to copy exactly than the simpler genome of a reptile. But for those genes that made it through the transition results were impressive. Mammals radiated into a huge variety of types, more diverse than reptiles, but conserved 70% of base expressed genes in all this variety. For great apes homology is even higher, with 96% of genes in common able to express a variety of types. For humans, although genome DNA is shuffled each gamete, 99% of human genes are highly conserved throughout the species. As humans have also largely moved adaptation outside of biology these genes might also not be forced to alter much in future. So while evolving the large brain must have borne high costs some genes undoubtedly benefited. We can say that as new complexity accumulates genome spectrums extend to the loose end, growing longer and raising the overall cost to genome fitness. But conserved genes at the tight end of the spectrum either hold their existing place or might gain slightly increased stability from expressing a new homology that will radiate once the type matures.

Still, the cost of change is just an efficiency of nature. Nature has no teleology. It is not compelled to evolve complexity, but will do so if it can find a cost-efficient way. Organisms too do not become fitter by increasing complexity, but will loose genome fitness if there are easier ways to survive at the existing complexity levels. Only as existing complexity levels saturate, populations get pushed into marginal niches. Pressure to alter and attenuated competition in the niche will allow some organisms a broader fitness cost margin. Any change of DNA extracts a cost but there are different ways to pay as life evolves. Evolution from prokaryote to eukaryote DNA was a large change. Much DNA in eukaryotes had to evolve from scratch, which would extract a huge cost, so it took a billion years for eukaryote life to evolve. Even then it was restricted to a single kingdom although two prokaryote kingdoms existed. However, once it evolves, eukaryote life brings non-expressed DNA, chromosomes, and expression mechanisms that allow genes and chromosomes to be copied first and modified later. This lowers the cost of future change by providing cheap DNA templates for future designs. Sex further lowers the cost of change, by providing greater variety for selection to act on, at reduced risk of lethal disruption. (High mutation rates are not a good way to create variety as things can go catastrophically wrong. Here at least sex is safer!) So though about ten times more DNA had to be invented or modified to evolve eukaryote life than existed in prokaryotes, the cost was paid in a billion years of accumulation. By contrast, humans evolved from great apes in a few millions years, but only 1-2% of great ape DNA had to be modified. Only most costs of human evolution were paid for earlier in the evolution of mammals, or still earlier in the evolution of sex or eukaryote life.

Evolution of complexity then is a balance of costs. Any change of genome DNA extracts a cost, but costs are less at the floating right end of the spectrum where change occurs every gamete than at the left, fixed, conserved end. Only in the eons of early life very high costs could be paid for with time, because change occurred slower in generations than genes mutated and evolved. But as the pace of evolution increased costs of change among entire gene sequences become harder to bear. Mammals evolved in about 10⁸ generations, or roughly 100 myrs at one generation per year. This allowed further change over time at moderate cost because most genes mutate in a 10^-5 to 10^-8 rate that allows evolution within 10⁸ generations of time. Yet not only mammals, but all the modern classes such as insects or flowering plants now have high rates of evolution at 10⁵ generations, or less than a million years in modern life. This affects how costs can be paid, at least with time and slow accumulation. And while it is argued that larger populations will allow slower mutating genes to affect evolution, we only see minor speciation among modern classes and orders, not the upheavals of the past. The most dramatic evolutionary changes today seem more among viruses, parasites and diseases. But genes for these often do mutate faster than 10^-5, which correlates to the general pattern of how all life evolved.

How then from these very preliminary remarks on what must be a most complex and difficult to understand model of evolution, do we explain human evolution?

Again, we caution that there is great dispute about whether intelligent life evolves inexorably. A separate debate concerns the rarity of planetary conditions to even allow prolific life to evolve. But even when planetary conditions are very favorable to life, as on Earth, most biologists today see human evolution as a toss of the dice. A few alleles the other way and we might have been another ape. Or a few alleles a different direction three hundred myrs ago or no asteroid to wipe them out, and dinosaurs would not have given way to mammals. In the new model too we would not claim that if any of these events had unfolded differently, a man called Brutus would still have stabbed Caesar precisely on the Ides of March. Yet certain trends occurred in the evolution of life on Earth, such as the increasing rate at which species were able to evolve as life became more complex, and we need to explain why.

Ironically, only by allowing that complexity evolves at a fitness cost can we understand why it evolves. Simple organisms exist first. While these have an impetus to refine design by incremental fitness there is no impetus to vastly increase genome size or complexity. Organisms that already exist at any stage of complexity evolved from preceding refinement and are optimized to that mode of existence. From that level no organism will enhance fitness through a large change if a rival can be slightly fitter from a small change. This is why simpler forms of life are still the most enduring. Bacterial designs from billions of years ago persist only slightly modified today, and are the most prolific forms of life. And if we seek life on near-dead planets we seek a bacterial mode that will need a very low cost to sustain it. Early life was also thermophilic, so it could evolve near rich energy sources at the least evolutionary cost removed from nonliving thermodynamic equilibrium. Only rather than measure the cost of evolution in each tiny balance of time or energy, in the new model we suggest that it is easiest to measure the cost of evolution the way nature does, by change of genome DNA. But the real cost of change is in the abundance of a planet, in energy, time, stability, and raw materials to feed the engine of change. Nature is not forced to evolve complexity, and organisms loose genome fitness as they become more complex. Just that once existing levels of complexity become saturated with fit types other types will seek less fit existence at higher complexity levels in order to survive. If the ecological and genetic resources of the planet available at the time can afford the cost of a further increase in life's complexity, selection will search out a solution.

