Chapter 128 21.2 What is the purpose of evolution

Even if we admit that the evolution of life does not show any signs of progress, does it have a general direction? Looking through the books on evolution, I can't find a book with the words "trend" or "direction" in the table of contents.Many neo-Darwinists never mention the two words, almost fanatically eradicating the concept of progress in evolution.One of the most outspoken of these was Steven Jay Gould, one of the few biologists who has publicly discussed this idea. Gould's popular science work "Wonderful Life" gave a new interpretation of the Burgess Shale fossil group.At the heart of the book is the idea that the history of life can be viewed as a videotape.We can try to rewind the tape back to the beginning, and with some magical power, change some key scenes at the beginning of life, and then replay the course of life from that point on.This tried-and-true literary device reaches its apex in the American Christmas classic "It's a Wonderful Life": in this film, the protagonist Jimmy Stewart's guardian angel reenacts for him the lives of others who have become unhappy and miserable without him. human life.Therefore, Gould borrowed his name and used it as the title of his own book.

If we were able to replay the evolution of life on Earth, would it follow our known history?Will life replay those familiar phases, or surprise us by making the opposite choice?Gould uses storytelling to tell us why he thinks that if evolution could be repeated, we would be completely unrecognizable to life on Earth. Besides, now that we've been able to play this amazing videotape in our machines, maybe we can go a step further and do something more interesting.If we turned off the lights, flipped the tape around at will, and played it again, would a visitor from another world be able to tell whether the tape was playing forward or rewinding?

What would we see on screen if we played this epic "It's Amazing Life" in reverse?Now, let's dim the lights and take a closer look.The story unfolds on a magnificent blue planet: the surface of the earth is covered with a thin layer of biofilm, some are moving animals, some are rooting plants.There are tens of thousands of different types of actors in the film, about half of which are various insects.In this opening, not much story happens.Plants have evolved in countless shapes.Some dexterous large mammals gradually evolved into similar looking but smaller animals.Many insects gradually evolved into other insects; at the same time, many new faces appeared, and they gradually changed into other forms.If we look at an individual closely and watch its changes closely in slow motion, it is difficult to discern any particularly obvious forward or backward changes.In order to speed up the pace, we pressed the fast forward button.

From the screen, we see that life on earth is getting rarer and rarer.Many animals—but not all—began to shrink in size.The number of biological species is also decreasing.The development of the storyline slowed down.Creatures play fewer and fewer roles, and each role has fewer and fewer variations.Life gradually decays in scale and size until it is reduced to tiny, monotonous elementary elements.In the uninteresting finale, the last living creature disappears as the creature evolves into a single, tiny, shapeless ball. Let's recap: an intricate, interconnected and vast biological network composed of diverse groups of organisms eventually degenerates into a few protein particles with simple structures, single styles, and mostly self-replicating.

What do you think?Friends from Star of Thor?Do you think this particle is the beginning or the end? Neo-Darwinists argue that life certainly has a direction in time, but beyond that, nothing is certain.Since organic evolution has no directional trends, the future of life cannot be predicted.The unpredictable nature of evolution is thus one of the few predictions we can make with confidence.Neo-Darwinists believe that evolution is unpredictable.When fish were having fun in the oceans—the "peak" of life and complexity—who would have guessed that some ugly monster was doing something of vital importance in a dry mire close to land?And land, what is that?

Post-Darwinists, on the other hand, keep referring to "necessity". In 1952, British engineer Ross Ashby wrote in his influential book Designing for the Brain: "The development of life on Earth must not be regarded as an extraordinary event. On the contrary, it is Something that must happen. A system as large and basically polymorphic as the surface of the earth has remained tepid for 5 billion years, and all variables have aggregated into a form that is extremely self-sustaining. Unless it is a miracle Take it out of this state. In this situation, the birth of life is inevitable."

True biologists, however, recoil when "necessary" is placed in the same sentence as evolution.I think this is a normal reaction, since "necessity" has historically referred to "God".Still, even the most orthodox biologists agree that one of the few legitimate uses of artificial evolution is as a test bed for the study of directional trends in evolution. Are there some basic limiting conditions in the physical world, so that life can only move forward along a certain trajectory?Gould likened the possibility space of life to a "broad, low-lying, uniform slope."Droplets of water fell randomly on the slopes and trickled down, eroding many small chaotic ravines.The gullies that formed deepened as more water washed over them, soon forming small valleys and eventually larger canyons.

In Gould's metaphor, each tiny gully represents a historical path in the development of a species.And the initial gully sets the course of the subsequent genera, families, and classes.Initially, the orientation of these tiny grooves is completely random, but once formed, the orientation of the subsequent canyons is fixed.Although he concedes that there is an initial slope in his metaphor that "does set a preferential flow for the precipitation on the crest," Gould insists that nothing disturbs the uncertainty of evolution. sex.The explanation he likes to repeat is that if you repeat an experiment like this over and over again, each time starting with the exact same blank slope, you will get a very different terrain of valleys and peaks each time.

