The Quaternary consists of only two epochs, the Pleistocene and the Holocene, an interglacial period that persists to this day.
- Earth enters an ice age
- Homo erectus evolves
- Early humans colonize Eurasia
- Neanderthals evolve
- Modern humans appear
- Toba supervolcano erupts
Glacial Advances Herald a New Ice Age
No one is quite sure exactly what causes these glaciations, which typically last many millions of years. However, the reason these periods tend to last so long is probably down to both positive and negative feedback processes. In other words, ice sheets increase the reflectivity (albedo) of the Earth’s surface as such that much of the heat from the Sun is beamed back out into space. On the other hand, erosion caused by moving glaciers themselves mitigates these effects, helping bring about interglacial intervals such as the one of the last 12 millennia.
By the beginning of the Quaternary, glacial advances had gripped much of the northern and southern hemispheres, with ice sheets reaching as far south as the north of France and perhaps even further. The last glacial period took place between 110,000 and 11,700 years ago, and is thus popularly referred to as the Ice Age itself. However, this event is, in scientific terms, known as the Last Glacial Maximum, and was only one part of a cycle that has persisted for the last 2.58 million years.
During glacial periods, sea levels drop significantly, sometimes by hundreds of feet. These events allow land bridges to form, such as those that existed between Britain and Europe, Australia and New Guinea and Alaska and Kamchatka. Thanks to the appearance of these land bridges, the migration of both animals and humans alike were made possible. Just as camelids once moved from their native North American homeland into South America and Africa using the Bering Strait land bridge, humans migrated all over the world during the Last Glacial Maximum between 18 and 12 thousand years ago.
A New Land of Giants Survives the Lingering Cold
It’s not strength or intelligence that allows a species to survive as much as it is its ability to adapt to extreme conditions. Throughout the history of evolution, countless millions of species have failed to adapt, disappearing off the face of the Earth to make way for more successful organisms. The Quaternary glaciations may have seen global cooling on an enormous scale, but they also saw the expansion of important environmental niches.
Larger animals, particularly those with thick coats of hair or fur, are generally better equipped to survive in cooler climes. Many iconic megafaunas that we know today, such as elephants and rhinoceroses, had tundra-dwelling counterparts throughout much of the Quaternary. Woolly rhinos and mammoths, for example, are very much like their modern relatives, albeit much better adapted to the cold. Mammoths, for example, were among the most successful species of their time, spanning much of the globe and living even in places where winter temperatures regularly reached −50 °C. The last mammoth died a mere 4,300 years ago in Wrangel Island.
The Pleistocene, the first of the two Quaternary epochs, saw a new land of giants colonize the Earth. Mammoths reigned across Eurasia, while their close relatives the mastodons ruled in North America. Other examples include the megaloceros with its 12-foot antlers (3.6 metres), the largest species of deer that ever lived. Beavers, lions and bears also broke records.
Despite the effects of the Great American Interchange, South America was still home to unique giants of its own, such as the elephant-sized ground sloth megatherium and the car-sized glyptodonts, which were relatives of modern armadillos.
Australia, which had enjoyed tens of millions of years of isolated evolution, also saw the appearance of enormous ancestors to its current fauna. Among the most notable was the 6.6 foot-tall (2 metres) procoptodon, a giant kangaroo, and the diprotodon, a truly bizarre marsupial that grew larger than a hippopotamus.
It wasn’t only mammals that broke size records during the Pleistocene Epoch. Various bird species also grew to enormous proportions, such as the North American teratornis, a bird of prey twice the size of the modern Californian condor. Many of the carnivorous flightless birds, such as the terror birds (phorusrhacids), that had appeared during the Neogene, still terrorised the Americas. Meanwhile, in New Zealand, moas reigned supreme as they had done for some 15 million years, only to be wiped out a mere 600 years ago by the arrival of the Māori people.
Early Man vs. Prehistoric Beast
During the Early Pleistocene, the genus homo, to which modern humans belong, appeared in East Africa, possibly emerging from the australopithecine genus, which went extinct at around the same time. Among the earliest progenitor of the modern human race was homo habilis, one of the first animals to learn how to use basic tools.
