Should rewilding science account for the Younger Dryas Impact Hypothesis?

Those who know me, know that I can get a bit overexcited about ideas. There's nothing I love more than walking and exploring concepts with a fellow rewilders or sitting around debating issues and science in a pub.

Earlier this month, I started watching Graham Hancock's "Ancient Apocalypse" on Netflix. Its a sugar rush of ideas - a cocktail of appealing evidence assembled in an attractive narrative with a compelling punch.

Like all trained scientists, I'm wary of pseudoscience. But I'm worldly enough to know that science and esteem are intertwined which can create resistance to radical new synthesis and Hancok's collapse story is rooted in a genuine scientific hypothesis.

Hancock argues for the existence of an ice age civilisation that flourished in warmer regions between the vast ice caps. This civilisation, he argues, collapsed due to a catastrophic event 12,850 years BP which scientists refer to as the 'Younger Dryas Impact Hypothesis'. This posits that the Earth passed through the tail of a comet and fireballs hit the ice caps, causing immense flash floods and vast wildfires elsewhere. The impact was not on the scale of the asteroid hit that caused the extinction of the dinosaurs, but it was enough to be 'earth changing'.

Stories of human civilisation apart, Ancient Apocalypse interested me because it suggested there was more to the collapse of the Pleistocene mega fauna than I had appreciated. When I wrote about this in my book, 'Rewilding: The radical new science of ecological recovery', I discussed the competing ‘overkill’ (human hunting) and ‘over chill’ (climatic change) hypothesis and came down in favour of the former. In truth, I wasn’t altogether satisfied with the overkill hypotheses - 20,000 years ago the world and the mega fauna were big compared to the numbers and agency of human hunter groups.

At the time of writing, I wasn't aware of the Younger Dryas Impact Hypothesis. It wasn't something that had ever been discussed in my academic circles, but Netflix offered me a new line of thinking.

There isn't a massive amount of academic literature on the YDIH, and up until 2022, authors were understandably cautious. However, two recent review papers strongly support it. The first, by John Lawrence, was published in Science Progress. He exposes flaws in the counter evidence and argues that the hypothesis should be 'upgraded' to theory. While it is a well-argued perspective, Lawrence roundly criticises scientists for prematurely rejecting novel hypotheses. This appearance of an agenda and it being published in a relatively minor journal detracts from its credibility.

The second review paper, written by Martin Sweetman in Earth Science Reviews, is a heavyweight in terms of the quality of the reviewed geochemical evidence, critical examination of studies contradicting the evidence, and the standing of the journal itself. Sweetman concludes that "the overwhelming consensus of research undertaken by many independent groups suggests that claims of a major cosmic impact at this time should be accepted."

He goes on to state 'Given the strength of the impact evidence, reviewed here, it is now imperative that future research into the Younger Dryas climate change and associated human population and cultural changes and end- Pleistocene megafaunal extinctions should take this cosmic impact event into account'.

So if we accept that 12,850 years our planet was hit by debris from the break up of a comment in our solar system and the fragments upon entering Earth's atmosphere experienced intense heating leading to explosive fragmentation and massive releases of energy what and disposals of materials - how might rewilding scientists re-explain the demise of Pleistocene mega-fauna.

Writing the last sentence, I had to sit back to comprehend the magnitude of the event for megafauna, humanity and our planets ecosystems. We know that it flipped the climate back into a 1200 long mini-ice age (the Younger Dryas) and there is evidence that it induced mega flash floods reforming landscapes along with devastating wildfires. The shock to the earth’ systems must have caused huge loss of life and disruption.

In responce to all this I’m starting to outline a more nuanced story of Pleistocene megafauna decline. It goes something like this and I’d welcome additional evidence that confirms, extends or contradicts this outline

Between 20,000 and 14,000 years BP the planet warmed, ice caps and glaciers melted and sea level rose (with a meltwater pulse 14600-14,300 yr BP). This brought wetter winds to the arid and vast Mammoth Steppes -which stretched across northern Eurasia and North America - which become boggier and less suitable for mega-herbivores (NB Tom Halliday offers a good account of this in his book Motherlands). These wetter and warmer conditions allows signifiant human migration into the region who came with advanced weapon technologies u and cooperative strategies. They hunted and maybe largely survived off megafauna whose populations were in decline due to vegetation change.

If we accept that 12,850 years ago, our planet was struck by debris from the breakup of a comet in our solar system, causing explosive fragmentation, massive energy releases, and material disposal upon entry into Earth's atmosphere, how might rewilding scientists explain the decline of Pleistocene megafauna?

So should we be accounting for the YDIH in our long-term analysis of megafaunal demise and ecosystem change?

I would be interested to hear the views of fellow rewilding and earth scientists.

[addendum - I should have made clear in this article that I meant in relation to North America and Eurasia. As colleagues pointed out megafauna extinctions occurred much earlier in Australasia and maybe Sunderland (present day SE Asia). In posing this question I was also thinking more about the processes of megafauna extinction and how these might vary is different geographies]

#rewilding #youngerdryas #megafauna #extinction #iceage #pleistocene #ecology #earthsciences #ecosystemrestoration #paleoecology