Drought Reveals Rare American Lion Fossil in Dried Up Mississippi River | Hacker News Reader

Drought Reveals Rare American Lion Fossil in Dried Up Mississippi River

smithsonianmag.com

75 pointsakeck31 comments

I'm always amazed when reading about the sheer size of ice age animals that existed. I kinda get how dinosaurs were able to get so large, due to environmental factors at the time, but you would assume that food was sparse during the ice age. How did the ecosystem support large mammals?

Ice age was not that much colder than now. Most of Canada was covered with ice, but most of United States wasn’t. Places which are hot today were warm at the time, and places that are warm were temperate. This means that there is no reason to assume that food was scarce.

Here is a way to think about it: Alaska today is probably colder than southeastern US was during ice age. Is food in Alaska so scarce today that it does not support megafauna? Obviously it’s not, quite the opposite. Same was true about most of US during last ice age.

> Obviously it’s not

To be honest I don't think that's obvious to people who don't know much about Alaska.

I feel like you're understating it a bit; 20k years ago Manhattan was covered in over a thousand feet of ice. The Wisconsin Ice Sheet was huge and covered a substantial portion of the modern day United States: https://en.wikipedia.org/wiki/Wisconsin_glaciation#/media/Fi...

On the other hand, the planet was only 4~4.5ºC cooler than at the beginning of the industrial area, so it was not that much cooler. For those who think that warming up the planet by 3 or 4ºC is not a big deal...

We are nowhere close to that kind of pace for temperature change. But it was that much warmer during several eras in the past, including the age of dinosaurs. Life arguably thrived even more under such conditions.

And, as always, the devil is in the rate of change. Living during slow changes is not hard but if the rate of change exceeds your ability to adapt, you are screwed.

Was the whole planet 4-4.5 degrees cooler, or on average?

Correct, but this is more about the slow accumulation of snow, not all of which melts during summer. Over thousands of years, this leads to thousands of feet of packed snow.

The Mississippi must have been gigantic in summers when some of the glacier ice did melt.

The size of the river is related to the amount of ice that melts.

But the amount of ice that melts is completely unrelated to the amount of ice contained in the glacier.

I live on glacier shit (Long Island, New York). It's called a "terminal moraine"[0]. Cape Cod and Nantucket are also glacier poop.

Glaciers were huge. There's an xkcd that talks about that.[1]

[0] https://en.wikipedia.org/wiki/Terminal_moraine

[1] https://xkcd.com/1225/

Larger animals retain heat better. The square-cube law in action. Hence why dragonflies in the lowlands of my country are quite small, but the ones in sub-alpine regions are fricking massive. (Ditto the hares).

https://en.wikipedia.org/wiki/Square–cube_law

Interesting note and a curious thing to apply in my local area. We have lots of cross breed lizards like horned toads and newts and anoles. We love their feeding habits.

Compared to the rainforest lizards, our prairie ones are 4x larger on average. Like dwarf iguanas in some respects with large claws and speed.

I’m also a huge fan of dragonflies here in north Texas - quite common seeing 3-5” long ones zooming about with gorgeous variety of colors. I’ve noticed they appreciate outdoor fans and treat the breeze path as a playground.

The earth was much warmer during the era of dinosaurs, and yet they still grew to such sizes. I'm not sure that body heat retention is a great explanation, especially given the thick fur coats of most modern mammals that were evolved for the cold.

I'm mostly curious how the ecosystem was able to support so many large animals, from the base layer of the food chain up. If there was an ice sheet a mile thick covering all of Canada down to Wisconsin, then most of north America must have been tundra. Were there less trees? Did grasslands thrive across the continent which supported ruminants more, which in turn provided more food for large predators?

Fair comment. :)

I was referencing Bergmann's Rule [0], which really only applies to warm blooded animals but there's also a theory that evolving a larger size helps ectotherms maintain a stable temperature also. [1], and relating to your question on carrying capacity of the food available - the Jarman-Bell Principle [2] that larger herbivores can subsist better on low quality food than smaller herbivores.

And, for interest, Allen's Rule on body appendages for temperature regulation. [3] There's also Cope's Rule - that animals just tend to evolve to get larger, until that's no longer viable. [4]

I can't comment on how valid any of them are, as I'm just an armchair biologist :D

[0]: https://en.wikipedia.org/wiki/Bergmann%27s_rule

[1]: https://en.wikipedia.org/wiki/Gigantothermy

[2]: https://en.wikipedia.org/wiki/Jarman-Bell_principle

[3]: https://en.wikipedia.org/wiki/Allen%27s_rule

[4]: https://en.wikipedia.org/wiki/Cope%27s_rule

Megafauna were actually the norm. Just look at the Dinosaurs and Mammoths. So being smaller is a recent change.

Larger animals are more efficient with their calories, expending less energy per pound vs a smaller animal. Large animals also have a better volume to surface ratio, making it easier for them to keep themselves warm.

>Larger animals are more efficient with their calories, expending less energy per pound vs a smaller animal.

Interesting. If this is true, why do feed efficiency graphs look like this?

https://ib.bioninja.com.au/options/option-c-ecology-and-cons...

That's a pretty unfair comparison.

Cows eat grass.

Pigs and chickens are omnivores that can save themselves from the synthesis of a lot of protein building blocks.

Fish are cold blooded so they don't waste a big portion of calories that they eat keeping warm.

Only the comparison between chickens and pigs is really relevant here.

Glyptodons in South America made huge burrows:

https://www.discovermagazine.com/planet-earth/get-lost-in-me...

Then consider that plants have a symbiotic relationship with animals.

And think about the size of Avocados (for example), and in particular the seed in the middle. Birds aren't going to distribute them...

I'm assuming any fruit or veg grown by humans are heavily tuned versions of some wild ancestor, and may seem to have little in common with it. How 'original' are the avocados we all know and love?

I’ve read that sloths we’re responsible for spreading avocado seeds, but it makes me wonder whether those seeds were always that large?

Yes. I used avocados as an example because everyone is well aware how large the seed is. I couldn't find the original reference, but there's a few papers on how there are South American plants that now geographically isolated because there's no megafauna to eat and disperse the seeds.

Cold favors a large body with a higher mass to surface area. But an ice age isn't all ice, snow and eternal winter. There were still seasons south of the ice sheets where the animals lived.

Maybe slower metabolism/heartbeat since they retain heat better

Also, is it a coincidence that tech gets smaller over time? Maybe there is a shared reason why larger systems are easier to implement, at first

Square-cube law - larger animals retain heat better.

In a similar vein, the drying of Lake Mead is revealing bodies of victims of accidents and foul play: https://www.thefocus.news/culture/why-is-lake-mead-drying-up...

Unfortunate they don't seem to have any pictures in the article of this animal. Just a top level image showing some barges on the river. Anyone have an alternate link that shows images?

It's just a tooth but it's pretty cool https://www.sunherald.com/news/state/mississippi/article2682...

It’s not even the Mississippi River it’s a log chute arm of the river. If you look up top you can see where the arm ends.

The American Lion: it's BIGGER than other lions!

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