'Evolution' is a change from an indefinite, incoherent homogeneity, to a definite coherent heterogeneity, through continuous differentiations and integrations' [Herbert Spencer, 1862, First Principles II iii p.216]
'Those who cavalierly reject the Theory of Evolution, as not adequately supported by facts, seem quite to forget that their own theory is supported by no facts at all.' [H. Spencer, 1858, Ist Series, ix, 389, both quoted as examples of 8b and 10 meanings of 'Evolution' in the Oxford English Dictionary]

Evolution was one of the central ideas of Victorian intellectual life. Although today it is associated chiefly with Charles Darwin and natural history, there are many sources in books and on the web which make it clear that the roots of evolutionary thinking go back far earlier than the publication of On the Origin of Species in 1859, and were applied by many people to more than natural science.

Pitt-Rivers applied evolution to the development of ideas made concrete in the form of artefacts; the development of function and form in specific types of objects, the movement of the design of a specific artefact from 'the simple to the complex'. In most of 'his' thoughts in this area he seems to have been most heavily influenced by Herbert Spencer (1820-1903), his near contemporary, writer and philosopher and an early evolutionary thinker. As Spencer's wikipedia entry puts it:

"Spencer developed an all-embracing conception of evolution as the progressive development of the physical world, biological organisms, the human mind, and human culture and societies."

Pitt-Rivers is known to have owned the following books on evolutionary themes:

Darwin, Charles The Descent of Man Murray London 1871

Spencer, Herbert. Descriptive Sociology, or Groups of Sociological Facts London 1873-8

Spencer, Herbert. Political Institutions 1882

Spencer, Herbert. First Principles 1870

Spencer, Herbert.  Study of Sociology 1874

Spencer, Herbert. Principles of Sociology 1876

Spencer, Herbert. Principles of Psychology 1870

This list was taken from the catalogue of his library [CUL Add.9455 volume 10]

The view that evolution, or progress as it was often called when applied to the material arts, was important and if not present would lead to 'degeneration' was held by Pitt-Rivers and many other people. To pluck two examples fairly randomly from one source, the banker Benjamin Heywood said that 'the undeviating adherence to established practice, - the mere imitation of what others have done before, - precludes all advancement: it reduces man to the condition of a machine', and the British Institutions founding statement 'If we do not advance, we must recede; and that when we cease to improve, we shall begin to degenerate'. [both quotations from Pergam, 2011: 19, quoting  B. Heywood, 'An Address to the Mechanics ... delivered at the opening of the Manchester Mechanics Institute ... 30th March 1825, Manchester, Robinson and Bent, p.3] For both of these sources, as with Pitt-Rivers the key to the evolution of humans was education, if the working classes were educated then they could progress.

For Pitt-Rivers' evolution was one of the major themes of his publications from the earliest days, underpinning almost every word he published. He often linked it with the need to educate the working classes in the need for steady progress rather than radical revolution. In most of his publications it was effectively a 'given', his writing was based on the assumption that evolution of form must have occurred, so it was mostly concerned with the need to present this 'given' in physical form in a display, and often to discussing the broad concepts rather than the supporting evidence.

Pitt-Rivers' views on evolution have always been seen as central to his philosophy and to his collection, but they were not uniquely his. Even for his contemporaries his views and his application of them to objects seemed remarkable, but again many other people collected and were interested in the use of objects to explore evolution, and its associate, decline. For example, Bram Hertz (1794-?), a gem dealer of German descent who lived in London, also collected widely. A catalogue of his collection, written in 1857 explains:

'The collection of Antiquities, described in the present Catalogue, was formed with the intention of gathering, so far as possible, the scattered monuments of ancient art, in order to illustrate the rise, progress and decline of the Fine Arts, and to obtain satisfactory corroboration of the veracity of ancient traditions respecting the religious habits, arts, and employment of bygone nations and the achievements of illustrious men and heroes.' [Koner, 1857: iii, quoted in Tythacott, 2011: 108]

Here are a selection of Pitt-Rivers' publications to give a flavour of his thoughts on the subject:

1858 On the improvement of the rifle:

...out of all the numerous contrivances which, in successive ages have been put forward for the improvement of the musket, some few may be taken to serve as links in the chain of progress, whilst others have branched out of the main line, and contributed nothing of permanent utility. In tracing the history of the rifle through its various phases, I therefore propose to confine my remarks to what may be considered the main chain of improvement, disregarding all those varieties which, however ingenious in themselves, have embodied no principle of practical benefit to our own times, nor served as stepping-stones to further improvement ...

