[ExI] Complexity and Evolution (was extropy-chat Digest)

[John Clark]

On Wed, Apr 29, 2020 at 10:13 PM Rafal Smigrodzki via extropy-chat <
extropy-chat at lists.extropy.org> wrote:


> *> There are multiple cases of animals and plants undergoing dramatic
> simplification of their function during both phylogeny and ontogeny. There
> are parasites that started out with having a nervous system and then
> devolved to just chunks of flesh.*
>

True.


> *> There is no general tendency for any given species to become more
> complex. *
>

Well there is Cope's rule, the general tendency of species to get larger
over geological time, although I'm not sure larger size and more complexity
is necessarily the same thing. And there are exceptions to Cope's rule,
large mammals that colonize islands tend to undergo dwarfism, the fossils
of Elephants the size of ponies have been found on the islands of the
Mediterranean. But although the average may decline I do think the most
complex species in one age is more complex than the most complex creature
in a previous age, at least usually.

*> On the other hand, the ecosystem as a whole tends to become more complex*


I think a good example of that would be the Carboniferous Age that started
359 million years ago and is where most of the oil, gas and coal we use
today came from. Evolution had just figured out how to make Lignin, an
organic polymer that gives wood its strength, and so it was the age of huge
trees. There was probably more tonnage of living material during the
Carboniferous than any other time in Earth's history, and as a result of
all that photosynthesis the oxygen level in the air was about 35% versus
21% today; and so you could have 9 foot millipedes, dragonflies the size of
falcons, and 18 inch long cockroaches.

But Lignin is very tough stuff and nothing had yet figured out how to break
it down, so when a tree died it didn't rot and, apart from some massive
forest fires, the carbon in the dead trees didn't return to the atmosphere
as CO2 and instead got buried and just piled up. Eventually after 60
million years a few species of fungi did find an enzyme that could break
down Lignin, and so the Carboniferous Age ended 80 million years before the
first dinosaur evolved. But by then there was a huge amount of inaccessible
carbon in the ground, inaccessible until Homo sapiens came around.

 John K Clark
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