[amatic]

Apparently, there were horses in the Americas, but they went extinct about 12k years ago, along with the other megafauna. What I understand is that different images could have been made in multiple time periods, from the first inhabitants up to today.

[mjan22640]

Younger Dryas caused megafauna extinction worldwide

[gort52467]

s/went extinct/were hunted to extinction by man

[atlantic]

Blaming megafauna extinction on humans aligns with current misanthropic fashions, but rapid global warming at the end of the last ice age is a far more likely culprit. https://www.nature.com/articles/s41467-021-21201-8

[AbrahamParangi]

I don’t think it’s very credible to conclude the disappearance of both large herbivores has nothing to do with the arrival of a new, exceptionally adept and general apex predator.

Do you know when the megafauna of Madagascar went extinct? Right around the arrival of humans. What about New Zealand? Shortly after the arrival of humans. In every historical, known example of human introduction to a new ecosystem, most animals over 50lbs get eaten.

[throwuwu]

So what’s up with Africa then? Those ones didn’t taste good or what?

[AbrahamParangi]

I would propose that the megafauna of Africa is less naive regarding hominid predators.

Elephants will go out of their way to kill lion cubs and, according to Tanzanian anecdote, human children.

[thunkle]

The animals there evolved with humans.

[saalweachter]

It's also interesting that essentially none of the native animals in Africa are domesticatable -- I think donkeys are the one thing we managed to domesticate there, most everything else was brought back from other continents.

Animals you'd think would be basically like other species we've domesticated, like zebras or gnus, take a strong "fuck you" attitude towards people and have resisted modern efforts to domesticate them.

[throwuwu]

So NA megafauna had no problems with wolves but people come along and it’s game over. Still not buying this. Why did horses die out but not bison or deer? How did mammoth go extinct while elephants didn’t when elephants faced more technologically advanced humans over a longer time period? Just doesn’t add up.

[olddustytrail]

Pretty much the same thing it's just that Africa is huge.

[throwuwu]

And North and South America aren’t?

[EdwardDiego]

> but rapid global warming at the end of the last ice age is a far more likely culprit.

Firstly, your linked paper is focused on North America, so we can't say it's also applicable to, say, the extinctions of Homo floresiensis and Stegodon florensis insularis that correlate rather well with the arrival of modern humans.

Secondly, it repeatedly refers to global _cooling_ through the Younger Dryas Event. Just to clarify.

And tbh, claiming the overkill/big black hole hypothesis is merely current fashion is overly simplistic. It was described in the 60s based on available data, and hey, we're getting better data now, so yay, science is incorporating new data, like we expect.

And I'll note that the data points for human predation of megafauna used in that paper are likely to change also with time, so who knows how correct that paper's conclusions will be in another 20 years?

I don't see why "it was probably both" shouldn't be the default position. We know humans hunted megafauna, but like the fossil record, we know that only some evidence will be preserved, and only some of that evidence has been found.

But logically, both environmental change and the introduction of a novel predator (and other novel predators that predator may have brought with them) are bad for populations of species which a low replacement rate.

Kākāpō are a very good example. Human settlement brought habitat loss, causing their numbers to decline, and their breeding success rates to drop (and they were slow breeders to start with) as the more clement habitat was modified by humans, thus pushing them into areas with lower productivity.

But what ultimately pushed them to nearly going extinct was the introduction of very effective mammalian predators (mustelids). They had evolved for a land where the only predators were avian and sight based. So they became flightless because no point in flying away from danger when the danger was flying above you, and they developed cryptic colouration, they'd freeze when they sensed danger and became nocturnal. And most importantly, they used scent in lieu of dramatic colours to find each other in dense forest in the breeding season. No harm there, because raptors hunt by sight, not scent.

But being a smelly bird who is camouflaged and nocturnal and stands still, is no defense against ground predators who hunt by scent and quite appreciate not having to run after you.