So we are not saying that life evolves inexorably towards intelligence, but near the opposite. Complexity evolves at a cost, which must be paid by the energy, chemical, time, ecological, and genetic resources a planet. If life on any planet cannot afford the cost to evolve beyond simple forms its life will arrest at that level of development. Only Earth, for reasons not altogether clear, retains a prolific ecological account. Not just for human evolution, a recent event, but for billions of years, evolution of life on this planet has never encountered a cost to evolve further complexity that the planet could not afford to pay. When costs have been high evolution has only slowed, if we can measure such a thing, but not halted. Life evolved in a half a billion years, but it took another two billion years to evolve from prokaryotic to eukaryotic life. But the eukaryotic cell dramatically lowered the cost barriers to further evolution because with its new machinery DNA sequences that took billions of years to evolve the first time could be quickly copied and modified into new needs.

What we want to know then, scientifically, is not how different history would be if an asteroid had not killed the dinosaurs. Such a question has no answer that we can verify. We want to know instead what happens when the resources of a planet, any planet, can seemingly furnish the cost of any level of biological complexity that can evolve. Will biological complexity increase without limit, or is there an inherent upper limit to how complex living forms can become? And if a limit exists, what form will life at that limit take?

The answers lie in trending rates of evolution against costs to evolve easy and hard to enact changes. Only for life on Earth once complex phylogenies evolved they have tended to saturate. Complexity makes newly evolved types highly variable, so that they can adapt much faster than simpler types for equivalent cost. The eukaryotic cell evolved at a huge cost over time, but once it evolved no more cell kingdoms were possible. Nothing else could evolve into anything as versatile as a eukaryotic cell at such a cost, faster or more cheaply than a eukaryotic cell could adapt to new requirements. Similarly, mammals evolved at a huge cost. But it was also a cost that no other creature could later afford to pay, to evolve into something a mammal already was, faster than a mammal could evolve into something better. If a reptile with a two-chamber heart can evolve a bigger heart, a mammal can also evolve a bigger heart in the same time, only it with a more efficient four-chamber heart. Yet, no other creature could evolve a four-chamber heart in the short time a mammal could adapt another part of its phylogeny, to win any race for adaptation. (Competition is more between members of the same species, in competition for fitness against another species, etc.)

But as life advances and a broad phylogeny like that of mammals saturates it breaks down into sub-phylogenies, which also saturate. Some early mammals were confined to forests, which evolved a primate phylogeny, more variable again. Litter sizes went down, paws evolved into hands, backbones and limbs became flexible, brains become larger, and behavior became more social and complex. This in turn allowed the new creatures to adapt even faster. Learned, social behavior can be adapted faster than inherited behavior. A hand can adapt faster to a new means of food gathering than a paw. Flexible limbs and backbone can adapt faster to new means of locomotion than rigid designs. Only once primates can adapt fastest of all species to climate and vegetation changes, phylogenies of species who cannot adapt as fast as primates also become saturated for like fitness. If a cat has a paw, but the primate already has a hand, a cat cannot evolve a hand at the speed a primate can adapt behavior. Once a family has hands, versatile limbs, large brain, varied diet, social behavior, stereoscopic vision, opposed thumb, and crude tools, little more can be squeezed from evolution of large animals as new novelties. At least, nothing can evolve as fast as other simple changes can be adapted.

Another factor causing saturation is evolution of the brain. Early neurology evolved for specific functions we call reflex. Then circuits evolved for simple learned behavior such as imprinting, as in birds. But mammals evolved learning circuits, and these can move evolution outside of DNA. DNA can express the design of a "learning circuit" and multiply the number of circuits in a brain, but DNA does not have to design each learning circuit by selection. This produces an effect similar to the microchip in technology. When each circuit in a computer had to be designed each time computers were expensive. But once computer chips became programmable, costs fell, because the same chip could perform many functions. Similarly, while each neural circuit must be selected for each function, brains can only increase size slowly. But once we have universal self-learning 'design once, use-many-times' neural circuits, brain size can increase faster than any other attribute of biology can adapt. Or, as with human evolution, evolutionary costs become morphological, such as how a large brain can egress the womb, rather than any cost to additional neural circuitry.