1868 Primitive Warfare 2:
... The resultant of these contending forces is continuity. If we could but put together the missing links; if we could revive contrivances that have died at their birth, and expose piracies; if we could penetrate the haze that is so often thrown over continuity by great names, absorbing to themselves the credit of contrivances that belong to others, and thereby causing it to appear that progress has advanced with great strides, where creeping was in reality the order of the day; we should find that there is not a single work of man’s hand which has not its history of slow and continuous development, capable of being traced back, like branches of a tree, to its junction with others, and so on until the roots of all are found to lie in the simplest contrivances of primeval man. But we must not expect that we shall be able, in the existing state of knowledge, to trace this continuity from first to last, for the links that are lost, far exceed in number those which remain. The task may be compared to that of putting together the fragments of a tree that has been cut up for firewood, and of which the greater part has been burnt. It is only here and there, after diligent search, that we may expect to find a few pieces fitting in such a manner as to prove that they belonged to the same branch. ...

1869 Remarks on Westropp's paper on cromlechs [JESL ns I pp.59-67]
... The more we examine into the culture of the primitive inhabitants of the globe, the more we perceive it to have expanded and developed upon a plan analagous to that which has been observed in the development of species, and the more evident it becomes that the method of investigating these memorials [ie the cromlechs] should be the same systematic method which we employ for investigating the phenomena of the animal and vegetable kingdoms.For example, we should derive but little knowledge from the bare assertion that the class of mammalia is very widely distributed over the surface of the earth, but by studying the several varieties of the mammalia, and noticing their geographical distribution, naturalists have come to a knowledge of external causes which particular localities have favoured the development of particular kinds, and by tracing back the relics of these varieties in geological order, they are by degrees arriving at the power of assigning to each variety its true position in the order of creation. So, in like manner, by observing the distribution of the several varieties of each class of the relics left to us by the aborigines of our species, we shall be enabled to see to what extent their variations are attributable to design, and on the other hand, how far they were necessitated by the imperfect command the fabricators had over the constantly varying forms of nature. For it appears to be a law, applicable alike to all people in a low stage of culture, whether ancient or modern, that being devoid of rule or measure, and the materials on which they worked being of innumerable different shapes, and requiring enormous labour to fashion them into form, no two products of a primitive people ever exactly resemble each other, but all present slight modifications of size and outline ... As new ideas slowly spring up, and still more slowly receive acceptance, some of the numerous varieties of older forms become adapted, by a kind of natural selection, to newer uses, whilst at the same time, force of habit, and a spirit of conservatism, influence the retention of older types long after they have been superceded by new ones, so that the links of connection between older and newer forms are so continuous as to be almost imperceptible. Hence the importance of systematically classifying the varieties of prehistoric antiquity in the same manner that the naturalists have classified their evidence of the varieties of species, in order that we may be enabled to trace out the channels through which progress has flowed in the gradual evolution of higher types. One of the greatest obstacles to the comprehensive study of these subjects is the absence of any recognised terminology; this is so great defect, that there is hardly any relic of antiquity to which a definite and well-understood name can be attached, tending greatly to the confusion of ideas, and to impede the collection of fresh evidence. ...

1870 'Note on the use of the New Zealand mere'
‘...That analogy [of meres to some Irish clubs in Pitt Rivers collection] would lead one to suppose that so peculiar a weapons as the Mere, not being the best adapted, either as to its form or composition, to be used as a hand-club, must have been derived from some other implement of traditional usage amongst the people, it being a fact capable of demonstration that nearly all the weapons of savages have derived their form from an historical development, and are capable of being traced back through their varieties to earlier and simpler forms, with as much certainty as the various forms of animal and vegetable life.’

