Errors in the attribution to early Homo of African fossils

July 14 () –

A dental examination of 23 specimens attributed to early Homo from southern Africa from between 2.5 and 1.4 million years ago, indicates that only a maximum of seven of them represent Homo.

The others probably belong to Australopithecus or Paranthropus, according to analysis of fossil teeth by Southern Cross University geochemist Dr. Renaud Joannes-Boyau, published in Proceedings of the National Academy of Sciences.

These results have direct implications regarding our interpretations of hominin diversity, paleobiology, and ultimately our understanding of human evolution, according to the author.

Dr. Renaud Joannes-Boyau used specialized equipment, located at the Lismore campus of Southern Cross University, to detect lactation behavior based on geochemical analysis of tooth fossils.

The origins and biogeographical diversity of the earliest members of the genus Homo remain an important topic in paleoanthropology.

These results highlight the importance of correctly identifying the taxon to which a fossil belongs. Otherwise, any erroneous attribution to the genus Homo when in fact it represents Australopithecus or Paranthropus would completely bias the interpretations on paleobiological aspects, such as dietary behavior, ecological interactions, hominid paleodiversity, adaptations, and evolutionary relationships.

Proper identification of the earliest representatives of our genus Homo is crucial to understanding when, where, and how our genus arose on the African continent. However, there is no agreed definition of the genus Homo, leading to endless debates over the identification of early Homo.

In southern Africa, remains of early Homo have been described at various sites (Sterkfontein, Swartkrans, Kromdraai, Drimolen), in geological levels dated between 2.5 and 1.4 million years. Some of these specimens were also considered to be potential representatives of Australopithecus and/or Paranthropus, which complicates the taxonomic attribution of these fossils. These uncertainties prevent any reliable assessment of hominid paleodiversity, as well as the evolutionary relationships between Homo, Australopithecus, and Paranthropus, ultimately obscuring the conditions for the emergence of Homo.

MANY WERE WRONGLY ATTRIBUTED

Dr. Renaud Joannes-Boyau was part of an international team of researchers whose comprehensive review of early Pleistocene dental remains from southern Africa attributed to early Homo showed that many specimens were misattributed.

This study is based on geometric morphometric analyzes of the enamel-dentin junction, an internal structure of teeth that has been shown to be a reliable taxonomic proxy. to distinguish hominin species down to the subspecies level.

“It’s exciting when new techniques, such as microtomography, allow us to extract new and valuable information from fossils that have been in our collections for decades,” said Professor Matthew Skinner of the University of Kent.

As a result, among the 23 putative Homo specimens, only four of them (SK 27, SK 847, SKX 21204 and Sts 9) are statistically classified as Homo, and three others retain more primitive characteristics (StW 80-81, SE 1508 et StW 669) possibly also belong to the human genus.

All other specimens probably represent Australopithecus or Paranthropus.

One of the most emblematic remains of the paleoanthropology of southern Africa is the SK 15 mandible, which was attributed to Homo erectus for decades and which in this study was shown to be it is more likely to be related to Paranthropus.

“These quantitative analyzes of the shape of the enamel-dentin junction allowed us to objectively reassess the taxonomy of a number of putative Homo specimens, while also revealing greater hominid paleodiversity than previously accepted,” he said. it’s a statement Dr. Clément Zanolli, researcher at the University of Bordeaux.

Geochemical analyzes and elemental mapping were also performed on two putative early Homo specimens from southern Africa. Both were shown to most likely represent Australopithecus (SKX 268) and Paranthropus (KB 5223) using geometric morphometric analyses, and interestingly, the geochemical signature corroborates these results.

In particular, SKX 268 shows a weaning signal comparable to that reported in Australopithecus. and different from what we know in Homo.

“Early hominin nursing behaviour, which has been put forward as a versatile adaptive trait for surviving in challenging ecological niches, could be one of the key features that distinguishes Homo from other hominins,” said Dr. Renaud-Joannes- Boyau.

In his opinion, the confusion around the three genera is due to the fact that Homo, Australopithecus and Paranthropus lived at the same time in the same area of ​​southern Africa. “Australopithecus is probably the ancestor of both Homo and Paranthropus”, said.