Controlled climate change where early humans lived

Asian scientist (May 10, 2022) – Astronomical climate change has influenced where various archaic humans – a large group comprising Homo sapiens, Denisovans, and Homo neanderthalensis that roamed the earth about 2.3 million years ago – lived and when they moved to new places. The link was made clear in a recent Nature study by an international research team, led by scientists in South Korea.

Astronomical climate change refers to a phenomenon where the Earth’s climate is affected by astronomical factors. For example, gravitational disturbances from other planets, notably Jupiter and Saturn, affect the Earth’s axis of rotation. This is one of the reasons why the Earth has experienced a succession of glacial and interglacial epochs in the past.

The researchers recorded extensive archaeological data on human habitation in a computer-simulated model of Earth’s climate history spanning the past two million years. They wanted to determine what environmental conditions archaic humans probably lived in. While the impact of astronomical climate change on human evolution and migration has long been suspected, this study establishes it, and is the first to do so.

“Even though different groups of archaic humans preferred different climatic environments, their habitats all responded to climatic changes caused by astronomical changes in the wobble, tilt, and orbital eccentricity of the Earth’s axis with scales time ranging from 21 to 400,000 years ago,” said Axel Timmermann, lead author of the study and director of the IBS Center for Climate Physics (ICCP) at Pusan ​​National University, South Korea. “Changes in Earth’s orbit and axes influence the seasonality of sunshine at a given latitude. These parameters oscillate with periods of 20,000, 40,000, 100,000 and 400,000 years. For example, 10,000 years ago, the Northern Hemisphere summer was closer to the Sun than it is today.

In an earlier paper linking climate change and human migration, Timmermann found that orbital-scale global climate fluctuations played a crucial role in the migration and population distribution of early humans.

In the recent study, the scientists first used their computer simulation of paleoclimate conditions to see what the climate was like at various times and places where early humans lived, according to archaeological records. Through this survey, they were able to find the preferred environmental conditions of different groups of hominids. After that, the team tracked down all the places and times these conditions occurred in their simulation. This helped them create maps of the potential habitats of various hominid species at different times in Earth’s history.

To test the robustness of the link between climate and human habitats, the scientists repeated their analysis by randomizing the archaeological record and the age of the fossils. The idea behind randomization was that if climatic variables had no impact on the choice of where humans lived, then both methods would yield the same results. This was not the case however. The researchers found significant differences in habitation patterns for the three most recent hominid groups (Homo sapiens, Homo neanderthalensisand Homo heidelbergensis) when using the random and realistic archaeological record.

Scientists were also able to demonstrate that astronomy-induced climate change was a key factor in driving not only the distribution of hominin species, but also their diversification or mixing with each other. “This result implies that at least over the past 500,000 years, the actual sequence of past climate change, including glacial cycles, has played a central role in determining where different hominin groups lived and where their remains were. found,” Timmerman said. Following this study, the researchers hope to study the impact of past climate change on human genetic diversity.

A key benefit for the researchers doing this study was access to one of South Korea’s fastest supercomputers, called Aleph. Located at the Daejeon Institute of Basic Sciences, Aleph has operated continuously for more than six months to complete the longest comprehensive climate model simulation to date. Over 500 terabytes of data were generated during the study. “This study is based on what are called ‘transient simulations’ – the climate reconstruction is therefore not done in pieces for these periods, but as one long continuous simulation,” said Earth systems scientist Raghu Murtugudde at the University of Maryland. Asian scientist. “It’s computationally expensive, but it’s the best way to ensure consistency throughout the study period.” Murtugudde, who is Indian, was not part of the study.

He added: “Combining the main findings of the study with the climate impact on civilizations during the Holocene, it is clear that humans are quite vulnerable to climate change even when disturbances are relatively low. But now we are making massive disruptions. The biggest follow-up would be to see how the evolution of bipedalism and cranial growth itself has been affected by climate transitions and where we are heading now with this warming.

Source: Pusan ​​National University, South Korea; Photo: Shutterstock

The article can be viewed at: Timmermann et al. (2022) Effects of climate on archaic human habitats and species successions

Teresa H. Sadler