Thursday, 28 August 2014

Changing one’s mind about Creation - or not.

William Henry Fox Talbot (1800-1877), the pioneer of photography and refiner of the calotype process, was a mathematician and keen archaeologist who lived at Lacock Abbey in Wiltshire. His family home is now owned by the National Trust and it is easy for a visitor to imagine life in the old house, and the adjoining village, during the Nineteenth Century.

During a recent trip to Lacock Abbey, I had a chance to look through the library (only at the spines of the books, as they were wired in for security purposes - see above) and was drawn to a copy of Foot-prints of the Creator: or the Asterolepis of Stromness by Hugh Miller. I have no idea whether Fox Talbot read this copy, but I’m sure that he did. The book was an important contribution to debates about apparent conflicts between the literal truth of the Bible and mounting support for the reality of geological time scales and for the evolution of organisms, especially humans. Foot-prints of the Creator was written as a response to the ideas put forward in Vestiges of the Natural History of Creation published, anonymously, by Robert Chambers in 1844. That book, very popular at the time, described the evolution of both the physical and biological world, using, in part, ideas that had earlier been propounded by Lamarck. Of the development hypothesis, Miller wrote:

If, during a period so vast as to be scarce expressible by figures, the creatures now human have been rising, by almost infinitesimals, from compound microscopic cells,-minute vital globules within globules, begot by electricity on dead gelatinous matter,-until they have at length become the men and women whom we see around us, we must hold either the monstrous belief, that all the vitalities, whether those of monads or of mites, of fishes or of reptiles, of birds or of beasts, are individually and inherently immortal and undying, or that human souls are not so. [1]

It was this latter point that was so important to Miller who, as a committed Christian, could not countenance the idea of humans without souls. There was no conflict, however, with the view of geological time scales, and Miller described periods of creation and extinction in The Testimony of the Rocks; or, Geology in its Bearings on the Two Theologies, Natural and Revealed. The book was published posthumously and is based on several lectures, with the addition of further chapters “written mainly to complete and impart a character of unity to the volume of which they form a part” [2]. In the preliminary section entitled “To the Reader”, Miller writes:

It will be seen that I adopt.. ..[a] scheme of reconciliation between Geologic and Mosaic Records which accepts the six days of creation as vastly extended periods; and I have been reminded by a somewhat captious critic that I once held a very different view, and twitted with what he terms inconsistency. I certainly did once believe.. .. that the six days were simply natural days of twenty-four hours each,-that they had compressed the entire work of the existing creation,-and that the latest of the geological ages was separated by a great chaotic gap from our own. [2]

He continues by stating that:

..the conclusion at which I have been compelled to arrive is, that for many long ages ere man was ushered into being, not a few of his humbler contemporaries of the fields and woods enjoyed life in their present haunts, and that for thousands of years anterior to even their appearance, many of the existing molluscs lived in our seas. That day during which the present creation came into being, and in which God, when he had made “the beast of the earth after his kind, and the cattle after their kind,” at length terminated the work by moulding a creature in his own image, to whom he gave dominion over them all, was not a brief period of a few hours’ duration, but extended over mayhap millenniums of centuries. No blank chaotic gap of death and darkness separated the creation to which man belongs from that of the old extinct elephant, hippopotamus, and hyæna; for familiar animals such as the red deer, the roe, the fox, the wild cat, and the badger, lived throughout the period which connected their times with our own; and so I have been compelled to hold, that the days of creation were not natural, but prophetic days, and stretched far back into the bygone eternity. After in some degree committing myself to the other side, I have yielded to the evidence which I found it impossible to resist; and such in this matter has been my inconsistency,-an inconsistency of which the world has furnished examples in all the sciences, and will, I trust, in its onward progress, continue to furnish many more. [2]

Although unable to accept ideas about the evolution of humans, Miller had changed his mind about the literal description of the days of Creation in The Bible. He made extensive studies of the fossils in his native Scotland, and elsewhere, and found geological time periods the only possible explanation for the changing flora and fauna in different rock strata.

