Tonight's PBS NOVA on extinctions.

[turbo]

Tonight's NOVA is about the extinction of giant land mammals and others and possible mechanisms for that. It will be interesting to see how this is packaged for popular consumption and see if (and how) some of the controversies pointed out by Andre and others here on PF are addressed. Check local listings!

http://www.aptv.org/Schedule/showinfo.asp?ID=218336

 

[Evo]

My friend, a PF member, was one of the experts that was consulted in making this documentary. I'd say that he does not agree that the impact would have caused the extinction. From what he was telling me last week, the show is "pro" extinction.

 

[wolram]

It was the salt lakes that did it

http://www.sciencedaily.com/releases/2009/03/090330102659.htm

 

[mgb_phys]

I'd say that he does not agree that the impact would have caused the extinction.

An impact that wiped out all the large tasty animals in an entire continent just as humans arrived while leaving all the puny humans and large fierce animals intact ?

 

[Evo]

It was the salt lakes that did it

http://www.sciencedaily.com/releases/2009/03/090330102659.htm

That was an older extinction, tonight's show is about the last megafaunal extinction around the beginning of the Younger Dryas.

 

[Andre]

On a global scale there was no extinction event at the beginning of the Younger Dryas as the steppe fauna continued to trive in Siberia until sometimes after the end of the Younger Dryas.

Apart from that, the extinction of many species happened before or after the Younger Dryas. The extinction of camels, horses and giant sloths in America was well before the Younger Dryas, while giant deer or Irish elks, Woolly mammoths (Wrangel Island) and American Mastodons lived well into the Holocene. See for instance this thread. Other problems with the hypothesis have been discussed here.

It's not to say that there was no comet or that it made no victims, it's just that it's role in the extinctions cannot be that pronounced.

 

[Evo]

On my station it just ended abruptly when they started to discuss finding nanodiamonds. No end to the show. What?

 

[wolram]

On my station it just ended abruptly when they started to discuss finding nanodiamonds. No end to the show. What?

Were there any conclusions?
May be they found the mother load and scarpered.

 

[Evo]

Were there any conclusions?
May be they found the mother load and scarpered.

No, no conclusions, no summary, no closing credits. I'm wondering if my local PBS station just cut the show off prematurely, or if this happened everywhere.

It ended with "oh look, there are nanodiamonds in the ice". Big whoop, so what? That doesn't mean that a meteor shower killed off the megafauna.

 

[turbo]

You can get the whole show in QuickTime or Windows Media here. http://www.pbs.org/wgbh/nova/

One thing that got me was a bone-headed assertion that the Clovis people couldn't have caused extinctions of large land-mammals because they didn't have the capability to locate and kill every last individual. What great reasoning! If you put severe hunting pressure on large herd-animals, and reduce their ability to reproduce, sudden changes in environmental factors could have much greater-than-expected effects on the survival of the herds. We should also remember that giant lions and saber-toothed cats were probably well-balanced (predator vs prey) before the Clovis people ever showed up. Apart from some of these over-simplifications and the emphasis on impact-caused extinctions, the show was not bad.

 

[Skyhunter]

He was asserting that under normal conditions the Clovis people could not have wiped out the large land mammals.

They probably did contribute after the fact and perhaps by inhibiting re-population.

 

[turbo]

My point is that predation of the mega fauna was already underway before the Clovis people showed up. If we can extrapolate to today's herd animals, it is obvious that having an optimum distribution of ages in the herds is valuable, and until they can press the carrying-capacity of their forage ranges, it is also valuable to them to have large healthy herds. If you can cull a herd to the point at which pre-existing predation and a series of sub-optimal breeding/feeding seasons can cause more mortality, then you can lose viable herds without insisting that the Super-predator (Clovis in this case) be responsible for eliminating the final remnants of the herds, as that fellow insisted, and he did make that point explicitly, as you will see if you will watch the program on-line.

I'm not saying that an impact by a comet or asteroid could not have been responsible for at least some portion of the extinction, but it is quite evident that smaller mammals did not get wiped out then. Denying that an impact event could have been a major player in the disappearance of megafauna is bad science. IMO, denying that human predation could have been a major factor in the disappearance of megafauna is equally bad science. In nature NOTHING happens in a vacuum.

 

[turbo]

Rather than edit the previous post, let's expand here. In the segment about the Clovis people, geologist Kennet says that the Clovis people could not have caused the extinction of mega-fauna because North America was too big, and the Clovis people did not have helicopters, machine, guns, and GPS technology. He might be a crackerjack geologist but as a large animal biologist, he is certainly out of his league. A predator does not have to be the proximate cause of death for every single individual of a herd in order to wipe them out - it is sufficient only to reduce their numbers or skew their age-distributions such that the herd cannot survive.

Remember that very large mammals (even today, which are much smaller than their pre-extinction relatives) have long gestation periods and long dependency-periods for infants. If someone moved into Africa and said "Mmm, baby elephants are not very fast runners, and not very wary of traps, and they taste good, and they are about right for the size of our tribe as we kill for meat and follow the tuskers" how long would the African elephants last? A small group of human hunters could have a pretty significant effect on the viability of elephant herds that way. Not so much gnus, wildebeest, antelopes, etc - they could have the most significant impact on the very largest herd animals with the fewest natural predators. Herd animals that relied heavily on herd-behavior to protect the weakest from predation...

 

[Evo]

He was asserting that under normal conditions the Clovis people could not have wiped out the large land mammals.

They probably did contribute after the fact and perhaps by inhibiting re-population.

Actually, what they said was that this event wiped out Clovis people and in fact Clovis people did not get wiped out. The people that made up this hypothesis aren't familiar with the archaeological facts, and went on conjecture.

 

[mgb_phys]

So "Head-Smashed-In Buffalo Jump" in Alberta should really be called.
Indigenous peoples living in harmony with nature and only eating nuts and tofu buffalo jump ?

 

[Evo]

So "Head-Smashed-In Buffalo Jump" in Alberta should really be called.
Indigenous peoples living in harmony with nature and only eating nuts and tofu buffalo jump ?

What happened is that the mammoths got all sparkly from the nanodiamonds and this started a trend where "bling' became a status symbol.

The subsequent "bling' wars wiped out the mammoth herds.

Or maybe not.

Ok, we joked about this in last week's chat. I will ban myself for joking about this.