What Happened to Ancient Megafauna?

The linked nautil.us article is a one sided poor summary of what is still an ongoing debate with strong beliefs on either side.

Two people are quoted:

* Jens-Christian Svenning, director of the Danish National Research Foundation’s Center for Ecological Dynamics in a Novel Biosphere at Aarhus University. He’s also the lead author on a recent paper published in Cambridge Prisms: Extinction that argues it was not climate change but rather human hunting that caused the extinction of most megaherbivores over the past 50,000 years.

and

* Felisa Smith, a conservation paleoecologist and professor at the University of New Mexico, believes that the human impact on megafauna extinction is no longer up for debate. “I think work over the past few decades has rather convincingly demonstrated that humans had a pretty substantial part in the extinction,” says Smith.

and ... no other views are given.

This, currently, isn't a slam dunk for one side, there are strong voices on the other side who can cite examples where humans certainly ate megafauna but not, apparently, enough to wipe them out and also point at concurrent pockets (eg: Tasmania) where there were megafauna, as yet no humans, and still the megafauna died out.

> Defined as large-bodied terrestrial mammals with a mean adult body mass of 2,200 pounds or more, today’s remaining megaherbivores comprise the likes of elephants, rhinoceroses, giraffes, and hippopotamuses.

Was there difference in hunter-gatherers in europe/asia/americas compared to africa? Why hadn't the ancient elephants, giraffes, etc been hunted to extinction?

> I think work over the past few decades has rather convincingly demonstrated that humans had a pretty substantial part in the extinction

A substantial part in the extinction? What does that mean? The extermination of the buffalo in the US required industrial scale resources ( guns, railroads, etc ) along with the migration of millions of europeans and habitat loss ( via farming ). It was a conscious and intentional effort. Are they claiming something similar happened throughout much of europe, asia and americas more than 50,000 year ago?

> “When we restore forests, we can’t just think about the trees,” he says. “We must think about the animals that belong there.”

This. The most devastating blow for the buffalo, wolves, bears, etc was habitat loss. It was ultimately what did them in. Did ancient hunter-gatherers alter their environment to such a degree to wipe out herds of giant animals from entire continents?

I have a hard time believing that hunter gathers in tiny tribes traveling on foot with primitive weapons could have hunted and wiped out entire species of large animals from continents. I wish they would give more specifics.

One idea I had a while back is this: with all our modern technology in stem cell research, gene modification and cloning, shouldn't it be possible to recreate actual living clones from prehistoric dinosaur DNA? I mean, sure, these giant wild animals could potentially become dangerous, but how about we confine them to a remote island or so?!

The (Nautilus) article is confusing in the way it conflates "megaherbivores" (herbivores weighing more than 1 [metric] ton) and "megafauna" (any animal, regardless of what it eats, weighing more than 45 kg[1]).

Also: "Giant ground sloths, musk oxen, and short-faced kangaroos: All have gone the way of the dodo" -- A) Of those three animals, only the giant ground sloth was big enough to qualify as a megaherbivore; and B) musk oxen are very much not extinct!

[1] Which I assume is a translation of an older definition using 100 lb as the lower limit.

It's always seemed patently obvious to me that humans were the primary cause of megafauna extinctions. First and foremost because the timing of extinctions aligns so closely with the arrival of humans in a given region, but also because the climate has changed dramatically over the past few million years or so, with cooler or warmer periods happening frequently over geological timespans, yet we don't see similar extinction events happening around climatic cycles / events other than those that happen to align with the arrival of humans in a given region. The Mammoths of North America for example survived numerous cycles of warming and cooling, some far more drastic than the most recent ice age and subsequent warming period, so why was it only the most recent one that caused their extinction? We already have control data for the effect climate had on megafauna populations, the only variable left is us humans.

This is not about assigning blame, says Svenning. “People who lived thousands of years ago never had access to the full picture. These things took place across long time scales and big spatial scales over which no one had an overview; whatever people did, it was difficult to see the consequences. Plus, of course, people just had to survive the best they could.” - lol even

I always figured they were delicious.

This guy (https://www.youtube.com/@Antonio_Zamora) makes a very solid argument that in the Younger Dryas a meteorite impactor hit the ice sheet over the Great Lakes, sending huge ice chunks flying that created elliptical craters that then quickly refilled that are called the Carolina Bays, and which are ubiquitous in the South East, and which point back at the impact point(s) (I think he says there were two impact points) in Michigan. The amount of energy delivered by all those ice chunks seems to have been several megatons (of TNT) per square mile. Enough chunks were ejected, and carolina bays formed, to have likely caused an extinction event.

I'm still digesting the full paper [1] but it looks like the gist is that when you put all the previously published data together, the timing of megafauna extinction statistically lines up with human arrival better than climate change.

The most important pieces of evidence they seem to look at is fungal spores in fossilized poop and sedimentary ancient DNA:

> Further, other studies show contrasting patterns. For example, a sedimentary ancient DNA (sedaDNA) study from the Yukon shows strong megafauna decline between 21 and 14,500 years ago, prior to the loss of the mammoth steppe biome and the Younger Dryas. In addition, as already mentioned, many extinct megafauna species have last occurrences in the Early or even Middle Holocene, that is, during the relatively stable climate of the Holocene, meaning that a climatic cause for their extinction is unlikely given their previous survival through numerous, massive climatic shifts throughout the Pleistocene, including long and warm interglacial periods.

> An increasing number of studies look at local and regional dynamics in the overall abundance of large herbivores at high spatiotemporal resolution using dung-associated fungal spores. Many of these are able to pinpoint declines to timeframes where the climate was stable, for example, North America ~14–13,000 years ago, prior to the Younger Dryas cooling, and 41,000 years ago in Australia at a time of no substantial climate change

These techniques are still very new and they're so sensitive that they should be taken with a grain of salt, sedaDNA especially since it amplifies tiny snippets of DNA found in permafrost. We assume permafrost behaves like an annually laminated sediment but that's controversial and archaeology/paleontology have had plenty of problems before with DNA snippets and contamination.

[1] https://www.cambridge.org/core/journals/cambridge-prisms-ext...

It died.