The mystery of the vanished giants is no easy one to solve.
This is still very much a dynamic field where new research reveals more
dimensions of the puzzle and throws up more questions than answers. After
gaining a better understanding of the topic through keeping this blog, I am
ever more aware that the answer is not a simplistic, uni-dimensional one.
I found the arguments where human impacts are the ‘last
straw’ for already stressed populations struggling to adapt to climate change
the most convincing. Critics have argued that megafauna survived the previous glacial-interglacial
transitions, citing anatomically advanced humans with sophisticated hunting
technologies as the only differentiating factor. This is a simplistic view of
past climates which assumes that all transitions are the same. There is evidence
that the late Pleistocene was unusually, warmer rather than cooler than the
Holocene and supported a rich mosaic of vegetation types which was in turn able
to support a huge variety of megafauna. This disappeared during the Holocene. Besides, ‘megafauna’ is not a static concept;
Graham and Lundelius (1985) concept of ‘co-evolutionary disequilibrium’
suggests that species often co-evolve in unique and individualistic ways,
meaning that the species composition of ecosystems change all the time. The
late Pleistocene was a biotically unique period, limiting comparability with
other glacial-interglacial transitions.
Besides, extinctions did not happen in the rapid
‘Blitzkrieg’ manner that some researchers have argued. Especially in Eurasia,
where humans were not necessarily present in all areas, extinctions occurred
gradually and even happened in areas where there were no humans, e.g. the Irish
Elk. The African Anomaly also adds another piece to the puzzle – African
hunters were also sophisticated but it is the continent which experienced the
fewest extinctions, and there is evidence that climate change was less
pronounced in Africa.
Whispers from Ghosts
Past: Lessons for the Future
So where does this all leave us? I do not think it is
possible to provide a conclusive answer to the mystery of the vanished giants,
but I hope I have left room for more thought. I also hope that a better
understanding of past climates and extinct species would lead us to be more
aware of the importance of modern conservation – once species are lost, they
are irrevocably gone.
I can see 3 major takeaways from this blog:
Today, our actions are themselves causing climate change. In the late Pleistocene, climate change was essentially separable from human impacts such as hunting. Today, we have entered what Nobel Prize winner Paul Crutzen (2002) calls ‘The Anthropocene’ – human impacts have reached such unprecendented levels that they have become significant geological forces.
The late Pleistocene megafauna extinction event has shown that the adverse impacts of humans and climate change are a lethal combination for species biodiversity, and the effects are further amplified today.
Crutzen, P. J. (2002) The ‘anthropocene’, Journal de Physique IV, 12, 10, pp. 1-5