4 What Does It Mean to be Human?
Since Darwin published his opus, On the Origin of Species by Natural Selection, in 1859, many have labored under a fundamental misconception—that humans are descended from contempoary gorillas, chimpanzees, or monkeys that populate the earth along with us. Darwin never claimed this. Neither have biologists since then. Are we a primate? Yes. Are we descended from gorillas, chimpanzees, or monkeys? No. We share a common ancestor with our fellow primates but that does not mean we “descend” from them. Other living primates have a different evolutionary path than humans.
In this chapter, you will explore how humans are related to other primates and what distinguishes us from our primate cousins. But first, it is important to understand the relationships between organisms, which is highlighted by the Linnean taxonomic system.
Constructing Relationships
Taxonomy is the field of biological classification that uses nested sets of categories of increasing specificity to illustrate relationships between organisms (Park 2014, 99). Prior to the availability of DNA data, comparative anatomy was used to establish relationships between organisms. Today, when suitable samples are available, DNA sequencing is used to establish relationships. Paleontologists and paleoanthropologists continue to use comparative anatomy to construct relationships among fossil species. A notable exception is with the fossil species Homo neanderthalensis and archaic Homo sapiens. In some instances, researchers were able to collect DNA samples to sequence.
But what does DNA sequencing tell us? Because DNA mutates at a known rate, scientists can determine how alike the sequences are. The more alike, the more recent the divergence from a common ancestor. This data can then be used to create evolutionary trees (Lewis 2016). Establishing these relationships demonstrates a unity to the natural world—an interconnectedness that is key to understanding how earth’s ecosystems work.
From philosophers such as Aristotle (384-322 BCE) to naturalists such as John Ray (1627-1705), people attempted to classify life, providing some order to the vast amount of knowledge that was being accumulated. The taxonomic system created by Carolus Linnaeus (1707-1778) in 1758 is the basis of the system still used by scientists today.
Linnaeus created a hierarchical system to organize living organisms by likeness, starting with the general rank of kingdom to the specific rank of species. This system is a phenetic system based on the similarity of existing features and adaptations. Additionally, he created a naming system called binomial nomenclature, or binomial naming. At the time Linnaeus created his system, botanists named ‘new’ organisms whatever they liked, making everything quite confusing. Remember, this is a time of European expansion and non-European species were being encountered relatively quickly. Linnaeus proposed using a genus and species name in Latin for each type of