1874 Catalogue of the Anthropological Collection ... at Bethnal Green
... The objects are arranged in sequence with a view to show, in so far as the very limited extent of this collection renders such demonstration practicable, the successive ideas by which the minds of men in a primitive condition of culture have progressed in the development of their arts from the simple to the complex, and from the homogeneous to the heterogeneous. Evolution and development are terms which, it is now beginning to be admitted, are as applicable to the progress of humanity as to all other mundane affairs. ... Up to this point the development of species has gone on in accordance with the laws of procreation and natural selection. Man being the last product of this order of things, becomes capable by means of his intellect of modifying external nature to his wants, and from henceforth we have to concern ourselves with a series of developments produced by art. It is the province of anthropology to trace back the sequence of these developments to their sources ...

1875 'Principles of Classification':
... The collection does not contain any considerable number of unique specimens, and has been collected during upwards of twenty years, not for the purpose of surprising any one, either by the beauty or value of the objects exhibited, but solely with a view to instruction. For this purpose ordinary and typical specimens, rather than rare objects, have been selected and arranged in sequence, so as to trace, as far as practicable, the succession of ideas by which the minds of men in a primitive condition of culture have progressed from the simple to the complex, and from the homogeneous to the heterogeneous. .... The classification of natural history specimens has long been a recognised necessity in the arrangement of every museum which professes to impart useful information, but ethnological specimens have not generally been thought capable of anything more than a geographical arrangement. ... Since the year 1852 I have endeavoured to supply this want by selecting from amongst the commoner class of objects which have been brought to this country those which appeared to show connection of form. Whenever missing links have been found they have been added to the collection, and the result has been to establish, however imperfectly, sequence in several series. The primary arrangement has been by form - that is to say, that the spears, bows, clubs, and other objects above mentioned, have each been placed by themselves in distinct classes. Within each there is a sub-class for special localities, and in each of these sub-classes, or whenever a connection of ideas can be traced, the specimens have been arranged according to their affinities, the simpler on the left and the successive improvements in line to the right of them. This arrangement has been varied to suit the form of the room, or of the screens, or the number of specimens, but in all cases the object kept in view has been, as far as possible, to trace the succession of ideas. ...

1875 Early modes of Navigation
... In inquiries of this nature it is always necessary to guard against the tendency to form theories in the first instance, and go in search of evidence in support of them afterwards. On the other hand, in dealing with so vast a subject as Anthropology, including all art, all culture, and all races of mankind, it is next to impossible to adhere strictly to the opposite of this, and collect the data first, to the exclusion of all idea of the purpose they are to be put to in the sequel, because all is fish that comes into the anthropological basket, and no such basket could possibly be big enough to contain a millionth part of the materials necessary for conducting an inquiry on this principle. Some guide is absolutely necessary to the student in selecting his facts. The course which I have pursued, in regard to the material arts, is to endeavour to establish a sequence of ideas. When the links of connexion are found close together, then the sequence may be considered to be established. When they occur only at a distance, then they are brought together with such qualifications as the nature of the case demands. ... Whilst, however, deprecating the influence of forgone [sic] conclusions, there are certain principles already established by science which we cannot afford to disregard, even at the outset of inquiries of this nature. It would be sheer moonshine, in the present state of knowledge, to study Anthropology on any other basis than the basis of development; nor must we, in studying development, fail to distinguish between racial development and the development of culture. The affinity of certain races for particular phases of culture, owing to the hereditary transmission of faculties, constitutes an important element of inquiry to be weighed in the balance, with other things, just as the farmer weighs in the balance of probabilities the nature of the soil in which his turnips are growing; but when particular branches of culture do run in the same channel with the distribution of particular races, this is always a coincidence to be investigated and explained, each by the light of its own history. It would be just as reasonable to assume with the ancients, that the knowledge of every art was originally inculcated by the gods, as to assume that particular arts and particular ideas arise spontaneously and as a necessary consequence of the possession of particular pigments beneath the skin. ... To study culture is, therefore, to trace the history of its development, as well as the qualities of the people amongst whom it flourishes. In doing this it is not sufficient to deal with generalities, as, for example, to ascertain that one people employ bark canoes, whilst another use rafts. It is necessary to consider the details of construction, because it is by means of these details that we are sometimes able to determine whether the idea has been of home growth or derived from without ...