Although there remains a great deal of debate regarding the taxonomic classification of early hominids, the Old Stone Age (Palaeolithic) was undoubtedly in full swing by at least two million years ago. Homo erectus, or upright man, for example, learned how to make basic tools and light fires some 1.9 million years ago. There’s even strong evidence that homo erectus built the first campfires and cooked their food, possibly as part of social gatherings.
Several unique human species existed during the Pleistocene, including the Neanderthals, all of which are now extinct save for modern humans. Our own species, that being homo sapiens, appeared some 280,000 years ago, coexisting with many of the iconic ice age animals, such as woolly mammoths and sabre-toothed cats.
While modern humans, along with most other members of the genus homo, evolved in East Africa, the Neanderthals were an offshoot that evolved in Eurasia, their own ancestors having originally evolved in Africa too. The Neanderthals, which appeared at about the same time (or perhaps even some time before) modern humans, were also advanced tool users and may have even mastered language.
Like the Neanderthals, early modern humans also built rudimentary structures out of wood and mammoth tusks and wore clothes to keep warm in the cold climes of Ice Age Eurasia. However, only early humans managed to migrate to the Americas and Australasia, around 13,000 and 50,000 years ago respectively. Neanderthals, by contrast, typically lived in small and relatively isolated communities, and were never particularly great in number. As such, due to competition with homo sapiens and, possibly, interbreeding, they disappeared around 40,000 years ago.
Man Rises to Dominance with the New Stone Age
The current geological epoch began around 11,700 years ago. The Holocene refers to the ongoing interglacial period, beginning at the end of what is popularly known as the last ice age. It also coincides approximately with the end of the Old Stone Age, which is also known as the Palaeolithic. These prehistoric periods refer to human history rather than geological and evolutionary history.
By the beginning of the Mesolithic, the Middle Stone Age, mankind had spread across most of the globe, and was already well-established in the Americas and Australasia. They continued to coexist with many of the iconic ice age animals, but this was soon to change as a result of a warming global climate and increasing human encroachment from the beginning of the Holocene.
The Mesolithic remains a vague term, since it’s largely defined by the progress of pre-agricultural cultures around the world, which evolved in isolation on separate timescales. More relevant was the Neolithic, which began, in certain areas, at the dawn of the Holocene Epoch. This was the time when mankind truly rose to dominance as the Neolithic Revolution started to transform the face of our world.
Also known as the Agricultural Revolution, this period saw the first domestication of plants and animals and, thus, the first agriculture. Although hunter-gatherer societies persisted and, in some isolated cases, continue to do so to this day, many cultures around the world underwent a transition to animal-rearing and crop growing. Populations boomed as a result, forming the foundations of modern civilization.
Although a mere footnote in terms of the enormous amount of time we’ve been here, the Neolithic Revolution was the direct progenitor to the world we live in today. Hard on the heels of early technological advancement was the Bronze Age and then the Iron Age, as mankind learned how to smelt metal ore and create everything from advanced tools to ancient works of art.
The development of modern human cultures sped up at an unprecedented rate through the Holocene. Vast swathes of land were given over to farming, populations boomed and civilization spread throughout Eurasia and beyond. As mankind came to dominate almost every corner of the globe, countless species disappeared in what is now known as the Holocene Extinction Event. Consequently, the path of evolution was forever changed, and no longer would nature alone sculpt our planet’s future.
Once upon a time, we were nought but microscopic organisms living in a very different world to the one we know today. Over more than 3.5 billion years, the story of life on Earth has developed and transformed on an unprecedented scale, ultimately giving rise to mankind and its incredible technological (and, sadly, often destructive) advances.
We have now reached the end of our journey through the history of our world, a time when the development of our species has become the defining influence in the Earth’s future. Mankind has, without doubt, left its mark upon the world like no other species before it.
Traces of our progress will remain long after we’re gone. The probes we’ve sent into space will likely continue their eternal journeys through the cosmos after even the Earth itself has been incinerated by the Sun. No matter our living future; the human race has put its eternal stamp on our tiny and insignificant corner of the Universe. This is the legacy of the evolution of our world.