Blake , thank you for your first post in this thread: it was informative, well-written, and interesting. I appreciated it and learned from it.
Daniel
mr.jp
March 10, 2006, 9:09pm
62
Hmm, how did the humans arrive in Australia so early?
Didnt they settle india, thailand and indonesia first? Why all the rush to get to the impoverished continent. I mean, you even have to sail quite a bit.
Blake:
I answered this question once before but it was buried in a mostly unrelated thread. Anyway I’m lazy so I’ll simply re-post the same answer
Why does Australia have so many poisonous creatures? That’s a complicated question, but broadly speaking it’s because Australia is an ecological hellhole. No offence meant, that’s a statement of fact.
Seriously, Australia is a terribly impoverished continent and a tough place for any species to make a living. The soils are extremely old and thus extremely infertile. The seas off the Eastern coast particularly are warm, clear, tropical waters and thus totally nutrient deficient, moreso even than the soils, and because the soils are so impoverished the oceans can’t even be fertilised by runoff. The oceans are as much a desert as the land itself.
The continent gets very little rain due to being predominantly located under a high pressure system. On an annual basis the rain tends to be highly concentrated in the summer months with long, dry periods for 8 months or more. The rainfall is also extremely erratic from year to year, with frequent droughts punctuated with floods and relatively few ‘average’ years.
What all this has meant is that there is s chronic resource shortage for most of the continent. Not just water but protein and minerals are in very limited supply in most places. That in turn has produced an ecosystem that greatly favours slow-burn efficiency and an ability to conserve resources. Species that can manage to horde resources have been greatly favoured, as are species that are able to grab the scarce resources ain the brief periods when they are available. That’s seen in the plants, which are almost all sclerophyllous evergreens but it’s also seen in the animals, especially the predators.
Australia has a real dearth of mammalian predators. There have only ever been 5 species of cat size or larger, and currently only 2 survive. Compare that to the 30 odd species that currently live in the US alone, and the 50 or so that lived there before human interference. That’s because mammals require a lot of resources just to keep running and predators even moreso. Impoverished ecosystems just can’t support large numbers of mammalian predators. Instead Australia has an overrepresentation of reptilian and other ‘cold-blooded’ predators that can keep ticking over in the lean times on little or no food. A python or crocodile can ride out the worst droughts and periods of overhunting on one good meal a year. A dog or of the same size still needs to eat once a month. These cold blooded predators also have the ability to invest heavily in reproduction during the good season and can afford to take a gamble on the next season being able to support the offspring, something no mammal can afford to try.
And because the cold-blooded predators dominate those with venom also tend to dominate. That’s further amplified by the need to grab nutrients when they become available. A predator that only gets to hunt once a year really needs to eat at that time, it may never see another chance. A snake or spider or other predator with potent venom greatly increases its chances of making that successful kill.
Basically Australia has an over-representation of poisonous species because of a species desperately need to be able to ride out bad times and conserve resources. This has led to an overabundance of cold-blooded predators but also to an overabundance of predators that are able to sacrifice a small amount of energy in venom production to conserve or capture the small amount of energy available.
Check out the big brain on** Blake!** Very impressive!
Blake
March 11, 2006, 12:33am
64
They walked most of the way and paddled the last few bits.
They sure did.
It wasn’t really a rush. People arrived in southern and eastern Asia around 100, 000 years ago. They arrived on Australia around 40, 000 years later. That’s an average travel rate of about 100 metres a year, or about 2 centimetres and hour. Not even rushing by the standard of a sloth.
The longest water leg was about 80 kilometres. Maybe 3 day’s travel.
mr.jp
March 11, 2006, 9:42am
65
ok thanks. The wikipedia article sure is messed up then.
Was it too cold in southern Europe at the time?