To the layman it may sometimes seem that every time paleontologists unearth a fossil hominin, it is described as a new species and given a brand-new name. This is particularly true of the Middle Pleistocene (now renamed Chibanian), a time period that lasted from 774,000 to 129,000 years ago and that saw the advent of our own species (Homo sapiens) in Africa, as well as our closest extinct relatives, and the Neanderthals (Homo neanderthalensis) in Europe.
The details of human evolution during this time period are not well understood and the number of different putative species has led paleoanthropologists refer to this confusion as “the muddle in the middle.” This situation is further confounded by the fact that fossil hominin finds often consist of a single tooth, or a piece of jaw bone, fragments that are not easy to classify as one species or another.
A team of international researchers, led by University ofWinnipeg palaeoanthropologist Dr. Mirjana Roksandic, has now reassessed the existing Middle Pleistocene fossils from Africa and Eurasia. The experts suggest that some of the fossils should be reclassified as a different species of human ancestor with the name Homo bodoensis, to help clarify the situation.
In the past, these fossils have been classified as H. heidelbergensis or as its African counterpart, H. rhodesiensis, both of which carried multiple, often contradictory definitions. The first specimen of H. heidelbergensis consists of a single lower jawbone, found in 1907 near Heidelberg in Germany. Since no cranium was present, and since most other Middle Pleistocene specimens have their jawbones missing, it has always been challenging to identify new specimens as heidelbergensis.
“Talking about human evolution during this time period became impossible due to the lack of proper terminology that acknowledges human geographic variation,” explained Dr. Roksandic, lead author on the study that proposes renaming some of the species in order to reduce the confusion.
Recently, DNA evidence has shown that some European fossils which were classified as H. heidelbergensis, were actually early Neanderthals, making the name redundant. For the same reason, the name needs to be abandoned when describing human ancestor fossils from east Asia according to co-author, Xiu-Jie Wu, from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China.
The name “bodoensis” derives from a skull found in Bodo D’ar in Ethiopia, and the new species is understood to be a direct human ancestor. The authors of the study propose that, under the new system of classification, H. bodoensis will describe most Middle Pleistocene humans from Africa and some from Southeast Europe, while many from the latter continent will be reclassified as Neanderthals.
“Terms need to be clear in science, to facilitate communication. They should not be treated as absolute when they contradict the fossil record,” said study first author Predrag Radović of the University of Belgrade.
According to study co-author Christopher Bae of UH Manoa, the introduction of H. bodoensis is aimed at “cutting the Gordian knot and allowing us to communicate clearly about this important period in human evolution.”
Dr. Roksandic agrees: “Naming a new species is a big deal, as the International Commission on Zoological Nomenclature allows name changes only under very strictly defined rules. We are confident that this one will stick around for a long time; a new taxon name will live only if other researchers use it.”
The study is published in the journal Evolutionary Anthropology Issues News and Reviews.
Image Credit: Artist rendering of Homo bodoensis by Ettore Mazza
By Alison Bosman, Earth.com Staff Writer