The Third Chimpanzee: Summary & Review

the third chimpanzee book cover

The Third Chimpanzee takes an evolutionary psychology approach to investigate these wonderful animals we call “humans”, ranging from sexuality and sexual strategies, human nature, extraterrestrial life, future challenges and solution to world problems.

Bullet Summary

  • We will soon reach the biological limits of earth’s capacity to feed us and provide us with resources
  • We have no predators’ left to control our population, we risk destroying ourselves by destroying our resource base
  • The solutions are easy though:
    • Halting population growth
    • Reducing our impact on the environment 
    • Preserving species and national habitats
    • Eliminating nuclear weapons
    • Developing better means to solve international disputes


About The Author: Jared Diamond is an American anthropologist, historian, and author.
He is most famous for his Pulitzer-winning book “Guns, Germs, and Steel“.

We Lived Dumb Far Long After We Got Smart

It would seem natural to think that we developed as we got smart, right?

Well, that’s not the case.

There is no parallel between brain size and sophistication of humans’ tools.
Our stone tools remained similar and unsophisticated for hundreds of thousands of years after we had already undergone most of our brain’s size expansion.

As recently as 40.000 years ago the Neanderthals had brains even larger than ours yet they show no signs of innovativeness or art.
Even once our ancestors had achieved modern skeletal anatomy their tools remained the same as Neanderthals for a long time.


That remains one of the unsolved puzzles of human evolution.

Jared Diamond says that in that small DNA difference between us and the great apes, there must have been an even smaller percentage not responsible for physical attributes but responsible only for what makes humans: innovation and art.

My Note:
DNA evidence has now shown that our ancestors also interbred with Neanderthals.

When We Started Behaving Like Humans: The Great Leap Forward

In Europe, we started showing signs of innovation and growing tools complexities when the Cro-Magnons started replacing the Neanderthals around 40.000 years ago.

That’s happened almost abruptly, says Diamond, and that’s when we stopped being “just another species of mammals”.

Of course not all innovations appeared exactly at the same time, but this was the period when humans developed:

  • Spears
  • Harpoons
  • Bows and arrows
  • Beads, pendants and paintings
  • Using animals for more than eating (clothes, bones for houses, etc.)

Cro-Magnons also had the important advantage of living longer.
Living longer before writing meant more time to grow skills and the capacity of holding and transmitting more knowledge and wisdom for the future generation.

My note:
Diamond, as he does a few times, presents his theory as if they were accepted consensus. However, there is no consensus on this “sudden” leap forward and some other archeologists believe the change has been more gradual.

The Myth of Cavemen Hunters

It’s only from around 100.000 years ago that we have good evidence of human hunting skills.

But even then, humans were very ineffective at big game hunting. 
The idea of “macho male hunters” is not rooted in reality and male hunting likely had no major impact on our lives or in our evolution.

Even when we consider the evidence from modern hunter-gatherers, we see that it’s more bravado, alpha male posturing and made up stories.
Most New Guineas, for example, eventually admitted that they had killed only a few kangaroos in their lives and that most of their hunting is of smaller animals.
Most of the food was gathered by the women.

It’s only in the Arctic that big game hunting became the major source of food. 
But we only reached the arctic in the last few thousand millennia.

My Note: This is “machismo puncturing ethos”
Steven Pinker in “How the Mind Works” says that our ancestors have been characterized as “weak scavengers” because of the culture of “machismo-puncturing ethos”.
I believe Pinker is right: out gut has evolved to process more meat than the our cousins great apes, so albeit humans weren’t “hunting machines”, they did bring home some bacon (sometimes).
Furthermore, as Buss points out in “Evolutionary Psychology“, a strong theory suggests that the hunting/gathering labor divide provided gender-specific psychological adaptations.

Intelligence Won Over Strength

The Neanderthals were much stronger than our ancestors the Cro-Magnon.

But the Cro-Magnon were better equipped, and probably smarter.
Muscles were no match against better weaponry, though, and the big-muscles Neanderthalians died out.

Also, consider that it’s different than it is today.
Any gym rat can afford food today, but back then feeding bigger muscles meant the necessity of finding more food while giving no advantage against people with better food.

The Tradeoffs of Growing Old (and Menopause)

Someone just approaching evolutionary psychology might wonder what’s the point of having menopause in women, or why do we die.

Doesn’t it make more evolutionary sense to live at least until 200 years and never stop producing children?

Well, no, that’s the wrong way of approaching it.
That question focuses on a few certain characteristics without considering the whole.

Evolution needs to optimize for the whole, and uses tradeoffs.

