

The relatively unknown megafauna tragedy and its relevance today - vjvj
http://barefootmuse.wordpress.com/2014/08/19/the-relatively-unknown-megafauna-tragedy-and-its-relevance-today/

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ealloc
I highly recommend the book "Ghosts of Evolution" about the lingering effects
of these extinct megafauna on our lives today. Many of our ecosystems and even
many species evolved in response to their presence.

A major theme of the book is how many of the fruits we see today (especially
avocados, osange oranges, honey locust pods, possibly mangoes and many other
large fruits) originally evolved to be eaten by megafauna. The idea is they
would eat the fruit whole and swallow the pit, and poop it out somewhere.
Evidence for this is that many of the trees have defenses against non-
megafauna eating the fruits, or others have out-of-proportion defenses against
any living animal today, the fact that many pits will only grow if they have
been scoured (for example by the digestive system of an animal), and that the
pits often seem over-defended, and the fact that many of these fruits are not
eaten by any living animals and often fall from the tree and rot in place.

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lifeisstillgood
Thank you - I had never even thought of that despite eating those fruits every
day. (Well every week)

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buttcoinslol
This article is poorly written, bringing up Paraceratherium is disingenuous
considering they went extinct 23 mya. It took 400 years after Columbus for the
American Bison population to drop to near extinction, not 70 years.

Do people upvote articles without reading them?

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pflanze
> It took 400 years

This is not a meaningful number either if the drop (or, more to the point, the
overhunting) only really started 70 years before the end of the period.

I haven't found any clear statement about this, but the following article
talks about the "19th century hunts".

[https://en.wikipedia.org/wiki/Bison_hunting](https://en.wikipedia.org/wiki/Bison_hunting)

~~~
mturmon
Yes, I assume the bison of the Great Plains were somewhat nonplussed when
Christopher Columbus landed on an island in the Caribbean.

The point being that Columbus is not the relevant marker, even though the
article brought him up. In this sense the GP comment has a point, that's bad
writing.

It is interesting that the bison continued to thrive (until the 1800s), and I
guess I never thought about why they outlasted the Ice Age/predation thing
that killed off the other large animals.

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droithomme
I'm curious. How do you figure the natives killed off all the tens of millions
of megafauna given that extinction occurred when they had just arrived over
the bering strait, numbering a few thousand across north and south america?

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mturmon
I read the summary reports by experts, and that's their explanation
(incidentally, I'm not sure about counts, but "tens of millions" sounds high
for most megafauna species -- their small numbers is part of their survival
problem).

If I remember right, the last time I read this story was at the elephant
exhibit at the San Diego Zoo, or perhaps the standing exhibit at the La Brea
Tar Pits. I'm just an interested outsider, so that's good enough for me.

IIRC, the whole Bering Straits story is itself more complex than I learned in
grade school. It was open longer, and was wider and bigger than originally
thought. I believe humans came across in several waves that are genetically or
archeologically separable. I read a lot of stuff in _Science_ , and remember
about 20%, and 50% of those memories are part-wrong, so take this with a grain
of salt. ;-)

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dmix
If you're wondering how overkilling can happen, the Romans killed 9,000 wild
animals (lions, bears, etc) in _one_ day during an opening event for the
colosseum. And proceeded to sport kill thousands after:
[https://en.wikipedia.org/wiki/Colosseum](https://en.wikipedia.org/wiki/Colosseum)

I can imagine exotic and big game has been the prime target of humans for a
very long time.

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lifeisstillgood
A terrible article about a fascinating subject.

I am inclined to give the benefit if the doubt in the whole " The only place
megafauna has survived to some extent to the present day is in Africa where
people traditionally have lived in harmony with nature". In many hands that
would be hippy happy pseudo racist claptrap. And it might be but the next
paragraph points to the more realistic "harmony with nature = avoiding humans"

I have severe doubts about the overkill theory - the fossil record is fairly
sketchy and so many species died out within a few hundred thousand years of us
arriving on the scene that exact timings are hard to believe. On top of which
the practicality seems a bit hard - I can accept that some creatures might be
defenceless against men and spears (giant sloths seem likely to lose out) but
I am going to struggle seeing sabre tooth tigers as easy prey for man.

Climate change, Eco system collapse and diseases carried by apes and their
dogs seem to hold the occam razor prize for most likely explanations. A spear
through the kidneys would just be making a bad day at the office worse for
megafauna.

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underbluewaters
"The only place megafauna has survived to some extent to the present day is in
Africa where people traditionally have lived in harmony with nature."

Bullshit.

From what I understand it's attributable to megafauna evolving alongside
humans as they emerged in Africa. They had time to "learn" how to survive in
the face of this new predator. In places like North America humans slaughtered
and multiplied faster than their prey could adapt.

~~~
nitrogen
Though by many standards I could be considered an environmentalist, I find the
"harmony with nature" trope to be laughable. Nature is not harmonious; it is a
vicious battle of killing, eating, and survival. We should absolutely preserve
and protect our environment. We can never live in "harmony" with something
that is far from harmonious.

~~~
yaks_hairbrush
I likewise find the "harmony with nature" idea to be laughable, but for a very
different reason. If "nature" has any meaning at all, then we are part of it.
Other animals are perfectly happy to change their situation to their benefit.
Beavers, for example, can create lakes by choking off rivers. Are they living
"in harmony" with nature? That feels like a strange question to me, and so I
wonder why it shouldn't feel like a strange question when the beavers are
replaced by humans.

~~~
deciplex
Animals without a natural check on their population and resource consumption
can also experience a population boom followed by a sharp decline and even
collapse, possibly extinction.

~~~
lutusp
Yes, very true. I've recently been working on a mathematical extension of the
Logistic function that models this process that's often seen in nature:

[http://arachnoid.com/peak_people](http://arachnoid.com/peak_people)

~~~
nitrogen
I wonder, could you create a closed form of the final solution by allowing
only a portion of the nonrenewable resources to be consumed? At least, this
should remove the sudden discontinuity in the slope of the nonrenewable
resources function.

~~~
lutusp
> I wonder, could you create a closed form of the final solution by allowing
> only a portion of the nonrenewable resources to be consumed?

You may not be surprised to hear that that was my original, much desired goal,
but after much thought and experiment I realized that the abrupt discontinuity
caused by the exhaustion of the nonrenewables is real, for the reason that, in
practice, the rate of nonrenewable use increase as their exhaustion
approaches, creating an abrupt knee that resists conversion to a closed form.

> At least, this should remove the sudden discontinuity in the slope of the
> nonrenewable resources function.

But that abrupt end to nonrenewables is real -- it reflects the fact that the
growing colony becomes increasingly reliant on them as their exhaustion
approaches. So the knee can't be removed without changing the meaning of the
equation.

Oh, well -- as it turns out, there are many very common differential equations
that resist conversion to closed form. Orbital systems with more than two
bodies are a classic example. Another one is the integral to the common
exponential function that gives us the normal distribution -- very commonly
used in statistics and elsewhere, but no closed form. All applications of the
normal distribution use a numerical algorithm called the "error function" to
produce results -- all of them approximate, and having the drawback that they
cannot be symbolically differentiated or integrated.

Maybe a much more skilled mathematician that I am could find a way around this
obstacle, but I doubt it.

