Myths and Misconceptions

Myths and Misconceptions - "The Linearity of Evolution"

A common misconception of evolution is that it is a linear process, meaning evolution is progressive and insinuating that there is an "end goal" (or predetermined destiny) surrounding evolution. However, there is no true goal or even intention of evolution, it is better to think of this process as a means of trials and errors, causes and effects, or experimentations and adaptations. 

My interest in this misconception of evolution is its direct usage in the history of entomology. Theodor Eimer, a German zoologist, published a paper in the Oxford Press in 1897 disapproving of the Darwin's theory (which theorizes that variation occurs randomly among populations/species and that individual traits could be inherited by its offspring) in favor of orthogenesis. The term "orthogenesis" states that variations in evolution follow a linear direction and are not randomized.

In this paper, Eimer argues for the relevance of orthogenesis using butterflies, specifically Papilio telesilaus (also known as "Eurytides telesilaus"). I have included an image sourced from Butterflies of the World (page 23, figure 14) of the species below. 

Eimer argued Darwin's theory was incapable of describing the origination of the species, as he stated they originated through (1) genepistasis: outlined as the cessation of development in the history of a species or race, (2) halmatogenesis: the cessation of development at different stages, and (3) kyesamechania or hindrance to impregnation.

However, it has now been proven that this theory is false. This species, along with all butterflies, evolved due to a group of moths becoming active during day (abandoning their nocturnal nature) and consuming nectar-rich flowers that had co-evolved with bees (you can find more about their super cool evolution on Florida Museum of Natural History). Further species began to randomly evolve based on factors such as environmentally-favored specialization adaptation, environmental species competition, and adaptive radiation. Some species for better and some for worse and some adaptations biologists are still trying to understand today (see here). The evolutionary history of butterflies is not of one with a definitive goal of improvement, it is based on these findings that is an ever-evolving process. 

Now let's step away from viewing evolution through the lens of butterflies and turn to look at why orthogenesis in humans is also incorrect. Examine the family tree below of a fake example of a person named Tiffany Jamerfly below. If you were to draw a family tree with only Tiffany's patrilineal ancestors, the tree is in a straight line (please note only her father,  James, and grandfather, Bob, were included due to lack of space).

However, this portrayal of Tiffany's lineage, while appearing to be linear and in a straight line, is incorrect because it does not adequately depict her matrilineal family tree and the abundance of her cousins, uncles, aunts, etc.. This family tree is only an over-simplified, up-close depiction of her lineage. Stating species (both non-human and human) evolution is  a straight line is similar to this example, it leaves out the many complexities of reproduction evolved in species evolution and falsely assumes there is a specific end goal to evolution.

Thank you for reading!