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The Triz Journal | November 18, 2017

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The (predictable) Evolution of Useful Things

| On 04, Sep 1999

Darrell Mann
Industrial Fellow, Department Of Mechanical Engineering
University Of Bath, Bath, BA2 7AY, UK
Phone: +44 (1225) 826465
Fax: +44 (1225) 826928


‘The Evolution of Useful Things’ by Professor Henry Petroski (Reference1) is a fascinating historical account of the evolution of everyday objects. Thebook uses a number of richly detailed case studies – from cutlery to hamburgerwrappers, and paper clips to telephones – to build up a general picture of whythings evolve the way they do.

This article takes a brief glimpse at some of the case studies in ProfessorPetroski’s book from the perspective of Altshuller’s predicted trends ofevolution, and examines how some of the findings in the book might in turninfluence the manner in which the evolution trends are interpreted and used.

The Fork

One of the most interesting historical accounts in the book concerns the evolution of the eating implement we know as the fork. The fork story begins inthe Middle Ages, when diners would usually be found eating with a pair ofknives; one knife to do the cutting, and the other to take care of the holdingof the food being cut. This method of eating prevailed – in Europe at least -until around the 14th Century, when two-tined forks first appeared in largequantities at the dinner table. It is suggested that the evolution from pointedknife to two-pronged fork occurred because of the problems of holding food inplace with a single pointed device where the food in question was largely freeto rotate about the point and thus impeded the cutting action. Introduction ofthe second prong eliminated this rotation problem.

The problem then, however, was that, although good for holding, the fork wasof little use in carrying food from the plate to the mouth. And thus emergedthree-tined forks, and, even better, by the early eighteenth Century, thefour-tined fork we know today.

Perhaps unsurprisingly, this evolution from the single point to a multiplepoint device correlates closely to the TRIZ ‘mono-bi-poly evolution’ trendillustrated in Figure 1.

Figure 1: Mon-Bi-Poly Evolution of the Fork

The fork evolution story forms the first chapter in the book. It serves tointroduce Professor Petroski’s hypothesis that devicesevolve the way they do because of a dis-satisfaction on the part of the user inthe way the current system works. Or, to use the author’s words, ‘formfollows failure’.

The fork story raises a number of interesting side issues. The first concernsthe manner in which fork designs have multiplied to meet specific requirements.The proliferation of designs illustrated in Figure 2, not only provides furtherjustification for the ‘form follows failure’ argument, but also demonstratesthe enormous level of compromise required when trying to achieve the ‘generic’fork design which most of us end up buying.

Figure 2: Diversity of Fork Designs (picture adapted from Reference 1)
Specialised fork designs include; ‘oyster’, ‘berry’, ‘pickle’, ‘ice-cream’,‘lettuce’, ‘pastry’,
‘salad’, ‘fish’, ‘terrapin’, and ‘lobster’ variations.

Also interesting is Petroski’s view that luxury– and not necessity – is the mother of invention,and that evolution of artefacts is driven by our desires rather than our actualneeds. Thus, while we need to eat food, we don’t need to use a fork. Onthe other hand, if we are using a fork, we want a design which performsthe function without the adverse effects – and hence the proliferation of designshown in Figure 2. Similarly, while we need air, we do not intrinsicallyneed air conditioning. If we have air conditioning, however, we want itto become quieter, cheaper, more efficient, less intrusive, more attractive,etc, etc.

With respect to the predicted trends of evolution it is worth noting the nextfork evolution step – to a ‘combined poly-system’ – in relation to theemergence (and disappearance) of inventions like the ‘splade’ and otherknife/fork/spoon amalgam designs – and how they have thus far failed to achievesufficient added value to capture the public imagination.

We might also care to look at other predicted trends (e.g. ‘dynamization’)to see how the fork might evolve when addressing the diverse requirementsillustrated in Figure 2.


Among a myriad other examples, the history of fasteners is anotherentertaining and instructive story told in Professor Petroski’s book. In thestory, we watch as clothing fasteners evolve from pins and brooches to clips andbuttons, hooks and eyes, and on through to the zip fastener.

The evolution history is highly consistent with both the ‘mono-bi-poly’trend illustrated in Figure 1 and the ‘geometric evolution of linearconstructions’ trend illustrated below in Figure 3:

pin broochsafety-pin button hook/eyezip fastener

Figure 3: ‘Geometric Evolution of Linear Constructions’Evolution Trend
(picture from TechOptimizer (Reference 2) software)

(Note also how the geometric evolution trend can also be applied in theprevious fork evolution story with respect to the evolution from 1D points, to2D flat forks, to the three dimensional curved fork we see today.)