Of course, not all creatures need large brains to survive. Only once brains can evolve quickly, somewhere in the vast concatenating system of life the cost of evolving new novelties in any species must be measured against what it would cost an ape to evolve a bigger brain. In the Age of Reptiles one can calculate an evolutionary cost for a large animal adapting its phylogeny to flight. Until birds have evolved feathers, pterosaurs can evolve wings at the least cost from a given starting point. Yet once feathers evolve, these are so efficient that long-range flight becomes saturated for all other tetrapods. Mammals can adapt short-range flight as bats, but this saturates too once the bat phylogeny matures. Except there is one other option for flight among advanced mammals. It is to build an airplane! Remarkably, this adaptation is very fast. It is only five million years of evolution from human ancestors to airplanes. So, although traits like wings have evolved many times, any trait is still only easy-to-evolve if there is a fitness impetus to do so, in rivalry to other means of adaptation. If a wing, eye or flipper is easy to evolve, it does so many times. But if a trait like limbs, feathers, or four-chamber heart evolved at a large fitness cost, no modern creature can afford the fitness penalty to evolve that novelty again, facing the fiercer competition the new novelty brings

Thus as life evolves, phylogenies become more versatile. A hand is more versatile than a paw, learned behavior can be adapted quicker than inherited behavior. Groups can learn faster than individuals, and a brain that can learn not only learns, it can evolve faster for a lesser genetic cost than designing each neural circuit for reflex. As species evolve so do underlying phylogenies, and what one phylogeny becomes already another cannot be. When the trait in one phylogeny cannot evolve at the speed or minimal fitness cost of the trait in a rival, that phylogeny is in saturation. Great Ape evolution brings a state of general saturation for large animal life on Planet Earth. This means that all the major classes, orders, families and even the genus of large animals have been established. And nothing could evolve a significant new novelty to break this pattern, faster than a Great Ape could evolve into a human. Unfortunately, this is now bringing tragedy. Humans have already destroyed many species such as the Mammoth, which could not adapt fast enough, and threaten many more. Humans have also deforested whole continents, and might bring on a global extinction.

The new model proposes then that there are trends to the way life on Earth evolved, apart from its accidental or historic aspect. Life on any planet always begins at a base layer of simple, small organisms, but if the planet can sustain the cost, new layers will add above the older ones. Because there is a cost adding new complexity, it will only evolve if by doing so it can lower the cost of further change. On Earth, this need to increase adaptability for any increase in complexity produced discernible trends. Everywhere, rates of evolution among more recently evolved types, whether large animals, insects, birds, viruses or flowering plants went down. Especially, large animal evolution displayed trends of increased intelligence, emotion, versatile behavior, and metabolic rate, plus trade-off trends such as decreased litter sizes in exchange for increased parental care. Parental care is another expression of higher adaptability. Learning is more flexible than inherited behavior, so if greater parental care is spent on fewer infants, who survive longer, learning is easier to pass on. How these trends unfolded on Earth in a purely historic or accidental sense is not a cast iron law that intelligent life always evolves, or that it will be bipedal with smiling faces. But evolution of complexity increases evolution of adaptability. For large animals that means shifting adaptation from altering hard biology, to altering the easier attributes to adapt first, such as intelligence, learning, behavior, and emotion.

To those who have built electronic machines this trend in nature is striking because it is the trend technology has followed. Competition and the cost of building new machines requires that all machines be increasingly adaptable to change. This focuses the design of machines on the easiest parts to alter, such as the electronic program. Yet the mammal, primate, or human form reflects how one would build a costly machine. (Computers are costly machines, just that today we mass-produce them by the millions.) Almost half the genes in primates are for expressing neural functions. Even then, much of the mental adaptation is moved outside of biology into learning, and in humans about 80% of adaptation is moved into learning. For the non-neural functions too, the hand, the face and the body are designed for adaptation. Litter sizes are also small, with emphasis on parental care, nurturing, learning, and keeping progeny alive, exactly how one would treat a costly biological machine. So, we do not see the precise human form as an inevitable result of trends begun by Archaean bacteria four billion years ago. But we do see that complex life would evolve in ways leading to increased versatility and adaptability as the cost of evolving further complexity increased. The end point would be life that could adapt mostly outside of biology, although we could never predict exactly what form that would take.

Despite the controversies and contentions then, the remaining chapters of this book will use this new model of evolution to explain the broad impulse of why humans evolved. Allowing that intelligent life evolves other than by pure chance does not make a theory true, any more than allowing it only by chance makes a theory false. Any theory is only as good as the mechanisms it explains as facts we know. The current dogma of ultra-Darwinist orthodoxy is that all evolution results from no force other than selection acting on chance mutations among genes. So nothing scientifically can be concluded from humans randomly evolving by this process, more than any other organism. But it is also not without notice that the same upholders of a rigid ultra-Darwinist orthodoxy in general evolution have insisted on explanations of human evolution and behavior that have been lamentably unconvincing. In this sense the new model leads to a theory of human behavior more in accordance with facts we do know, than any current model of evolution

In the new model, we say there must be important lessons in evolutionary theory from the fact that humans have evolved, and why they behave the way that they do. Evolutionary theory, to be complete, must explain all the biological forms that have evolved on Earth, from the most simple to the most complex.