Technologists are always on the lookout for quantifiable metrics. Measurable inputs to a model are their lifeblood, and like a social scientist, a technologist needs to identify concrete measures, or "proxies," for assessing progress. This need for quantifiable proxies produces a bias toward measuring things that are easy to quantify. But simple metrics can take us further away from the important goals we really care about, which may require complicated metrics or be extremely difficult, or perhaps impossible, to reduce to any measure. And when we have imperfect or bad proxies, we can easily fall under the illusion that we are solving for a good end without actually making genuine progress toward a worthy solution. The problem of proxies results in technologists frequently substituting what is measurable for what is meaningful. As the saying goes, "Not everything that counts can be counted, and not everything that can be counted counts."

Development of the human body from a single cell provides many examples of the structural richness that is possible when the repeated production of random variation is combined with nonrandom selection. All phases of body development from embryo to adult exhibit random activities at the cellular level, and body formation depends on the new possibilities generated by these activities coupled with selection of those outcomes that satisfy previously built‐in criteria. Always new structure is based on old structure, and at every stage selection favors some cells and eliminates others. The survivors serve to produce new cells that undergo further rounds of selection. Except in the immune system, cells and extensions of cells are not genetically selected during development, but rather, are positionally selected. Those in the right place that make the right connections are stimulated, and those that don't are eliminated. This process is much like sculpting. A natural consequence of the strategy is great variability from individual to individual at the cell and molecular levels, even though large‐scale structures are quite similar.

It is a common assumption that most vagrant birds are ultimately doomed, aside from the rare cases where individuals are able to reorientate and return to their normal ranges. In turn, it is also commonly assumed that vagrancy itself is a relatively unimportant biological phenomenon. This is undoubtedly true for the majority of cases, as the most likely outcome of any given vagrancy event is that the individual will fail to find enough resources, and/or be exposed to inhospitable environmental conditions, and perish. However, there are many lines of evidence to suggest that vagrancy can, on rare occasions, dramatically alter the fate of populations, species or even whole ecosystems. Despite being infrequent, these events can be extremely important when viewed at the timescales over which ecological and evolutionary processes unfold. The most profound consequences of vagrancy relate to the establishment of new breeding sites, new migration routes and wintering locations. Each of these can occur through different mechanisms, and at different frequencies, and they each have their own unique importance.