Under changing environmental conditions, a species may begin to branch genetically and morphologically in numerous directions, transforming from a single, uniform species into a group of heterogeneous subspecies, each with one or more special characteristics that may give it a survival advantage in the new environment. Time determines which subspecies is truly best adapted to the new environment, and the rest often die off.
A process of precisely this sort is believed to have occurred in human evolution--a decisive break when a species of ape decided to move from a familiar tree environment to a new environment on the African Savannah. A whole collection of early hominids emerged from these first land apes, each with its own set of special survival characteristics. But only those with the biggest brains survived to become human.
It has often been noted that the evolutionary process of branching and pruning occurs in the domain of human inventions, as well. When a new technology is first born, there are all kinds of different designs as inventors let their imaginations run free in search of the most effective and least wasteful design possible. The bicycle is good example.
In the early days of the bicycle, in the mid-nineteenth century, bicycle designs were all over the place. Some had no pedals, others had front-wheel pedals, and still others had pedals attached to cranks and a drivetrain. Some had two small wheels, while others had two big wheels and still others had either a big front wheel with a small rear wheel or vice versa. Frame styles and materials were also widely divergent.
Over time, the simple pruning mechanism of racing determined which designs worked best, and the rest were gradually eliminated. So today's bikes, despite their many differences on the level of details, are all pretty much the same as compared to the vast array of disparate designs that existed a century and a half ago.
Evolving Your Bike Fitness
The phenomenon of branching and pruning even applies to the development of fitness on the bike. A fascinating new study from the University of Queensland, Australia, has provided evidence of branching and pruning in the building of cycling fitness.
Researchers used electromyographic (EMG) sensors to compare patterns of leg-muscle recruitment, coactivation (or the contraction of muscles other than those doing the main work of pedaling) and cadence in novice and highly trained cyclists.
The overarching difference they observed was a much higher degree of variation in these variables among novices than among well-trained cyclists, indicating that the novices' bodies were searching for effective and efficient ways to pedal (branching), whereas the experienced riders had found more or less optimal pedaling styles (pruning).
The specific thing that the trained cyclists had trimmed from their pedaling was waste. EMG data revealed that trained cyclists were able to produce shorter, tidier bursts of muscle activity at various moments of the pedal stroke and minimize unnecessary muscle activation between these primary bursts.
The amount and variability of coactivation was also much smaller throughout the pedal stroke among the trained cyclists, meaning they had developed a greater ability to relax muscles not needed to turn the pedals, thus conserving energy.