Again, with the fastener story, the ‘form follows failure’ argument isconvincingly used to justify the evolution path:

  • pins were replaced because they fell out or injured the wearer.
  • brooches and safety pins were superseded because they were either difficult to put on or there were not enough of them to provide an effective seal against the weather.
  • buttons are easier to fasten, but still don’t seal against the weather very well unless there are lots of them – in which case they are still time-consuming to do up and they weaken the structure of the fabric.
  • hook and eye arrangements do less damage to the underlying fabric, but are still tedious to fasten, and are expensive to manufacture because they have to be individually attached to the fabric.
  • Etc.

Zippers first appeared in the last century, but new variants are still beingpatented today – e.g. the 1998 patent illustrated in Figure 4. Although clearlyusing three-dimensional design methods (and thus laying at the farthest point onthe geometric evolution trend), and sitting a long way along the ‘poly’evolution path, the zipper is still some way away from an ideal final form. Thefact that we can still see ‘problems’ like poor water-proofing capability,cleaning difficulty, starting difficulty, tendency to snag and trap flesh orother clothing, etc, clearly suggests that the zipper – or its successor – stillhas a long way to travel before we will finally be satisfied.

Figure 4: Typical Zip Fastener – US Patent 5,791,023
(aimed at improving ease of joining and starting)

Form Follows….

Large sections of Professor Petroski’s book are concerned with argumentsagainst the doctrine ‘form follows function’.

He argues that the single largest factor behind technological change is thefailure of existing devices to live up to their promise. The fork and fastenerexamples above are just two of a large number of examples consistent with this‘form follows failure’ hypothesis.

The book, however, also contains the observation of two other variants on the‘form follows..’ theme: ‘form eschews function’, and ‘form followswhere the future leads’.

‘Form eschews function’, or ‘form follows fashion’is a design strategy in which the designer ignores function requirements andplaces aesthetics, novelty and style at the top of the list of aims for theartefact. Examples are numerous, particularly across the worlds of fashion,packaging design and certain consumer goods (e.g. boom-boxes). In purelytechnological evolution terms, few if any ‘form eschews function’ designshave much to offer by way of either long term impact or predictability. Thepoint here is that although Altshuller’s observations on the predictableevolution of technical systems offer companies a very powerful productdevelopment strategy tool, consideration also needs to be given to transient ‘formfollows fashion’ possibilities.

Regarding the ‘form follows where the future leads’observation, Petroski states, ‘There are a lot of difficult problems indesign, and their solution necessarily depends not only upon where designersunderstand the problems with the past to be but also upon how clearly designerssee the road to the future’. In essence, ‘form follows where the futureleads’ is a plea for designers to look forwards as well as backwards whenconfiguring design solutions. The main example used in the book is McDonald’spolystyrene-foam clamshell hamburger container. At the time of it’sintroduction in the mid-70s, it was felt that the clamshell overcame all thefailings of previous packaging; it kept in heat and moisture, it absorbedgrease, it was simple to operate, easy to store, and it was attractive.Unfortunately, little attention was apparently given to possible futurecircumstances and situations in which the product would operate – namely, as itturns out, a greater public awareness of environmental issues, and the enormousdifficulties in adequately disposing of literally tons of used polystyrene foam.

There are connections here to both Axiomatic Design and TRIZ – AxiomaticDesign via the correct definition of Functional Requirements (see the pizza boxexample in Reference 3), and TRIZ via both Anticipatory Failure Determination(Reference 4, 5) type techniques, and the more general use of inventive problemsolving techniques to eliminate the anticipated future designcontradictions.


1) How Poly Is Poly? – Taken together, the fork and the fastener storieshighlight a distinct characteristic surrounding the deployment of the ‘mono-bi-poly’trend. The fork, despite occasional forays into five and even six-tine designs,has stuck resolutely to the four-tine design since it’s first appearance atthe dinner table. The zipper meanwhile has evolved to progressively greaternumbers of meshing teeth. Petroski argues that four tines is an optimum (i.e.five or more tines means either the fork is too wide for the mouth or the tinesare too thin to provide the necessary strength and durability), while the zippermay be seen to still be evolving towards an optimum in which there are aninfinite number of teeth (and sealing performance is thus maximised). Strength,durability and other limits will again, however, ultimately limit the maximumpractically achievable tooth density (and the zipper will be replaced). In otherwords; ‘poly’ will evolve to a practical limit before the system becomessuperceded.