Hugh Miller (1802-1856) was brought up in Cromarty and left school at around sixteen. His father had died when he was five and his maternal uncles were an important influence on the young Hugh, encouraging his fascination with the natural world and also with folklore and legend, interests that remained with him for the rest of his life. He had always been a keen reader and liked to write, but he needed a job and so became a stonemason, travelling to wherever there was work. His skills with hammer and chisel aided his developing interest in geology and he was expert in breaking open nodules that contained fossils. As described in the excellent biography Hugh Miller: Stonemason, Geologist, Writer by Michael A. Taylor [3], Miller achieved fame as an expert on fossil fish from sandstones and this despite his natural shyness and difficulty in enjoying formal meetings. After a spell working in a bank, he was appointed the editor of an Edinburgh newspaper, The Witness, that enabled him to write on a number of subjects and he was involved in debates on the future of the Free Church in Scotland, holding strongly Calvinist views. It is perhaps surprising, then, that Hugh Miller ended his own life and the reasons for his suicide are not clear, although he suffered from severe health issues caused by silicosis, acquired when he worked in an atmosphere thick with stone dust in his younger years. To the end, he was a committed Christian and his faith was not challenged by the difference between the “geologic and Mosaic records”. He was “not a man torn between science and religion, but, on the contrary, one who is comfortable with both.” [4]

Another book published in 1857 took a quite different line to that in The Testimony of the Rocks. Philip Henry Gosse (1810-1888) was a member of the Brethren and could neither accept ideas on evolution or anything that questioned the literal truth of the Holy Bible. The developing ideas on the mid-Nineteenth Century were thus a challenge that he felt he must address. Like Hugh Miller, Henry Gosse had no formal training but he, too, became an expert in his field, in this case Natural History. In his early years he was encouraged in his observations by a maternal aunt and he went on to be fascinated by all the living organisms around him. His work on sea anemones and corals is still recognised as important, but he also published on a wide range of other topics. Interestingly, like Hugh Miller, he was a shy man and an excellent writer, but Henry Gosse was also a gifted painter and illustrator and his books became widely popular as a result. One book was not a success and this was Omphalos, sub-titled an attempt to untie the geological knot, and this was Henry Gosse’s way of resolving the conflict that Miller also addressed. Although primarily an observer of living organisms, Henry Gosse had an excellent knowledge of rock strata, the fossil record and geological time and he accepted this reality. However, Gosse theorised that they were part of the six-day Creation, with the structure of the Earth’s crust, including the remains of organisms, having been created in a few days. Unsurprisingly, this view was considered absurd by scientists at the time and, to Henry Gosse’s surprise, it was also regarded very unfavourably by Christians, as they found it unlikely that God would wish to deceive by hiding fossils within rocks [5].

It seems strange that devout Christians, working with the same Holy Book, have such disparate views and the debate about Creation, and what was meant in Genesis, continues today. Of course, it causes such strong feelings because there are always differences of opinion in human culture and we have a tendency to only fully acknowledge our own personal beliefs. Hugh Miller was able to accept a change in his views in the light of changing evidence and it did not impact his faith, but Henry Gosse found himself boxed into a corner. Gosse had the satisfaction of maintaining the purity of his position, but it left him isolated and disappointed. No more so than in his relationship with his only son Edmund, with whom he had been very close and who, as a youth, could not follow his father’s dogmatic approach.

I greatly admire Henry Gosse as a Natural Historian and find his books, and illustrations, quite wonderful. He was a caring man whose religious beliefs underscored everything that he did, but whether we could have sustained a conversation, or a friendship, is debatable. In contrast, I think I would feel less guarded when meeting Hugh Miller, although his energy and time-keeping might be a strain. Both men are important parts of the period of Natural History described by Lynn Barber as its heyday [6] and Miller and Gosse are given adjacent chapters in her book. The transformational work of Darwin in On the Origin of Species published in 1859, just two years after The Testimony of the Rocks and Omphalos, provided, in natural selection, a mechanism to explain evolution and it transformed our thinking. It is such an important book that it has overshadowed the contributions made by Miller and by Gosse, yet the change of mind of one, and the determination not to change by the other, give insights into current debates on Creation and evolution. Their books are worth reading.

