7.2 Directional Selection in Nature

Marcos Antonio de Lima Filho, PhD.

In this section, I revisit the data from two recent studies that have tracked the directional selection process in two distinct species in nature. When comparing these findings with the evolution of technologies, the pace, magnitude, and visibility of technological evolution far exceed that of biological evolution. In fact, in the biological context, a 2.1% reduction in the mean length of a salmon population is considered a significant indicator of directional selection. In contrast, the evolution of technologies often exhibits double-digit percentage increases. Despite such drastic results, the concept of directional selection remains under-appreciated in the field of technology and innovation.

The evolution of finches and peppered moths are two classic textbook examples of directional selection. However, there are only a few recent studies on this topic. Evidence of this quality is a rarity in the scientific literature because evolutionary trends often take years to manifest. Studies of this sort require a long-term commitment to data collection and monitoring of wild species in their native habitat. The following graphs review data from two modern studies, covering a time frame of 30 and 60 years. Given the decades-long effort, both studies were published in prestigious journals, such as Nature (Coltman et al., 2003) and Nature Communications (Oke et al., 2020).

Figures 7.2.1 and 7.2.2 compare the directional selection of Pacific salmon and bighorn sheep with the directional innovation seen in passenger aircraft and smartphone evolution. Oke et al. (2020) report widespread declines in Pacific salmon size based on 60 years of measurements from 12.5 million fish across Alaska. The authors associate such declines with climate change and competition at sea. As for bighorn sheep rams, Coltman and colleagues (2003) attribute declines in mean body weight and horn length to selective hunting.

In summary, smaller individuals of Pacific salmon and bighorn sheep have had greater fitness than larger individuals. In these species, being smaller results in lower predation risks, which ultimately leads to higher survival rates and greater reproductive success. This has led to a gradual decrease in their average body size and weight.

Likewise, smartphones have become thinner, and the distance between passenger seats has shrunk. Directional selection has led to the reduction of smartphone thickness because most users tend to regard thin devices as modern, while chunkier devices are perceived as outdated. This trend has also affected other categories of consumer electronics, including laptops, televisions, and tablets. As in aviation, passengers appreciate the comfort of more legroom when it comes to passenger seats. However, because extra legroom equals fewer seats — and consequently less potential income — this feature negatively impacts flight economics.

Directional selection can, of course, also produce an evolutionary increase in body size if larger individuals have higher fitness (Ridley, 2004). Such has been the case with smartphone weight and aircraft engine diameter. Heavier smartphones are associated with powerful batteries and larger displays, both of which are valuable product dimensions. Thus, positive directional selection has led to an increase in smartphones’ display size (Figure 5.2.1), CPU speed (Figure 5.2.2), battery capacity (Figure 5.2.5), memory and storage (Figure 5.2.6), and camera sensors (Figure 5.2.7). The evolutionary increase in engine diameter results from another trend: the increase in turbofan bypass ratios (Figure 4.2.2), which also affects fuel efficiency (Figure 4.2.1).

As previously stated, these studies with animal models are rare, costly, and time-consuming. Consequently, scientists have been limited to just a few genetic traits, such as weight and size. As for the evolution of technologies, the sheer volume of data enables researchers and practitioners to analyse several product parameters. This will certainly lead to the discovery of numerous evolutionary patterns in the data.