A great read that explains evolution, natural selection, darwinism, and why these are not only the theories most strongly supported by the evidence, but also why they are the only theories we have that, in principle, could even begin to explain the existence of life. Dawkins takes a complicated subject—in fact, many subjects, including biology, chemistry, physics, math, probability, programming, geology, and more—and manages to explain them in a clear, approachable way that can be understood by just about any educated person.
There are lots of wonderful insights and explanations in the book:
Order from disorder
The physical “shape” of an object is enough to create order from disorder.
For example, consider a natural sieve, which is any item that just happens to have a small hole in it:
- Small objects will tend to go through the hole and large objects will not.
- The result is that items get sorted by size.
- We get order from disorder, but no designer was involved!
Similarly, the “shape” of biological devices can create order:
- The key idea behind life is that certain molecules can create copies of themselves solely because of their “shape” and normal physical/chemical processes.
- It seems highly orderly, but no designer is necessary to make this order possible.
How life might have started
The book goes through a few possible theories for how life could’ve started on earth—how these initial self-replicating “shapes” could’ve formed. One interesting idea was that life developed from clay crystals (silicates):
- These crystals live in river beds and take various shapes based on the flow of the water and the other crystals they touch.
- Occasionally, the crystals just happen to form a shape that tends to stick together very well and as more clay runs into this shape, it clumps up more and more, and eventually forms a small dam in the river.
- This causes stagnant pools of water to form near these dams and, during the dry season, these pools dry up.
- The clay also dries, cracks, and then wind blows this crystalline structure around, like spores.
- Some of these crystals end up in other rivers, where their shape cause clumping to happen again, creating more of the same “shapes”, and repeating the entire process with dams, pools, and drying.
- In other words, the shape of these clay crystals allows them to “replicate” themselves.
Of course, clay crystals are inorganic, but perhaps the organic molecules that are the building blocks of modern life were able to somehow build on top of the replication abilities of these inorganic crystals.
- For example, some organic material that happened to be in the river may have bonded with the clay, and changed its shape in some way that happened to increase the odds of the clay replicating.
- Now not only are clay crystals being replicated from river to river, but the organic molecules also come along for the ride.
- Eventually, the organic molecules may be all that’s necessary.
The probability of life
How could the order and complexity of modern life arise from such “random” events? What are the odds that clay silicates blowing in the wind leads to something as intricate as the human eye? The book has a great discussion on the probability of life, with two key points:
- The odds of something as complicated as an eye forming are so vanishingly small as to effectively be impossible.
- The odds of the basic building blocks of life forming, given that those building blocks are much, much simpler than the eye, are much higher. Those odds may still be low, but not impossibly low, and given that there are billions of planets and billions of years, even fairly unlikely events can happen.
Single-step vs multistep
Note that while the events (i.e., mutations) are random, the selection process is not!
- Complexity didn’t appear randomly, in one giant leap, going from a simple replicator to a fully-formed eye.
- What we’re seeing is adaptive complexity, where complexity increases step by step, generation after generation.
- Each change is a tiny increment that happens randomly, and if it happens to increase the chances of replication, it will be passed down to future generations.
Consider a simpler version of the infinite monkeys on infinite typewriters theorem: how long would a single monkey typing randomly at a single typewriter take to come up with just one specific sentence from Shakespeare?
Single-step version:
- Each sentence was written separately.
- There’s no relation to previous sentences.
- The odds are extraordinarily low: even with a very fast monkey (that is, a computer program simulating a monkey), it would take longer than the age of the universe.
Multistep version:
- The monkey starts with one sentence.
- At each step, it makes a bunch of variations on the sentence, each with random mutations to it.
- Some “selection pressure” (e.g., a computer) selects the sentence that, in some way, resembles the chosen Shakespeare sentence the most, and the process repeats.
- The odds of ending up with the desired sentence are actually quite good: our computer program can get it done in a matter of minutes.
Examples of multistep
We can see real-world examples of this idea. Dawkins walks through the step-by-step process that evolved the eye:
- We start with a tiny spot that just happens to be sensitive to light
- The spot becomes a small indentation
- Eventually, the indentation becomes an eye
There are entire books that walk through every stage of this evolution and show real, living creatures that have eyes at all of these stages.
It turns out that “half an eye” really is better than “no eye,” in the sense that even a little bit of vision is better than none at all!
Species are not so clear-cut
Speciesism is believing that some species have more rights than others, such as believing in “human rights,” but not the rights of other animals. Many believe this because:
- The vast majority of “intermediate” species in evolution just happen to have died off.
- If all of them were still around, and we could see all the tiny increments from us to our primate ancestors and other mammals, we’d realize that there is no clear point where “human” begins and “primate” ends.
- If we could see all the species in between, we’d realize that the definition of which animals are “human”—and which ones deserve special rights—is not at all clear-cut.
I suspect the same will happen if we ever develop general AI. There may be countless small increments from simple, unthinking, mechanical computer algorithms to self-aware, sentient AI, and there probably won’t be a single, clear point where we can declare the AI as “alive” and start pondering what rights it has.
