Linked: Why Everything is Connected to Everything Else and What it Means for Business, Science, and Everyday Life

Author: Albert-Laszlo Barabasi



This book explores the diversity and significance of networks, tackling topics ranging from the synchrony of cardiac pacemakers and the menstrual cycle (page 45), to the web-like nature of cells (page 185), and the spread of viruses and ideas (page 135). It discusses the ‘topology of the web‘ (page 56) and the ‘hublike nature’ of the cancer-related p53 protein (page 63). It details the nature of networks and how they influence us.

The author, a physicist, describes the basic structure of networks and their constituent nodes or units. Using the concepts of ‘preferential attachment’ and the ‘Bose-Einstein condensate’, he explains why older nodes grow faster than newer ones (page 86), and this ‘explains how some winners get the chance to take it all’ (page 106). He shows how other principles such as fitness (quality) and topological robustness (tolerance of failure) allow some newcomers to a network rise rapidly to the top and remain there. Citing the example of Google, he says ‘independent of when a node joins the network, a fit node will soon leave behind all nodes with smaller fitness’ (page 97).

The fundamental concept behind networks is the mathematical power law that governs them, and the book returns to this theme repeatedly. Without a central peak, the power law distribution is a ‘continuously decreasing curve’ unlike the better known bell curve distribution. This distribution, akin to the 80:20 or Pareto principle (named after Vilfredo Pareto), explains why many natural distributions have a dominant peak at one end rather than in the middle. Networks such as the internet that observe this law are described as ‘scale-free‘ (page 70) and they are capable of self-organisation and emergent behavior (page 221).



The sociological relevance of networks is an important subject the book explores. It discusses the close knit clusters that characterise social systems and how the Erdos number, named after the mathematician Paul Erdos, predicts this (page 49). He considers the strength of links between small groups and how this correlates to the clustering coefficient, a mathematical concept based on the work of Duncan Watts and Steven Strogatz (page 47). Referring to the work of Mark Granovetter, the author explores the importance of the weak links that connect small groups; he calls these ‘our bridge to the outside world’, and discusses how they influence many of life’s significant decisions such as employment and marriage (page 43).

The author dedicates a significant part of the book to the spread of epidemics. Relating the story of Gaetan Dugas, the French-Canadian Patient Zero of the AIDS epidemic, the author explains how highly connected nodes or hubs maintain and spread epidemics (page 126). Viruses seem to operate in scale-free networks and do not need to cross any critical threshold to be self-sustaining. This is because highly linked hubs like Dugas allow the viruses to persist and spread (page 135). Just as with the spread of fads, innovations, and ideas, ‘if the hubs resist a product, they form such an impenetrable and influential wall that the innovation can only fail’ (page 130). The author emphasises the ‘vital need to be able to predict and track deadly viruses in this increasingly mobile world’ (page 141), and he argues that, to be successful, epidemic control measures need to target the influential hubs (page 139).” target=”_blank”>

The author talking of intracellular protein networks and disease


This is an important field by an author who is very active in it. The book discusses many important issues regarding networks and it complements other books on this topic such as Connected. The book’s running title is rather long and a shorter one would have sent the message just as well. I didn’t think the book really kicked off before the 4th chapter when its central themes became clear. The author has a very engaging manner and his thorough grip of the topic showed through all the chapters. His anecdotes are very interesting and I particularly enjoyed the story of Gaetan Dugas who typified a ‘highly connected node’. The book made reference to many mathematical concepts and showed how relevant they were to the subject of networks. These concepts are not easy to grasp but this did not detract from understanding the message of the book. The author predicts that ‘network thinking is poised to invade all domain of human activity and most fields of human inquiry’ (page 222). The importance of networks cannot therefore be overestimated because we all function within them and they influence  the success of the teams and collaborations we form.



The book is well-written and does a great job of explaining the structure and function of networks, an important issue for doctors. The discussions on epidemics and scientific collaborations are particularly relevant to doctors. I found this a very enjoyable and enlightening book and I recommend it.


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