This is a story about evolution's traps, its huge barriers, its blind spots, its compromises, its compromises, its failures.
Through this, we will learn why animals always lag behind slightly, why they generally become less efficient over time, why predators often lose, and why parasites often win.

It's an evolution, but it's not a great success.

---From "Entering"

Lawrenson estimated that the cheetah cubs had a 4.8% chance of surviving to 17 months (roughly the number of months they are independent).
Now, let's compare these figures to the people of the Central African Republic, the country with the lowest life expectancy today.
Here, 91% of children survive their first birthday, and 88% survive their fifth birthday.
Therefore, the life of a young cheetah is far more precarious than that of a child living in the most impoverished country on Earth.
So, is the cheetah the perfect predator? Quite the opposite.
Most cheetahs cannot kill anything.

---From "Chapter 1 Dead or Hungry"

Just as a lawyer might advise a divorcing couple to settle out of court rather than spend thousands of dollars each to arrive at the same conclusion of property division, a benevolent authority would have provided each side with only what was necessary to maintain the status quo, rather than wasting countless hours of effort on longer bones, stronger tendons, denser muscles, and larger hearts.
But without this strategic oversight or purpose, that never happened, and the cost of survival for everyone steadily increased.

---From "Chapter 1 Dead or Hungry"

But what if the nest had been over-prepared from the start? The cuckoo chick would have hatched before the other eggs and, like other European cuckoo chicks, would have knocked the other eggs out of the nest one by one.
The only chick that hatches accordingly will be a cuckoo, and the parent birds will imprint on the cuckoo.
After this, all attempts at breeding will fail, whether or not they are swarmed.
Because the bird will happily raise another cuckoo or reject its own chicks.
In this case, it is actually better for the host to occasionally pay the price of accidentally raising a cuckoo than to evolve a chick imprinting response that would prevent it from reproducing for the rest of its life.
It may not seem obvious right away, but the answer to the question, "Why don't cuckoo hosts reject the big monsters in their nests?" is, "Because in the long run, it's not beneficial to reject them."

---From "Chapter 2: One Flew Over the Cuckoo's Nest"

The appeal of parasitism as a way of life is beyond question.
This is especially true for internal parasites, as the host provides not only food but also the entire environment.
The only problem that matters to them is contagion (since the inevitable death of the host will also lead to the disappearance of the habitat).
Therefore, internal parasites must find a way to jump from one host to another, and to do this, as we have seen, they have evolved many methods, some of which have become extremely sophisticated, such as making the host commit suicide or finding an intermediate organism (vector) to act as a transmitter.
But what is even stranger is why the host tolerates such methods.

---From "Chapter 3 Free Riders"

The most attractive males die earliest and are least likely to produce male offspring that survive to maturity.
But this obvious handicap doesn't matter at all.
Because the most ornately decorated males leave behind the most offspring.

---From "Chapter 4: The Beautiful and Cursed"

The males with the widest eyes a million years ago were just as attractive to females in their generation as the males with the widest eyes are today, but they would have fared better throughout their lives because they didn't waste as much energy growing and maintaining eye stalks or compensating for air resistance during flight.
This is a comparison of the fittest males a million years ago and the fittest males today.
In short, this species has become more messed up over time.
It is an evolutionary product of natural selection.

---From "Chapter 4: The Beautiful and Cursed"

Organisms are usefully conceptualized as mere vehicles for the continued proliferation of existing genes.
So we should remember this when we wonder why animals didn't evolve to live forever.
In short, genes don't care where they are, as long as they exist somewhere.

---From "Chapter 5: The Whereabouts of the Seventh Tooth"

The selfish behavior of a gene can easily be converted into altruistic behavior within the organism in which the gene resides.

---From "Chapter 6: Extreme Altruism"

In conclusion, neither malice nor altruism is purely praiseworthy or detestable.
You shouldn't expect that to happen.
Like other evolutionary forces, kin selection operates blindly, without goals or purpose.
The cooperative social relationships of species such as lions and elephants are shaped by the same pressures that cause premature death and the suffering of aging.
Likewise, as seen in honeybee colonies, the "unified thinking" of the superorganisms of the membranous order can present us with the plausible appearance of cooperation, diligence, and miracles of organization, but it can also lead to suicidal aggression and enslavement.
It also suggests that in the cozy yet cruel world of social species, there are always tricksters willing to manipulate the altruistic actions of others for their own ends.

---From "Chapter 6: Extreme Altruism"

Egg throwing, miscarriage, and countless other acts of filicide observed in the natural world can be thought of as trade-offs between present and future investments.
As with any compromise, the optimal balance point is often determined by external circumstances.

---From "Chapter 7: A Cruel Compromise"

The way for males to maximize their fitness is to have as many offspring as possible.
These different limits to fitness mean that while females play a game of chance, males play a numbers game.
These two games don't really go together.
From this basic dynamic arises much deception, cruelty, and suffering.

---From "Chapter 7: A Cruel Compromise"

Steller's sea cow, Dreadnoughtus shurani, and Tucson's Cooper's hawk were faced with a situation for which evolutionary history had not prepared them.
The two animals above showed that lack of preparation was fatal, and they paid the price of extinction.
In the case of the eagle, the bullet may have missed, but the threat of a mismatch between what was expected and what was encountered remains, and in other times and places it may be eliminated.
But it is extremely harsh to be punished like this for insufficient adaptation.
All species, even those that appear to be thriving on the outside, have flaws.
They are just 'okay enough' and have one or more of several potential flaws: evolutionary quirks, laziness, clumsiness, etc.

---From "Chapter 8: Evolution in Trap"

The same goes for animals.
Animals enjoy the benefits of evolution accumulated over billions of years, but along with those benefits, their range of choices for the future is narrowing.
The lungs of a gray whale stranded in the Beaufort Sea are a decidedly unhelpful legacy of hundreds of millions of years of terrestrial evolution.
Whales have distant ancestors from fish, but they evolved relatively recently from four-legged creatures living on land.
And when the whales returned to the water, they were less acclimated to it than when they last left it.
Because they lost their gills a long time ago.
Here we can ask the rather obvious question (though of course we should not be satisfied with this): 'Why don't whales re-evolve gills?'
In any case, it is clear that although fish ancestors started out with gills, some of their descendants evolved lungs at some point.
So, conversely, wouldn't it have been possible to evolve gills at some point?
---From "Chapter 9: A Pretty Good Weakness"

Evolution is purposeless, passive, and amoral.
This is one reason why it is impossible to draw a connection between what natural selection favors and what we, as civilized humans, should aspire to.
Another reason is that the most direct agents of evolutionary change are genes, not individuals.
So even if we can find 'purpose' in this arduous river of survival, reproduction, and death, we can be sure that we are not its beneficiaries.

---From "Chapter 10 Where Humans Are Heading"

The natural world is full of events and actions that cannot be considered morally instructive.
So far, we've looked at elephants that starve unnecessarily, ants that create slaves, spiders that mutilate female genitalia, pathogens that drive their hosts to suicide, evolved malice, deceptive partners, and various forms of survival killing, filicide, and fratricide.
In addition, we could add cases of otter rape of a baby spotted seal (or seal rape of a king penguin), a pair of deer fighting and dying with their horns entangled, a babirusa (wild boar) tusk growing curved toward its skull, and many other predators continuing to eat their prey while it is clearly still alive.
If any human behavior doesn't fall into this miserable and absurd lineup that unfolds under the label of "natural," can it be defined as immoral? I hope the answer needs no further explanation.

---From "Chapter 10 Where Humans Are Heading"