During an immune response the affinity of antibodies that react with the antigen that triggered the response increases with time, a phenomenon known as affinity maturation. The molecular basis of affinity maturation has been partially elucidated. It involves the somatic mutation of immunoglobin...

We introduce an analytical model that predicts the dynamics of a simple evolutionary algorithm in terms of the flow in the space of fitness distributions. In the limit of infinite populations the equations of motion are derived in closed form. We show how finite populations induce periods of...

We analytically study the dynamics of evolving populations that exhibit metastability on the level of phenotype or fitness. In constant selective environments, such metastable behavior is caused by two qualitatively different mechanisms. One the one hand, populations may become pinned at a local...

We compare the frequency distribution of gene family sizes in the complete genomes of five Bacteria ({\it Escherichia coli, Haemophilus influenzae, Mycoplasma genitalium, Mycoplasma pneumoniae,} and {\it Synechocystis sp. PCC6803}), one Archaeon ({\it Methanococcus janaschii}), one eukaryote...

We analyze the population dynamics of a broad class of fitness functions that exhibit epochal evolution|a dynamical behavior, commonly observed in both natural and artificial evolutionary processes, in which long periods of stasis in an evolving population are punctuated by sudden bursts of...

Technological change at the firm level has commonly been modeled as random sampling from a fixed distribution o f possibilities. Such models, however, typically ignore empirically important aspects of the firm's search process, notably the observation that the present state of the firm guides...

Epochal dynamics, in which long periods of stasis in population fitness are punctuated by sudden innovations, is a common behavior in both natural and artificial evolutionary processes. We use a recent quantitative mathematical analysis of epochal evolution to estimate, as a function of...