Since we can live offspring, it doesn’t make sense for nature to invest in costly self-repair mechanisms.

The perfect trade-off between length of life and offspring optimization depends on a number of variables including reproductive biology, risk of death, and the cost of various repairs.

Pursuit of Extramarital Sex: We’re Not Fully Monogamous

Culture and upbringing greatly influences the pursuit of extramarital sex.

Yet, both the institution of marriage and the occurrence of extramarital sex have been reported in most human societies.

Human food gathering does require a social system where men and women “stick together”.
It seems like neither full monogamy for life, nor a total lack of attachment has been the norm in human evolutions

Looking at today’s humans, we realize that:

  • Human parenting is monogamous in most political states (officially)
  • Hunter gatherer tribes are mildly polygynous 

Looking at our body, we realize that:

  • Male testicles are smaller than chimps, but bigger than gorillas

Testes size tells us whether a species is highly polygynous or not. 
Bigger bodies mean that men fight for women and don’t need to fight at a sperm level.
Biggest tests tell us that females mate with many men.
We are in between chimpanzees and gorillas suggesting mild polygyny. 

  • Male bodies are slightly bigger than female, but not much bigger

In polygynous species, males are much bigger because they fight for women.
Human sexual dimorphism suggests that we are mildly polygynous.

We Are Serial Monogamers With Mild Incidence of Extramarital Affairs

It’s difficult to get accurate information on adultery as there are obvious reasons to lie.

The author says that the first blood samples in the 1940s showed around 10% of children to be the fruit of adultery.
The figure might be even higher as those old techniques might have downplayed the incidence and of course not all extramarital affairs led to children.

Subsequent researches showed between 5% and 30% of children being born from adulterous affairs.

Still, overall, most fathers are raising their children and as a species we are not chimps just pretending to be otherwise.
But extramarital affairs are still part of our species and the incidence might be higher than most people expect.

My Note:
As far as I read from other sources the 30% is misleading as it was the figure of blood samples from fathers who requested the test because they suspected being cuckolded. So that skews the sample, of course.

Extramarital Sex Strategies

Researchers have applied game theory studies to extramarital sex (EMS).

There are two ways to measure the payoffs of EMS: number of children and confidence of parenthood.

Because of the biological differences, a man stands to gain much more from extramarital sex or polygamy than a woman if we measure the final result as the number of offspring.
And that’s why, I would add, men complaining about “female hypergamy” and untrustworthiness” are really only seeing less than half of the truth or simply hiding their misogyny (also see “The Red Pill” and “The Rational Male“).

Here are the different strategic theories one could adopt:

  1. A man should always seek EMS because he has very little to lose and much to gain
  2. Seek to maximize gains and minimize losses
  3. Must take into account the female’s own strategy

Number 1 says the author is obviously simplistic as it doesn’t take into account the potential costs.
And number 2 still ignores the female’s own strategies.

The author wonders why a woman should even seek an EMS since the genetic payoffs are much more limited for her.
One possibility is shopping for better genes, of course, see “female hypergamy” for more.
But Jared Diamond does not fully flesh out that possibility.

In short, humans cheat because the pursuit of a “mixed reproductive strategy”, such as a stable relationship plus affair on the side, can pay off.

Yet, it’s not as simple as it sounds.
There are plenty of risks in engaging in EMS.

The Principle of Optimal Intermediate Similarity

People seek women who are similar to their parents, but not too similar.

As for most things humans, there is a tradeoff and an optimal balance. Interbreeding with similar people is good, but up to a certain point.

Intelligence Matters More Than Body Size

The author says:

However, at some point in human evolution, male intelligence and personality came to matter more than size. 
Male basketball players and sumo fighters don’t have more wives

The author talks about “size”, but he seems to imply that physical traits matter less.

My Note:
However, I think Diamond is wrong here.
Basketball players don’t have more wives maybe, but they probably have more partners. 
Of course, that’s not only because of size, but size and physical traits still matter.


Concealed Ovulation & Female Sexual Strategies

Why are women the only species of apes to hide ovulation?

There are many competing theories, also reflecting the biases and preferences of each proponents.
Here are all of them:

1. Enhance Cooperation Among Males

Open ovulation would lead to more arguments and fights and who is going to have sex with whom and when.
Men would be distracted by available female and disrupt their normal activities of bonding and hunting.

This has been the theory of traditional male anthropologists.

2. It cements the bond between man and woman

The man doesn’t know when she’s fertile, so he has to copulate with her multiple times and over an extended period of time.

Not knowing herself when she is pregnant, she is also must oblige to provide him with sex.

