When the climate became drier a few million years ago in the east of Africa, the ancestors of mankind left the crown roof of the rainforest. They straightened up on their hind legs and hiked through the huge savannas, which still shape this part of the continent today. Around three million years ago, it got even drier. This time, some bipeds mastered the problem of the scarce food, because their cognition and their dexterities had developed - they used scree stones as tools for the first time. And when the anatomically modern people finally emerged from these first craftsmen, climate changes also played a crucial role. So far, however, it has hardly been assessed how strong this influence was. Axel Timmermann from the South Korean University of Busan and his team stipulate in the specialist magazine "Nature" from the regions relevant to human history are simply not sufficient to reconstruct the former climate.
For this reason, the researchers led by Timmermann had a supercomputer calculate extensive data sets in order to determine the climate and vegetation conditions of the past two million years. In addition, the working group linked various current climate models with its results: From important factors such as the concentration of the greenhouse gas carbon dioxide and the inclination of the Earth's axis, which can each cause climate fluctuations up to an ice age, it calculated important parameters such as precipitation, temperature and the mass of plants on a certain area. Because the representatives of the genus Homo once fed on greenery – either directly or via the detour of grazing animals that fell into the hands of Stone Age people.
3245 data records were added to the calculation - via the locations of stone tools, human fossils and their age. Timmermann's group also included the human form for which the finds are expected. They differentiated between Homo Habilis, Homo Ergaster, Homo Erectus, Homo Heidelbergensis as well as the Neanderthal and the anatomically modern man. The researchers then determined the habitats in which these early people were at home and where they found suitable regions in Africa, Europe and Asia. As a result, the University of Busan's supercomputer listed how the habitats of the various man -forms changed over time and where the archaeological places are in the modeled cards.
Maps showing where human forms found favorable conditions
"These are excellent, very well-designed climate models, which also provide a look at the habitats of various early human lineages every 1000 years," explains Mike Petraglia, who was appointed director of the Australian Research Center for Human Evolution at Griffith University in Brisbane in spring 2022 by the Max Planck Institute for the Science of Human History in Jena. The paleoanthropologist was not involved in the study presented in "Nature", but summarized the methods and results in the same journal. "These habitat maps also show which regions might have been suitable for the different human lineages, even if no traces of them have been found there yet," explains Petraglia.
Ottmar Kullmer agrees with Petraglia's assessment. "The simulations are very exciting and show very nice how the habitats of the different early people have shifted according to the climate changes triggered by the earth's axis," says the Paleoanthropologist from the Senckenberg Research Institute and Nature Museum in Frankfurt am Main. "However, it is a model that can deviate from reality," Kullmer judges the new study in which he was not involved either.
The background to his admonishing words are the huge gaps in the findings of the incarnation. Thus, fossils and stone tools remain well preserved in some areas and can be discovered relatively easily. In other regions, weather and soil conditions cause the remains to deteriorate rapidly. The chances for researchers to discover something else are minimal. "Although the few finds provide us with important pieces of the puzzle for a mosaic of habitats, there are huge gaps in them," explains Kullmer.
Why Stone Age Reality and Computer Model May Differ
Hardly by Homo Habilis and Homo ergaster hardly any sites in the African fracture of Graben are known. Correspondingly few, narrowly limited regions depict the maps of the computer models for these human forms. "Now nobody can rule out that these groups have also lived in other areas in which no traces of them appear so far," says Kullmer. In addition, researchers can usually only document stone devices, rarely bone material that would reveal more precisely which early people lived in a place of sites and which tools they used. For the Senckenberg researcher, however, this is not only problematic for computer modeling, but in general for paleoanthropology.
"The study provides us with very interesting suggestions that should not be over-interpreted, but should certainly be examined further," says Kullmer. Mike Petraglia argues in a similar way. The computer models show that Homo heidelbergensis lived for a long time in Africa, Europe and the western regions of Asia until the species slowly disappeared a few hundred thousand years ago. At the same time, the climate changed – and Neanderthals appeared in Europe and anatomically modern humans appeared in Africa. Axel Timmermann and his team conclude that the new climate had an influence on the development of Homo heidelbergensis towards Neanderthals and modern humans. Where exactly, they also conclude from their calculations. They pinpointed the places where living conditions have changed and found that Homo sapiens probably originated in southern Africa rather than eastern continent.
However, this approach could easily lead to a fallacy. "There are some indications and many considerations according to which different early human groups met again and again and mixed up," says Petraglia. "Until, finally, modern man, Homo sapiens, emerged from these mixtures." This scenario is much more convincingly compatible with the theory that the cradle of mankind was in several areas of Africa, not just in a relatively small region in the south of the continent. The "Nature" study by Timmermann and his team would nevertheless offer a new approach to the exploration of human history and provide the anthropologists' guild with many suggestions for further research. Mike Petraglia and Ottmar Kullmer also agree on this.