1875 Talk at Whitechapel ...
... My collection at Bethnal Green has been collected and arranged so as to shew at a glance the gradual development of savage and prehistoric implements from the forms of nature, so that by running the eye from left to right along the several specimens as they are arranged on the screens, the visitor may see the gradual divergence of the forms, from that of the simple stick or stone, as the case may be, out of which they [3 words illegible] mark. ... [see here for full transcript]

1875 Evolution of Culture
... If we accept the definition of the term science as ‘organized common sense’, we necessarily reject the idea of it as a ‘great medicine’ applicable only to certain subjects and inapplicable to others; and we assume that all those things which call forth the exercise of our common sense are capable of being scientifically dealt with, according as the knowledge which we pretend to have about them is based on evidence in the first place, and in the sequel is applied to the determination of what, for want of a better word, we call general laws. ... We use [this term] in the sense of a result, rather than a cause of what we observe, or at most we employ it to express the operation of proximate causes; and of the ultimate causes for the phenomena of nature we know nothing at all. Further, in this development of the principle of common sense it has been said that the inductive sciences pass through three phases, which have been termed the empirical, the classificatory and the theoretical. ... The principles of variation and natural selection have established a bond of union between the physical and culture sciences which can never be broken. History is but another term for evolution. ... The task before us is to follow by means of them the succession of ideas by which the minds of man has developed, from the simple to the complex, and from the homogeneous to the heterogeneous; to work out step by step, by the use of such symbols as the arts afford, that law of contiguity by which the mind has passed from simple cohesion of states of consciousness to the association of ideas, and so on to broader generalizations. ... It is, I venture to think, by classifying and arranging in evolutionary order the actual facts of the manifestations of the mind, as seen in the development of the arts, institutions, and languages of mankind, no less than by comparative anatomy, and far more than by metaphysical speculation, that we shall arrive at a solution of the question, to what extent the mental Ego has been, to use Professor Huxley’s expression, a conscious spectator of what has passed. ... Now we know from all experience, and from all evolution which we can trace with certainty, that progress moves on in an accelerating ratio, and that the earlier processes take longer than the later ones ... In tracing the evolution of prehistoric implements, we are of course limited to such as were constructed of imperishable materials. No doubt our prehistoric ancestors used also implements of wood, but they have long since disappeared; and if we wish to form an idea of what they were, we must turn to those of his nearest congenitor, the modern savage ... If the Australians, for example, were the degenerate descendants of people in a higher phase of culture, then, as all existing ideas are made up of previous ideas, we must inevitably find amongst their arts traces of the forms of earlier and higher arts, as is the case amongst some of the savages of South America who early came into contact with Peruvian civilization; but the reverse of this is the case; all the forms of the Australian weapons are derived from those of nature. ... But in dealing with evolution we have to speak not only of growth but, as in all other natural sciences, of the principle of decay. By decay I do not mean the decay of the materials of the arts, but the decomposition of the mental ideas which produced them. As complex ideas are built up of simple ones, so there is also a further process by which they become disintegrated, and the parts go to form parts of other ideas ... My object in this discourse had been not ... to extol the material arts as being intrinsically of more interest or importance than other branches of culture, but to affirm the principle that it is by studying the psychology of the material arts alone that we can trace human culture to its germs. .. There are huge gaps in our knowledge of the history of the human race, ... but surely, if slowly, science will open up these desert places, and prove to us that, so far as the finite mind of man can reach, there is nothing but unbroken continuity to be seen in the present and in the past....

