For a country with so chequered a recent history, Hungary is a surprisingly friendly place. At least, that was the verdict of the international community which gathered in Debrecen in September 1991 for the Third Congress of the European Society of Evolutionary Biology.
The meeting covered a wide range of topics, many with a mathematical or highly conceptual emphasis, but including a fair sprinkling about molecular and gross phenotypic aspects. Two towering performances by Stuart Kauffman dealt with the implications of spin-glass modelling for evolution theory. The general idea is that binary coding, for example in relation to expression of a particular gene in adjacent cells, can be represented as a two-dimensional array of contiguous dipoles. Computer simulation indicates that if mutual interaction occurs between adjacent dipoles, the system will eventually settle down with islands of order in a chaotic sea. The implication is that even with a large number of genes in operation, a defined number of stable cell types would eventually be created, as a natural property of the system. When applied to Sewall Wright’s landscape of adaptive fitness, the idea emerges that evolution can best occur within the transition zone between order and chaos.
The related concept, that the most effective site for introduction of evolutionary novelties probably lies at the interface between organism and environment, was taken up by Pritchard in a symposium on recapitulation led by Tim Horder. Over the years Haeckel’s Biogenetic Law, which states that during initial development we each retrace the phylogenetic path taken by our ancestors, has taken many a knock. Nevertheless, it still provides an important guiding principle, although it may be mainly ‘‘landmark states’’ that are recapitulated, while organisms find their way by diverse means between the landmarks.
Tracing the origins of proteins by their amino acid sequences runs into problems when entering the twilight zone around 10-15 percent identity, as that is the expected similarity of randomly chosen sequences. However, x-ray crystallography reveals three-dimensional structure that is conserved and this provides illumination through and beyond the twilight zone. By this means R. F. Doolittle traced the origins of actin and haemoglobin as far back as the bacteria; together with a concentration of sequencing studies on the active sites of proteins, this approach promises exciting findings in years to come.
A very important topical issue is the risk associated with release of genetically modified organisms. Draft regulations were to be implemented throughout the EEC by the end of October 1991, but we still lack a rational scientific framework on which to base decisions. Of the 32,000 vascular plants that have been introduced into Britain, only 0.12 per cent have caused ecological problems, but the danger which arises with genetically modified organisms, is that the artificial gene constructs may undergo horizontal transfer into established species. As yet the potential risks are quite unquantifiable. Considerable concern was expressed about these issues, but attention was diverted into another area; a declaration signed by many of the attenders of the whole conference, that they would not knowingly use their genetic expertise to further the causes of war.
When high-powered mathematicians start to work on biological problems it often seems that they lead one through impermissible assumptions into a mathematical wonderland that bears little relation to reality. Such experiences were not absent from this meeting, but rescue was at hand in some inspired down-to-earth studies, among the most interesting of which was one on migratory behaviour in blackcaps (Sylvia atracapilla). Francisco Pulido reported an association between lack of migratory restlessness and a particular variant of an enzyme that links glycolysis to lipid metabolism and which is thought to be involved also in insect migration. If this stands up to scrutiny it could be the beginning of a whole new field of study.
Investigation into the mating songs of fruit flies revealed control by a gene concerned with circadian rhythm. This has a threonine-glycine repeat similar to that in the ‘‘clock gene’’ of the mould, Neurospora, suggesting that the appreciation of time may have a similar genetic basis in many widely separated species.
Wandering through the towns and countryside of central and southern Europe, it is easy to infer the inspiration for the traditional radial patterning of their cobblestones, in the arrangement of seeds in sunflower heads. These follow the Fibonacci series represented in other forms in pine cones and branching patterns of many plants. S. Berczi has taken this idea and deduced several mathematical series from plant forms that are represented in the elegant and intricate ornamentation on ancient Celtic belt buckles. One wonders whether this decoration had some function other than the purely ornamental.
Following the conference there was a 2-day tour of the Hortobagy National Park, the largest dry alkaline steppe in Central Europe, abounding in rare plant associations, butterflies, birds and rare breeds of domestic animals. All were thrilled to see marsh harriers and red-footed falcons by the score, black storks and one of the rarest and certainly the largest of European birds, the great bustard, But, despite the wealth of natural and intellectual wonders to which the participants were treated, the abiding memory is of the friendliness of the people.
Dorian Pritchard