How Many Friends Does One Person Need?: Dunbar's Number and Other Evolutionary Quirks [Hardcover]

Prof. Robin Dunbar (Author)

Book Description

Publication Date: November 1, 2010

Why do men talk and women gossip, and which is better for you? Why is monogamy a drain on the brain? And why should you be suspicious of someone who has more than 150 friends on Facebook?

We are the product of our evolutionary history, and this history colors our everyday lives—from why we joke to the depth of our religious beliefs. In How Many Friends Does One Person Need? Robin Dunbar uses groundbreaking experiments that have forever changed the way evolutionary biologists explain how the distant past underpins our current ­behavior.

We know so much more now than Darwin ever did, but the core of modern evolutionary theory lies firmly in Darwin’s elegantly simple idea: organisms behave in ways that enhance the frequency with which genes are passed on to future generations. This idea is at the heart of Dunbar’s book, which seeks to explain why humans behave as they do. Stimulating, provocative, and immensely enjoyable, his book invites you to explore the number of friends you have, whether you have your father’s brain or your mother’s, whether morning sickness might actually be good for you, why Barack Obama’s 2008 victory was a foregone conclusion, what Gaelic has to do with frankincense, and why we laugh. In the process, Dunbar examines the role of religion in human evolution, the fact that most of us have unexpectedly famous ancestors, and why men and women never seem able to see eye to eye on color.

Editorial Reviews

From Publishers Weekly

Starred Review. In an entertaining and informative new work, evolutionary psychologist and Director of the Institute of Cognitive and Evolutionary Anthropology at Oxford, Dunbar (Evolutionary Psychology) investigates the ways in which evolution is still at work in homo sapiens, and the brain functions and abilities that separate us from other species. Covering an impressive breadth of topics and disciplines, Dunbar explores the ways in which our brains control every aspect of our social lives (surprise, we are less complicated than we think). Our needs, preferences, and commonalities are a function of what-not who-we are. Dunbar addresses the unusually large size of the human brain and concludes that monogamy is at fault; the brains of more promiscuous species are much smaller. Comparing the length of pregnancy in various species, he states that "human babies are born wildly premature"; in mammals, gestation time is dictated by the size of the brain, and humans "ought to have a gestation of twenty-one months." Full of interesting facts and Dunbar's winning personality, his effort reads like a fascinating lecture that most readers would be all-too-happy to attend.

From Booklist

150. Dunbar’s Number: the number establishing the limit on meaningful relationships one person can maintain. In showing how this number reflects the biological history of humans as distinctively social primates, Dunbar illustrates how recent advances in evolutionary science have enlarged the explanatory power of the Darwinian paradigm. Within this increasingly potent paradigm, readers learn, for example, why societies experiencing birth ratios unfavorable to females face serious crime surges in the decades ahead and why tall politicians (e.g., Obama) enjoy a pronounced advantage over short rivals (McCain). Dunbar’s work, of course, connects with the sociobiological theories advanced by E. O.Wilson in the 1980s, leaving some readers with the same questions about the potentially reductive implications of an overly biological framework. Does the distinctively human impulse to worship, for instance, manifest only the way that ritual behavior biochemically fosters group cohesion among anthropoids? Some readers may indeed wonder if Dunbar might not use his science more plausibly if he shared with biologist Peter Medawar an appreciation for its limits. Still, this is lucid and provocative. --Bryce Christensen

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Product Details

• Hardcover: 312 pages
• Publisher: Harvard University Press (November 1, 2010)
• Language: English
• ISBN-10: 0674057163
• ISBN-13: 978-0674057166
• Product Dimensions: 8.3 x 5.8 x 1 inches
• Shipping Weight: 1.2 pounds (View shipping rates and policies)
• Average Customer Review: 4.3 out of 5 stars  See all reviews (11 customer reviews)
• Amazon Best Sellers Rank: #673,672 in Books (See Top 100 in Books)

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Most Helpful Customer Reviews

12 of 12 people found the following review helpful

5.0 out of 5 stars Provocative short course in anthropology December 25, 2010

By Ursiform TOP 500 REVIEWERVINE™ VOICE

Format:Kindle Edition

I first encountered Robin Dunbar with his excellent book* "Grooming, Gossip, and the Evolution of Language", where he put forth the theory that gossip replaced grooming as we evolved from ape to human, thus allowing larger social groups to form. (This, in fact, is the topic that inspired the title of the current book. His answer is about 150, "Dunbar's Number".)

This book is a collection of previously published articles which have been updated for the book. As such, it doesn't have a strong, integrating theme. But it does provide a series of provocative insights into why we are as we are. Dunbar explains how our evolution has shaped how we are, what traits we share with the great apes and where we have surpassed them, and why we act as we do.

