Ecology

The remote island of Ingle Pingle has a simple ecosystem, consisting of:
Ingleweed, a type of grass
Pingle beetle, a beetle which only eats ingleweed (and is only found on this island).

The island is fairly large, and can sustain a large population of both ingleweed and beetles. One day, a ship is wrecked on the island. None of the crew survive, but a small group of insects emerge from the wreck. They belong to one of the following species:
Greenleaf beetle, which only eats grass
Burgundy-striped beetle, which only eats other beetles

Which of these beetles would be more of a threat, in the long run, to the survival of the Pingle beetle?

Originally posted by Acolyte
The remote island of Ingle Pingle has a simple ecosystem, consisting of:
Ingleweed, a type of grass
Pingle beetle, a beetle which only eats ingleweed (and is only found on this island).

The island is fairly large, and can sustain a large population of both ingleweed and beetles. One day, a ship is wrecked on the island. None of the crew survive, but a ...[text shortened]... these beetles would be more of a threat, in the long run, to the survival of the Pingle beetle?

The Greenleaf beetle would be the greater threat. The burgundy-striped beetle would have three different spieces to prey upon, but would likely not be able to completly destroy the population of Pingle beetles. Whereas the greenleaf beetle would focus all it's efforts on the base of the ecosystem, destroying the balance beetween the pingle beetles and the ingleweed grass. Of course, I guess it's possible that a new balance would form, due to the fact that the pingle beetles are going to be eaten by the burgundy-striped beetles. (I'd elaborate more, but I have to run to a rehearsal now).

Originally posted by Acolyte
The remote island of Ingle Pingle has a simple ecosystem, consisting of:
Ingleweed, a type of grass
Pingle beetle, a beetle which only eats ingleweed (and is only found on this island).

The island is fairly large, and can sustain a large population of both ingleweed and beetles. One day, a ship is wrecked on the island. None of the crew survive, but a ...[text shortened]... these beetles would be more of a threat, in the long run, to the survival of the Pingle beetle?

Well, obviously the pingle beetles were destined for doom anyway, because their population would have expanded until they consumed all available Ingleweed and then they would have all starved to death. Another beetle that eats the grass as well can hardly help, but if the rates of reproduction and consumption (and grass growth) are just right then the Burgundy-Striped beetle might be able to keep their numbers in check, avoiding disaster.

Originally posted by iamatiger
Well, obviously the pingle beetles were destined for doom anyway, because their population would have expanded until they consumed all available Ingleweed and then they would have all starved to death. Another beetle that eats the grass as well can hardly help, but if the rates of reproduction and consumption (and grass growth) are just right then the Burgundy-Striped beetle might be able to keep their numbers in check, avoiding disaster.

The Pingle beetles weren't necessarily destined for doom: grasses can be remarkably resistant to having their leaves eaten, so it's likely that the grass and the beetles would have reached some kind of equilibrium. But you're right in saying that under the right conditions a predator would actually increase the survival prospects of the Pingle beetle, whereas a rival could only decrease them.

I once saw a very silly-looking TV show called 'Prey'. The premise is that humanity has somehow overcome its genetic homogeneity and speciated, and the minority 'superior' species is trying to wipe out the majority species, which is more closely related to homo sapiens. Why the superior people are in such a rush to wipe out everyone else isn't really explained (wouldn't it be better to just rise to the top of human society and then sponge off it, instituting birth control for everyone except other superiors?), but even worse, the intro goes something like this: 'In the past we killed off the other hominids because we were better than them. This time humanity is the prey...'
Are they suggesting that Neanderthals et al were eaten en masse by humans? We were something far more dangerous to other hominids, rivals for food and other resources. If humanity speciated into predator/prey, the result would be as in 'The Time Machine'. While this isn't a great position to be in, the Eloi are hardly an endangered species.

I believe that on Discovery they explained that Neanderthals didn't die out, but were taken in in the rest of the society then, the genes mixed.

Originally posted by TheMaster37
I believe that on Discovery they explained that Neanderthals didn't die out, but were taken in in the rest of the society then, the genes mixed.

The lack of distinctive Neanderthal features in modern Europeans suggests that their population was heavily depleted by the time this happened. It's a bit like the way many Mexicans will have some Aztec or Maya ancestry, but in most it will only account for a small proportion of their genes. If there had been a large number of Neanderthals left, Europeans would have many genes which aren't found in Africa; this isn't the case.

Originally posted by Acolyte
The lack of distinctive Neanderthal features in modern Europeans suggests that their population was heavily depleted by the time this happened. It's a bit like the way many Mexicans will have some Aztec or Maya ancestry, but in most it wi ...[text shortened]... ve many genes which aren't found in Africa; this isn't the case.

Hmm, is the way people look any particularly accurate guide to their number of shared genes? I guess as our brains have to be quite big and our heads don't get hit by clubs so much there isn't so much call for us to have massively thick skulls....

Since genetic analysis, a lot of quite similar animals have been shown to completely different evolutionary lines, and a lot of quite different animals have been shown to be closely related.

Originally posted by iamatiger
Hmm, is the way people look any particularly accurate guide to their number of shared genes? I guess as our brains have to be quite big and our heads don't get hit by clubs so much there isn't so much call for us to have massively thick skulls....

Since genetic analysis, a lot of quite similar animals have been shown to completely different evolutionary lines, and a lot of quite different animals have been shown to be closely related.

I realise that phenotype and genotype are very different things (by 'features' I wasn't particularly thinking of appearance). What I should have said was that there aren't large numbers of genes that aren't found in areas formerly populated by Neanderthals but not elsewhere, which is what you would expect if we had a large amount of Neanderthal ancestry.

Originally posted by Acolyte
I realise that phenotype and genotype are very different things (by 'features' I wasn't particularly thinking of appearance). What I should have said was that there aren't large numbers of genes that aren't found in areas formerly populated by Neanderthals but not elsewhere, which is what you would expect if we had a large amount of Neanderthal ancestry.

Could you point me at a reference? I'm not sure that what you say is completely proven - this site: http://www.neanderthal-modern.com/ for instance seems to be saying that the genetic evidence points towards neanderthals and modern humans merging into 1 race.

they will all leave in the ship