2) Symbiotic Evolution – Petroski makes an important point about the waythe evolution of objects can be strongly influenced by the evolution of otherobjects. This ‘symbiotic evolution’ appears to take two forms: Firstly,evolution due to the possible inter-relationship between different objects, andsecondly evolution which occurs as a function of the way in which man interactswith the object.

By way of example, note how in Figure 1 the evolution of the fork influencedthe evolution of the knife – and particularly how, as soon as the fork was ableto adequately perform the holding function, the knife no longer needed to bepointed and became a much more friendly rounded shape.

With respect to the interaction between man and object, Petroski cites thelovely example of waste-paper bins, and the evolution of the now ubiquitousbin-liner. Bin-liners evolved from a desire to prevent soiling of the binthrough the occasional disposal of organic or liquid based waste materials(Inventive Principle; Intermediary). But the emergence of bin-liners has nowaffected the way in which we use waste-paper bins – i.e. we now rarely thinkabout what we put into the bin – more organic materials, more liquids, etc -which in turn has now created all sorts of other types of problems – like odour,seepage, leakage when the liner splits, vermin, etc. Not to mention the factthat the bin-liner itself – and particularly the way it inelegantly folds overthe top of the bin – is apparently immune to elegant design solution.

Designers need to be aware of both of these symbiotic evolution effects.

3) Ideal Final Result – the final chapter of the Evolution of UsefulThings is entitled ‘Always Room For Improvement’. In the chapter, Petroskimakes a suggestion that any artefact is perpetually amenable to improvement. Thebasic idea thus fails to acknowledge the possibility of an ideal solution inwhich the function is achieved without the resource or penalties. Admittedly theTRIZ Ideal Final Result concept is often most useful as a problem definition orlong term strategic visioning tool, but there are cases (e.g. Reference 6) inwhich the IFR is a practical, achievable possibility. The central difference inthinking here is that Petroski takes the traditional Western incrementalevolution approach which uses today’s solution as its start point, whereas theIFR philosophy deliberately prompts the problem solver to put aside today’sbaggage in order to envision what the ideal tomorrow might look like. The latteris quite probably the more powerful thinking strategy.

4) ‘Patent It Yourself’ – Professor Petroski’s book mentions DavidPressman’s book ‘Patent it Yourself’ (Reference 7) with specific referenceto that book’s description of the importance of impartially assessing thepositive and negative aspects of any design. Pressman lists 44 positiveand negative evaluation factors – covering a broad spectrum of parameters fromcost, weight, size through to market dependence, distribution andservice-ability. Although beyond the scope of this article, there areinteresting comparisons to be made between Pressman’s list and the 39 elementsof the Contradiction Matrix.

5) Good Problems – many of the examples given in Professor Petroski’sbook are seen to still be some way away from what might be seen as their IdealFinal Result form. As such they present good material upon which inventors andproblem solvers might care to propose improvements. The book catalogues a numberof other such ‘good problems’ which would still clearly benefit from somenew ideas. Included are:-

  • re-sealable soda cans
  • better bottle sealing methods
  • better child-proof medicine containers
  • openable airline peanut packets

Perhaps there are opportunities here for TRIZ to help generate some novelsolutions.


  1. ‘The Evolution of Useful Things’ is a highly entertaining, highly instructive read. Professor Petroski’s ideas on why things evolve the way they do are forcefully and convincingly argued.
  2. Ideas and trends illustrated in the book are seen to be both consistent and compatible with the trends of evolution identified by Altshuller. There is significant common ground between the two approaches, suggesting significant potential for use of the two philosophies in combination when conducting trend analyses.


  1. Petroski, H., ‘The Evolution of Useful Things’, (New York, Alfred A Knopf, 1992)
  2. TechOptimizer V3.1,
  3. Mann, D.L., ‘Axiomatic Design And TRIZ: Compatibilities and Contradictions’, TRIZ Journal, June 1999.
  4. Kaplan, S. ‘Anticipatory Failure Determination (AFD): The Application of TRIZ to Risk Analysis’, 9th Symposium on QFD, QFD Institute,, 1997.
  5. Frenklach, G., ‘Usage of the direct and preliminary extra-effect determination methods for diagnostic problem solving’, TRIZ Journal, May 1998.
  6. Salamatov, Y., ‘TRIZ: The Right Solution At The Right Time’, (The Netherlands, Insytec B.V., 1999) pp157-8.
  7. Pressman, D. Elias, S., ‘Patent It Yourself’, (Berkeley, Nolo Press, 1985, (7th Ed. 1999))