In a lively skip through many topics, Dunbar covers topics like why gossip is good, why we like presidential candidates who are tall and have symmetrical faces, and why kissing may be an adaptation for choosing mates with desirable immune systems. (Yes, really.) He even considers why humans are such religious critters. All-in-all, a highly engaging and thought-provoking book.

* Grooming, Gossip, and the Evolution of Language

14 of 15 people found the following review helpful

3.0 out of 5 stars An enjoyable book, albeit a bit lacking in depth April 24, 2010

By M. Moran

Format:Hardcover

This is a collection of previous material from New Scientist, The Scotsman, and other periodicals. Stylistically, this makes it quite repetitive. For example, he says several times within a few pages that babies are born "wildly premature". A little more tight editing would make it feel like a cohesive whole.

What I find more grating is how he continually speaks as if our ancestors, and their genes, had changed behaviour based on knowledge of future hardship:

"... their descendants decided to increase the size of their brains dramatically ... The inspired solution our ancestors eventually came up with was ..."

Maybe I'm going a bit Dawkins, but this is not how it works. I know Dunbar doesn't think anything other than evolution is involved here, but it'd be far better if his wording reflected this. I know this is hard to do, and I struggle now to think of an alternate wording, but the assignment of intentionality should be avoided if possible.

Factually, it raises itself above a lazy New Scientist article by delivering an occasional nugget of information you wouldn't often see. For example, men have only one X chromosome meaning they have a heightened chance of colour vision defects arising from mutations, compared to women who have two X chromosomes and hence a backup copy. This also means that mutations in one X chromosome can lead to extra receptor types in women. In a very real way, women may see differently than men. I don't buy his followup argument that this is why women are supposedly more colour conscious than men. Still this is populist science, and a nice hook.

I've previously read Dunbar's The Human Story, and wrt Dunbar's Number this book is mostly a recap. Back then 150 didn't have a name, but it did have a reasoned argument behind it. A little of that is repeated here, but without the useful explanatory graphs (that seem so anathema to science in public today).

He drops in a bit of irrelevant numerology in as well: he claims something special about the scaling of three which relates the respective size of shells of friendship groups (people you choose to see daily/weekly/monthly/yearly). This could just be happenstance. Similarly, there are some interesting examples of where groups of 150 people appear in modern life. However, if you go looking for numbers, you will find them. I'd like some more concrete examples backed up by reasoning, not just anecdotal evidence.

Overall, it's an enjoyable book, albeit a bit lacking in depth. If you are really interested in some more tighter arguments (with graphs!) then I'd recommend his previous book, "The Human Story".

24 of 28 people found the following review helpful

3.0 out of 5 stars Interesting, but flawed. January 16, 2011

By Wayne Robinson

Format:Hardcover|Amazon Verified Purchase

I thought it was a very good book. I found it very enjoyable to read. I also thought that it provides a lot to think about.

However, I didn't give it 4 or even 5 stars, because it has major flaws.

For one thing, at least in the Kindle edition, the author doesn't cite any references.

More seriously, a lot of the author's statements are just wrong.

For example:

In chapter 10 'The Darwin Wars', it's stated, "Chris Organ from Harvard University and his colleagues carried out the first successful extraction of DNA from a 65 million year old Tyrannosaurus rex ..." Well, no actually, it was collagen protein. DNA is so fragile that around 100,000 years remains its limit for recovery. The only reference to dinosaur DNA and Chris Organ I can find is his observation that the lacunae in fossil T rex bone (which previously contained the bone cells, osteocytes, are smaller, so therefore the osteocytes were smaller, so therefore the nuclei were smaller, so therefore the genomes were smaller (with less 'junk' DNA)-like contemporary birds (there might be one or two 'therefores' too many).

In the very same chapter, it's stated, discussing Kennewick Man the 9,000 year old remains found in Washington state, "There is now compelling evidence to suggest that the earliest inhabitants of North America did in fact come from Europe (the vicinity of Spain, as it happens)" sometime around 20,000 years ago". Again no; extraordinary claims (humans managed to cross the Atlantic, in a glaciation, and then crossed the entire North American continent?) need extraordinary proof. The alternate interpretation that Kennewick Man more closely resembles the Ainu of northern Japan and came from there is more plausible.

In chapter 5 'The Ancestors That Still Haunt Us', in a discussion about Indo-European languages, it's stated " ... Finnish and Hungarian, both of which derive from the invasions by Mongolian peoples, the latter most famously associated with Attila the Hun and his chums". Again no; Hungarian (and Finnish and Estonian) are derived from an Ugric language of western Siberia 3,000 years ago. Nomads, but not Mongolian.

The book would have been considerably improved if someone else had read it before publication and checked the 'facts'. The errors don't damage the authors arguments seriously, but I'd advise that I'd check any 'facts' proffered before using them, particularly if they seem difficult to believe.