Blog #15 - Ice, Water and Rising Sea Levels: “Global” Flooding before the Last Glacial Maximum (LGM)
There is rightly a lot of interest in the history of Homo sapiens in the critical developmental period since the last “Ice Age”. In particular, Hancock in his most recent book proposes that a highly evolved civilization was eradicated at the beginning of the Younger Dryas period 12,800 years before present (YBP)[1]. He suggests that the remnants of this civilization jump-started present-day modern society. His proposal is that the world was warming up from the last glacial maximum (LGM) and becoming quite habitable when a comet struck the North American ice sheet, causing it to catastrophically collapse, resulting in a large amount of flooding, raising sea levels and eliminated the core of an established civilization. The suggestion is that this flood event is represented in the existence of flood myths around the world including the “sinking of Atlantis” that was reported to Plato from the Ancient Egyptians. While this hypothesis continues to be explored, it is important to first consider human awareness in connection with other climatic events over the 2 million-year time period covering the evolution of modern humans. Events such as repeated sea level rise/fall and the mega-volcano Mount Toba explosion 74,000 YBP. What and where were humans and what would they have experienced from these climatic catastrophes?
This blog explores what we know about human development over the past 2 million years up to the end of the last glacial maximum 25,000 years before present (YBP). It is during this period that hominins became distinguished from other primate species. Here we consider hominins as modern day humans, Homo sapiens and the other biological species that were involved in our evolution. Hominins include the well-known Homo Neanderthals, the recently discovered Homo Denisovan and at least one other unknown species. These species are close relatives and are known to have interbred. This exploration involves looking at what we know about hominin genetics and living location and putting that information together with what we know about the temperature, genetics and sea levels. It draws from the recent research of Bruce Fenton [2]. The objective is to consider what hominins would likely have experienced at different times in their evolution and how this may have become recorded in our cultural memories.
We start the examination with the evolution of H. erectus in Africa at the beginning of the Quaternary Period of the Pleistocene Epoch that began 2.6 million years ago[2]. For those who think dinosaurs, it is important to note that at this time the global temperatures were as cold as they had ever been (Figure 1). Global temperatures were 2 to 3 degrees C colder than when the dinosaurs roamed the earth 65 million YBP. Any and all species to have survived the event that killed the dinosaurs were being subjected to colder and colder environments.
Figure 1. Climate record for the past 65 million years showing the dramatic decrease in temperature in recent epochs (https://en.wikipedia.org/wiki/Geologic_temperature_record).
At the beginning of the Pleistocene Epoch temperatures were slightly warmer than present day, but they were declining (Figure 2A). Throughout this Epoch, the climate cycled through a number of warm and cold periods (Figure 2A). The cold periods we refer to as “ice ages”. It is important to note that although the global temperatures continued to periodically fluctuate up to roughly present day levels, each successive cold period continued to get more extreme, reaching levels not seen in the previous 65 million YBP (Figure 1). Coincident with the warm and cold periods, sea levels cycled through high and low levels, periodically reaching low levels never before experienced (Figure 2B).
Figure 2A. Temperatures and Oxygen record from the Vostok, Antarctica, ice core. The horizontal dashed line represents approximately present day levels. (https://en.wikipedia.org/wiki/Geologic_temperature_record).
Figure 2B. Sea Level over the past 5 millions years (https://www.e-education.psu.edu/earth107/node/901).
In the early Pleistocene, around 1.8 million YBP, the hominin species H. erectus had migrated out of Africa and made it as far as the border of Eurasia. The climate had cycled through at least a dozen cold glacial periods and was then reaching levels 4 or 5 degrees C below present day levels (Figure 2A).
Around the middle of the Pleistocene Epoch, 1.2 to 1 million YBP, H. erectus ranged throughout most of Africa and Eurasia. The temperature minimums were reaching 7 to 8 degrees C below present day levels. At about this time, the length of the warm/cold cycles lengthened from 41,000 years to much longer periods of 100,000 years. This is referred to as the Mid-Pleistocene Transition. Climate change was changing. Analysis of our genetic makeup shows that there was a population bottleneck around this time period. The total number of H. erectus individuals in the world collapsed to only 55,000[3]. Perhaps the extreme cold temperatures occurring over much longer time periods played a role in this collapse. Nevertheless, this climatic change would have given rise to robust individuals who could survive in this new environment.
Following this first population bottleneck, the population expanded and spread over a wide geographic area of Europe and Asia. By at least 750,000 YBP H. erectus extended their range into Southeast Asia. There is archeological evidence that they had successfully sailed to the Island of Flores in the Indonesian archipelago (Figure 3).
Figure 3. Map of Southeast Asia showing the ancient shoreline around the time that hominins journeyed to the island of Flores (http://humanorigins.si.edu/research/asian-research-projects/hobbits-flores-indonesia).
By this time, the cold periods were reaching temperatures 8 degrees C below present (Figure 2A). Glaciers would have trapped a lot of water and sea levels were lowering to almost 100 m below present day levels (Figure 2B). Figure 3 shows Sundaland, a landmass that would have connected present day Sumatra, Java, Borneo and other islands. To reach Flores, they would have had to island hop from the mainland over a number of water barriers of between 15 and 30 km.
It has been suggested that H. erectus could have observed islands in the distance[4]. But it is another question if and how a group of what is currently thought of as primitive species could imagine, plan and coordinate to sail across such significant water barriers. It is improbable that the population of H. erectus could have become established on Flores through individuals accidentally floating across clinging to driftwood. Such a migration across water would have required higher concepts of exploration in the face of difficulties, communication and convincing of others to engage members of the groups as well as the technical expertise to achieve such a successful move.
