Think of human evolution, and you might picture Rudolph Zallinger’s knuckle-walking ape evolving into modern man in the artwork March of Progress.
Over the years, imitations of the original have further simplified the illustration, contributing to the idea that evolution was a linear process of constant improvement and increasing complexity. Yet, fossil evidence suggests the opposite.
Given recent discoveries and advances in the field, some paleoanthropologists say it is time to overhaul how we name and classify human ancestors. In a new paper published in the American Journal of Biological Anthropology, Ian Towle, a Research Fellow at Monash University’s Biomedicine Discovery Institute, makes the case for rethinking traditional taxonomy.
“Recent fossil discoveries and advances in evolutionary and genetic analysis make this an ideal time to reconsider whether our traditional taxonomy still accurately reflects human evolution,” Towle said in a statement.
Towle said the groups Australopithecus, Paranthropus and Homo “do not necessarily represent distinct evolutionary branches,” pointing out “differences in [behavior] and ecology once used to distinguish them have become increasingly difficult to maintain.”
Read More: 800,000 Years Ago, Ancient Humans Knew Which Stones Made the Best Tools
How Are Species Named And Classified?
Taxonomy is the practice of naming and organizing organisms into categories. Under the standard system of classification, there is a hierarchy, starting with the largest category (domain) and ending with the smallest (species or subspecies), with kingdom, phylum, class, order, and genus in between.
Explore All OptionsBut organisms can also be described in terms of clades (or monophyletic groups), which include a common ancestor and all of its descendants. It is this system — with its emphasis on genetics and evolutionary history — that is increasingly adopted by biologists over older models that classify species by shared traits.
However, this clade-based approach is applied less consistently to hominins and other human ancestors than to other animals, Towle said.
Our Family Tree Is Getting Bigger And More Complicated
In the second half of the nineteenth century, anthropologists discovered the very first non-sapiens fossil: the Neanderthal, according to the Smithsonian National Museum of Natural History. However, over the last century and a half, our family tree has grown to include relatives such as Homo erectus and Homo floresiensis (the Hobbit) — as well as other ancient hominins, such as Australopithecus afarensis.
But as new discoveries have been made, it has become increasingly difficult to distinguish genera such as Homo, Australopithecus and Paranthropus by key traits, Towle said. The addition of species such as Homo habilis and Homo naledi, for instance, has undermined the principle that members of the genus Homo have larger brain sizes.
Meanwhile, species of Paranthropus may have been more sophisticated than previously thought, using tools and adapting to different niches. Towle also points to Australopithecus species that appear more closely related to Homo than to other species within their genus.
“The more we learn about our ancestors and close fossil relatives, the more we realize how complex and non-linear our family tree is,” said Towle.
Rethinking How Human Ancestors Are Classified
While Towle's primary objective is to show the current system of classification isn’t working, he does propose a solution — expanding the genus Homo to include Australopithecus and Paranthropus.
Though he acknowledges this could result in the loss of some taxonomic information, the change “will allow us to account for differences without regularly reclassifying particular groups,” said Towle.
Read More: Humans Arose From Two Ancestral Populations That United 300,000 Years Ago
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in the American Journal of Biological Anthropology: Clades, Grades, and the Genus Problem: A Case for Revising Hominin Taxonomy
- This article references information from the Smithsonian National Museum of Natural History: Homo neanderthalensis
