The Pleistocene occurred from about 1.8 million years ago up to 10,000 years ago. During this time frame, early man as well as all species living on Earth at the time was subject to extreme climatic changes which may have shaped their evolution. The late Pleistocene and its transition into the Holocene were marked by extreme climate changes. The Pleistocene was the time of homogenous cold weather throughout the world. However, during the latter part of the Pleistocene, from about 18,000 up to 11,000 years ago, the weather began to warm up, resulting in glacial retreat and marked differences in seasonal temperatures. This increase in temperature was temporarily reversed by a phenomenon called the younger Dryas.(Buchdahl) These changes severely altered the then present ecological systems. Populations were separated, most migrated and some went extinct. The ecological disruption that resulted led to mass mega faunal extinctions, as well as grave evolutionary impacts on surviving species.
Which of these changes would have most affected human populations?
Most humans during the period were hunter-gatherers, dependent on the flora and fauna of a given area for their primal needs. With the changes in weather, plants, primary producers in the ecosystems populated humans began to die out. The loss of these plants would have led many species of primary consumers to migrate in search of foliage. Since plants, man’s source of sustenance, were dying, and since the animal’s, also dependent on plants were migrating, man then had no choice but to follow their food and themselves migrate.
Humans are, as compared to other species, more adaptive to their surroundings. However, the harsh climatic conditions and their variability would have meant that a single generation would have had to adapt to different circumstances. Although not all species are more susceptible to dying out in the circumstances then, the effect of a lost species on an established ecosystem would be disastrous. The loss of megafauna during the times, whether due to over-hunting of the starved humans or as a result of the environmental changes occurring would have led to an imbalance in the system, allowing for an increase in the prey population, most of which feed upon herbage, so that what little herbage at that time which was present was now consumed at a much more rapid rate.(Messer, 2006)
The general warming would have led to a new series of established ecosystems. However, the occurrence of the Younger Dryas resulted into a throwback unto glaciations. Ecosystems that were adapting to the warming climate, plants, animals and humans, once more had to adapt to a different set of circumstances. (Buchdahl)
Evidence shows that the Younger Dryas, an approximately 1000 year event ended abruptly, in a span of only several decades. This rapid change would have again upset communities and ecosystems. The melting of glaciers resulted in flooding of areas where ecosystems thrived during the ice age. The marked changes in seasonal temperatures again brought upon the extinctions of plants which have already adapted to the previously prevalent cold climate, again resulting in disruptions in ecosystems. The impact of these was felt by man, who where at the top of the food chain. (Messer, 2006)
In terms of genetics, the changes brought upon by the migrations of human populations would have led to isolation. This isolation would have then resulted in inbreeding among a single population, further genetically separating one population from another, which could have led to differentiations in terms of race.
Do you see parallels with issues of climate change today?
The main issue in today’s climate is global warming. The Earth, as expressed from numerous scientific accounts is warming up. This could be seen as a parallel to the late Pleistocene warming that preceded the Younger Dryas. The younger dryas was said to be caused by the influxe of freshwater coming from the melting of glaciers. These freshwaters mixed with established saltwater streams, the resulting change in salinity disrupting the ocean currents that shaped the climate. Like the late Pleistocene, we are now experiencing variations in local weather as well as in over all climate. Extinctions, which lead to disruptions in ecosystems, are at present occurring at alarming rates.
What issues are particularly relevant?
Man during the late Pleistocene has come a long way to be the man we are today. However, what is still the same is our dependence on the ecosystem that sustains us. It is still plant and animals that provides us sustenance, trees that provides us raw materials and fuel. Marked fluctuations in the weather would lead to disruptions in these ecosystems, which would force us to alter the life we are living at the present in order to adapt. Also, unlike then, our species advances in civilization have introduced a new aspect, economics. No longer would hunter-gatherers, survival, when such a drastic phenomenon occurs, be based on a populations resources at and, dooming those of our species that, in these times, already have nothing to eat, to wear, to shelter in.
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Buchdahl, J. Palaeoclimatic Change: The Younger Dryas Event [Electronic Version]. Retrieved June 4 2007 from http://www.ace.mmu.ac.uk/resources/gcc/5-3-2-1.html.
Messer, A. E. (2006). Early Americans faced rapid late Pleistocene climate change and chaotic environments [Electronic Version]. EurekAlert. Retrieved June 4 2007 from http://www.eurekalert.org/pub_releases/2006-02/ps-eaf020606.php.