TWH – Climate change has already happened. When he did, he threatened access to resources. This may have spurred human evolution. Examining past climate change can tell us about our likely future.
Two recent studies deal with the impact of past climate change. In one study, the authors examine the effects of sea level rise on part of the Spanish Mediterranean coast. The other study explains how Pleistocene climate change drove human evolution.
A brief reminder of prehistory
The Paleolithic age had a much more turbulent climate. Geologists call this period the Pleistocene epoch. It began 2.58 million years before present (BP). It lasted around 12,000 BP, around 10,000 BCE
During this period, the glaciers advanced and retreated more than once. It is often called the “Ice Age”. An unknown number of hominin species, including Homo sapiens (modern humans), evolved and lived during this time. Hominins refer to species of bipedal primate mammals that walk upright. Hominins include modern humans and Neanderthals, among others. In the Paleolithic, all species of hominids could only hunt and harvest the resources they needed.
The Mesolithic is a period of transition between the Paleolithic and the Neolithic. Global natural events defined the beginning and end of the Pleistocene. In contrast, technological and cultural changes in humans define the beginning and end of the Neolithic. The beginning of the Neolithic varied according to regions and cultures. There is no global and universal date for the beginning of the Neolithic.
Around 12,000 years BP, the climate began to stabilize. In the Fertile Crescent (Iraq, southern Turkey and Syria), people began to domesticate crops and animals. In other places, humans have domesticated different crops and animals. Anthropologists have defined this group of inventions as the “Neolithic tool kit”. It did so in the context of a relatively stable climate. All of human history has taken place in this period of this relatively stable climate. Geologists call this epoch the Holocene epoch.
In prehistory, evidence is sparse and suffers from survival and availability bias. Scientists have studied Europe and the Middle East far more than the rest of the world. All dates are rough approximations.
Climate change in Mesolithic-Neolithic Spain
In an article in the “Journal of Maps”, its authors reported on sea level rise along part of the Spanish Mediterranean coast.
The authors of this study chose to focus on a narrow part of the central Mediterranean coast of Spain. In prehistoric times, two human communities existed in this region. During the Mesolithic (9830 to 8060 BP along the Spanish coast), humans lived in “El Collado”. At the beginning of the Neolithic (7550-7320 BP along the Spanish coasts), humans lived in “El Barranquet”. This coastal area also had a lagoon.
Earlier researchers have found evidence for the location of the shoreline and lagoon at 9000, 8800, 8500, 8100, and 7300 BP For most of this time sea level rose. This sea level rise flooded the coastal areas and the lagoon. By the end of the period under review, the sea had displaced 4 km (2.5 miles) of land. Data from these five dates allowed the authors to plot coastal changes over time
Humans need resources for food, water, clothing, shelter, adornment, and other necessities. Each colony would need a resource area nearby to hunt and gather these resources. The people of El Collado would have hunted and gathered these resources in nearby areas. No evidence exists for pets. This would mean that they would have traveled on foot to hunt and gather.
Based on case studies and ethnographic literature, archaeologists can estimate the size of a settlement’s resource area. The resource area of El Collado should be less than two hours away. If this area were to shrink, the loss of access to resources would threaten the colony.
Archaeologists have been able to take historical data for the location of the shoreline over time. Their software created a visual display showing how sea level rise is changing the region. Archeology Network News posted a link to this video display.
What did the people of El Collado eat?
After eating an animal, people threw its bones into a dump, a “prehistoric dump”. The remains of a dump provide archaeologists with a way to examine what people ate. In the nearby lowlands, the people of El Collado hunted red deer and aurochs. The latter, now extinct, were the wild ancestors of domestic cattle. In the nearby hills, they hunted ibex and wild boar. From the sea and the lagoon, they ate Mediterranean fish, molluscs and cockles.
As the sea level rose, the water covered more of the lowlands. Salt water also began to flood the lagoon. Habitat for El Collado resources has declined. Animal remains show a decrease in lagoon foods and an increase in terrestrial foods. This would suggest that sea level rise had more impact on the lagoon than on the lowlands.
In the Neolithic, the sea had engulfed the lagoon. A major food resource for the people of El Collado had disappeared. Its inhabitants had abandoned El Collado.
Then, people with the Neolithic “tool kit” settled in El Barranquet. The inhabitants of El Barranquet practiced agriculture and the domestication of animals very early on.
El Barranquet had much less land available. The shore had moved far inland. The lagoon had disappeared. Studies of Neolithic settlement patterns provide a means of calculating a minimum Neolithic resource area.
Their use of the Neolithic toolkit enabled them to live in a resource area an hour’s walk from their settlement. Their resource area would have been half the size of El Collado. The inhabitants of El Barranquet had adapted to a modified climate.
Climate change and speciation
Scientists who study human evolution believe that climate change has played a key role in the evolution of species among the various hominid species.
The newspaper Nature recently published an article about climate change in the past. Its authors used computer modeling to analyze climate change over the past 2 million years. They also analyzed the availability of resources.
Then they compared this data with data on five hominin species. These five species include homo habilis, homo erectus, homo heidelbergensis, homo neanderthalensis, and homo sapiens.
The Pleistocene epoch
The Pleistocene epoch generally had a cold and dry climate. It was the time of the glaciations. Periodic warming separated each of the ice ages.
These shifts between increasing cold and increasing heat have altered environments around the world. The changes would have caused a process of Darwinian natural selection.
A random genetic mutation would have produced a new trait and one that might be better suited to the new conditions. If so, people with this mutation would be more likely to survive and reproduce than those who don’t.
The mutation would then become more common in the gene pool. This process could eventually lead to the evolution of new species or to speciation.
The authors of this study plotted the locations of the remains of each species. Then they linked these locations to known climatic factors in these regions. This allowed the researchers to estimate the climatic conditions to which each species had adapted. It also allowed them to predict potential contact areas for interbreeding between hominid species.
How different species have adapted to different climates
Homo habilis (2.4–1.5 million years BP) had a restricted range in eastern and southern Africa. They had adapted to a limited and specific climate and habitat. Changes to either would threaten this species.
In contrast, Homo erectus (1.9–0.1 million years BP) had a much wider range of habitats in Africa and Eurasia. Anthropological evidence indicates that Homo erectus was a “flexible generalist”. Homo erectus were wanderers who had adapted to multiple environments.
Homo heidelbergensis (600,000 to 200,000 BP) migrated out of Africa into Eurasia. The authors of the study say climate variability has driven them out of Africa. In these wanderings, they would have encountered many different climates. These new climates would have required adaptations. Their northern branch left Africa and evolved into Neanderthals. Their southern branch evolved into homo sapiens (modern humans).
Homo sapiens (315,000 BP so far) was more adapted to drier conditions than any of the other four species. This aptitude for dry conditions may have helped many waves of our species across the Sinai to reach Eurasia.
Humans have evolved to prefer drier conditions. Coming climate change promises to be warmer and wetter.
Ancient Rome depended on its aqueducts for its water. When the Germanic tribes attacked, they cut off some of the aqueducts. Without the water from the aqueducts, the population of Rome had no water. The population of Rome decreased.
Advanced countries depend on complex supply chains involving global shipping all over the world. These networks are port dependent. Complex supply chains are the aqueducts of the modern world.
Over the past two and a half years, the world has seen what disruptions to supply chains can have on modern, globalized commerce. Rising sea levels are threatening ports critical to global trade. The disruptions of the past two years should seem minor by comparison.