[1] Hugh Miller (1849) Foot-prints of the Creator: or the Asterolepis of Stromness. London, Johnstone and Hunter.

[2] Hugh Miller (1857) The Testimony of the Rocks; or, Geology in its Bearings on the Two Theologies, Natural and Revealed. Edinburgh, Thomas Constable & Co.

[3] Michael A. Taylor (2007) Hugh Miller: Stonemason, Geologist, Writer. Edinburgh, NMS Publishing Limited.

[4] Simon J. Knell and Michael A. Taylor (2006) Hugh Miller: fossils, landscape and literary geology. Proceedings of the Geologists’ Association 117: 85-98.

[5] Roger S. Wotton (2012) Walking with Gosse: Natural History, Creation and Religious Conflicts. Southampton, Clio Publishing.

[6] Lynn Barber (1980) The Heyday of Natural History. London, Jonathan Cape.

To add symmetry to this blog post, I end with a calotype of Hugh Miller posed as a stonemason, standing next to a gravestone that he has carved. If it hadn’t been for Fox Talbot’s refinement of the technique, this portrait may not have existed.

Monday, 18 August 2014

Garden plants, seeds and being unnatural

Flowering plants produce seeds and these are dispersed away from the parent plant, many mechanisms having evolved for this purpose. These mechanisms range from winged seeds, to those with parachutes, plants having “pepperpots” to scatter seeds, to those that use explosive discharge. Wide-ranging dispersal is achieved after attachment to, or ingestion by, animals, and seeds may also be carried very long distances by wind and water. Providing conditions in newly-colonised regions are suitable for development, plants are then able slowly to increase their range. With changes in climate, and the movement of continents, through geological time, flowering plants have been very successful in colonising almost all terrestrial habitats and even some aquatic ones. This success is not the result of dispersal ability alone, but also of mutations in their genetic structure, resulting in adaptations of both structure and physiology. As a result, flowering plants are found in deserts, on mountains and in high latitudes as well as the profusion of types we find in temperate and tropical regions.

When early humans began to cultivate some of the wild plants around them, they began to select those that could be bred to produce crop plants, this being accompanied by a reduction in diversity, as the natural community was managed by our farming practices. Yet further along in human evolution, when we started having plants for decoration, even more selective breeding was undertaken and, as humans began to migrate, it was possible to take the seeds of plants that we liked, or needed, with us. That is the background to the work of botanical collectors who, for centuries, journeyed to find new wild plants in distant countries and then bring their seeds back for cultivation. The extent of such deliberate imports is unique to the activities of humans; no other organisms do this.

Many gardeners are familiar with the huge array of types of garden flowering plants that are available (and we not only propagate from seeds), but less familiar with their origins. Below are some suggested plants for borders given by Anna Pavord, the excellent writer on gardening [1]; the types of borders (Anna Pavord’s headings) being for gardens in temperate Europe. The scientific names of plants are given, together with their common names and varieties (the latter resulting from selective breeding by horticulturalists) and the original geographical locations of the parent plants [2]:

Cottage-garden border

Viola labradorica (Purple-leaved violet) - North America, Greenland
Bellis perennis (Double daisy) - Europe, Turkey
Camassia leichtlinii (Quamash) - North America
Aquilegia vulgaris (Columbine) - Europe
Daphne x burkwoodii - Europe, North Africa, Asia
Geranium pratense (Meadow cranesbill) - Europe, Central Asia, China
Paeonia Sarah Bernhardt (Peony) - Europe, Asia, North America
Salvia sclarea (Vatican sage) - Europe, Central Asia
Thalictrum delavayi (Meadow rue) - Western China
Campanula lactiflora (Milky bellflower) - Caucasus, Turkey
Gypsophila paniculata (Baby’s breath) - Europe
Lychnis coronaria (Rose campion) - Europe

Of these twelve plants, eight (67%) have European origins and one further has a wide distribution with many European relatives. A characteristic of cottage gardens is their “naturalness” and the recommendations above contain cultivars of wild flowers likely to be found in close proximity to the garden, cottages being characteristic of the countryside - at least, that is the image to be created. The planting is boosted by the appearance of plants that are not part of the natural flora of Europe.

