Climate Change And Human Evolution
February 27, 2013

Drastic Evolutionary Changes Present Effects That Are Visible Today

Alan McStravick for - Your Universe Online

In a field of study that remains largely in the dark, we have relied on the voice talent of Ray Romano, John Leguizamo and Denis Leary to instruct our children about life in the time of the Ice Age. While the lessons learned aren´t necessarily accurate, one Bournemouth University lecturer on palaeoenvironmental reconstruction and environmental change seemingly thinks it might be a good place to start.

Dr. John Stewart, throughout his academic and professional career, has provided several important contributions to this still growing body of work that aims to explain how the evolution of ecosystems must be factored when a geographic region is looked upon in differing geologic eras. Whether we look back to the origin of life on this planet some four billion years ago or we examine a more recent and larger life form, in dinosaurs, it is important to recognize the ecosystems that provided a home for them have, like the life that inhabited them, evolved.

Dr. Stewart points out that most drastic evolutionary changes, while occurring over exceptionally long spans of time, present effects that are visible in the modern day.

And Stewart is no armchair academic either. His study of the interaction between ancient ecosystems, known as paleoecology, along with the study of the evolution of life in humans and other organisms has taken him around the globe to caves in Belgium and the desert of Abu Dhabi.

In his latest study, a collaboration with London´s Natural History Museum, Stewart builds upon his previous research regarding the geographical spread of plant and animal species throughout the warming and cooling of the Ice Ages. This new and ambitious study appears to provide new insight into the origin of humans, including the evolution and extinction of our precedent cousins, the Neanderthals.

Along with Professor Chris Stringer of the museum, Stewart examined the appearance on the world stage of a group termed the ℠first Europeans´ along with another group previously shrouded in mystery, the Denisovans. Though only newly discovered, the Denisovans, related also to the Neanderthals, had an impressive footprint on the globe, with evidence of their existence reaching across the breadth of Asia and Europe. Their ability to adapt was impressive when considering they thrived not only in different locales, but also widely divergent climes.

It was this adaptability of our early ancestors that was the most significant insight of the study. When the planet would undergo some form of major climate change, a species, seeking to mitigate a harsher condition, would seek what is known as refugium. Their success or failure in this endeavor played an important influence on the evolutionary future of the species. As the climate undergoes another change, these refugium can expand or even connect once again.

The geologic span when refugium are separate and distinct entities is an important time for the act of evolution. Through genetic mutation, inhabitants of a particular refugium become different from the original population. Additionally, when refugium become smaller and separate from other safe areas, the twin species in both become new and different from not only their predecessors, but also from one another.

In another study that involved hedgehogs, polar bears and other animals, there was a suggestion that the new evolutionarily modified species, even with the culmination of an Ice Age, never fully resumed their pre-Ice Age relationship as a single group. It is this process that is responsible for the evolutionary changes that can, ultimately, lead to the origin of an entirely new species, altogether.

According to Stewart and Stringer, this provides an explanation as to why Homo sapiens thrive today while Neanderthals and our other cousins experienced a mass extinction some 30,000 years ago. Simply put, it was our direct ancestors who chose the right refuge in which to await the end of the Ice Age.

The bulk of Stewart's previous study has had him sifting through bones and other fossilized remains. His newest work shifts his focus to ancient DNA. Paleontologists have long known fossils are important in achieving insight into the evolution of a species. Now we know the genetic changes responsible for a major change in the shape of a body can be, in fact, fairly minor.

“The most exciting development in my field has been the ability to analyze ancient DNA, which has begun to allow us to see evolution happening over the last several dozen thousand years,” explains Stewart.

Previous study, conducted by Love Dalén of the Swedish Museum of Natural History in Stockholm, serves to bolster Stewart´s claim that the Neanderthals extinction was hastened by a major climate change. Dalén studied the genes of 13 individual Neanderthal fossils found across southern Europe and western Asia.

Dalén´s work shows fossils of Neanderthals from more than 48,000 years ago, along with those excavated in Asia, typically have a higher level of genetic diversity than fossils found later in Europe. Dalén explains this suggests the Neanderthals most probably experienced an evolutionary ℠bottleneck´. A bottleneck would be responsible for a largely significant die-off of a species.

It has been noted when a bottleneck occurs, those individuals of the species that remain often exhibit a diminished diversity which makes it far more difficult for them to evolve and adapt to a changing environment.

Stewart, whose DNA studies have focused primarily on humans and our ancestors, is now focusing on the use of genetics to highlight the evolution of a wide range of members of the animal kingdom.

In fact, Stewart conducted a study in Belgium at the cave site of Trou Al´Wesse. Trou Al´Wesse was a refugium for Neanderthals. However, Stewart is studying how other animal populations also changed as a direct result of climate change associated with the Ice Age. Stewart hopes insight gleaned from this study will aid in understanding the evolutionary processes that have taken place over the last 50,000 years.

Not everything Stewart does has an eye on the past, however. His work has current real world application, as well. In the UK, for instance, there had been an undertaking intended to kill off the Eagle Owl. Experts cited the owl´s propensity for killing other birds along with the belief the Eagle Owl was not a native species as cause for the massive cull. When Stewart stepped in with specific fossils and archaeological records, he was able to reveal that the Eagle Owl, or at least something very similar, had existed in Britain for the past 700,000 years. Needless to say, the massive avicide was cancelled.

Most importantly, Stewart´s fascination with the distant past might also aid in our ability to accurately predict our future. Stewart contends the only way to understand the true scope of the human impact on our planet and whether or not it will lead to a catastrophic ecological collapse is to look far back into the past.

"By studying how organisms have reacted to past climate change,” explains Dr Stewart, “we can learn lessons about what may take place due to human-caused global warming.”