By 500,000 hominins on Java were engraving geometric patterns on shells. This is possibly a continuation of the higher thoughts of H. erectus that got them to the distant island location of Flores.
There were two periods of extreme low sea level associated with the extreme cold periods at 650,000 and 450,000 YBP (Figure 2B). Sea levels at these points in time were 125 m below present day levels. By 400,000 they likely had made their way across the watery Lydekker's Line to Sahulland, which included Australia (Figure 3). There is one proposal built on archeological finds and recent genetic data that they began to differentiate into modern H. sapiens here in Sahulland, rather than in Africa which is the current dogma. By 400,000 YBP we can reasonably expect ancient humans to be sufficiently conscious and competent to sail across water boundaries and to create carved art on shells. They would have experienced a number of dramatic changes in sea level that would have had major impact on any coastal habitations. Whether they could conceive of a “global flood” or just be aware of the flooding of entire world, they certainly would have been sufficiently impacted to remember and transmit this information across generations.
The last, most-recent warm period in the Pleistocene epoch occurred about 125,000 YBP. The temperature over Greenland was as much as 5 degrees Celsius warmer than present day (Figure 4). Sea level was about 6 meters (about 19.7 feet) higher than it is at present (Figure 2B).
Figure 4. Temperature fluctuations in the Vostok Ice Core showing the cycling of warm and cold periods. Note the last warm peak before present was at around 125,000 years before present.
During this relatively warm cycle, there were a number of different hominins living in the world including H. sapiens, Neanderthals, Denisovans and possibly a couple of others yet to be discovered. Genetic analysis suggests that the genetic mixing into modern humans was geophysically centered in this area of South East Asia.
It is in this area that in 73,880 YBP, the gigantic volcano Toba erupted for 14 days on the island of Sumatra (Figure 3). This was the largest volcanic eruption of the last 2.5 million years. It would have had associated powerful earthquakes and tsunamis. It was sufficiently large to influence global climate by reducing sunlight and reducing temperatures. Rain that fell following the eruption would have been black and acidic from the ash that it contained. This was a time that the hominin population experienced a second population bottleneck. Many died, leaving only about 10,000 adults surviving. Other large biological species such as chimpanzees also show such a genetic bottleneck at this time[5]. Hominins in South East Asia at the time would have been significantly impacted by the eruption and its after effects. If the core of hominins was co-located with the mega-volcano’s impact, it may explain why later humans around the Globe share a common myth of global flooding and disaster[2]. Maybe the present Noah’s Ark story of a small number of families surviving the disaster is only a slight exaggeration of what might really have transpired 74,000 YBP, resulting in the most recent population bottleneck.
Shortly after the Toba event, around 70,00 YBP, modern H. sapiens were living on the southern coast of South Africa in the Blombos Cave creating art. Neanderthals were widespread over Europe and Central and Northern Asia. This is the time period during which it has been proposed that H. sapiens migrated out of Africa, but it is conceivable that they may have dispersed from South East Asia in response to the Toba destruction.
It is clear that by this time, hominins had been expressing higher thought for millennium. The evidence includes:
1) H. erectus had made it to Flores likely by an organized sailing effort;
2) H. erectus had created decorated shells on Java;
3) H. sapiens in Blombos Cave, South Africa, had created art and used red ochre;
4) H. sapiens in Pinnacle Point, South Africa, were using a complex, multi-step process for producing silcrete by use of fire.
Following the last warm maximum, 124,000 YBP, the Northern Hemisphere began its final cycle of gradual cooling. Glaciers increased in both depth and geographic extent until the time of the last glacial maximum (LGM) about 25,000 years ago. Glaciers extended in North America down into present New York State and in Europe south to the middle of England, Germany and Poland. There was similar expansion of ice sheets in the southern Hemisphere with the southern third of Chile and the neighboring portion of Argentina being covered. Sea level was about 125 meters (about 410 feet) lower than it is today.
While climatic conditions were harsh during the last glacial maximum, 24,000 YBP, Neanderthals were still surviving along the edge of a fertile coastal plain in Gibraltar until around that time. Denisovans appear to have survived in Siberia until as recently as 30,000 YBP. Modern humans were living in what has been defined at the Gravettian culture, in occupying areas in Europe from France in the west to Siberia in the east. They produced small pointed blades for hunting and a large number of Venus statuettes. Hominins were also living in Southern Australia around 40,000 YBP.
So by this point in time hominins had experienced many extreme changes in sea level and coastal flooding. There had been at least two periods of significant population die off, possible, linked to the climate change and flooding events. It could be that the basis of the global flood myth was laid down during these early events. The representation of more recent flooding events may be overlain on an older, more shared experience by hominins.
More on these events in the next blog post.
[1] Hancock. G. 2015. Magicians of the Gods The Forgotten Wisdom of Earth's Lost. Civilisation. Hodder & Stoughton.
[2] Fenton, B. 2017. The Forgotten Exodus: The Into Africa Theory of Human Evolution. Ancient News Publishing. http://brucefenton.info/into-africa-theory/
[3] https://www.scientificamerican.com/article/humans-might-have-faced-extinction/
[4] Fenton, B. 2017. The Forgotten Exodus: The Into Africa Theory of Human Evolution. Ancient News Publishing. http://brucefenton.info/into-africa-theory/