What killed the Pleistocene megafauna?

[Infinity Blade]

I was just wondering if there is now a more accurate, up-to-date answer to this age-old question, plus it would be nice if there was debate/discussion on said topic on this forum.

Title explains all.

[Deleted]

A comet is the likely culprit.

www.livescience.com/7283-catastrophic-comet-chilled-killed-ice-age-beasts.html
www.sciencedaily.com/releases/2012/09/120918111320.htm
www.space.com/17676-comet-crash-ice-age.html
www.dailymail.co.uk/sciencetech/article-2550915/Did-comet-kill-woolly-mammoth-Study-backs-theory-impact-13-000-years-ago-triggered-extreme-cold-snap.html

[creature386]

I am no expert there, but I'd say climate change with a little bit human help:
www.researchgate.net/profile/Barry_Brook/publication/235438451_Quaternary_extinctions_and_their_link_to_climate_change/links/09e415125a72025461000000.pdf

[coherentsheaf]

Humans. The other hypotheses fail all criteria for good explanantions by a huge margin. Climate in particular is an example for a bad idea if ever I saw one.

[Infinity Blade]

Good to see differing opinions.

Now, do keep in mind that I'm not just talking about the Pleistocene megafauna in just one time and place (so while you may think a comet was the cause in North America ~11.7k years ago, it won't explain the extinctions in Australia ~50k years ago).

For the record, I've been thinking for a while now that a well-balanced combination between climate change and hunting (and maybe even disease) was the cause. I would however like to be convinced otherwise, as I only got my current opinion simply because I couldn't decide between some of the theories and thought "why not a combination of them?".

[coherentsheaf]

Climate is unlikeloy. All of these megafaunae endured varying climate changes and iceages and whatnot, they were probably very robust regarding this. Human on the other hands are just a recipe for mass extinction, especially after they had atlatls and even worse bows. I cannot imagine megafauna not coevolving but suddenly confronted with them surviving well.

[creature386]

I admit that I shouldn't have written "humans helped a bit", but the thing is, climate changed and increased extinction rate nevertheless fall together. This is from the conclusions of my paper:

Rather, the key point is that where direct human impacts and rapid climate change coincide, fatalities are higher and faster than where either factor operates alone.

It looks like a combination of humans and climate is a good explanation, given that it is supported by the observed fatalities.

[coherentsheaf]

Except that the climate on its own would not have killed the majority of the fauna, while humans would have. Hence humans are the explanation not climate.

[Infinity Blade]

Would anyone else like to voice their opinions?

[stomatopod]

Too much Red meat.
Better eat Chicken.
Seriously, ANE/WHG/ENA.

[Infinity Blade]

^I'll take that as humans.

[stomatopod]

Well, at least some specifically subsets of humankind.

[Derdadort]

I would also agree with a multifactor explanation as its written here

I am no expert there, but I'd say climate change with a little bit human help:
www.researchgate.net/profile/Barry_Brook/publication/235438451_Quaternary_extinctions_and_their_link_to_climate_change/links/09e415125a72025461000000.pdf

However, it may be right that global warming alone is an unlikely explanation. Nevertheless the influence of a changing climate in addition with habitat loss and a low reproduction rate especially in large mammals shouldn't be undermined, so I'm a bit sceptical whether the anthropogenic impact would have been similar high under a different climatic or ecological situation.

Regarding the impact or burst of an extraterrastial object, there seems to be more than one hypothesis with different contradictioning views. See here: www.researchgate.net/profile/Jacquelyn_Gill/publication/259950697_Arguments_and_Evidence_Against_a_Younger_Dryas_Impact_Event/links/0a85e535501575dca8000000.pdf

[Infinity Blade]

I just watched a documentary that touched a bit on the Pleistocene extinctions and it reminded me of this thread. Would anyone else like to voice their opinions?

[Infinity Blade]

Recently on Carnivora, I voiced my objections to the idea of there being some direct, close correlation between the arrival of humans in the Americas and the extinction of most of the North American megafauna.

How and when the Americas were populated remains contentious. Using ancient and modern genome-wide data, we find that the ancestors of all present-day Native Americans, including Athabascans and Amerindians, entered the Americas as a single migration wave from Siberia no earlier than 23 thousand years ago (KYA), and after no more than 8,000-year isolation period in Beringia. Following their arrival to the Americas, ancestral Native Americans diversified into two basal genetic branches around 13 KYA, one that is now dispersed across North and South America and the other is restricted to North America. Subsequent gene flow resulted in some Native Americans sharing ancestry with present-day East Asians (including Siberians) and, more distantly, Australo-Melanesians. Putative ‘Paleoamerican’ relict populations, including the historical Mexican Pericúes and South American Fuego-Patagonians, are not directly related to modern Australo-Melanesians as suggested by the Paleoamerican Model.

www.sciencemag.org/content/early/2015/07/20/science.aab3884

This seems to suggest that people could have arrived in the Americas as early as 23k years ago (ergo, much earlier than previously thought). If true, then that's a huge amount of time between the first Americans and the extinction of the North American megafauna.

Anyone can feel free to correct me if I'm wrong.

Edit: to add to this, it seems H. sapiens was present in South America before the Clovis culture.

The Arroyo Seco 2 site contains a rich archaeological record, exceptional for South America, to explain the expansion of Homo sapiens into the Americas and their interaction with extinct Pleistocene mammals. The following paper provides a detailed overview of material remains found in the earliest cultural episodes at this multi-component site, dated between ca. 12,170 14C yrs B.P. (ca. 14,064 cal yrs B.P.) and 11,180 14C yrs B.P. (ca. 13,068 cal yrs B.P.). Evidence of early occupations includes the presence of lithic tools, a concentration of Pleistocene species remains, human-induced fractured animal bones, and a selection of skeletal parts of extinct fauna. The occurrence of hunter-gatherers in the Southern Cone at ca. 14,000 cal yrs B.P. is added to the growing list of American sites that indicate a human occupation earlier than the Clovis dispersal episode, but posterior to the onset of the deglaciation of the Last Glacial Maximum (LGM) in the North America.

journals.plos.org/plosone/article?id=10.1371/journal.pone.0162870

If people were in South America as early as 14k years ago, imagine how much earlier they arrived in the northernmost parts of the Americas. I'm not really sure what killed off the North American megafauna at this point, but the fact that humans arrived well before the megafauna actually became extinct suggests that there isn't so much of "a direct correlation between these animals' extinction and the timing of the arrival of humans in Siberia and the Americas."