This article, written by Nathaniel Dominy and Peter Lucas, analyses the relationship between chromatic vision and food source selection in various primate species. In particular, Dominy and Lucas sought to determine the evolutionary force that led to trichromatic vision in howler monkeys and a number of cattarhine primates. Most primate species possess dichromatic vision, which means that they have retinal cones designed to discriminate between yellow and blue light. However, these trichromatic primates also have cones that distinguish between red and green light. For some time, primatologists believed that this additional type of retinal cone evolved in order to help primates separate ripe fruits from unripe fruits. In this journal, Dominy and Lucas propose that trichromatic vision actually developed to help primates find young reddish leaves, which are more nutritious and less tough than mature leaves. In order to support their hypothesis, Dominy and Lucas observed a number of primates located in the Kibale National Park in Uganda. Dominy’s and Lucas’ team logged an impressive 1,170 hours of observations and collected about 700 different types of foliage that had been partially consumed by the primates. Next, the team measured the specific wavelengths of the half-eaten food using a spectrometer, along with the nutritional value and relative toughness of the foliage. The food samples that were collected contained all sorts of leaves and fruits with various levels of ripeness. Overall, Dominy’s and Lucas’ hypothesis that trichromatic vision was more closely related to leaf selection than fruit selection was supported. They found no significant difference in ripeness between the fruits consumed by trichromatic primates and dichromatic primates. However, their data demonstrated that the trichromatic primates were much more efficient in locating the younger red leaves, which are more nutritious.
This scientific article contained several characteristics that added to its credibility and readability. First, Dominy and Lucas compiled an astounding amount of data. They spent almost a year in the field collecting the half-eaten food of primates. In total, they examined 624 pieces of food that were taken from 118 different species of plants. They also increased the legitimacy of their data by switching target individuals every ten minutes of feeding. I was also impressed by Dominy’s and Lucas’ ability to offer possible explanations for their hypothesis, without trying to force its validity. For example, they suggested that the dichromatic primates were just as able to locate ripe fruits as the trichromatic primates because they relied more heavily on olfaction and touch. Another reason I approve of Dominy’s and Lucas’ article is the unique nature of its subject. I have never considered the different types of vision primates possess, let alone their functional differences. Unfortunately, this article did contain one slight weakness. As far as I could tell, the authors never mentioned the specific primate species that they studied in the Kibale National Park. They gave examples of dichromatic and trichromatic primates but failed to identify the specific species that they observed. Overall, I support this article because the uniqueness of the subject matter and substantial amount of evidence provided far outweigh this small weakness.