1889-1890 Talk at Blackmore Museum 'Uses and arrangement of Arts museums'
... In a well-arranged Museum, the history of any material Art or Industry, or the development of any species of animal in Natural History, or of Man himself, can be displayed by means of objects arranged is [sic - in] sequence, in such a manner that the successive changes that have taken place in the perfecting of them, can be brought to the knowledge of the student in a short time. By becoming acquainted with the history of material and visible objects, acquired in this way, a clue is afforded to the development of other Arts, Institutions and Customs of mankind, in which the successive ideas, that have followed each other, not having been embodied in material forms, cannot be so displayed, and the History of which consequently, cannot be attained without diligent research and book-learning. By this, is afforded, a correct and easy means of learning History, and by shewing that all the most useful Arts and Institution, that exist amongst us at the present time, are the growth of ages; by contrasting the slow and laborious processes of their development, with the facility with which they are destroyed, the public, the less-informed portion of the public that is, may gradually acquire greater respect for Antiquity, and become in some measure disabused of that strong desire to break rudely with the past, which is so often found amongst the half-educated classes of our time. The education afforded by Museums is on this account eminently progressive and conservative, using that term in its general, and not in its political sense. ...My first initiation into the subject of Arts Collections was brought about in a practical way. In the years 1851-1852, I was employed as a Military Officer on the Sub-Committee of Small Arms at Woolwich, and in 1853, as the first Chief Instructor of Musketry at Hythe, on the formation of that establishment by Lord Harding. My duties amongst others, consisted in making experiments with all the new inventions both British and Foreign, that were submitted to Government for the improvement, or rather I should say at that time, the first introduction of the Rifle Musket. In the course of these investigations, I was led to observe how very slow and gradual the steps of improvement were, and how very slightly the inventions of one person differed from those of another. In 1858 I read a Paper at the Royal United Service Institution, in which I gave an account of the development of ideas upon the subject, during the time that I had engaged in the manner I have mentioned. The Paper gave offence at the time to some of the Inventors, most of whom either supposed themselves, or wished it to be supposed by others, that their inventions sprang full-blown out of their inner consciousness, and were independent of anything that had gone before. The Collection of Rifles that I made at that time, ultimately expanded into a Museum of Savage and Barbarous Weapons, and later on, was made to include various other Arts, such as Ship-building, Textile Fabrics, Pottery and substitutes for Pottery, Dress, Tools, Personal Ornament, and several series illustrating the development of Ornamental Patterns. To which was added a series of Palaeolithic, Neolithic, Bronze Age and Iron Age implements, in all of which I endeavoured to collect only specimens which represented links in the development of the several Arts. ... [see here for full transcript]

1891 'Typological Museums'
It is true that the history of laws, customs and institutions cannot be displayed in museums. You cannot place the successive links of development side by side in such a manner as to appeal to the eye; but the material arts are capable of such an arrangement, and the knowledge acquired in the one branch will be, to some extent, available in the other. The law that Nature makes no jumps, can be taught by the history of mechanical contrivances, in such way as at least to make men cautious how they listen to scatter-brained revolutionary suggestions. The knowledge of the facts of evolution, and of the processes of gradual development, is the one great knowledge that we have to inculcate, whether in natural history or in the arts and institutions of mankind; and this knowledge can be taught by museums, provided they are arranged in such a manner that those who run may read. ...
If it were taken to imply the study of fixed types as characteristic of particular phases of the arts, it would be erroneous. It includes the growth, varieties, and developments of the several types. It supplies the want of dates by showing how certain forms must have preceded or followed others in the order of their development, or in the sequence of their adoption. It may be said, as a rule, that simple forms have preceded complex ones. Within certain limits this must be true, but it is not always the case, for, in many instances, progress consists in eliminating superfluous complexity, and reducing the expenditure of time and labour. We have in this, as in all mundane affairs, to deal with degeneracy and decay, as well as progressive growth: the two have gone on side by side. It is the work of typology to unravel the true thread of events, and place the objects in their proper sequence for the use of students. Typology forms a tree of progress, and distinguishes the leading shoots from the minor branches. The problems of the naturalist and those of the typologist are analogous. The difficulties are the same in both. In some cases the number of missing lines makes it impossible to determine the true succession of forms. In such cases recourse must be had to survivals, as in the case of the majority of savage weapons or forms of art, in which the successive links, being made of wood or perishable materials, have decayed. But a theoretical, and fairly accurate development, may nearly always be traced amongst the arts of savages by object in present use. When a simple form is suited to its environment, or when its use fulfils common purposes that cannot be better served by its successors, or when economy of labour is a desideratum, the simple form survives; as, for example, in the case of the common door-bolt, which is the father of all kinds of complex door locks, and which is still used upon the same doors as the contrivances that have sprung from it; or in the case of the common hand-made pots that are still baked in an ordinary turf fire in the Hebrides, at the same time as the most skilled production of our modern potteries. So in natural history, invertebrate and vertebrate animals and mammalia are all found living side by side in the same localities, although we know that they represent successive stages in the development of species. Typological sequence, or typological continuity, may be said to be established when the true succession of forms have been brought out. This is the object of an educational museum.

You will find many more examples if you read his own words in his various journal papers. See here for a selection of these that have been transcribed.

AP, September 2011