Adaptation is a term that emerged before evolutionary thinking. Creationists presupposed that individuals are perfectly adapted to their functions in nature. In this view, cats are perfectly adapted in all details for hunting mice. Born to kill. This line of reasoning of course overestimates the efficiency of individuals. Watching a single episode of Tom and Jerry may change this preconception.
Actual living beings do not play their roles perfectly
After Darwin and his theories, structures in living beings began to be perceived as having been previously shaped by natural selection. The form of a structure is polished by natural selection to adapt to a specific condition. This process is essential to evolution and is the guiding principle behind modern Biology. But historically it is difficult to determine what is the cause if you only see the product or a consequence. It is no surprise that “Who Moved My Cheese?” was such a best-seller.
This is not a spoiler
Natural selection became the common-place explanation for pretty much all structures seen in nature. Some scientists argue that natural selection by itself is responsible for all biodiversity. Employee of the month. However, other forces such as genetic drift and self-organization are able to promote evolution. It is difficult to allege that a structure has been molded exclusively by one of these forces.
A specific structure or a gain in complexity may have been originated with other forces. Small populations are more affected by random events, a case in which the force of genetic drift arises. It is easy to tell a history that fits to (adapts to?) a pattern, claiming something was “obviously natural selection shaped”, but other forces may have acted. What is the need for a word that indicates the result of a process if you can’t determinate the process?
The processes of the past are nebulous
Complexity is not necessarily positive. Bacteria are doing pretty well, thank you. Which is more complex: an ant or an elephant? A cat or a mouse? Novel structures may have been originated by other forces such as self-organization. In a scenario where a gene product controls some other gene’s expression, a random nucleotide deletion between them can eliminate a structure but promote a link making a…promoter. The advantage of this union is evident and complexity is merging, but with an origin that is independent from the classic natural selection process.
Increased cephalization is claimed as evidence for adaptation. But is not always better
The adaptation concept is more complicated when considered in a genome-wide scale. Genes interact with each other in a web-like pattern. Though individual genes may be an adaptation to their roles on the web, changes of relations alter their historical origin. The utilization of previously existing pieces is frequent. The term bricolage is often used: the creation of a new whole from a diverse range of preexisting pieces. Evolution is more of a Lego joke than an engineer’s plan. In this context of new uses for old parts, adaptation is an idea with restricted explanatory powers. Adaptation is a complex term that does not cover a complex world.
Are these pieces adapted to these functions?
Literature:
Lynch, M. 2007. The frailty of adaptive hypotheses for the origins of organismal complexity. Proc. Natl Acad. Sci. USA 104 (Suppl. 1), 8597-8604
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