This has been the theory of a different group of male anthropologists.

3. Women can take advantage of men (command more resources & cheat)

Modern anthropologists realized that male apes share more with females when they are ovulating, so they hypothesized that women hid their ovulation to keep getting treats from men.

An offshoot of this approach is that hidden ovulation helps women to seduce and use other men beside their partners.

4. Demand relationship by exploiting his paranoia for parenthood

Women developed concealed ovulation to force men into a permanent marriage bond by exploiting male paranoia of fatherhood.

When he doesn’t know about her fertility days, he must guard her and he must have sex with her repeatedly.

On the other hand, he also gains higher confidence of paternity and his woman will attract less competition.

This theory was from male and female biologists and it’s more about sexual equality.

5. Prevent men from killing children and enlist their help

Men killing other men’s offspring is a relatively common occurrence in nature.

Human females might have prevented that by confusing the issue of paternity.
That way, they can also enlist the help of more men to raise children.

This is the theory of a female biologist.

6. Trade sex for favors, with sex being less risky

Sex can be risky for women.
It can cost a child with a man she didn’t want, or it can be risky as deliveries were quite dangerous during our evolution.

With concealed ovulation, having sex slightly delinks from reproduction, thus allowing her to lower the bar for sex.
She can use copulation to ingratiate male favor

Which one is true?
Difficult to say, probably all of them factored in, but that cannot be an excuse to accept any theory.

The author says that 1 and 2 seem valid.

Men Smoke & Drink As Indicator of Good Genes

Jared Diamond says that one of the reasons men smoke, drink and do stupid things as indicators of skills and good genes.

Smoking and drinking function like some fitness indicators in animals, which are costly and dangerous on purpose, so as to function as truly honest indicators.

However, the author says that we smoke and drink based on the principle of proving ourselves strong by handicapping ourselves, and not because it really works.
Thus, smoking and drinking today do not help anyone get laid.

My Note:
I found this part to be quite far fetched. Very interesting, and he makes a good point. I believe there is some bravado, “look at me how strong I am” kind of thing here. 
But it’s still far-fetched and simpler answer apply, such as “pleasure of the drug” and addiction.

More Wisdom

  • Black skin is only loosely correlated with sun and the risk of cancer
  • We already appropriated 40% of the earth’s productivity (albeit: how can he say that accurately?)
  • Nuclear weapons bypass our inhibition to kill other humans by acting from far away, at the push of a button
  • Genocide is more common than we care to admit, and otherwise good humans can contribute to it (also see “Evil” and “The Lucifer’s Effect“)
  • Our species has escaped population control from any other predator, and now overpopulation has become an issue
  • We are in the middle of an extinction crisis =, an event that’s been accelerating in the last 50.000 years and which will reach completion by our children’s lifetime
the third chimpanzee book cover


I loved “The Third Chimpanzee” and learned quite a bit from it.
Yet, I think there are many imperfections, including:

Misguided Blank Slate approach

Writes Jared Diamond:

In contrast, every human population living today has interbred with every other human population with which it has had extensive contact. 
Ecological differences among existing humans are entirely the product of childhood and education

Wow, I almost can’t believe he wrote that, with accent on “entirely”.
Also read: “The Blank Slate“.


Same as with “Guns, Germs, And Steel“, the book reeks of ideology.

Diamond says:

Until we can come up with a convincing, credible alternative explanation, the suspicion that racist genetic theories might be true will linger.

Diamond doesn’t have to “come up with convincing alternatives”. He has to come up with evidence-based, scientific alternatives.

SJW Approach: Diamond searches what’s convenient, not what’s true

I quote from the author:

At last, a theory grounded on sexual equality

Who cares what it’s grounded on?
Give us what’s grounded on data and empirical evidence! 

And later on:

Whether this theory is right or wrong, we must applaud her for overturning a conventional male sexism and transferring sexual power to women

No, we must applaud scientists who help us get to the truth, Diamond, not those who further your political agenda.

Jumping to (Unfounded) Conclusions

The author rarely stops pondering at the possibility that his own theories might be wrong.

And he never admits it when it’s conjectures he is sharing, preferring instead to pretend he is presenting scientific truths.

For example, the author says that most life outside of earth is extremely unlikely to evolve towards intelligence.
Sure, he can draw on millions of multi-cellular species here on earth, and yet… His theory is still resting on one planet only. 
That alone should lead anyone to be wary of general conclusions. But instead, he is always so sure of himself.

He says: 

Other intelligent civilizations that arose elsewhere probably reversed their own progress overnight, just as we know risk doing

But based on what does he say that?

