An Evolving Tale

We should not underestimate the importance of climate change – humans are part of the environment, not masters of it.

Originally published by the Guardian 3rd April 2007

There really seems to be very little doubt that human activity is responsible for climate change: atmospheric concentration of CO2 (a major cause of global warming) is now significantly higher than at any time over the last 600,000 years. The start of this massive increase coincides very closely with the genesis of the industrial revolution.

We should be worried about the effects of climate change, not just because of the short-term problems it will undoubtedly lead to, but also because of the long-term issues we can only guess at. The media is full of speculation about the effect of relatively short-term climate change, such as rising sea levels and desertification.

Yet it is worth examining just how powerful a hold climate really has on our species from an evolutionary perspective. It would not be going too far to say that climate change has been one of the major factors in human evolution (the other is, of course, technology). A drop in global temperature during the Miocene epoch approximately 8-10 million years ago, resulted in the fragmentation of the large African forests, which in turn led to the development of savannahs (wide open grassland). It was this incidence of climate change that seems to have kick-started human evolution.

Around 7 million years ago our early ancestors ventured out of the forests and onto the savannah, slowly adapting to this new environment (while the ancestors of chimpanzees stayed within the forests). The key adaptation caused by this shift in habitat was that our ancestors began to walk on two legs (bipedalism), probably to reduce the surface area exposed to the sun. This left the hands free to do other things, aiding the development of stone tools, which could be used to scavenge and butcher meat, which in turn provided energy for bigger brains. Without that change in the global climate, it is fair to suggest that we might not have become the species we are today.

Human evolution continued to be highly influenced by the environment over the next 5 million years, but this changed dramatically around 2 million years ago when our evolutionary ancestor, a species called Homo ergaster, first started to significantly manipulate its environment. Over the last 2 million years we have been gradually lessening the hold that climate has on us, but never removing it. The extinction of the Neanderthals around 30,000 years ago seems to have been closely related to climate change. Our own species, Homo sapiens, has been able to populate almost every area of the planet; using technology to exploit areas our biological make-up would not be able to cope with.

The process has now come full circle: the environment had a massive impact on our evolution, we evolved strategies to reduce this impact, but these technological innovations have now caused the environment to start moving beyond our control once again. The lessons from our evolutionary past are very clear; humans are part of the environment, not masters of it.


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