I have a huge Osage orange tree. Generally nothing eats them, but when the snow stays on the ground for weeks, and forms a crust of ice… eventually the squirrels will tear apart the fruit and eat a few of the hundreds of oranges. It might be that the squirrels using it as a famine food in anomalous weather years is enough to spread it.
In my neighborhood the big Osage oranges were planted in the late 1800s along the property lines, so they are long lived. A once in a hundred year weather event would be enough to keep a population going.
On the hillside behind my parent's house are a few varieties of ivy and some St. John's wort. Based on what is getting eaten we can estimate the local deer population's hunger level - they have a distinct preference order.
That gives me a funny science fiction idea. Once we have self-building, self-repairing devices and infrastructure. Nanobots? Whatever. A tornado goes through destroying houses and in the aftermath cornfields are littered with little growing houses seeded from the debris.
> A once in a hundred year weather event would be enough to keep a population going.
The article notes that it was nowhere near enough, and with the loss of its primary dispersers the once-widespread genus had enormously shrunk in variety and range both before it got recycled as natural fencing:
> According to my field guide, Osage-orange has a limited natural range in the Red River region of east-central Texas, southeastern Oklahoma, and adjacent Arkansas.
> [...]
> fossils tell us that Osage-orange was much more widespread and diverse before the megafaunal extinctions. Back then, Osage-oranges could be found north up to Ontario, and there were seven, not just one, species in the Osage-orange genus, Maclura.
(sp: there are 12 extant species of Maclura according to the wiki — most of them from asia though one is native to south america and one central america, I expect the author implied "in NA")
I’m kind of miffed that he didn’t include humans in the list of megafauna. Certainly Americans are over 100 pounds.
Being an anachronistic species is not necessarily an inevitable decline. I have a magnolia tree in my front yard — the leaves and petals are frustratingly indestructible, because it was once beetle-pollinated long before bees existed. I wonder how many anachronistic species will do well in the future changed climate. I know dawn redwood has a small range now, in China, but their fossils are found in Alaska.
There is a book on my reading list about this, "The Ghosts of Evolution: Nonsensical Fruit, Missing Partners, and Other Ecological Anachronsims", by Connie Barlow. I saw a review of it somewhere, and given the timing, it may be an expansion of the article.
Glad to see them take on the "pristine forest" thing, ecologies are complex open systems. Human activity doesn't do them any favors, for sure, but also there's no edenic prior state to which they can be returned. The only way out is forward.
Osage orange produces wood that is the 2nd hardest in America, behind the live oak. It's exceptionally resistant to decay and insect attack. I've seen osage fence posts that are at least 70 years old and are none the worse for wear. If we could breed a variety that grew straight, it'd be a great source of dense decay resistant timber. Interestingly, the common mulberry is one of its closest relatives, and its wood has similar properties (but usually smaller and not quite as hard / dense). It's too bad there isn't more research being done around osage orange and its potential commercial value. Perhaps genetic modification will help.
NZ has a lot of divaricated plants, as well as species that have a very unpalatable juvenile form of foliage, that changes to more efficient leaves once the tree is above a certain height.
There's a lot of discussion if these were adaptations to browsing by moa.
Fenced (generally fenced forest), but surely wider range than the tree itself could reach. If there had been mustangs I wouldn't have been allowed near them. What I mean is that I don't know if the horses ate the seeds, and if they did eat them, I don't know if they mashed them into a non-viable paste.
Good, except it propagates the notion that the marginal human presence at the time wiped out continent-spanning species.
The best evidence now is that a meteor strike on the Canadian ice shield wiped out most of the megafauna, and the Clovis culture, at one stroke, initiating the 1200-year Younger Dryas cold spell. The damage reached as far as Syria and southern Africa, leaving a layer of platinum-enriched dust.
I would be every interested in reading this evidence :) The "Black Hole" hypothesis certainly explains close overlaps between "humans arrive and increase on population" and "megafauna go extinct".
