Theos-Talk Archives (November 2001 Message tt00282)

Hi Katinka,


> I have not heard of kangaroos as a pest in Europe. I
> live
> there, does not make me a know-it-all of course, but
> I
> think I would have heard about it. 


They are not a pest all over Europe but I have heard
that they have established themselves in parts. Which
part I am not entirely sure.


> 
> But then, I have no stake in feeling that Australian
> biota
> is winding down. On the other hand it might be
> argued that
> just because a few species are surviving and even
> thriving
> abroad, that does not mean that the general trend
> isn't as
> above described. Isn't the ant-eater (forget the
> English/latin name) a left-over from a certain place
> in
> evolution where there used to be a lot of relatives,
> but
> now it is the only one left? Evolution weeded out
> the other
> ones but the ant-eater was effective enough and
> capable of
> survival enough to stay on. 
> 
> Katinka
> 

The ant eater you are thinking of is the echidna. This
animal is part of the monotreme lineage which is,
indeed, a very old evolutionary line. They are
characterised by having one anterior opening and are
the only mammals that lay eggs. They have no true
mammal glands as placentals and marsupials do but
merely exctrete milk through pores on their belly that
is then licked by infants. Monotremes were thriving
around the time of the dinosaurs and beyond. The only
other living relative is the platypus. Currently the
echidna is well established all over Australia and can
be found in all habitats, from rainforest to alpine to
desert. The platypus, however, is not so fortunate.
This family had a number of species established right
across Gondwana from South America through Antartica
and, of course, into Australia. The modern platypus is
roughly 30cm long whereas relatives in the past have
been up to, and over, 1m in length. Old forms also had
morphological differences such as well formed teeth
which the extant platypus does not have. The range of
the platypus is now entirely restricted to the
freshwater rivers of eastern Australia - a marked
difference from its once widespread Gondwanan
distribution. So by all accounts and measures this
lineage is well and truly on the outer.

In regards to evolution winding down I am currently in
the process of compiling evidence for this occurring.
One strong indication that I can give is the
widespread prevalence in plants of an increase in
water conducting tissue relative to water evaporative
tissue. Although it is contended that this is a
response to aridity it is also seen in plants that are
very old. My theory is that evolution of life on
planet Earth is driven by the availability of water,
with nutrients and other materials being a secondary
factor. Australia is in the unfortunate position of
having aridity and low nutrient soils co-occurring
together - hence the unwinding of life. 

Although volcanoes and glaciation is virtually
non-existent on this continent the potential for these
renewing events to return in the future are there.
This being the case the whole karmic procession is
likely to start again.
Regards,
Mic

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