World news – African Union – Newly discovered fossils document small-scale evolutionary changes in an extinct human species


males of the extinct human species Paranthropus robustus were thought to be much larger than females – just like the differences in size we see in modern day primates like gorillas, orangutans and baboons but a new fossil discovery in South Africa suggests instead That p Robustus evolved rapidly during a turbulent period of local climate change about 2 million years ago, resulting in anatomical changes previously attributed to the sex

An international research team including anthropologists at Washington University in St. Louis reported their discovery from the fossil-rich Dremolin Cave System northwest of Johannesburg in Nature Ecology & Evolution on November 9

“This is the kind of phenomenon that is difficult to document in the fossil record, especially as it relates to early human evolution,” said David Strait, & Sciences professor of biological anthropology at the University of Washington.

The well-preserved fossil described in the paper was discovered by student Samantha Goode, who co-led Drimolen Cave Field School.

Researchers already know that the emergence of P. robustus in southern Africa roughly coincided with the early disappearance of Australopithecus, a somewhat primitive human being, and the appearance of the first representatives of humankind in the region, the genus to which modern humans belong. This transformation occurred very quickly, perhaps within a few tens of thousands of years. p>

“The working hypothesis was that climate change caused stress in the Australopithecus populations which ultimately led to their demise, but the environmental conditions were more favorable to humans and the Paranthropus, who may have spread to the region from elsewhere,” “We now see that the environmental conditions may be It was stressful for Paranthropus too, and they needed to adapt to survive. ”

It is clear that the new Drimolen specimen identified, identified as DNH 155, is male but differs in important ways from the other P. Robustus was previously discovered at a site near Swartkrans – where most fossils of this species have been found.

It can be difficult to see the intra-species evolution in the fossil record, the changes may be subtle, and the fossil record incomplete

The fossil record usually reveals patterns on a larger scale, such as the emergence or extinction of species or groups of species in the fossil record so this Drimolen discovery provides a window rarely seen in early human evolution

The new specimen is larger than the well-studied organ of the species previously discovered in Drimolen – an individual known as DNH 7, presumably female – but significantly smaller than the putative male of Swartkrans

“It now appears as if the difference between the two sites cannot be explained simply as differences between males and females, but rather as population-level differences between sites,” said Jesse Martin, PhD student at La Trobe University, first co-author of the study. The latter is that Drimolen precedes Swartkrans by about 200,000 years, so we believe that P robustus evolved over time, with Drimolen representing an early population and Swartkrans representing an anatomically derived later group ‘

« One can use the fossil record to help reconstruct the evolutionary relationships between species, and this pattern can provide all kinds of ideas about the processes that have shaped the evolution of specific groups, » Martin said, « but in the case of P robustus, we can see separate samples of species taken from the same geographic region but slightly different times showing subtle anatomical differences, this corresponds to the change within the species’

“It is very important to be able to document the evolutionary change within the ancestry,” said Angeline Less of La Trobe University, another first author of the study. “It allows us to ask very focused questions about evolutionary processes. For example, we now know that tooth size is Changes over time in the species, which raises the question of why there are reasons to believe that environmental changes put these populations under dietary pressure, and this indicates future research that will allow us to test this possibility. « 

Drimolen Project Co-Director, Andy Herez of La Trobe University said: “Like all other creatures on Earth, our ancestors have adapted and evolved according to their landscapes and environment for the first time in South Africa, we have dating precision and morphological evidence that allows us to see such changes. In the ancient hominin lineage during a short period of time « 

Evidence of rapid but important climate change during this period in South Africa comes from a variety of sources. Fossils critically indicate that some mammals associated with forest or jungle environments have either become extinct or less prevalent – while others associated with more drought have emerged. More open environments locally for the first time

« p. Straight said the robustus is distinct in that it possesses a number of features in its skull, jaws and teeth indicating that it has been adapted to eat a diet consisting of foods that are very tough or very tough “We think these modifications allowed it to survive mechanically more difficult-to-eat foods as the environment changed to become cooler and drier, resulting in changes in local vegetation.

“But the samples from Drimolen show structural features that indicate that the masticatory muscles have been positioned in such a way that they are less able to bite and chew with the same force as P. Strong population of Swartcrans Over the course of 200,000 years, the dry climate will likely lead to selection Naturalists who prefer developing a more efficient and robust feeding device in the species « 

Leece said that, notably, P. Robustus appeared around the same time as our direct ancestor Homo erectus, as documented by the infant H, the erect skull that the team discovered at the same site in Dreamolin in 2015

“These are two very different types, H erect with relatively large brains and small teeth, and P Strong with relatively large teeth and small brains, they represent varying evolutionary experiences. «  » While we were the strain that finally triumphed, the fossil record indicates that P. Robustus was more common than H. Erect on the landscape two million years ago « 

On a larger scale, researchers believe this discovery is a cautionary tale of identifying the species in the fossil record

A large number of fossil human species have been discovered over the past quarter-century, and many of the nomenclature of these new species are based on a small number of fossils from one or a few sites in small geographic areas and narrow time scales

“We think ancient anthropology needs to be more important in explaining the variation in anatomy as evidence for the existence of multiple species,” Stright said, “Depending on the ages of the fossil specimens, the differences in anatomy may represent changes within lineages rather than evidence of the existence of Multiple types « 

Added Project Co-Director Stephanie Baker of the University of Johannesburg: “Drimolen is rapidly becoming a hotspot for early hominin discoveries, a testament to the team’s current dedication to extensive exploration and post-field analysis. For science, this is an example of what a careful and fascinating search for our distant ancestors can tell us.

Paranthropus robustus, Extinction, Human, Drimolen, Hominini, Species, Evolution, Skull

World News – AU – Fossil documents recently discovered small-scale evolutionary changes in an extinct human species


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