But then I'm not claiming that it was all Homo sapiens - rather, climatic change had already placed species under stress, then man was the final stressor that pushed them over the brink.
And a single discrete coincidental event would not explain why the pattern "modern humans arrive, megafauna disappears" occurs repeatedly, throughout the fossil record, over 50kY.
Humans had been in the Americas for thousands of years, yet these 32 genera vanished all at the same geologic instant, simultaneously with the Clovis culture itself.
This does not mean humans have not also participated in numerous extinctions, ancient and modern. It only means we cannot be responsible for the sudden American extinctions.
Given more time, we would no doubt have wiped out many of the species. But horses and camels survive on other continents, exposed to humans. Why would Americans have, uniquely, chosen them to wipe out?
> This does not mean humans have not also participated in numerous extinctions, ancient and modern. It only means we cannot be responsible for the sudden American extinctions.
This is a may, not a can: a trivially fitting hypothesis is that the clovis culture was based around that megafauna, and when it finally went through everything it ended with them.
This also explains the synchronicity of the disappearance, because any megafauna hunted to extinction would lead the hunters to fall back on the next genera, increasing hunting pressure on it and thus accelerating its disappearance.
> Given more time, we would no doubt have wiped out many of the species. But horses and camels survive on other continents, exposed to humans. Why would Americans have, uniquely, chosen them to wipe out?
Either coevolution (meaning the megafauna would have had the time to adapt its reaction pattern to the rise of humanity), or environments which allow them to evade hunters and avoid extinction which may not have been available in the americas.
But did humans coexist with megafauna in America / Asia / Australia / Aotearaoa for thousands of years before they all died out?
As I'm a New Zealander, I'm far more familiar with mass extinctions in NZ, and let me just say, to paraphrase a Smash Mouth song, well, after the arrival of humans, the extinctions start coming and they don't stop coming.
For a few reasons.
1) Introduction of the kiore (Polynesian rat) - while now, somewhat ironically, nearly extinct in NZ due to competition by Norwegian and black rats, its predation of chicks and eggs was instrumental in pushing some endemic species to extinction.
2) Unsustainable hunting, and collection of eggs. The most prominent example is the thousands of moa and their eggs found in the middens of what was probably the first archaic Māori (aka "moa hunter") settlement on Te Waipounamu/South Island. Given that moa, like other large birds, were slow breeders, it was inevitable that moa populations would collapse shortly after human arrival given the level of exploitation seen in the middens.[1]
3) Fire. Archaic Māori used fire to drive forest dwelling moa for hunting, which destroyed large areas of old forest that were stable, but unable to re-establish under changed climatic conditions. For an example, the Mackenzie Basin[2], and the Torlesse Range[3], both now known for their extensive tussocklands, were previously covered in dense forest, which no longer existed by the time of European colonisation. With a loss of habitat comes increased risk of extinction.
4) Desperation - as moa became scarcer, the archaic Māori switched to alternative food species, and extinctions rapidly followed (e.g., the flightless South Island goose[4]). This is also the period where (most archaeologists agree) the ancestors of the Moriori[5] departed from the South Island and settled the Chatham Islands/Rēkohu, as archaic Māori society entered collapse.
I highly recommend this book[6] for insights into at least one confirmed example of the black hole theory. You can also explore the art of that book in the national museum's collections[7]. The fact that there's six pages of that art is rather depressing.
Island ecologies are fundamentally different from big continents, for obvious reasons. Even Australia displays island-like extinctions. So, yes, arrival of humans, with their animals, always has profound effects on islands. But that has little resemblance to what happens on continents.
Avocados are another seedpod (technically a berry, believe it or not) evolved to be eaten by mammoths and giant sloths. Unlike the osage orange, however, it didn't adapt to their extinction and would likely have gone extinct itself afterward, except for one saving grace: Mesoamerican humans thought they were delicious and started cultivating them.
In my neighborhood the big Osage oranges were planted in the late 1800s along the property lines, so they are long lived. A once in a hundred year weather event would be enough to keep a population going.