Interestingly, if you conduct a field experiment on a sand table exactly according to Gould's imaginary experiment, the result may just imply another contradictory point of view.When you repeat this experiment over and over again, as I have done, the first thing you notice is that the types of landforms you get are a very limited subset of all possible types.Many of the familiar geomorphic features — rolling mountains, volcanic cones, spandrels, hanging valleys — will never appear.Therefore, you can safely predict that the resulting valleys and canyons will generally be gentle valleys. Second, although the initial furrows appear randomly due to the randomness of the water droplets, subsequent erosion follows a very similar process.Canyons will be revealed in a certain order.To borrow Gould's analogy: the first drop of water is the first species; it could be any unexpected organism.Although its characteristics are unpredictable, the deduction of the sand table proves that according to the internal tendency of sand composition, its progeny show a certain predictability.So, although evolution is sensitive to initial conditions at some points (the Cambrian Explosion being one), this by no means excludes the influence of megatrends.

At the turn of the nineteenth and twentieth centuries, some reputable biologists made a big splash about evolutionary trends.One of the famous theories is vertical evolution.Vertically evolved organisms develop along a straight line, from the earliest organism A, down the alphabet of life, to the last organism Z.Some directed evolutionists in the past really believed that evolution was unbranched: they imagined evolution as an upward biological ladder, each rung home to a species, each rung closer to divine perfection. Even vertical evolutionists who are less prone to linear perfection tend to be supernaturalists.They feel that evolution has a direction because some force guides it.This guiding force is supernatural, or some kind of magical life force injected into living things, or even God himself.These concepts are obviously beyond the scope of scientific cognition, and they are not very attractive to scientists. In addition, mysticism and the worship of "new human beings" make people keep them at a distance.

But over the past few decades, godless engineers have built machines that can set their own goals and seem to have their own motivations.The founder of cybernetics, Norbert Wiener, was one of the first to discover the internal self-direction of machines.He wrote in 1950: "Not only can man set goals for machines, but in most cases a machine designed to prevent certain failures will seek out goals that it can achieve." Ner hints that purpose inevitably emerges once the design complexity of a mechanism crosses a certain threshold. Our own consciousness is a collection of unconscious elements out of which purpose emerges in exactly the same way that purpose emerges in other non-conscious living systems.As a most practical example, a low-end thermostat also has a goal and a direction—to find and maintain a set constant temperature.Shockingly, purposeful behavior can emerge from the many purposeless subbehaviors in software.Rodney Brooks' MIT mobile robot is designed from the bottom up to perform complex tasks based on goals and decisions, while its goals emerge from simple, purposeless circuits.Ever since, Genghis, the worm-shaped robot, "wanted" to crawl through the thick phone book. When evolutionists shake God out of evolution, they think they have shaken out all trace of purpose and direction.Evolution was a machine without a designer, a clock made by a blind watchmaker. However, when we actually build very complex machines and dabble in synthetic evolution, we find that both can function on their own, and each has developed its own set of ways of doing things.Is the order of self-organized disorder seen by Stuart Kaufman in adaptive systems, and the purposeful goals bred by Rodney Brooks in machines, sufficient to explain whether evolution How does it happen that it all evolves its own purpose and direction? If we look carefully, we may find that the direction and purpose that emerge in biological evolution can arise from a large number of purposeless and directionless constituent parts, without invoking vitalism or some other supernatural explanation.Experiments with computer evolution confirm this inherent purposefulness, this spontaneous "trend."Two theorists of complexity studies, Marc Bedow and Norman Packard, have carefully judged many evolutionary systems and concluded that "deterministic systems can be unpredictable , we believe that deterministic systems have purpose." For those confused by the "purpose and evolution" debate, this explanation will help them understand purpose as "drive" or "momentum". ” rather than a conscious, intentional goal or plan. In the next section, I lay out the large-scale, spontaneous momentum that evolution can have.The word "momentum" as I use it here is a general concept, and exceptions are allowed, not every biological species will follow these trends. Let's take the common principle "Cope's law" in textbooks as an example.Kopp was a famous collector of giant bone fossils in the 1920s, and he used to redraw the appearance of dinosaurs in various ways.He was a pioneer in the study of dinosaurs and relentlessly promoted the study of this strange creature.Kopp noticed that, in general, mammals and dinosaurs seemed to grow in size over time.Subsequent paleontologists took a closer look and found that his views applied to only about two-thirds of the fossils on record; one can find many exceptions, even among species he once paid close attention to.If there were no exceptions to his rule, the largest living things on Earth might be fungi as large as city blocks, rather than the "primitive" mushrooms that hide in the forest floor today.Nonetheless, there is certainly a long-term trend in evolution whereby smaller organisms such as bacteria predate larger ones such as whales.