I have the diaries of an explorer in the 1890s who would eat five kākāpō for breakfast, they were that easy for him to locate using his dogs, within 80 years of his parrot based breakfasts they were extinct on the mainland.

But yeah, habitat loss reduced their range, then human hunting reduced their range, then feral dogs and later cats reduced their range. But they were still around in decent numbers.

Then mustelids were introduced, and that was the tipping point, but only in the context of the prior stresses.

So for megafauna, hunting pressure places a population under stress, especially in species with a low replacement rate.

Climate change and the resulting changes in the ecosystem also puts populations under stress.

Maybe one of those stressors was survivable, but probably not both.

And for some megafaunal extinctions, especially on islands, it's pretty obvious humans were the deciding factor. Maybe not through hunting, just habitat loss could be sufficient (e.g., elephant bird), but often habitat loss went hand in hand with intensive hunting (e.g., moa)

This paper's worth a read. https://www.academia.edu/2644492/The_Associational_Critique_...

[mlhpdx]

What comes with people migrating to new environments? New diseases.

It’s bizarre to me that hunting is the “regular suspect” in so many imaginations of the far past when the diseases transported by humans and their animals was almost certainly as substantial a factor in the far past as it was more recently.

[EdwardDiego]

Actually was thinking on this, I suspect you're right that this is another potential stressor that should be considered.

Not so much diseases from animals brought by humans, but rather diseases/parasites from related animals who just mosied onto and sometimes over Beringia of their own accord.

E.g., wooly mammoths on the Eurasian steppes and American mastodons spent a lot of time developing in isolation, they could've had their own diseases they'd evolved to resist, then Beringia arises from the seas, and 100 years later, a mastodon catches the Mammmoth-flu or something.

From what little I understand, some of the N. American megafauna have been shown to have limited genetic diversity due to small founder populations, which we know can increase the vulnerability of a population to a novel disease.

I'm wondering how you'd be able to prove or disprove this though, maybe coprolites? Googling this briefly turned up this amazing website with the even more amazing tagline "#1 for fossilized #2"...

https://poozeum.com/

Brb doing a PhD in paleoepizootiology.

[varenc]

I don't believe there's any clear evidence for this theory, though that doesn't mean anything. Die offs from disease don't really leave anything in the fossil record. But it's hard to favor a hypothetical explanation when there's other theories with at least some data supporting them around.

[EdwardDiego]

Interesting point, what evidence is there of zoonotic vectors though?

[throwuwu]

Which domesticated animals would those be in north and South America?

[mlhpdx]

Domesticated? Human beings back then would have been a walking menagerie of pests, right? Seeds and plant matter, mice, mites, flees, pets, and yes if they managed to travel with livestock, them too.

All of which we know today are vectors for the spread of disease.

I have zero expertise to comment on what a primary contributor to population declines might’ve been for any given animal, I just find it fascinating (and baffling) that those who are experts seemingly ignore something that is undoubtedly a contributing factor.

As others point out this is of course understandable, because the story is less compelling. The image of humans with spears tracking down the last wild beast is one imaginations can’t resist. The image of slowly dying and decaying beasts, less so.

[JackFr]

Wouldn’t that work in both directions though?

[mc32]

Horses are not extinct.

[nobody9999]

>Horses are not extinct.

"While genus Equus, of which the horse is a member, originally evolved in North America, these horse relatives became extinct on the continent approximately 8,000–12,000 years ago. In 1493, on Christopher Columbus' second voyage to the Americas, Spanish horses, representing E. caballus, were brought back to North America, first to the Virgin Islands; they were introduced to the continental mainland by Hernán Cortés in 1519. From early Spanish imports to Mexico and Florida, horses moved north, supplemented by later imports to the east and west coasts brought by British, French, and other European colonists. Native peoples of the Americas quickly obtained horses and developed their own horse culture.[5][6]"

Source: https://en.wikipedia.org/wiki/Horses_in_the_United_States