A scheme for scent

Lilium candidum (Madonna lily) - Europe
Narcissus jonquilla (Jonquil) - Spain
Thymus x citriodorus (Lemon thyme) - Garden origin
Lavandula angustifolia (Lavender) - Mediterranean
Rosmarinus officinalis (Rosemary) - Mediterranean
Pelargonium Mabel Grey - ?South Africa
Iris graminea - Spain to Russia + Caucasus
Dianthus Prudence (Pink) - Europe, Asia, South Africa
Thymus serpyllum (Wild thyme) - Europe
Hemerocallis citrina (Daylily) - China
Daphne odora - China, Japan

There are eleven plants in this list, with seven (64%) that originate in Europe. In two cases (Pelargonium and Dianthus), the origins are vague as the possible parental stocks have a worldwide distribution.

A tropical summer border

Ensete ventricosum (Banana palm) - Ethiopia to Angola
Cleome hassleriana (Spider flower) - Southern South America
Canna indica (Indian shot plant) - South America
Argyranthemum frutescens - Canary Islands
Pelargonium Royal Oak - ?South Africa
Aeonium arboretum - Morocco
Felicia amelloides (Blue daisy) - South Africa
Cosmos Sensation - Mexico
Nicotiana sylvestris (Tobacco plant) - Argentina
Ricinus communis (Castor oil plant) - North Africa to West Asia

Given that the intention is to create a tropical summer border, it is no surprise that none of the plants originate in Europe and, indeed, many can only be grown outdoors during summer, as they cannot tolerate cold temperatures. This is another feature of the power of humans in gardening - we not only use transplantation of species, but choose where, and when, to locate them. There is a wide geographical spread of origins, including one representative found solely on an island chain.

A bold desert bed

Datura (Brugmansia) x candida (Angels’ trumpets) - Garden origin
Gazania uniflora - Tropical Africa
Agave Americana - Mexico
Fuchsia Thalia - Central and South America
Begonia rex (King begonia) - Himalayas
Phormium tenax (New Zealand flax) - New Zealand
Aeonium arboretum - Morocco
Kniphofia caulescens (Red hot poker) - South Africa
Eucalytus niphophila (Alpine snow gum) - Australia
Crassula falcata (Aeroplane propeller) - South Africa
Echeveria gibbiflora - Mexico
Yucca whipplei (Our Lord’s candle) - USA, North Mexico

As would be expected, there are no representatives from Europe in this list and the geographic spread is even wider than for the tropical summer border. It is worth pointing out that some desert plants cannot be grown outdoors in most of Northern Europe and fanciers of cacti and some succulents will need heated greenhouses for their collections. This is an example not only of human ability to transplant, but also to change the environment in which the imported plants grow.

Although a very large number of plants have been collected for gardens, some have escaped and invaded surrounding areas, mingling with the native flora. This represents a reverse of the position of weeds (wild, native plants) in gardens and, while many of the invaders from gardens provide an excellent “show”, some have habits which mean that they become a nuisance, sometimes dominating, and excluding, local plants that would not have to compete under natural conditions with these very recent invaders. There are many examples and I’ll just mention three.

Hedychium gardnerianum (Kahili Ginger - below, top) is native to the Himalayas and is a striking plant which has been imported both for its foliage and for its scented spikes. It produces sticky seeds that aid dispersal in its natural habitat and these also provide one of the means that encourage its spread elsewhere. It has become a serious invasive pest in several areas of the world and, once present, is difficult to remove. The same can also be said of my other two examples: Impatiens glandulifera (Himalayan Balsam - below, middle) and Fallopia japonica (Japanese Knotweed, below, bottom). As its common name suggests, I. glandulifera is, like H. gardnerianum, a native of the Himalayas and shares the same high dispersal ability. The balsam has attractive pink flowers which appeal to gardeners, and its success in dispersal results from the explosive release of seeds that scatter from the parent plant. As riparian zones of streams and rivers are especially favoured by these invading plants, the flowing water provides another excellent means of dispersal, as the seeds are carried downstream after being shot out.