And again, talking about how we humans abused other species, he says:

Any advanced extraterrestrial discovering us, would surely treat us the same way

Wait… “Surely”?
Based on what does he say “surely?” One single species behaving like we did?

Sometimes Sounds Idealistically naive

The author says:

We’re only beginning to realize how sophisticated the conservation policies of so called primitive people actually are

I have never really trusted these idealized representations of “backward but wise societies” that love animals and respect the environment.

Especially when the author himself discussed many opposing examples.

Exaggerates our genocidal tendencies and the nuclear weapons’ power of obliterating life

Diamond writes:

Together with the destruction of our environmental resources, our genocidal tendencies coupled with nuclear weapons now constitute the two most likely by which the human species may reverse all its progress virtually overnight

A nuclear war would be disastrous.
Genocide would be horrendous.
And yet, from a macro perspective, neither would “reverse our progress overnight”. Especially not genocide, which would only reduce the human population and not “revert our progress overnight”.

Again, Diamond writes:

The first species in the history of life on earth capable of destroying all life

This is silly and I’d expect a scientist writing about life to know a bit more about life.
How would humans exactly destroy all life on earth?
We haven’t even destroyed forms of lives that prey on us, from germs to annoying mosquitos.
How would we go about destroying all forms of life?

The truth is that if we start a nuclear war or another genocide, other forms of lives would continue living pretty much as if nothing happened.
As a matter of fact, many species would probably do much better with fewer humans around.

Nonsense Mediterranean example of collapsed civilization

The author says that the relative poverty of Mediterranean civilizations such as Greece and Persia is an example of societies that destroyed their own resource-base.

He talks about “deforestation, overgrazing and erosion” that turned a lush land into the barren places we see today.

What the hell is the author talking about?
Greece and Italy boast some of the best food and cuisine in the world. These are not “barren places”.
And today’s society doesn’t fare well or poorly based on agriculture anymore. How is Greece poor because of fewer forests?

This made little sense to me.

The male penis is not for females, but to intimidate other males? Not really

Jared Diamond says that anthropologists claiming that a big penis is a display for women are engaging in wishful thinking.
Women never say they are attracted by bigger penis.

Yet, the author confusing what women are comfortable saying and what they actually prefer.
At parity of everything else, a woman probably still prefer a man with a slightly bigger than average penis rather than a slightly smaller one.

Penises are hardly a tool of intimidation towards other men.

I think that aggression, muscles and a willingness to fight are far more intimidating.
Even raising one’s own voice is more intimidating and effective than a big penis.

The big penis is most likely the product of sexual selection by females (see “The Mating Mind”).

Some unsubstantiated data

The author says that we “already appropriated 40% of earth’s productivity”.

But first of all, based on what?
And second, that makes no sense to me. 
Nuclear energy is almost unlimited, and new technologies will improve the final energetical output of any input, thus making any estimate truly difficult to make.

Agriculture, idealism and poor analysis

The analysis on agriculture felt like one was reading a Paleo diet booklet.

Plus the usual political agenda.

Says Diamond:

With agriculture came not only an increase in food production, but also the gross social and sexual inequalities, the diseases and despotism that curse the modern human existence

Of course, almost any major change will present positive and negative aspects, but Diamond’s criticism feels naively idealistic

He then goes on to describe how better the life of hunter-gatherers were. Yet one would wonder: if it were so much better, why were people so stupid to take up agriculture, more complex and labor-intensive?

Because, maybe, it wasn’t such a poorer option… 

The author’s Chinese friends & anecdotal evidence

The author talks about the two Chinese female friends of his. One preferred white guys, the other Asian guys.
And that was because of where she grew up, he says.
That’s also poor anecdotal evidence, though.

Anecdotal evidence for anecdotal evidence, as a kid, I also preferred white women and couldn’t understand the appeal of black and Asians.
Now that I traveled, I am almost the reverse.

He ends up saying that “beauty is in the eyes of the beholder” which, again, is also a major generalization for a scientist.

Sexual selection must not necessarily produce two changes at once

The author says that sexual selection must produce two traits simultaneously: the change in taste and the change itself.

Yet, the changes do not need to be simultaneous. Anything eye-catchy can be an advantage, and that develops with the sense itself.


Like any book which help to shed more light on human behavior and psychology, I loved “The Third Chimpanzee”.

Yet, I couldn’t help at times but think that Diamond might not have enough deep expertise in evolutionary psychology to write a book about it.

Furthermore, is unscientific, ideology-based approach to knowledge sits rather uncomfortably with me.

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