F. japonica colonises many habitats.  A hollow-stemmed plant, it shows rapid growth and produces many leaves, giving effective ground cover and, with its height, a means of hiding unattractive or derelict areas. Vegetative growth by means of rhizomes ensures that there is strong lateral spread and only a small section of rhizome is needed for the successful growth of a new plant, the rhizomes possessing such strength that they can cause damage to buildings and any solid structures with which they come in contact. Once established, Japanese Knotweed is very difficult to kill and it is such an effective plant that special operatives may be necessary to remove it.

The collection of seeds from plants that grow in very distant regions, and then bringing them to countries that are highly unlikely to be colonised naturally, is a means of dispersal that is markedly unnatural. It should therefore not surprise us when some plants - and animals - "escape" and reach pest levels. They have been transplanted from the regions where they evolved over millions of years and where they are part of different, complex communities that contain natural controls.  It is another result of humans needing to modify Nature, rather than feeling part of it.

[1] Anna Pavord (1994) The Border Book. London, Dorling Kindersley.

[2] Christopher Brickell [Editor-in-Chief] (1996) The Royal Horticultural Society A-Z Encyclopedia of Garden Plants. London, Dorling Kindersley.

Friday, 8 August 2014

Cat fleas and chegoes: amazing examples of evolution

Anyone keeping cats is familiar with adult cat fleas (an example is shown below, upper). They may be discovered while combing the fur of our pets, or we may chase individuals we see on bed sheets, sometimes after they have bitten us. The females require a blood meal to gain the nutrients needed to produce eggs and, once laid, these hatch into larvae that live among cat fur, or fall off on to carpets and upholstery in our homes. Although cat owners recognise the adult flea, and its prodigious jumping ability, few know about the larvae (shown below, lower) - or even know of their existence.

Jumping in adults is achieved by extending the long hind legs very rapidly by means of muscles, aided by a pad of a protein, called resilin, at the junction of the leg with the rest of the body. Resilin is one of the most elastic substances known; meaning that almost all the energy stored by distortion is released, with the protein returning almost perfectly to its original form. This is what happens when the leg is extended, contraction of the leg then distorting the resilin pad to again store energy. It is an extraordinary adaptation and, while this special protein is found in a number of insects, where it is associated with flight and the beating of the wings, it has “migrated” through evolutionary time to the hind legs in many types of adult fleas, like cat fleas, that are, of course, flightless. Whatever the explanation for the location of the awesome resilin, it enables fleas to jump impressively on to their hosts - and to avoid potential predators.

While we are annoyed at being bitten, and do all we can to kill fleas, we should remember just what extraordinary insects they are. They have complete metamorphosis, with larvae of quite different form to the adults, and a pupal stage in which the transition of forms occurs. That in itself is remarkable, but so commonplace that we lose our ability to be impressed by its evolution. Add in the structure of the hind legs of fleas, the presence of resilin pads, and their jumping ability and we should be even more amazed.

Chegoes are certainly amazing. Those who travel to tropical Africa, the Caribbean and tropical South America will be familiar with chegoes and readers of Charles Waterton’s descriptive books will have been both fascinated, and horrified, by his accounts of these insects:

The chegoe resembles a flea; and, had you just come out of a dovecot, on seeing it upon your skin, you might easily mistake it for a small pigeon flea; although upon closer inspection, you would surmise that it is not capable of taking those amazingly elastic bounds so notorious in the flea of Europe. [1]

Waterton’s observations on the jumping ability of chegoes is corroborated by other observers and may explain why they attack the lower parts of the limbs of their hosts and why they tend to infest similar regions in humans. I will not provide illustrations of the pathological effects of chegoes (they are not for the squeamish) but leave it to Waterton to provide a description of his contact with the insects during his Third Journey to South America in 1820:

It looks exactly like a very small flea, and a stranger would take it for one. However, in about four and twenty hours, he would have several broad hints that he had made a mistake in his ideas of the animal. It attacks different parts of the body, but chiefly the feet, betwixt the toe nails and the flesh. There it buries itself, and at first causes an itching not unpleasant. In a day or so, after examining the part, you perceive a place about the size of a pea, somewhat discoloured, rather of a blue appearance. Sometimes it happens that the itching is so trivial, you are not aware that the miner is at work. Time, they say, makes great discoveries. The discoloured part turns out to be the nest of the Chegoe, containing hundreds of eggs, which, if allowed to hatch there, the young ones will soon begin to form other nests, and in time cause a spreading ulcer. As soon as you perceive that you have got the Chegoe in your flesh, you must take a needle, or a sharp pointed knife, and take it out. If the nest be formed, great care must be taken not to break it, otherwise some of the eggs remain in the flesh, and then you will be annoyed with more Chegoes.. ..Sometimes I have taken four nests out of my feet in the course of the day. [2]

Unknown to Waterton, chegoes are indeed fleas - “a very sharply defined order of insects without close connexion to any other group” [3] - and they are the smallest fleas yet discovered [4]. 

After landing on a suitable host by walking, or jumping weakly, female chegoes (see below) burrow into the skin and end up with the mouth parts able to suck up blood and the posterior tip of the abdomen only protruding to allow excretion of the dark, blood-rich faeces (a micrograph of a buried female chegoe is shown below - taken from the paper by Eisele et al. [4]). It is thought that mating occurs when the female is embedded, but this is debated currently [5] and an alternative view is that females mate after taking a blood meal from a temporary visit to a host [5]. There is agreement that feeding on blood occurs before mating and, once embedded, a dramatic change in the body of the female takes place. Although he didn’t know it, the “nest” that Waterton describes is the greatly distended abdomen of the female adult flea and it has a volume 2000-3000 times the original and fills with eggs that are then “ejected with considerable velocity” [4]. Most observers find larvae living in sandy soils, where they feed on detritus and it is unlikely that the bloody faeces produced by adults are a significant source of food, as they are, for example, for the larvae of cat fleas. Five weeks after the initial invasion by the female chegoe, the remains of her dead body are expelled from the skin [4] and there is little further adverse effect on the host.

Whatever your reaction to chegoes, it is impossible not to be impressed by their natural history. Humans are very recent in evolutionary terms and the adaptations of these, and other, fleas precede our appearance by millions of years. However, we cannot ignore such organisms when they affect us adversely by their behaviour and we can feel that their attacks are deliberate rather than opportunistic. As a devout Roman Catholic, Charles Waterton’s fascination was certainly anthropocentric and related to his view of the wonders of Creation, although, unlike some other Nineteenth-Century Natural Historians, he did not preach to his audience on the topic. For those who find evolution to be a more pleasing explanation of the extraordinary adaptations of organisms like fleas, there is the perpetual - and intriguing - question of how it all evolved. Was it by a succession of very small changes, or were there sudden, dramatic changes in the genetics of organisms that then controlled their structure and behaviour?

[1] Charles Waterton (1870) Essays on Natural History (edited, with a life of the author by Norman Moore B.A.). London, Frederick Warne and Co.

[2] Charles Waterton (1973) Wanderings in South America, the North-West of the United States, and the Antilles, in the years 1812, 1816, 1820 and 1824 with original instructions for the perfect preservation of birds and for cabinets of natural history (edited with an Introduction by L. Harrison Matthews). London, Oxford University Press.

[3] A.D.Imms (1964) A General Textbook of Entomology (edited by O.W.Richards and R.G.Davies. London, Methuen &Co.Ltd.

[4] M.Eisele, J.Heukelbach, E.Van Marck, H.Mehlhorn, O.Meckes, S.Franck and H.Feldmeier (2003) Investigations on the biology, epidemiology, pathology and control of Tunga penetrans in Brazil: 1. Natural history of tungiasis in man. Parasitology Research 90: 87-99.

[5] M.Thielecke and H.Feldmeier (2013) The fate of the embedded virgin sand flea Tunga penetrans: Hypothesis, self experimentation and photographic sequence. Travel Medicine and Infectious Disease 11: 440-443.